A more efficient management of MSW requires a combined effort that involves interplay of both social and infrastructural systems. Vacuum pyrolysis of waste tires with basic additives. Granules of waste tires were pyrolyzed under vacuum 3. It was obvious that with or without basic additives, pyrolysis oil yield increased gradually to a maximum and subsequently decreased with a temperature increase from degrees C to degrees C, irrespective of the addition of basic additives to the reactor.
The composition analysis of pyrolytic naphtha i. However, no improvement in pyrolysis was observed with Na2CO3 addition. Pyrolytic char had a surface area comparable to commercial carbon black, but its proportion of ash above Chemical pyrolysis of E- waste plastics: Char characterization. This work studied the disposal of the non-metallic fraction from waste printed circuit board NMF-WPCB via the chemical pretreatments followed by pyrolysis.
As a main heavy metal, the metallic Cu could be significantly removed by Subsequently, the organic-Br in the brominated flame retardants BFRs plastics could be converted into HBr by pyrolysis. The alkali pretreatment was benefit for the Br fixation in the solid char.
The Br fixation efficiency could reach up to Pyrolysis process for the treatment of food waste. After the pyrolysis process a mass balance of the resulting products, off-line analysis of the pyrolysis gas and evaluation of solid and liquid products were carried out. The gas from the pyrolysis experiments was captured discontinuously into Tedlar gas sampling bags and the selected components were analyzed by gas chromatography methane, ethene, ethane, propane, propene, hydrogen, carbon monoxide and carbon dioxide.
The heating values of the solid and liquid residues indicate the possibility of its further use for energy recovery. Influence of mineral matter on pyrolysis of palm oil wastes. The influence of mineral matter on pyrolysis of biomass including pure biomass components, synthesized biomass, and natural biomass was investigated using a thermogravimetric analyzer TGA. Pyrolysis appears to be a promising recycling process since it could convert the disposed polymers to hydrocarbon based fuels or various useful chemicals.
Production and characterization refuse derived fuel RDF from high organic and moisture contents of municipal solid waste MSW. Many cities in developing countries is facing a serious problems to dealing with huge municipal solid waste MSW generated. The main approach to manage MSW is causes environmental impact associated with the leachate and landfill gas emissions. On the other hand, the energy available also limited by rapid growth of population and economic development due to shortage of the natural resource.
The RDF was produced with various organic waste content. Then, the RDF was subjected to laboratory analysis to determine its characteristic including the calorific value. This results indicated that the RDF can be use to substitute coal in main burning process and calcinations of cement industry. Emission of volatile sulfur compounds during composting of municipal solid waste MSW. An addition of dry cornstalks at a mixing ratio of wet weight could significantly reduce the VSCs emissions and avoid leachate.
Compared to pure kitchen waste , VSCs were reduced Fuels from pyrolysis of waste plastic. A large quantity of carbon containing materials, such as waste plastic, used tires, food waste , and biomass end up in landfills. These materials represent a rich energy source that is currently untapped or underutilized. Pyrolysis of a waste from the grinding of scrap tyres. The fibres that are used to reinforce tyres can be recovered as a waste in the process of grinding of scrap tyres.
In this paper beneficiation through pyrolysis is studied since the fibres are made up of polymers with a small amount of rubber because the latter is difficult to separate. The three products - gas, oil and char - obtained from the pyrolysis were investigated. The composition of the gas was analyzed by means of gas chromatography. The oil was studied by gas chromatography and infrared spectroscopy. The char porous structure was determined by N 2 adsorption. In addition, the topography of the chars was studied by means of scanning electron microscopy SEM.
The products resulting from the pyrolysis of the fibres were compared with those obtained from scrap rubber. Pyrolysis kinetics behavior of solid tire wastes available in Bangladesh. The three tire wastes exhibited similar behaviors in that, when heating rate was increased, the initial reaction temperature decreased but the reaction range and reaction rate increased. The overall rate equation for the three tire wastes has been modeled satisfactorily by one simplified equation from which the kinetic parameters of unreacted materials based on the Arrhenius form can be determined.
DTA curves for all of the samples show that the degradation reactions are three main exotherms and one endotherm. Microwave pyrolysis of multilayer plastic waste LDPE using zeolite catalyst. To overcome the problem of garbage, especially plastic waste , environmental experts and scholars from various disciplines have conducted various studies and actions.
One way to degrade the multilayer packaging plastic waste LDPE Low Density Poliethylene with microwave pyrolysis process by using natural zeolite catalysts. The purpose of this experiment was to determine the effect of temperature and time of microwave pyrolysis process by using natural zeolite catalyst to degrade the plastic waste LDPE and compare them. Pyrolysis process was done by using a closed glass reactor with a capacity of ml, operated at a pressure of 1 atm and flowed nitrogen 0.
Plastic waste was LDPE, and natural zeolite was used as its catalyst. Thermal degradation of pyrolysis of waste circuit boards was investigated by high-resolution pyrolysis gas chromatography-mass spectrometry PyGC-MS and thermogravimetry TG.
In helium atmosphere, the products of FR-4 waste printed circuit board were pyrolyzed at , , , , and degrees degrees C, separately, and the pyrolysis products were identified by online MS. The results indicated that the pyrolysis products of the FR-4 waste circuit board were three kinds of substances, such as the low boiling point products, phenol, bisphenol and their related products.
Moreover, under degrees degrees C, only observed less pyrolysis products. As the increase of pyrolysis temperature, the relative content of the low boiling point products increased. In the range of degrees degrees C, the qualitative analysis and character were similar, and the relative contents of phenol and bisphenol were higher. The influence of pyrolysis temperature on pyrolyzate yields was studied. On the basis of the pyrolyzate profile and the dependence of pyrolyzate yields on pyrolysis temperature, the thermal degradation mechanism of brominated epoxy resin was proposed.
Under increasing pressure to minimize potential environmental burdens and costs for municipal solid waste MSW management, state and local governments often must modify programs and adopt more efficient integrated MSW management strategies that reflect dynamic shifts in MSW mana Incineration and pyrolysis vs.
Constructional complexity of items and their integration are the most distinctive features of electronic wastes. These wastes consist of mineral and polymeric materials and have high content of valuable metals that could be recovered. Elimination of polymeric components especially epoxy resins while leaving non-volatile mineral and metallic phases is the purpose of thermal treatment of electronic wastes.
In the case of gasification, gaseous product of the process may be, after cleaning, used for energy recovery or chemical synthesis. If not melted, metals from solid products of thermal treatment of electronic waste could be recovered by hydrometallurgical processing.
Three basic, high temperature ways of electronic waste processing, i. Application of pyrolysis to recycling organics from waste tantalum capacitors. Tantalum capacitors TCs are widely used in electronic appliances. WTCs, rich in valuable tantalum, are considered as high quality tantalum resources for recycling.
However, environmental pollution will be caused if the organics of WTCs were not properly disposed. Therefore, effectively recycling the organics of WTCs is significant for recovering the valuable parts. This study proposed an argon Ar pyrolysis process to recycle the organics from WTCs. The organic decomposition kinetic was first analyzed by thermogravimetry.
The organics were effectively decomposed and converted to oils mainly contained phenol homologs and benzene homologs and gases some hydrocarbon. These pyrolysis products could be reutilized as energy sources. Moreover, based on the products and bond energy theory, the pyrolysis mechanisms of the organics were also discussed. Finally, a reasonable technological process for products utilization was presented. This study contributes to the efficient recycling the organics before valuable material recovery from WTCs.
Investigations on the recycling of oyster shells and bone waste treatment using the plasma pyrolysis technique are presented in this paper. A arc based plasma torch operated at 25 kW was employed for the experiments. Fresh oyster shells were recycled using the plasma torch to convert them to a useful product such as CaO. Bone waste was treated to remove the infectious organic part and to vitrify the inorganic part.
The time required for treatment in both cases was significantly short. Significant reduction in the weight of the samples was observed in both cases. Biochemical, hydrological and mechanical behaviors of high food waste content MSW landfill: Preliminary findings from a large-scale experiment. A large-scale bioreactor experiment lasting for 2years was presented in this paper to investigate the biochemical, hydrological and mechanical behaviors of high food waste content HFWC MSW.
The experimental cell was 5m in length, 5m in width and 7. In the experiment, a surcharge loading of In this paper, the measurements of leachate quantity, leachate level, leachate biochemistry, gas composition, waste temperature, earth pressure and waste settlement were presented, and the following observations were made: 1 Leachate drawdown led to a gain of self-weight effective stress.
The compression strain tended to increase linearly with an increase of leachate draining rate during that two months. Pilot scale high solids anaerobic digestion of steam autoclaved municipal solid waste MSW pulp. Steam autoclaving is an efficient method for the separation and recovery of nearly all organics from MSW , yet a reliable alternative outlet for the large volume of organics produced has not yet been successfully demonstrated. The material produced by the autoclave contains a high concentration of s A novel approach of solid waste management via aromatization using multiphase catalytic pyrolysis of waste polyethylene.
A new and innovative approach was adopted to increase the yield of aromatics like, benzene, toluene and xylene BTX in the catalytic pyrolysis of waste polyethylene PE. The BTX content was significantly increased due to effective interaction between catalystZSM-5 and target molecules i. Catalytic pyrolysis were performed in three different phases within the reactor batch by batch systematically, keeping the catalyst in A type- vapor phase, B type- liquid phase and C type- vapor and liquid phase multiphase , respectively.
Total aromatics BTX of 6. Value added liquid products from waste biomass pyrolysis using pretreatments. Douglas fir wood, a forestry waste , was attempted to be converted into value added products by pretreatments followed by pyrolysis. Four different types of pretreatments were employed, namely, hot water treatment, torrefaction, sulphuric acid and ammonium phosphate doping.
The acid and salt pretreatments were responsible for drastic reduction in the lignin oligomers and enhancement of water content in the pyrolytic liquid. Although, the content of fermentable sugars remained similar across all the pretreatments, the yield of levoglucosan increased. Pretreatment of the biomass with acid yielded the highest amount of levoglucosan in the bio-oil The acid and salt pretreatments also elevated the amount of acetic acid in the bio-oils.
Addition of acid and salt to the biomass altered the interaction of cellulose-lignin in the pyrolysis regime. Application of pretreatments should be based on the intended end use of the liquid product having a desired chemical composition. Catalytic pyrolysis of car tire waste using expanded perlite. In this study, the non-catalytic and catalytic pyrolysis experiments were conducted on the sample of tire waste using expanded perlite as an additive material to determine especially the effect of temperature and catalyst-to-tire ratio on the products yields and the compositions and qualities of pyrolytic oils NCPO and CPO.
Then, the catalytic pyrolysis studies were carried out at catalyst-to-tire ratio range of 0. The characterization results revealed that the pyrolytic oils which were complex mixtures of C 5 -C 15 organic compounds predominantly aromatic compounds and also the CPO compared to the NCPO was more similar to conventional fuels in view of the certain fuel properties.
Investigating impact of waste reuse on the sustainability of municipal solid waste MSW incineration industry using emergy approach: A case study from Sichuan province, China. China has become the largest generator of municipal solid waste MSW in the world with its rapid urbanization, population growth and raising living standard.
Among diverse solid waste disposal technologies, MSW incineration has been becoming an attractive choice. In terms of systematic point, an integrated MSW incineration system should include an incineration subsystem and a bottom ash BA disposal subsystem. This paper employed an extend emergy assessment method with several improved indicators, which considers the emissions' impact, to evaluate the comprehensive performances of an integrated MSW incineration system.
One existing incineration plant in Yibin City, Sichuan Province, China, as a case study, is evaluated using the proposed method. The study results reveal that the ratio of positive output is 1. Therefore, reuse of BA can enhance the sustainability level of this integrated system greatly. Comparatively, scenario B has the best comprehensive performance among the three scenarios.
Finally, some targeted recommendations are put forward for decision-making. Published by Elsevier Ltd. Pyrolysis of virgin and waste polypropylene and its mixtures with waste polyethylene and polystyrene. A comparison of waste and virgin polypropylene PP plastics under slow pyrolysis conditions is presented. Moreover, mixtures of waste PP with wastes of polyethylene PE and polystyrene PS were pyrolyzed under the same operating conditions.
Not only the impact of waste on degradation products but also impacts of the variations in the mixing ratio were investigated. The thermogravimetric weight loss curves and their derivatives of virgin and waste PP showed differences due to the impurities which are dirt and food residues. The liquid yield distribution concerning the aliphatic, mono-aromatic and poly-aromatic compounds varies as the ratio of PP waste increases in the waste plastic mixtures.
Data summary of municipal solid waste management alternatives. Volume 12, Numerically indexed bibliography. This appendix contains the numerically indexed bibliography for the complete group of reports on municipal solid waste management alternatives.
The list references information on the following topics: mass burn technologies, RDF technologies, fluidized bed combustion, pyrolysis and gasification of MSW , materials recovery- recycling technologies, sanitary landfills, composting and anaerobic digestion of MSW. Volume 11, Alphabetically indexed bibliography. This appendix contains the alphabetically indexed bibliography for the complete group of reports on municipal waste management alternatives.
The references are listed for each of the following topics: mass burn technologies, RDF technologies, fluidized-bed combustion, pyrolysis and gasification of MSW , materials recovery- recycling technologies, sanitary landfills, composting, and anaerobic digestion of MSW. Analytical study of endocrine-disrupting chemicals in leachate treatment process of municipal solid waste MSW landfill sites.
Influent and processed water were sampled at different points in the leachate treatment facilities of five municipal solid waste MSW landfill sites. The concentrations of APs were as low as those in surface waters, and no OTs were detected detection limit: 0. BPA was considerably degraded by aeration, except when the water temperature was low and the total organic carbon TOC was high.
The objective function to be minimized in each plan is the sum of the annualized capital investment and annual operating cost of all transportation, treatment and final disposal operations involved, taking into consideration the possible income from the sale of products and any other financial incentives or disincentives that may exist.
For each plan formulated, the system generates several reports that define the plan, analyze its cost elements and yield an indicative profile of selected types of installations, as well as data files that facilitate the geographic representation of the optimal solution in maps through the use of GIS. A number of these reports compare the technical and economic data from all scenarios considered at the study area, municipality and installation level constituting in effect sensitivity analysis.
The generation of alternative plans offers local authorities the opportunity of choice and the results of the sensitivity analysis allow them to choose wisely and with consensus. The paper presents also an application of this software system in the capital Region of Attica in Greece, for the purpose of developing an optimal waste transportation system in line with its approved waste management plan. The formulated plan was.
The results indicate that utilization of all available Equine Reh Microwave assisted pyrolysis of halogenated plastics recovered from waste computers. A large amount of various different liquid fractions up to The liquid fractions showed low density and viscosity, together with a high concentration of useful chemicals such as styrene up to The catalytic pyrolysis of food waste by microwave heating.
This study describes a series of experiments that tested the use of microwave pyrolysis for treating food waste. Economic assessment of flash co- pyrolysis of short rotation coppice and biopolymer waste streams. The disposal problem associated with phytoextraction of farmland polluted with heavy metals by means of willow requires a biomass conversion technique which meets both ecological and economical needs.
Combustion and gasification of willow require special and costly flue gas treatment to avoid re-emission of the metals in the atmosphere, whereas flash pyrolysis mainly results in the production of almost metal free bio-oil with a relatively high water content.
Flash co- pyrolysis of biomass and waste of biopolymers synergistically improves the characteristics of the pyrolysis process: e. In all cases economic opportunities of flash co- pyrolysis of biomass with biopolymer waste are improved compared to flash pyrolysis of pure willow.
Of all the biopolymers under investigation, polyhydroxybutyrate PHB is the most promising, followed by Eastar, Biopearls, potato starch, polylactic acid PLA , corn starch and Solanyl in order of decreasing profits.
Taking into account uncertainties, flash co- pyrolysis is expected to be cheaper than composting biopolymer waste streams, except for corn starch. If uncertainty increases, composting also becomes more interesting than flash co- pyrolysis for waste of Solanyl. Only when the system of green current certificates is dismissed, composting clearly is a much cheaper processing technique for disposing of biopolymer waste.
Co-cracking of real MSW into bio-oil over natural kaolin. Municipal solid waste MSW is a potential material that can be converted into bio-oil through thermal degradation process or pyrolysis. The efficiency and productivity of pyrolysis can be increased with the use of natural catalyst like kaolin. The addition of catalyst also reduces the overall cost of conversion process. During the process 0.
Gas chromatography-mass spectrometry GC-MS was used to analyse the chemical composition of bio fuel. It is found that bio-oil production increases substantially with the use of catalyst. It is observed that the production of bio-oil is The hydrocarbon range distribution of oil produced through pyrolysis reveals that gasoline and diesel fuel C5-C20 are its main constituents. The functional group detected in bio-oil by GC-MS analysis is similar to that of diesel in which paraffin and olefin are major mass species.
Pyrolysis and hydrolysis of mixed polymer waste comprising polyethyleneterephthalate and polyethylene to sequentially recover. Quality improvement of pyrolysis oil from waste rubber by adding sawdust. This work was aimed at improving the pyrolysis oil quality of waste rubber by adding larch sawdust. The results indicated that the efficiency of pyrolysis was increased and the residual carbon was reduced as the percentage of sawdust increased.
The adding of sawdust significantly improved the pyrolysis oil quality by reducing the polycyclic aromatic hydrocarbons PAHs and nitrogen and sulfur compounds contents, resulting in an improvement in the combustion efficiency of the pyrolysis oil. Fundamental characteristics of input waste of small MSW incinerators in Korea. Waste incineration in a small incinerator is a simple and convenient way of treating waste discharged from small areas or from large facilities and buildings such as business centers, marketplaces, factories, and military units.
Despite their ostensible advantages, however, many small incinerators frequently suffer from serious problems, e. To obtain a better understanding of the characterization of wastes in small incinerators, we investigated a series of fundamental characteristics, i. The main waste components in small incinerators were identified as paper and plastic; the proportion of food waste was less than that in large incinerators.
Especially, a low ratio of food waste had a strong influence on other waste characteristics, e. Controlled catalytic and thermal sequential pyrolysis and hydrolysis of polycarbonate and plastic waste to recover monomers. Controlled catalystic and thermal sequential pyrolysis and hydrolysis of polycarbonate and plastic waste to recover monomers.
Bio-oil production from fast pyrolysis of waste furniture sawdust in a fluidized bed. The amount of waste furniture generated in Korea was over 2. Fast pyrolysis is available for thermo-chemical conversion of the waste wood mostly into bio-oil. In this work, fast pyrolysis of waste furniture sawdust was investigated under various reaction conditions pyrolysis temperature, particle size, feed rate and flow rate of fluidizing medium in a fluidized-bed reactor.
The optimal pyrolysis temperature for increased yields of bio-oil was degrees C. Excessively smaller or larger feed size negatively affected the production of bio-oil. Higher flow and feeding rates were more effective for the production of bio-oil, but did not greatly affect the bio-oil yields within the tested ranges.
The use of product gas as the fluidizing medium had a potential for increased bio-oil yields. Experimental study on the heat transfer characteristics of waste printed circuit boards pyrolysis. In order to study the appropriate and advanced technology for recycling waste printed circuit boards PCBs , a fixed bed pyrolysis device with stirring function has been designed and developed. The effect of rotating speed on the temperature distribution and mass change in the pyrolysis process of FR-4 PCB has been analyzed.
The heat transfer and pyrolysis characteristics of different granular layers with and without stirring have been investigated. The results indicate that the stirring can change the main way of heat transfer from conduction to convection in the PCB layers. As the increase of rotating speed, the temperature rising rate of material at the bottom of the pyrolysis furnace gradually decreases, while the heating rate is increasing at the upper layer, and the temperature difference between the upper and bottom layers is gradually reduced.
During the pyrolysis process, the material layer can be divided into three zones along the vertical direction, namely complete pyrolysis zone, partial pyrolysis zone and non- pyrolysis zone. Pyrolysis and dehalogenation of plastics from waste electrical and electronic equipment WEEE : a review. Pyrolysis has been proposed as a viable processing route for recycling the organic compounds in WEEE plastics into fuels and chemical feedstock.
However, dehalogenation procedures are also necessary during treat process, because the oils collected in single pyrolysis process may contain numerous halogenated organic compounds, which would detrimentally impact the reuse of these pyrolysis oils. Currently, dehalogenation has become a significant topic in recycling of WEEE plastics by pyrolysis. In order to fulfill the better resource utilization of the WEEE plastics, the compositions, characteristics and dehalogenation methods during the pyrolysis recycling process of WEEE plastics were reviewed in this paper.
Dehalogenation and the decomposition or pyrolysis of WEEE plastics can be carried out simultaneously or successively. It could be 'dehalogenating prior to pyrolysing plastics', 'performing dehalogenation and pyrolysis at the same time' or 'pyrolysing plastics first then upgrading pyrolysis oils'. The first strategy essentially is the two-stage pyrolysis with the release of halogen hydrides at low pyrolysis temperature region which is separate from the decomposition of polymer matrixes, thus obtaining halogenated free oil products.
The second strategy is the most common method. Zeolite or other type of catalyst can be used in the pyrolysis process for removing organohalogens. The third strategy separate pyrolysis and dehalogenation of WEEE plastics, which can, to some degree, avoid the problem of oil value decline due to the use of catalyst, but obviously, this strategy may increase the cost of.
This digester development work is part of a larger effort, sponsored by the Gas Research Institute GRI Southern California Edison, that provides effective community waste treatment and disposal options while recovering a valuable methane resource from these wastes. Data were collected on: 1 Wastes from experimental municipal wastewater treatment applications. Sorghum was selected as a candidate because it represents both a potential energy crop, as well as, a waste resource if only portions of the plant are converted after grain production.
MSW Transducers. For a finite number of strips, the array is simply truncated without altering the fields. The theoretical expression for hx is given in Eq. It is given in this report by Eq. The real average power going into MSW is now a function of z. PE and PP granules and films were used as typical plastics for testing, and influence of impurities was also investigated. During pyrolysis experiments, photographs of the testing samples were taken sequentially with a high-speed infrared camera, and the quantitative parameters that describe the morphological characteristics of these photographs were explored using the "Image Pro Plus v6.
The experimental results showed that plastics pyrolysis involved four stages: melting, two stages of decomposition which are characterized with bubble formation caused by volatile evaporating, and ash deposition; and each stage was characterized with its own phase changing behaviors and morphological features. Two stages of decomposition are the key step of pyrolysis since they took up half or more of the reaction time; melting step consumed another half of reaction time in experiments when raw materials were heated up from ambient temperatures; and coke-like deposition appeared as a result of decomposition completion.
Two morphological signals defined from digital image processing, namely, pixel area of the interested reaction region and bubble ratio BR caused by volatile evaporating were found to change regularly with pyrolysis stages. In particular, for all experimental scenarios with plastics films and granules, the BR curves always exhibited a slowly drop as melting started and then a sharp increase followed by a deep decrease corresponding to the first stage of intense decomposition, afterwards a second increase - drop section corresponding to the second stage of decomposition appeared.
As ash deposition happened, the BR dropped to zero or very low. A pyrolysis study for the thermal and kinetic characteristics of an agricultural waste with two different plastic wastes. In this study, thermochemical conversion of plastic wastes PET and PVC together with an agricultural waste hazelnut shell was investigated.
With the obtained thermogravimetric data, an appropriate temperature was specified for the pyrolysis of biomass-plastic wastes in a fixed-bed reactor. After pyrolysis experiments, pyrolysis yields were calculated and characterization studies for bio-oil were investigated. Waste tyre pyrolysis : modelling of a moving bed reactor. This paper describes the development of a new model for waste tyre pyrolysis in a moving bed reactor.
This model comprises three different sub-models: a kinetic sub-model that predicts solid conversion in terms of reaction time and temperature, a heat transfer sub-model that calculates the temperature profile inside the particle and the energy flux from the surroundings to the tyre particles and, finally, a hydrodynamic model that predicts the solid flow pattern inside the reactor. These three sub-models have been integrated in order to develop a comprehensive reactor model.
Experimental results were obtained in a continuous moving bed reactor and used to validate model predictions, with good approximation achieved between the experimental and simulated results. In addition, a parametric study of the model was carried out, which showed that tyre particle heating is clearly faster than average particle residence time inside the reactor. Therefore, this fast particle heating together with fast reaction kinetics enables total solid conversion to be achieved in this system in accordance with the predictive model.
Recycling WEEE: Polymer characterization and pyrolysis study for waste of crystalline silicon photovoltaic modules. Photovoltaic PV modules contain both valuable and hazardous materials, which makes its recycling meaningful economically and environmentally. In general, the recycling of PV modules starts with the removal of the polymeric ethylene-vinyl acetate EVA resin using pyrolysis , which assists in the recovery of materials such as silicon, copper and silver.
The pyrolysis implementation, however, needs improvement given its importance. In this study, the polymers in the PV modules were characterized by Fourier transform infrared spectroscopy FTIR and the removal of the EVA resin using pyrolysis has been studied and optimized. Moreover, the behavior of different particle size milled modules during the pyrolysis process was evaluated. It is shown that polymeric materials tend to remain at a larger particle size and thus, this fraction has the greatest mass loss during pyrolysis.
Investigation of waste biomass co- pyrolysis with petroleum sludge using a response surface methodology. The treatment of waste biomass sawdust through co- pyrolysis with refinery oily sludge was carried out in a fixed-bed reactor. Response surface method was applied to evaluate the main and interaction effects of three experimental factors sawdust percentage in feedstock, temperature, and heating rate on pyrolysis oil and char yields. It was found that the oil and char yields increased with sawdust percentage in feedstock.
The interaction between heating rate and sawdust percentage as well as between heating rate and temperature was significant on the pyrolysis oil yield. As a result, petroleum sludge can be used as an effective additive in the pyrolysis of waste biomass for improving its energy recovery. Prospects of pyrolysis oil from plastic waste as fuel for diesel engines: A review. The purpose ofthis study is to review the existing literature about chemical recycling of plastic waste and its potential as fuel for diesel engines.
This is a review covering on the field of converting waste plastics into liquid hydrocarbon fuels for diesel engines. Disposal and recycling of waste plastics have become an incremental problem and environmental threat with increasing demand for plastics. One of the effective measures is by converting waste plastic into combustible hydrocarbon liquid as an alternative fuel for running diesel engines. Continued research efforts have been taken by researchers to convert waste plastic in to combustible pyrolysis oil as alternate fuel for diesel engines.
An existing literature focuses on the study of chemical structure of the waste plastic pyrolysis compared with diesel oil. Converting waste plastics into fuel oil by different catalysts in catalytic pyrolysis process also reviewed in this paper. The methodology with subsequent hydro treating and hydrocracking of waste plastic pyrolysis oil can reduce unsaturated hydrocarbon bonds which would improve the combustion performance in diesel engines as an alternate fuel.
Pyrolysis of chromium rich tanning industrial wastes and utilization of carbonized wastes in metallurgical process. Pyrolysis is the thermal degradation of organic material in oxygen-free or very lean oxygen atmosphere.
This study evaluates the use of pyrolysis for conversion of leather wastes from chromium tanning processes into Carbonized Leather Residues CLR , and the utilization of CLR in metallurgical processes through the production of iron ore pellets. Experimental conversions were performed on a pilot scale pyrolysis plant and a pelletizing reactor of the "pot grate" type.
The results demonstrated the technical feasibility of using the charcoal product from animal origin as an energy source, with recovery of up to CCA-treated wood disposed in landfills and life-cycle trade-offs with waste -to-energy and MSW landfill disposal. Chromated copper arsenate CCA -treated wood is a preservative treated wood construction product that grew in use in the s for both residential and industrial applications.
Although some countries have banned the use of the product for some applications, others have not, and the product continues to enter the waste stream from construction, demolition and remodeling projects. CCA-treated wood as a solid waste is managed in various ways throughout the world. In other countries, the predominant disposal option for wood, sometimes including CCA-treated wood, is combustion for the production of energy.
Based upon production statistics, the estimated life span and the phaseout of CCA-treated wood, recent disposal projections estimate the peak US disposal rate to occur in , at 9. If the wood is managed via WTE, less landfill area is required, which could be an influential trade-off in some countries. Although metals are concentrated. Optimising the biogas production from leather fleshing waste by co-digestion with MSW.
Waste from the leather industry, known as limed leather fleshing LF , has a low C:N 3. This is a major disadvantage for anaerobic digestion due to ammonia toxicity for methanogenesis. This study describes co-digestion of LF with biodegradable fraction of municipal solids waste optimised over a range of C:N and pH to minimise ammonia and to maximise biogas yield. The optimum conditions were found with a blend that provided C:N of 15 and pH of 6.
At higher pH of 8. By contrast at a pH of 4. Biomass activity measured using ATP correlated well with biogas yield as reported previously. Co- pyrolysis of biomass and plastic wastes : investigation of apparent kinetic parameters and stability of pyrolysis oils. This work is dedicated to the co- pyrolysis of real waste high density polyethylene HDPE and biomass rice straw obtained from agriculture. The atmosphere was nitrogen, and a constant heating rate was used.
Based on weight loss and DTG curves, the apparent reaction kinetic parameters e. Furthermore, HDPE decomposition takes by one stage, while that of biomass was three stages. Pyrolysis oils were investigated by Fourier transformed infrared spectroscopy and standardized methods, such as density, viscosity, boiling range determination.
It was concluded, that higher plastic ratio in raw material had the advantageous effect to the pyrolysis oil long-term application. Lower average molecular weight, viscosity, and density were measured as a function of plastic content. Pyrolysis behavior of different type of materials contained in the rejects of packaging waste sorting plants.
In this paper rejected streams coming from a waste packaging material recovery facility have been characterized and separated into families of products of similar nature in order to determine the influence of different types of ingredients in the products obtained in the pyrolysis process. The pyrolysis experiments have been carried out in a non-stirred batch 3.
Pyrolysis liquids are composed of an organic phase and an aqueous phase. The aqueous phase is greater as higher is the cellulosic material content in the sample. The organic phase contains valuable chemicals as styrene, ethylbenzene and toluene, and has high heating value HHV MJ kg Therefore they could be used as alternative fuels for heat and power generation and as a source of valuable chemicals.
Pyrolysis solids are mainly composed of inorganics and char formed in the process. The cellulosic materials lower the quality of the pyrolysis liquids and gases, and increase the production of char. A steady state model of agricultural waste pyrolysis : A mini review. Agricultural waste is one of the main renewable energy resources available, especially in an agricultural country such as Serbia. Pyrolysis has already been considered as an attractive alternative for disposal of agricultural waste , since the technique can convert this special biomass resource into granular charcoal, non-condensable gases and pyrolysis oils, which could furnish profitable energy and chemical products owing to their high calorific value.
In this regard, the development of thermochemical processes requires a good understanding of pyrolysis mechanisms. Based on experimental and literature data analysis, empirical relationships were derived, including relations between the temperature of the process and yields of charcoal, tar and gas CO2, CO, H2 and CH4. An analytical semi-empirical model was then used as a tool to analyse the general trends of biomass pyrolysis.
Although this semi-empirical model needs further refinement before application to all types of biomass, its prediction capability was in good agreement with results obtained by the literature review. The compact representation could be used in other applications, to conveniently extrapolate and interpolate these results to other temperatures and biomass types.
Feasibility study for thermal treatment of solid tire wastes in Bangladesh by using pyrolysis technology. In this study on the basis of lab data and available resources in Bangladesh, feasibility study has been carried out for pyrolysis process converting solid tire wastes into pyrolysis oils, solid char and gases.
The process considered for detailed analysis was fixed-bed fire-tube heating pyrolysis reactor system. Vacuum pyrolysis characteristics and parameter optimization of recycling organic materials from waste tantalum capacitors. Recycling rare metal tantalum from waste tantalum capacitors WTCs is significant to alleviate the shortage of tantalum resource. However, environmental problems will be caused if the organic materials from WTCs are improperly disposed. This study presented a promising vacuum pyrolysis technology to recycle the organic materials from WTCs.
The organics removal rate could reach The oil yield and residual rate was All pyrolysis products can be recycled through a reasonable route. Besides, to deeply understand the pyrolysis process, the pyrolysis mechanism was also proposed based on the product and free radical theory. This paper provides an efficient process for recycling the organic material from WTCs, which can facilitate the following tantalum recovery. Biochemical, hydrological and mechanical behaviors of high food waste content MSW landfill: Liquid-gas interactions observed from a large-scale experiment.
The high food waste content HFWC MSW at a landfill has the characteristics of rapid hydrolysis process, large leachate production rate and fast gas generation. Based on the connected and quantitative analyses on the experimental observations, the following findings were obtained: 1 The high leachate level observed at Chinese landfills was attributed to the combined contribution from the great quantity of self-released leachate, waste compression and gas entrapped underwater.
The increase of the breakthrough value was associated with the decrease of void porosity induced by surcharge loading. Based on the above findings, an improved method considering the quantity of self-released leachate was proposed for the prediction of leachate production at HFWC- MSW landfills. In addition, a three-dimensional drainage system was proposed to drawdown the high leachate level and hence to improve the slope stability of a landfill, reduce the hydraulic head on a bottom liner and increase the collection efficiency for LFG.
A case study of pyrolysis of oil palm wastes in Malaysia. Biomass seems to have a great potential as a source of renewable energy compared with other sources. The use of biomass as a source of energy could help to reduce the wastes and also to minimize the dependency on non-renewable energy, hence minimize environmental degradation. Among other types of biomass, oil palm wastes are the major contribution for energy production in Malaysia since Malaysia is one of the primary palm oil producers in the world.
Currently, Malaysia's plantation area covers around 5 million hectares. If these wastes are being used as a source of renewable energy, it is believed that it will help to increase the country's economy. Recently, the most potential and efficient thermal energy conversion technology is pyrolysis process. The objective of this paper is to review the current research on pyrolysis of oil palm wastes in Malaysia. The scope of this paper is to discuss on the types of pyrolysis process and its production.
At present, most of the research conducted in this country is on EFB and OPS by fast, slow and microwave-assisted pyrolysis processes for fuel applications. Kinetic study of solid waste pyrolysis using distributed activation energy model. From the thermograms obtained from TGA, it is observed that the maximum rate of degradation occurred in the second stage of the pyrolysis process for all the solid wastes. The distributed activation energy model DAEM is used to study the pyrolysis kinetics of the solid wastes.
The kinetic parameters E activation energy , k0 frequency factor are calculated from this model. It is found that the range of activation energies for agricultural residues are lower than the municipal solid waste. The activation energies for the municipal solid waste pyrolysis process drastically decreased with addition of agricultural residues.
Production, characterization and fuel properties of alternative diesel fuel from pyrolysis of waste plastic grocery bags. Pyrolysis of HDPE waste grocery bags followed by distillation resulted in a liquid hydrocarbon mixture that consisted of saturated aliphatic paraffins Co-processing of agricultural plastic waste and switchgrass via tail gas reactive pyrolysis.
TGRP of switchgrass and plastic mixtures significan Recovery of materials from waste printed circuit boards by vacuum pyrolysis and vacuum centrifugal separation. In this research, a two-step process consisting of vacuum pyrolysis and vacuum centrifugal separation was employed to treat waste printed circuit boards WPCBs. Then, the obtained pyrolysis residue was heated under vacuum until the solder was melted, and then the molten solder was separated from the pyrolysis residue by the centrifugal force.
The results of vacuum pyrolysis showed that the type-A of WPCBs the base plates of which was made from cellulose paper reinforced phenolic resin pyrolysed to form an average of The pyrolysis oil and gas can be used as fuel or chemical feedstock after treatment. The pyrolysis residue after solder separation contained various metals, glass fibers and other inorganic materials, which could be recycled for further processing.
The recovered solder can be reused directly and it can also be a good resource of lead and tin for refining. Co- pyrolysis of swine manure with agricultural plastic waste : laboratory-scale study. Manure-derived biochar is the solid product resulting from pyrolysis of animal manures. It has considerable potential both to improve soil quality with high levels of nutrients and to reduce contaminants in water and soil. However, the combustible gas produced from manure pyrolysis generally does not provide enough energy to sustain the pyrolysis process.
Supplementing this process may be achieved with spent agricultural plastic films; these feedstocks have large amounts of available energy. Plastic films are often used in soil fumigation. They are usually disposed in landfills, which is wasteful , expensive, and environmentally unsustainable. The objective of this work was to investigate both the energetics of co-pyrolyzing swine solids with spent plastic mulch films SPM and the characteristics of its gas, liquid, and solid byproducts.
The heating value of the product gas from co- pyrolysis was found to be much higher than that of natural gas; furthermore, the gas had no detectable toxic fumigants. Biochars produced from co-pyrolyzing SPM and swine solid were similar to swine solid alone based on the surface area and the 1 H NMR spectra. The results of this study demonstrated the potential of using pyrolysis technology to manage two prominent agricultural waste streams SPM and swine solids while producing value-added biochar and a power source that could be used for local farm operations.
Research and development plan for the Slagging Pyrolysis Incinerator. Objective is to develop an incinerator for processing disposed transuranium waste. The program includes: incinerator, off-gas treatment, waste handling, instrumentation, immobilization analyses, migration studies, regulations, Belgium R and D test plan, Disney World test plan, and remote operation and maintenance. Pyrolysis of plastic packaging waste : A comparison of plastic residuals from material recovery facilities with simulated plastic waste.
Pyrolysis may be an alternative for the reclamation of rejected streams of waste from sorting plants where packing and packaging plastic waste is separated and classified. These rejected streams consist of many different materials e. For this study, a simulated plastic mixture and a real waste sample from a sorting plant were pyrolyzed using a non-stirred semi-batch reactor.
Red mud, a byproduct of the aluminum industry, was used as a catalyst. Despite the fact that the samples had a similar volume of material, there were noteworthy differences in the pyrolysis yields. The real waste sample resulted, after pyrolysis , in higher gas and solid yields and consequently produced less liquid. There were also significant differences noted in the compositions of the compared pyrolysis products. A review on thermal and catalytic pyrolysis of plastic solid waste PSW.
Plastic plays an important role in our daily lives due to its versatility, light weight and low production cost. Plastics became essential in many sectors such as construction, medical, engineering applications, automotive, aerospace, etc. In the case of the home gardener it is assumed that the MEI will not produce grain, cereals, or peanuts. As the human health endpoint RfD is for chronic lifetime exposure for the inorganics DA and AT must also be considered as lifetime values.
In fact the Agency has assumed these to be 70 years. The Food and Agricultural Organization and the World Health Organization have defined ADI acceptable dally intake as "the daily intake of a chemical which, during an entire lifetime, appears to be without appreciable risk on the basis of all the known facts at the time. It is apparent that this value is developed to protect the more susceptible members of the population and.
The Agency prefers the term reference dose RfD to avoid the connotation of acceptability. Doses less than the RfD are not likely to be associated with adverse health risks, and are therefore, less likely to be a regulatory concern. Thusrthe calculated RP represent the maximum allowable application of contaminants in sludge to land before exposure to the MEI has reached a level of regulatory concern.
A MEI can be human, plant or animal that is supposed to represent a living organism that. While this concept seems simple, it presents severe methodological problems to a risk assessment. Risk assessment is fundamentally a probabilistic analysis dealing with a random variable. Traditionally, risk assessment has dealt with two extreme ends of the risk scale.
One is the low probability-high consequence risk e. The other is the high probability-low consequence risk e. The MEI approach which is utilized by the Agency represents another extreme, namely a low probability-low consequence risk. That is, the probability that an MEI as defined actually exists is certainly very small, and it may approach zero.
The health consequence based on Agency policy, if this hypothetical person does exist, is , or less for carcinogenic chemicals or no greater than the RfD for noncarcinogenic chemicals. It is possible to discuss the upper 99th percentile or 90th or 95th , but an improperly defined MEI the individual with the greatest exposure is a concept without statistical relevance and represents a bounding estimate whose exposure is irrelevant.
When worst case assumptions about the MEI are made, do they lead to the 95th percentile, the 99th percentile, the At a certain point, which is a function of the size of the exposed population, there is a percentile which is not defined because there are no individuals in the group. Thus, exposure to this undefinable group is irrelevant as no one is at risk.
MEI and Exposure must be Linked The purpose of an exposure assessment is to estimate exposure and combine it with chemical specific dose response data to estimate risk. It is important that assessments for specific chemical source demonstrate a link between source and the exposed or potentially exposed population EPA, Further, when the exposure assessment is predictive in nature, a modeling and scenario development approach is recommended and the link between individuals and source is emphasized EPA, Thus, information on chemical concentration and time of contact data duration of exposure as well as information on the exposed population become critical.
It is apparent that not only is the definition of the MEI important, but also its exposure and the two must be linked if the scenario approach is utilized. Point Estimates of Exposure of the MEI In theory, statistical tools can be used to enter the values as frequency distributions and calculate the results in a frequency distribution. This requires that the frequency distribution of the variables be known and that they are independent.
Unfortunately, it is only in rare cases that such information is known. Thus, the alternative approach of selection of discrete values from the ranges of each variable is utilized to make the predictions. This approach results in a less precise estimate that is described with ill-defined terms e. As historically illustrated, use of these exposure scenarios has been a source of controversy regarding how conservative they are. In part conservatism can occur because of attempts to account for data uncertainty by becoming more conservative in expression of the data; without specifying what was done.
A clear distinction between the variability of exposures received by individuals in the population and the uncertainty of the data would help resolve the controversy. In many cases where estimates are termed "worst case", both a focus on the high end of the exposed population and a selection of high end value from the data set for uncertainty are used, leading to values that are quite conservative.
By using both the high end individuals variability and upper confidence bounds on data uncertainty , the estimates might be interpreted as approaching upper bound exposures received by high end individuals. Descriptions of these point estimates: During the time the Agency has been working on the CWA exposure assessment, others have been attempting to communicate where on the distribution these loosely defined terms such as "high end exposure", "reasonable worst case", "worst case" and "maximally exposed individual" might fall Figure 1.
The question now being ask is how does the Proposed Rule fit in with these definitions? This being the case an understanding of the distribution of each variable utilized in the regulation and its impact on the size of the most exposed population MEI as well as where on the exposure distribution the MEI falls needs further clarification.
Therefore, we will examine the exposure variables and evaluate their impact on the exposed population and its potential exposure. Terms used to identify exposure EPA Subsistence Home Gardeners As previously discussed, pathway IF home gardening represents the most limiting of the pathways for human consumption of agricultural crops. It is necessary to attempt to quantify the number of home gardeners and their production.
Thus most of the population of gardeners do not have a large enough area to produce a large part of their annual consumption, and only 46 x. It is evident that the subsistence lifetime gardener population would be classified as maximum exposure and may be worst case or bounding estimate.
While one might argue that this population exists, the size of the population diminishes drastically as some of the other assumptions are placed on them. For example how many subsistence lifetime gardeners use sludge or have gardens that are located on previously sludge soils? How many of these subsistence lifetime gardeners who use sludge are at the maximum application rate RP?
How many of these subsistence lifetime gardeners who use sludge and are at the maximum application rate are unaware of good agronomic management practices? Answers to these questions not only impact the potential MEI population but have significant impacts on its exposure. It would seem that only a small percentage of the gardeners would use sludge as there are many sources of organic material available and the subsistence gardener would already have their favored material which they were satisfied with and thus unlikely to change to an unproven product.
An estimate on conversion land application sites becoming gardens would be the percent of lands receiving sludge. It would be a conservative estimate as not all lands converted to residential use would have been agricultural land, thus the actual percent would be less. It is thus apparent that only a small percentage of the lifetime subsistence gardeners will be utilizing soil which received sludge.
The estimate of lifetime subsistence gardener on soil which received sludge is less than 0. What is the Potential Exposure It is important to recognize that in addition to Cd, other materials are being added with sludge which make the soil concentration dependent on the sludge concentration. In fact the ultimate soil concentration will be a function of the sludge concentration and percent sludge in the 15 cm. If no decomposition of the organic fraction in sludge occurs, then as the mixed 15 cm.
If sufficient sludge is applied such that the 15 cm. For example if a sludge is continuously mixed into the upper 15 cm. At a more reasonable agronomic rate, it will take in excess of 60 to yrs. It will be a long time before soil concentration approaches that of the material being applied. The same time frame will be required before the exposure can be at the projected RLC. With a DA of 70 yrs. Effect of time and rate of continuous application on the composition of the soil The implication is that even if there exists a population of subsistence lifetime gardeners who use sludge, it will take several lifetimes of continuous application at agronomic rates before the soil reaches a concentration equal to the sludge.
It is unlikely that continuous yearly applications will occur for these time frames; therefore soil concentrations are not likely to reach the levels in sludge. These requirement make the exposed population an upper bound estimate. At any rate it becomes apparent that the layering on of conservative assumptions about the exposed population makes it infinitely small and potentially undefinable.
Diet The use of this dietary exposure information for chronic exposure situations requires an integration of exposure over time. The Proposed Rule EPA, used the highest food consumption group to represent the diet of individuals from birth to age 70 Mega Eater.
This means that the diet of the teenage male yrs was used for the food groups: grain, potatoes, root vegetables, dairy, and dairy fat. The diet of the adult female yrs was used to represent the food groups: lamb and lamb fat. The diet of the adult male yrs was used to represent the food groups: legume vegetables, garden fruit, beef, pork, poultry, beef fat, poultry fat, and pork fat.
The diet of the adult female yrs was used to represent the food group leafy vegetables. The diet of the adult male yrs was used to represent the food groups: beef liver, eggs, and beef liver fat. This results in an over estimate of dietary consumption DC during a 70 year life time.
As illustrated by the comments received this assumption was viewed as a bounding estimate for exposure making it impossible to define the exposed population; thus leading to the conclusion that the exposed population did not exist EPA, To develop a more reasonable exposure we started with the Pennington revision of the total diet study as modified by EPA , averaged the dietary consumption rates across sex in the , , and age categories and calculated the Estimated Lifetime Average Daily Food Intake Chaney, a,b.
The use of the estimated lifetime diet as DC, results in an RP which is 1. The use of the lifetime DC should be encouraged as it is logical from the duration of exposure perspective and from a population perspective. The calculated lifetime DC value is based on short term dietary data and thus must be considered a over estimation conservative estimate of the true value.
One must be aware that extrapolation of short term exposure data to estimate long term exposure results in an overestimate of the true exposure EPA, However, at this time no data on lifetime consumption of individuals or the population exist; thus, this data is the best available. As sludge application rate increases, the binding capacity of the sludge solids becomes the controlling factor in metal chemistry of the system. Because of the importance of sludge capacity for specific adsorption of metals, the concentration of metals in sludge is important and the ratio of metals :metal adsorption capacity controls metal availability and thus plant uptake reaches a maximum as sludge application increases Corey et al.
An examination of the plant uptake data from field applied sludge shows the response curves tend to be curvilinear, however most of the individual observations of UC are based on experiments which do not have sufficient rates of application to test their lack of linearity. Therefore, the revised data on plant response UC utilized a linear response and must be recognized as an overestimation of UC conservative estimate and may in fact be a bounding estimate.
It becomes obvious that linear regression and extrapolation of plant concentration results in an overestimation of plant concentration as the extrapolation exceeds the bounds of the data. The degree of overestimation will be a function of where the maximum occurs and how far past it a linear extrapolation is used. The Cd application rate on which the UC data set is based, range from 0. Sludge quality: It has been observed that sludges with low metal concentrations have lower plant uptake at the same metal loading than do sludges with higher metal concentrations Corey et al.
In a recent pot study a linear relationship between the total Cd concentration of 17 anaerobically digested sludges and Cd concentration of Sudax was observed when the sludges were applied at a constant Cd rate Jung and Logan, In the present data set for UC, sludge composition has not been considered and it is important to note that most of the available studies with sewage sludge were conducted with sludges containing metals at levels higher than the median concentrations in current U.
The cited studies were either deliberately conducted with high metal sludges e. It is apparent that the data set will overestimate the UC values that would be observed from current lower metal sludges, but the amount of overestimation is not known. Sludge equilibrium: It has been observed from long term field sludge studies that plant availability of sludge-borne metals is highest during the first year after sludge is applied Hinesly and Hansen, ; Bidwell and Dowdy, ; and Chang et al.
This is contrary to the long-held popular belief that once the sludge applied organic matter is oxidized complexed metals will be released and plant uptake will increase Beckett and Davis, Nevertheless, most of the field studies used in the UC data set are from the early years of the experiment less than 5 years after establishment and are being utilised to develop long term 70 yrs exposure assessments.
Based on the observations of Bidwell and Dowdy and Chang et al. It is apparent that these two assumptions [lower bounding estimate plant response slope of 0. It is not possible to determine how large an overestimation these conservative approaches cause, but it could cause UC to be bounding estimates.
It is thus apparent that even though we have eliminated the error caused by utilization of salt pot studies for the development of the UC data set, we have allowed data uncertainties to cause the revised UC data set to overestimate the true long term data set and in fact the new set may represent upper bound exposures. With this conservatism built into the data set, it is apparent that any representation of the data set will also yield a conservative estimate of the true long term data set it is representing.
Therefore, the use of a conservative estimate of the distribution would only layer on another conservative factor which doesn't appear to be justified. As the UC data set for any food group appears to represent a log normal distribution, it is our contention that the geometric mean which best represents the distribution should be used.
This may appear to say that the UC value in the exposure assessment is a mid range value but as discussed above could be considered a bounding estimate. Therefore, it is necessary to consider this variable in the selection of UC from the data set. It is important to recognize that in natural soil systems as the pH decreases below 5. This increase in soluble Al and Mn plays havoc with plant growth and development in all but the hardiest species Pearson and Adams, Therefore, consideration of plant uptake in these strongly acid soils becomes questionable as even without the increased level of metals associated with high accumulative application of sludge, yield will suffer and little or no edible product will be available for consumption.
It would also seem that even before this reduction in yield associated with extremely acid soils could occur the visual symptoms of Zn, Cu or Ni phytotoxicity would likely occur and the subsistence gardener would learn about soil pH and lime the soil. Thus the required duration of exposure 70 yrs would not occur and the MEI would not exist. Further, if the MEI is defined as the subsistence gardener it-would seem unreasonable to assume that they were unaware of agronomic practices i. This would suggest that only those studies in well managed near neutral pH systems should be considered.
Concerns for deviations of soil pH during the chronic lifetime exposure 70 yrs coupled with the known effect of pH, resulted in utilizing plant response curves UC from all available sludge field data including both the acid and neutral soil conditions. It is apparent that the other two conditions occasional acid and neutral could occur and thus a potential MEI may exist and therefore become more tenable exposure events.
But, the necessity of adding the extra layer of conservatism inclusion of both acid and neutral observations in the data set on an already conservative representation of UC is questionable. As discussed in the MEI section, these are conservative assumptions and make for a small number of people within the defined MEI population. Changes in the fraction of food originating from sludge-amended soil FC would alter the size of the exposed population MEI. Leafy vegetables are consumed in a fresh state and it is not possible to produce them throughout the year, except in extreme situations.
Most gardeners are lucky to harvest a few weeks production, which means that they might have garden produced leafy vegetables for one month each year. TABLE 4. Effect of changing fraction of food group originating from sludge amended soil FC on the reference application rate RP of Cd where UC is the geometric mean of all data and DA is the lifetime diet. As discussed this is unrealistic as it requires several hundred years of continuous application at agronomic rates.
Thus, this is at least high end and most likely maximum exposure for a questionable MEI. As the potential number of MEFs increases with less absurd assumptions i. Effects of variation of UC and FC on the calculated soil concentration and the fraction of sludges which could exceed the soil concentration. Thus, even the drastic changes in the limitations from the proposed rule EPA a to those contained in the Nov. The limits are protective of the high end MEI Table 5.
In their development of the NOAEL no observed adverse affect level sludge limits Chaney and Ryan illustrated that some of the limitations derived on a technical basis could be adjusted to include value judgements, but that these changes need to be identified. Table 5. Thus, the most important research needs or questions remaining for MSW-composting and MSW-compost marketing are confirmation of the assumption that its environmental behavior is like sludge.
As these issues are discussed in detail in our other paper in the conference they will not be repeated. Research needs which are related to the risk assessment may not be specific for MSW-compost, but will help its regulation development and our understanding of the risk.
These include: 1 Plant uptake assumptions A. The assumption that plant response is relative all crops can be represented by the response of one crop needs to be validated. Description of the plant response curve linear or curvilinear needs to be confirmed. Does MSW-compost influence plant uptake of contaminants like sewage sludge? B What are the gardening habits of the U. C What are the agronomic management practices mulching, pH control, water management, etc. D What effect does source of a chemical in the diet have on its bioavailability.
Additional data for many species need to be collected. SUMMARY: The use of the proposed CWA methodologies for development of soil loading limits represents a valid technical approach for calculating maximum loading limits for the contaminants of concern. It must be remembered that the limits are conservative both by design as well as because of conservative expressions of the data caused by its uncertainties.
These data uncertainties need to be expressed and quantified where possible so that the conservatism becomes apparent rather than hidden. This will allow the composting technology to become a widely accepted national program for handling of MSW in the United States. Reference dose RfD : Description and use in health risk assessments. Regulatory Toxicology and Pharmacology Beckett, P. Davis, and P. The disposal of sewage sludge onto farmland: The scope of the problems of toxic elements.
Water PoUut. Bidwell, A. Cadmium and Zinc availability to corn following termination of sewage sludge application. Chaney, R. Sterrett, M. MoreUa, and C. Effect of sludge quality and rate, soil pH, and time on heavy metal residues in leafy vegetables, pp. In Proc. Fifth Annual Madison Conf. Wisconsin - Extension, Madison, WI. Twenty years of land application research Regulating beneficial use. BioCycle 31 9 Public health and sludge utilization Food chain impact. BioCycle 31 10 The future of residuals management after Ryan, and G.
Risk assessment for organic micropollutants: U. L'Hermite et al. EEC Symp. Chang, AC. Hinesly, T. Bates, H. Doner, R. Dowdy, and JA. Effects of long-term sludge application on accumulation of trace elements by crops, pp. In Page, A. Logan, and J. Ryan eds. Land application of sludge: Food chain implications.
King, C. Lue-Hing, D. Fanning, J. Street, and J. Trace element solid-phase associations in sewage sludge and sludge-amended soil. Hallenbeck, W. Cunningham Lewis Publishers, Chelsea, MI. D, and L. Effects of using sewage sludge on agricultural and disturbed lands.
Environmental Protection Agency. Hansen, and D. Effects of sewage sludge cadmium concentration on chemical extractability and plant uptake. Kaitz, E. Home gardening national report. Personnel communication. Logan, T. Sludge metal bioavailability. In Muralidhara H. Battelle Press, Columbus, OH. Utilization of municipal wastewater and sludge on land - Metals.
Gleason, J. Smith, jr. Iskandar, and L. Sommers eds Utilization of municipal wastewater and sludge on land. Calififornia, Riverside, CA. Lu, F. Toxicological evaluations of carcinogenic and noncarcinogens: Pros and cons of different approaches. Mahler, R. Ryan, and T. Effect on yield and cadmium availability to plants.
The Sci. Total Envir. Peterson, and C. Properties of agricultural and municipal wastes. In Elliott, L. Page, A. Lewis Publishers, Chelsea, ML pp. Pearson, R. Adams eds. Soil Acidity and Liming. Agronomy Monograph Pennington, J. Revision of the total diet study food lists and diets. Ryan, J. Pahren, and J. Controlling cadmium in the human food chain: A review and rationale based on health effects. Simms, D. Contaminated land: Setting trigger concentrations.
Summary of environmental profiles and hazard indices for constituents of municipal sludge. Guidelines for Estimating Exposures. Federal Register Development of risk assessment methodology for land application and distribution and marketing of municipal sludge.
Guidelines for exposure assessment, Draft final. Risk Assessment Forum. Washington DC. Veger, J. Roels and H. Soil quality standards: Science or science fiction. Wolf, J. Colon eds. Contaminated Soils, Klumer Academic Publishers. W Peer Review Committee. In press. Rufus L. ABSTRACT: This paper is a review and interpretation of research which has been conducted to determine the fate, transport, and potential effects of heavy metals and toxic organic compounds in MSW-composts and sewage sludges.
Evaluation of research findings identified a number of Pathways by which these contaminants can be transferred from MSW-compost or compost-amended soils to humans, livestock, or wildlife. The Pathways consider direct ingestion of compost or compost-amended soil by livestock and children, plant uptake by food or feed crops, and exposure to dust, vapor, and water to which metals and organics have migrated.
In research on these questions, the chemical properties of sludges and composts were found to be very important in binding the metals and toxic organics. Amorphous oxides of Fe, Al, and Mn provide persistent specific metal adsorption capacity for the heavy metals of concern in MSW-compost and sludges. When properly cured modern MSW-composts containing low levels of metals and organics were land applied, there was no evidence of adverse effects to humans, livestock, or wildlife except temporary B phytotoxicity.
High contaminant concentration sludges would continue to be regulated by cumulative contaminant application limits. Risk assessment for direct ingestion is very important since this allows the greatest potential for transfer for many constituents. Limited feeding studies have been reported for sludges, while research on ingestion of properly composted MSW has only recently begun.
Because Cd is ordinarily about 0. Presently, it appears that the most limiting heavy metal in MSW-composts may be Pb. Thus, MSW-compost may provide fertilizer and soil conditioner benefit in agriculture and horticulture if compost manufacturers carefully reject Pb rich wastes. This Pathway Approach is a comprehensive evaluation of potential worst-case risk to humans, livestock, soil fertility, and wildlife. It considers all receptors and pathways identified by researchers. As a result of the process, important lessons have been learned about risk assessment for land application of sewage sludge, a residual with properties somewhat similar to those of MSW-Compost.
This paper reviews the limited research on the potential environmental problems which might result from land application of MSW-compost, and relevant research on sludges and sludge composts which we believe should provide the basis for development of limitations for utilization of MSW-composts.
Table 1 shows the Pathways which may allow transfer of compost-applied contaminants to most exposed individuals humans, livestock, plants, microbes, or wildlife see Ryan and Chaney for detailed review of the risk analysis protocols.
As summarized in Chaney a, b, , Chaney, Ryan, and O'Connor , and other papers, several pathways predominate in risk for metals or organics because of the chemical properties of the contaminants, soils, etc. The importance of these pathways was identified during the last 20 years of sludge risk analysis research Logan and Chaney, ; Chaney et al.
Phytotoxicity from compost-applied Zn, Cu, Ni, and B is the principle limitation for these elements. Direct ingestion of composts or sludges by children, livestock or wildlife is the principle limitation on potentially toxic organics such as PCBs, DDT, etc, and from Pb, Fe, and F.
Plant uptake and transfer to the human food chain is the principal limitation on Cd application, while transfer to the feed chain for ruminant livestock is the principle limitation for Mo and Se. Although these summaries are based on a large body of sludge research in the field, it is necessary to consider the data from studies of MSW-compost application to see if results are sufficiently similar to allow development of limitations for MSW-compost to be based on the more complete sludge database.
Pathways for risk assessment of potential transfer of sludge-applied trace contaminants to humans, livestock, or the environment, and the Most Exposed Individual to be protected by regulation to be based on the Pathway Analysis US-EPA, a. Grazing livestock on sludge sprayed pastures; 1. Grazing Livestock; 2. Crops; vegetables in strongly acidic sludge amended soil. Earthworms, slugs, bacteria, fungi in sludge amended soil. Shrews or birds; habitat is sludge amended soil. Tractor operator. Water-quality criteria; fish bioaccumulation, lifetime.
Farm households. Perhaps the most important perspective on the potential for persistent risks from utilization of composts from separated MSW ignoring the short term problems from N-immobilization, inadequately curing, salts, etc. Neither Zn, Cu, or Ni phytotoxicity has been observed, nor have Cd, Pb, or xenobiotic organic compounds been observed to cause injury to humans, livestock or wildlife.
One adverse effect of compost has been lime-induced Mn-deficiency in low Mn light textured soils Haan, Where other problems from metals or organics have been identified, they have resulted from composting MSW with highly contaminated sewage sludge.
Although increases in metals or organics in compost-amended soils have been found as expected, demonstrations of potential risk from the increases in soil metals have not been reported. Some have expressed concern that soil metals or organics have exceeded background levels for agricultural soils. We conclude that the basis for regulating land application of MSW-composts and sewage sludge should be the potential for compost utilization to cause adverse effects on agriculture or on the environment due to the metals or organics in these resources, not the simple soil enrichment with known potentially toxic metals and organics.
In general, we believe that soil enrichment without demonstrable risk is a different perspective that agronomists and ecologists must learn how to deal with. We conclude that utilization of MSW-composts and sewage sludge can provide significant benefit to sustainable agriculture; compost utilization can safely continue for an indefinite period without risk to agriculture or the environment.
Thus, this paper is a review of the limited data on the potential adverse effects of land-applied MSW-compost, and perspectives on risk analysis from our work on municipal sewage sludge and sludge composts. We believe that an appropriate risk analysis methodology for potentially toxic contaminants in land-applied organic residuals has been developed, and that there is little evidence that compost prepared from MSW will be found to comprise risk to highly exposed individuals even at very high cumulative applications.
Others have reviewed these subjects, and readers should consider this paper an extension of the information summarized by these previous workers. The MSW-compost research in the s and s is important in increasing the efficiency of our research in the s. We need not "reinvent the wheel" about many of the questions about MSW-compost, considering that new plans to pre- separate the compostable fraction of MSW before it becomes contaminated by other materials will substantially decrease the concentration of many potentially toxic constituents.
Modern sludges contain far lower mean concentrations of metals than found in earlier large surveys, but many sludges still exceed levels attainable by industrial pretreatment and treating the drinking water to reduce corrosiveness of the tap water a significant source of Pb now that gasoline is Pb-free. The so called "green- wastes" composts prepared by separate collection of only the compostable fraction of MSW allow production of composts with lower metal residues than can be attained by general pre-separation, or by central-separation of MSW into different fractions.
However, just because lower concentrations can be reached in MSW- composts doesn't mean that they have to be attained to make utilization of MSW- compost on cropland a valuable practice of sustainable agriculture. Comparison of US soil metal levels with sludge and MSW metal levels indicates that modern MSW-composts are only somewhat enriched in metals compared to soils although Pb is now higher in MSW-compost than in sewage sludges. Analytical results of Lisk et al.
Lisk et al. TABLE 2. Samples 8 72 66 73 73 31 66 Geometric Mean 2. Mean NSSS 9 6 5 Fortunately, good management of MSW composting or utilization can avoid these serious limitations to beneficial use of MSW-compost. However, two significant persistent agricultural problems have occasionally been observed in fields amended with MSW-compost: Boron phytotoxicity and Mn-deficiency. Each has occurred under unusual conditions, and the potential for yield reductions were very site specific.
Further, high rates of compost application used in research were required to cause the B phytotoxicity or Mn-deficiency, and these rates are much higher than commonly applied in normal agricultural practices. Boron Phytotoxicity: In contrast with municipal sewage sludge, MSW- compost contains substantial levels of soluble boron B.
B toxicity from sewage sludge application was reported only for an unusual case of a sensitive tree species growing in soils amended with a sludge containing lots of glass fibers Vimmerstedt and Glover, ; see also Neary et al. The glass fibers contained borosilicate and release of B caused phytotoxicity. It has long been known that plant samples placed in paper bags can become contaminated from B from glue used to hold the bag together. El Bassam and Thorman and Gray and Biddlestone noted that the B level in MSW-composts was quite variable as might be expected if composts are not well mixed.
In general, B phytotoxicity has occurred when high application rates were used, and B-sensitive crops were grown. However, when MSW-compost is used at fertilizer rates in normal fields, the B might be important as a fertilizer rather than as a potential phytotoxicity problem. Boric acid and most borates are quite water soluble, although B can be adsorbed on clays and by organic matter.
Low soil pH facilitates B uptake by plants because the H3B03 molecule predominant form at lower soil pH is absorbed by roots rather than anionic borates Oertli and Grgurevic, Although most B toxicity has been reported on alkaline soils, this is due to the lack of leaching for most of these soils. Excess applications of soluble B are much more phytotoxic in acidic soils, and liming can correct B phytotoxicity. The usual liming action of compost should help prevent this problem.
There are large differences among crop species in tolerance of excessive soil B. Some crops are very sensitive, and these are the species which have suffered phytotoxicity from compost-applied B bean, wheat, and mum. Francois has summarized the significant differences among several groups of crops Francois and Clark, ; Gupta, ; Francois, Ornamental horticultural species have been examined to some extent information on individual species can be found by literature searching , but many horticultural crops have not been studied.
Perhaps the first report on B toxicity from MSW-compost is that of Purves who noted B phytotoxicity to beans on field plots which received high rates of MSW-compost. The full description of the compost experiment is reported in Purves and Mackenzie , and a careful examination to prove B phytotoxicity was reported by Purves and Mackenzie Bean but not potato or other species examined suffered severe yield reduction at high compost rates; this yield reduction was proportional to rate of compost application.
Bean is known to be especially sensitive to B phytotoxicity. Gray and Biddlestone also found B phytotoxicity in sensitive species grown in field plots with high rates of MSW- compost. Gogue and Sanderson reported B phytotoxicity to chrysanthemums in potting media containing MSW-compost. Foliar analysis clearly supported the conclusion that B was toxic and that Mn, Cu, Zn, and other elements were not at toxic levels.
They conducted a calibration experiment to determine the sensitivity of chrysanthemums Gogue and Sanderson, , and the levels found in the mums grown on the test media were in the phytotoxic range. In their research, they adjusted the pH of the media to 6 using sulfur, rather than allowing the MSW- compost to raise the pH of the media.
This probably contributed to the severity of B phytotoxicity observed. Some other horticultural species also suffered B phytotoxicity in compost-containing media Gilliam and Watson, Sanderson reviewed B toxicity in compost amended potting media. In contrast to MSW-compost, sewage sludge composts with wood chips have not been found to cause B phytotoxicity Chaney, Munns, and Cathey, Only a few acid-loving species require acidification of media to do well on neutral compost-amended media.
Interestingly, because the B which causes phytotoxicity is water soluble, the B phytotoxicity problem from MSW-compost is short-lived. Other studies noted that the B-phytotoxicity occurred only during the year of application, and that soluble B was leached out of the root zone over winter Volk, or by leaching potting media with normal horticultural watering practices.
Sanderson noted that perlite also adds B to potting media, and that use of both may cause B toxicity when either perlite or MSW-compost alone might not have done so. Lumis and Johnson studied leaching of B in relation to toxicity of salts and B to Forsythia and Thuja. Nogales et al. B phytotoxicity is significantly more severe when plants are N-deficient Gogue and Sanderson, ; Nogales et al.
This makes the B in MSW-compost which is not properly cured to avoid N immobilization potentially more phytotoxic than in well cured composts. Further, B flows with the transpiration stream and accumulates in older leaves. In environments with low humidity, more transpiration occurs e. Diagnosis of B phytotoxicity requires a knowledge of relative plant tolerance of B, or analysis of the leaves bearing symptoms.
Thus, in general use, compost application at a reasonable fertilizer rate would simply add enough B to serve as a fertilizer for B-deficiency susceptible crops such as alfalfa or cole crops. However, use of MSW-compost at high rates in soils or potting media could cause phytotoxicity if high soluble B were present. The B phytotoxicity would not be persistent because soluble B would leach from the root zone with normal rainfall or irrigation.
Compost-applied B would be more phytotoxic in N-deficient soils, which might result from application of improperly cured compost. Water soluble B should be one chemical which is regularly monitored in MSW-composts so that the need for warning about rates of application and use with sensitive crops can be identified.
Deliberate use of MSW- compost as a B fertilizer for high B-requiring crops such as the cole crops cabbage family might become a regular agronomic practice. Compost-induced Mn deficiency. In contrast with most sewage sludges, application of MSW-compost usually raises the pH of the soil-compost mixture.
Sludges usually contain more reduced N and S, and oxidation of these after mixing sludge with soil generates acidity. Some sludges from areas with hard water do contain enough lime equivalent to correct the acidity they add to the soil, but all MSW-composts have been reported to contain lime equivalent.
This could come from use of CaCO3 and other materials as fillers in paper, or from stabilization of crop residues. When MSW-compost was added to naturally low Mn acidic soils, the resultant high pH was been found to cause Mn-deficiency in some cases. Haan noted that Mn deficiency occurred in several cases in the Netherlands, and Andersson noted this effect in some Swedish soils. Composts usually contain fairly low Mn levels. Most alkaline soils do not cause Mn deficiency if they contain high enough total Mn, and composts with added Mn should prevent this problem.
Crops differ substantially in susceptibility to lime-induced Mn deficiency. Soybean and wheat are well known to suffer severe Mn deficiency when other crops e. Besides the pH of the soil and the susceptibility of the crop, the native Mn level of soils are important in whether Mn deficiency will be induced by lime rich sludges or composts. In general, Mn concentration in soils increases with increasing clay content.
Besides coarse texture, a very important factor in affecting loss of Mn from soils is height of the water table. Thus, coarse-textured, Coastal plain soils are often very susceptible to Mn deficiency. Chaney and B.
James, unpublished. In previous years, corn had been grown and no apparent deficiency occurred. Lime induced Mn-deficiency has also become a problem in some cases when high metal sludges were used at such high cumulative rates that the soils had to be limed to prevent metal phytotoxicity. Spotswood and Raymer noted that crops on a sewage farm which also received a high metal concentration sludge suffered Mn deficiency when lime was applied to prevent Zn toxicity.
In that case, the repeated heavy irrigation with sewage caused depletion of soil Mn, increasing the potential for liming to induce deficiency as was observed at sewage irrigated light textured soils on sewage farms at Paris, France, and Berlin, Germany; Doring, ; Rinno, ; Rohde, ; Trocme et al. It seems clear that MSW-compost manufacturers need to consider the potential of MSW-compost to induce Mn deficiency if the soils in their marketing region are susceptible to Mn deficiency, and the crops commonly grown include susceptible species.
The manufacturer could warn users of this potential problem, or could choose to add Mn during composting to assure that Mn deficiency would not occur. Research has not yet clarified the amount of compost-Mn required to avoid Mn deficiency on susceptible soils. Many scientists have expressed concern about this simple increase in soil metals, and have implied that this is a problem.
As noted above, we believe the potential for adverse effects of heavy metals should be the basis for concern, not the simple presence of metals in soils. It is important that we understand that metals in sludges and composts with low concentrations of metals have not been shown to cause adverse effects, and that an improved understanding of the chemistry of sludges and composts appears to explain the low potential for phytotoxicity and phytoavailability of metals in low metal concentration sludge and compost materials.
Proper approach to evaluate potential compost heavy metal questions: Over 25 years of research have been conducted to better understand the potential for risk from heavy metals in sewage sludge applied to agricultural land. During this period, a number of principals of "heavy metal agronomy" have been identified. Many studies were conducted to determine the relationship between plant uptake and tolerance of metals in pots vs.
Some studies included comparison of plants grown in pots inside and pots outside the greenhouse compared to plants grown with equal sludge applications in the field deVries and Tiller, ; Davis, When sludge was applied in the field, much lower [ plant metal concentration : soil metal concentration ] slopes were obtained than when outdoor pots were used with the same soil; indoor pots had even higher slope, about fold higher than in the field.
This is now understood in terms of the differences between salts and sludge, and between pots vs. Based on this model, Chaney et al. This indicated that use of simple linear regression to evaluate data from sludge studies was in error. Subsequently, Logan and Chaney used plateau regression to evaluate these data. Figure 1 shows several approaches to evaluate the effect of application rate of a low Cd sludge on the uptake of Cd by lettuce averaged over to The plateau regression predictions, and their 95 percent confidence intervals are shown for each soil pH, as are the simple linear regressions.
These data clearly demonstrate the over-estimation of Cd uptake when simple linear regression is used to evaluate plateau response data. With time, other studies were evaluated and found to fit this curvilinear response pattern Corey et al. Based on these understandings, researchers attempted to characterize the chemical aspects of sludge which made metals so much less available to plants phytoavailable than were metal-salts.
A review and interpretation of this information was published by the Corey et al. As noted below, because the sludge chemistry controls the phytoavailability of sludge-applied metals, plant uptake approaches a plateau with increasing sludge application rate rather than showing the usual linear increase with increasing applications of metal- salts.
Another aspect of these data showing that sludge chemical factors reduce the phytoavailability of sludge metals is that it takes time for the reactions of metals to reach their lowest "free energy" condition; by this we mean that by the time sludge metals are applied to soils, the metals have reached strong adsorption sites in the sludge, greatly reducing their phytoavailability compared to fresh additions of metal salts to soils.
Soils and sludges contain metal binding with a wide range of specificity for metal adsorption; freshly added metals are bound to the population of all binding sites, then slowly equilibrate to the strongest specific adsorption sites. Several scientists evaluated the extractability and phytoavailability of sludge metals when the metals were added to the sludge before anaerobic digestion, or after digestion Bloomfield and McGrath, ; Cunningham et al.
In each case, adding the metals after digestion immediately before application to soil caused the metals to be much more phytoavailability than metals added during sewage treatment or before sludge stabilization. However, metals added to sludge were less phytoavailable than metal salts added to the soil without the sludge. This could result from the presence of high levels of many metals competing for the strong adsorption sites. The weaker sites are filled and equilibration is more rapid during sludge stabilization when concentrations are higher compared to dilution with soil.
Reaching the strongest binding sites should take a long time when metals salts are added directly to soils. Sanders and co-workers found for each sludge and metal, that as pH was decreased, some threshold pH was reached below which metal solubility was sharply increased. They then studied the effect of metal concentration in the sludge on this threshold pH. Adams and Sanders found that the higher the sludge metal concentration, the higher the threshold pH point of increasing metal solubility see also Sanders and Adams, ; Sanders et al.
This can readily be interpreted in terms of filling the specific metal adsorption sites vs. These bodies of data on specific metal adsorption by sludge constituents is very important in understanding sludge metal research. In studies of phytotoxicity of sludge-applied metals, it is now clear that phytotoxicity to sensitive crop species has only resulted when high metal concentration sludges were used, or extremely low pH was reached: 1 When high cumulative applications of low metal sludges NOAEL quality were applied, and soil pH allowed to drop to near 4.
Specific metal adsorption is involved in the effect of sludge metal concentration on the phytoavailability and bioavailability of sludge metals. It had been apparent from many studies that sludges with higher metal concentrations could cause higher metal uptake by plants when equal amounts of metals were applied i.
This was part of the plateau response data set. Recently, Jing and Logan reported on the phytoavailability of sludge applied Cd from many different sludges, where equal amounts of Cd were applied in each pot. Crop uptake of Cd increased with increasing sludge Cd concentration. This is explained in terms of the filling of specific Cd binding sites in the sludge; the population of Cd binding sites vary widely in strength of specific Cd adsorption; as sludge Cd concentration increases, the least strongly bound Cd is more phytoavailable.
Similarly, when amounts of metals required to reduce yields of barley or vegetables were determined with salts in greenhouse pots, with mixtures of high metal sludges in pots in the greenhouse, or with normal quality sludges in the field, the salts and high metals sludges caused phytotoxicity Davis and Carlton-Smith, , but the normal quality sludges caused only yield increase Johnson, Beckett, and Waters, Some field plots have been studied up to 20 years after the last sludge application.
Other soils from long-term sludge or sewage farms have been examined by basic studies in the greenhouse. The demonstration of persistence of the "sludge effect" on metal sorption was well illustrated by the data of Mahler et al. The slope of the crop response to the added salt-Cd or fresh sludge-Cd was lower for soils with historic sludge application due to the increase in metal adsorption capacity of the sludge- amended soils pH was not different between treatments. All evidence available indicates that the specific metal adsorption capacity added with sludge will persist as long as the heavy metals of concern persist in the soil.
Although this effect strongly confounds estimating the phytoavailability of Cd in different soils which received different amounts of different sludges, it is clear that the specific metal adsorption capacity added by sludge plays a very significant role in controlling the phytoavailability of metals of concern regarding phytotoxicity or food-chain contamination. The inorganic part of the sludge contributes much of the sludge-applied specific metal adsorption capacity.
As summarized by Corey et al. As noted above, even though sludge organic matter is oxidized over time, if soil pH does not fall, the ability of crops to accumulate soil metals is only decreased over time. This indicates that the non-organic matter adsorption sites are adequate to protect against metals added in sludges. Part of the sludge-applied specific metal adsorption capacity is due to humic acids formed from sludge organic matter; interestingly, metals stabilize soil humic acids against biodegradation.
Further, in the long term, part of the added metals become occluded in Fe oxides Bruemmer et al. All these data from research on sludge vs. They concluded that a plateau response would be the expected pattern of response, and that some sludges could be so low in metals, and so high in metal specific adsorption capacity that addition of sludge could actually reduce metal uptake by plants.
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But real quick: The pick here is KC. And I'll have you know, that is not because my longtime friend Sam is a diehard Chiefs fan. Super Bowl LV total points scored: Over or under? Here's why: The Bucs have averaged over 34 points a game during their last seven games four regular-season ones and then the last three postseason games. Does anyone believe this Super Bowl is not going to be a shootout?
Over 60 sounds correct. Slideshow continues on the next slide. A loss and under. A Bucs win isn't out of the question, but I still like the over. You'll just have to decide which team to back. Figure it out. Go for it. Here's why Worst case scenario, maybe, possibly as always, who really knows -- refs? Beats me, but best of luck out there over the next two weeks as you mull it over. Gannett may earn revenue from audience referrals to betting services. Newsrooms are independent of this relationship and there is no influence on news coverage.
Von Roll has performed full-scale tests in order to optimize the design and operation of the overfire jets. The current Von Roll design is provided in Table and the orientation of the jets relative to the furnace nose is shown in Figure An array of complex injection schemes has been developed with multiple rows and nozzle diameter to achieve adequate penetration and coverage of the flow. In-furnace profiling of carbon monoxide concentrations performed during system start-up is used as the indicator of proper air distribution and mixing.
The various air flows are adjusted to minimize CO peaks. The CO profiling and air adjustment is performed both at unit startup and annually. Von Roll relies on exhaust CO concentration measurements as an indicator that the system, once tuned, is being maintained in the proper operating envelope. According to Von Roll, the typical operating range for CO is in the range of 50 ppm. The final important feature of the Von Roll system is the combustion control system.
All waste-to-energy systems must have combustion controls that respond to changes in steam demand and account for the variability of the fuel characteristics of the refuse. Von Roll systems also include furnace temperature monitoring using thermocouples in the roof of the radiant furnace previously corrected for radiation by comparison to suction pyrometry measurements. Furnace temperatures are used to control the secondary air flow rates.
For example, if steam production rate goes down, then primary air is increased in the middle grate region; if temperature goes down, then secondary air flow is decreased. The grate movement rate is not automatically controlled but is manually adjusted depending on the refuse burnout characteristics. Preheat air is also started manually for wet refuse. Finally exhaust oxygen is measured but is not used in the automatic control system.
The Von Roll system also uses automatic control for auxiliary burners. It is a TA Luft German regulation that there is capacity for 60 percent of the load as auxiliary fuel with startup at high CO and during system startup. Widmer and Ernst is a wholly-owned subsidiary of Blount Inc. Montgomery, Alabama and is located in Zurich, Switzerland. The grate is horizontal with the reciprocating blocks pushing the refuse over the next block in what is termed an "overthrust" motion.
The double motion overthrust tends to first drop ignited particles as the block moves out from under the layer and then pushes the ignited particles back underneath the non-burning waste layer. The ignited material is constantly pushed downwards by intensely rotating and stirring the waste layer and forcing ignition to start at the bottom of the bed. The air slot design causes a high pressure drop across the grate and ensures uniform air flow.
High air velocities at the slots also prevents blockage of the slots. The relative movement of blocks acts to continually clean the grates and acts to keep them open. As with most of the other mass burn systems the overfire air injection is primarily used for furnace mixing and flame height control.
High velocity air jets on the front and rear walls are employed to achieve jet penetration across the furnace and coverage of the entire furnace flow. The front and rear wall jets are not directly opposed but rather they are staggered to achieve an "interlacing" of the air streams. In addition, some configurations include directing the jets to a firing circle which creates a vortex motion in the region adjacent to the overfire air jets.
No enhancement in mixing was achieved with these noses alone; however, the noses provided less penetration differences for the overfire air jets. Thirty percent of the total combustion air was used in the overfire injection with an 80 to percent overall excess air. This change was introduced to improve low load operation where overfire air jet velocities will decline.
The proper air distribution into underfire plenums and overfire air jets is established at startup by in-furnace CO profiling and air adjustments to minimize CO concentration peaks. Under optimal conditions CO levels as low as ppm could be achieved. However, some correlation was suggested to exist if CO was greater than ppm, i. The current systems have both control and upset loops.
The primary control loop monitors the steam production rate and controls the ram feeder, grate speed and air flows. Oxygen is monitored and if the value falls below a set value typically 6 percent alarms will sound and feeding of the grate will be stopped. Finally if load falls below 60 percent of design, then the system will shut down. Future control loops will focus on the use of furnace temperature monitoring and control of primary air.
This new emphasis is to allow extensions to lower load operation. Martin Systems is one of the largest manufacturers of mass burn municipal solid waste-to-energy plants. Wurzburg, Stockholm and Munich plants and the United States e. Chicago, Marion County and Tulsa.
Some of these data are available in the comprehensive municipal waste study series. The design features of Martin refuse combustors are shown schematically in Figure and design details are provided in Table The Martin design philosophy for the minimization of trace organic emissions is described in Martin technical literature Martin and Schetter, and relies on optimization of the combustion process. The approach is based not on one feature alone but rather to the combined aspects of the Martin combustion system.
One of the main features of the Martin system is the grate shown in detail in Figure The grate is inclined downwards from the feed end at an angle of 26 degrees. The grate blocks are "reverse acting" i. This action forces burning refuse back underneath freshly fed material and promotes more complete burnout. The grate underfire air is introduced through gaps at the sides of the head of grate blocks which are 2 mm wide. The gap area is small enough so that the grate has a high pressure drop and therefore there is uniform air distribution through the refuse layer regardless of the refuse bed thickness.
The underfire air is divided into 5 to 6 zones along the length of the grate through the use of separately controlled plenums. For larger systems, the air plenums are doubled with side-by-side plenums. The underfire air to each plenum is individually controlled by dampers and flow orifices for each grate section. The current secondary air nozzle design should actually show in Figure two rows of air nozzles on the front wall, below the front arch, for refuse with higher volatile content.
The adaptation of the secondary air injection scheme from older designs burning lower volatile refuse to designs for higher volatile matter is shown in Figure The amount of overfire air is between 20 and 40 percent of the total combustion air percent excess air. Another important aspect of the Martin approach designed for low emissions are combustion control systems which attempt to reduce the disturbances resulting from changes in refuse characteristics and limits load variations.
New Martin facilities have automatic combustion control systems which consist of two independent loops see Figure The first loop monitors wet flue gas 02 Zirconium oxide probe and controls the refuse ram feeder and grate speed to control MSW feed rate. The second control loop monitors steam production rates and controls underfire to maintain desired steam production rate. Development work is continuing on the combustion control system including monitoring on furnace temperature and controlling secondary air.
Finally the Martin combustion control approach is to limit load variations to percent of design full load. Adaptation of secondary air injection to changed refuse conditions in Martin Systems. In the United States, Waste Management has the technology license and has a new operating plant in Tampa using the Volund system. Volund provides a combustion system that is distinct from other European mass burn technology. Two separate concepts are available depending on the refuse characteristics as shown in Figure For difficult to burn materials such as vegetables, coarse pieces of wood, and high water content refuse, a rotary kiln is added at the exit of the traditional grate region.
In addition, the lower furnace is constructed of high grade, low conductance refractory not SiC clad water tubes as in other European designs. The combustion zone also includes a refractory arch which tends to keep radiation heat losses from the burning zone to a minimum. Hence, the combustion zone temperature is somewhat elevated over waterwall systems. For these reasons, Volund Systems can achieve impressive solids burnout levels.
The features of the Volund System are provided in Table The Volund grate is a forward-push, tilted design with longitudinal fixed and movable beams. Underfire air is introduced between the beams and is controlled by three separate plenums.
The Volund System has a relatively low air pressure drop across the grate and relies on the even distribution of refuse on the grate to ensure uniform air flow. The secondary air is added into the primary zone over the grate region using overfire air jets and aspirated side walls. Volund System designers indicated that good mixing in the various zones is a key factor to controlling the emissions of trace organics. Volund's approach, after extensive water-table flow modeling studies, has been to position the refractory arch above the grate which splits and guides the buoyantly rising gases such as to stimulate mixing.
The Volund furnace is oriented above the discharge area of the grate. Mixing is augmented by the introduction of overfire air but not dependent upon it. Volund System mass burn design features. Volund can incorporate a flue gas recirculation technique to moderate temperatures in the combustion zone to effectively reduce thermal NOX.
For particulate and acid gas removal, Yolund offers a variety of air pollution control device configurations. These configurations include wet scrubbers alone with flue gas reheat, semi-dry spray dryers with either ESP or baghouses, and dry injection of calcium compounds again with either baghouses or ESP. These data clearly indicated lowering of 2,3,7,8 TCDD emissions as time progressed after startup; almost an order of magnitude lower 2,3,7,8 TCDD emissions were achieved in 10 hours after startup versus 1 hour even though the average temperature increased only slightly in the same period.
For example, the emissions of 2,3,7,8 TCDD dropped from 2. For example, just after ignition, CO levels were near ppm without auxiliary fuel start-up while after 10 hours exhaust CO were below ppm Volund, Their first major entry into the MSW area was through the facility at Braintree, Mass, which began operation in That grate design was a direct adaptation of the Riley stokers for coal and wood-fired boilers.
Turner provides a thorough review of the Braintree facility's operating history. Another project - Jackson County, Mich. Riley has licensed the Takuma grate which is a Japanese developed design. As shown, there are four grate sections including a feeder grate, a drying grate, a firing grate, and a finishing grate. Underfire air is provided to the drying, combustion and finishing grates through plenums located under each grate section. Each plenum is equipped with dampers and venturi sections to modulate and measure flow to the particular plenum.
Normally, the total underfire air flow will provide to percent of the theoretical air requirements with the majority of the underfire air proportioned through the combustion grate. They hope to achieve a uniform spatial and temporal release of volatile matter from the burning grate. The boiler is a straight wall configuration above the combustion grate. Silicon carbide refractory cladding is provided to a height approximately 30 feet above the grate.
Overfire air ports are provided at three locations and are designed to achieve complete coverage of flow from the lower furnace. Overfire air quantities usually amount to approximately 20 to 30 percent of the total combustion air. Overall, the system is designed to operate at 80 to 90 percent excess air. This is accomplished through use of a sophisticated automatic combustion control system in conjunction with auxiliary burners.
Measurements are made of exhaust oxygen concentration and the furnace exit gas temperature i. The ACC will modulate the overfire air flow to maintain constant 02 concentration. This is primarily a trimming operation on the overfire air. That minimum condition will be maintained by modulation of the fuel-charging rate, grate speed and underfire air flow rate, as well as through the use of an auxiliary burner.
The auxiliary burner is located in the lower furnace region near the grate in order to maintain the time-at-temperature requirement. This required positioning has generated operational problems associated with burner openings getting covered with slag. Riley is currently working on an advanced auxiliary burner design to circumvent that problem.
Further inquiry into operational control at reduced load conditions indicated that the overall excess air level was allowed to increase. Exhaust 02 concentration versus load curves were not provided. There is obviously concern over maintenance of overfire air jet penetration and mixing at reduced load.
Riley personnel noted that there were three levels of overfire air ports and that levels could be shut down at reduced load. That procedure should maintain jet penetration. However, shutting down a row of overfire air jets is accomplished manually d is not automatically controlled through the ACC. Even though there is significant operating experience on Takuma grates in Japan, it is reasonable to expect that Riley will fine-tune its design and control strategy through experience gained at Olmsted.
The combination of Detroit Stoker grates with various boiler manufacturers Foster Wheeler, Babcock and Wilcox, and Keeler reflects the historic contracting procedure in the United States. That procedure generally involves selection of an engineering firm to design the plant with major component selection based on competitive bids. The preceding sections of this chapter have discussed design and operating philosophy of various firms marketing complete resource recovery systems. Detroit Stoker is not a MSW system supplier.
Typically, they supply fuel feed, grates and air supply hardware underfire and overfire to the boiler manufacturer. Significant testing has been undertaken of the Hampton plant in Virginia over the last several years. Current Detroit Stoker hardware design is significantly different from that used at Hampton Detroit Stoker, Figure and Table illustrates the current design.
Major changes have occurred in the distribution of underfire air, addition of flow constrictions and modifications to the overfire air system design. Each of these areas are discussed below. The underfire air system now consists of separate plenums under each grate section. The grates themselves are constructed as standard width modules. Thus, depending upon the unit size the grate may consist of a 3 x 1 or 3 x 2 module configuration with either 3 or 6 underfire air plenums.
Air flow to each is individually adjustable. Detroit Stoker is convinced, however, that this pressure level is sufficient to achieve uniform air distribution across the drying, firing and finishing grates. Establishment of the underfire air flow distribution is based on visual observation of the flame. Normally, 70 to 75 percent of the underfire air is directed through the firing grate. As the combustion gases leave the grate region they are directed through a constricted flow region formed by "noses" on both the front and rear boiler walls.
Clearly, construction of the throat region is the responsibility of the boiler manufacturer. This is a critical area requiring close coordination between the boiler and grate manufacturer. Overfire air ports are located on both the front and rear walls.
Automatic Sifting Removal Figure Cross-section of boiler with current design Detroit Stoker firing system. Typically 30 to 40 percent of the total combustion air is supplied as overfire air. The lower furnace region - to an elevation above the overfire air ports - is covered with approximately 1 inch of silicon carbide refractory to prevent tube corrosion. Detroit Stoker feels that the combination of insulated walls, flow constriction and careful design of the overfire air jets will lead to high combustion efficiency.
They do not, however, have emission data to establish the vajidity of that belief. Startup and shutdown rely on auxiliary burners. These burners are either gas or oil-fired and are located well above the grate. Exact location, size, fuel, and control sequence for the auxiliary burners is the responsibility of the boiler manufacturer. Detroit Stoker grates are designed to operate with a turndown ratio but Detroit Stoker prefers to have base-loaded systems.
The lower limit for turndown is generally established by furnace temperature. This condition will also be characterized by deterioration in overfire air mixing as well as increased CO and unburned hydrocarbon emissions. Detroit Stoker suggested that a row of overfire air ports could be dropped from service at low load but that is not an integral part of their suggested control strategy.
The Detroit Stoker design for overfire air mixing strategy has evolved through experience gained in numerous MSW projects. They are currently considering cold-flow modeling studies to refine their current designs. This will be the first C-E designed mass burn facility in the United States. Figure illustrates the db grate design which consists of alternate moving and stationary steps in an overlapping configuration Combustion Engineering, Each grate section is equipped with its own plenum to allow control of underfire air.
It should be noted that various grate sections are shown to be configured in a continuous path, without steps between grate sections. The C-E personnel indicated that the grate motion provided sufficient aeration of the fuel and felt that steps between grate sections could result in uneven burning.
Unlike most other grate designs, the slope of db grates can vary from horizontal to as much as 21 degrees. C-E sales literature indicates the slope of the grate is based on waste composition. Design features of DeBartolomeis grate. That entry was accomplished through a percent purchase of the O'Connor Combustor Corporation Westinghouse, The O'Connor combustion system represents a unique approach for burning municipal solid waste. A typical plant configuration is illustrated in Figure and shows that the heart of the system is a water-cooled rotary combustor.
The rotary cylinder consists of alternating watertubes and perforated steel plates. MSW is metered into the combustor via a feed chute and ram feeder. Preheated combustion air is divided into six zones and enters the combustor through the perforated plates forming the walls of the cylinder. The rotary section terminates within a waterwalled boiler allowing the residue to fall into an ash removal system. Combustion air is drawn from the waste pit and passes through an air preheater at the boiler exhaust.
In the Gallatin facility a portion of this air was drawn off by a second fan and directed to three overfire air port elevations in the boiler - one below the rotary combustor dump and two elevations above the rotary combustor. As shown in Figure , the main combustion air is distributed axially down the rotary combustor.
Each axial section is subdivided into two zones. With counterclockwise rotation, air passing through the right zone is forced through the burning material bed. Air admitted to the left zone will enter the rotary combustor in a region which is effectively above the burning bed. In comparison to the grate firing systems discussed in earlier sections of this chapter, there are several other unique features of the O'Connor combustor.
Traditional grate systems for MSW firing provide silicon carbide cladding to the lower waterwalls to prevent corrosion. There is no refractory on the waterwalls of the O'Connor rotary combustor. As noted previously, the Gallatin, Tennessee facility was equipped with "overfire air" ports at three elevations in the boiler.
In that facility, the region from the rotary combustor to the ash pit of the boiler was equipped with a stationary grate referred to as an "afterburning grate. A report Cooper Engineers, states that "it was found from earlier Cooper Engineers testing that the boiler overfire air and grate air was ineffective, so these systems were no longer used and all of the combustion air is now introduced through the combustor as underfire and overfire air.
It is not known whether the boiler overfire air system had an impact on those pollutant emissions. All of the existing facilities using the O'Connor combustor system were constructed prior to the Westinghouse purchase of O'Connor.
For a variety of technical and marketing reasons, Westinghouse has entered into a long-term contractual arrangement with Sumner County. They have made a variety of major system repairs including replacement of the stacks which collapsed due to corrosion.
It is also reported that the facility has a new superintendent who is a Westinghouse employee. Basic Environmental Engineering located in Glen Ellyn, Illinois builds multistaged mass burn combustors for smaller scale applications Basic Environmental Engineering, The construction of these units is done in a "unitized" modular fashion as opposed to field erected which is common for larger mass burn systems.
The primary zone of the Basic system is not starved air so that the technology can be classified as small modular mass burn combustion. There is currently little information available on trace organic emissions from Basic Environmental Engineering Systems and hence it is uncertain whether current design practices are sufficient; however, the design and operating approach employed by Basic is worthy of consideration because Basic is one of the leaders in advanced small unit systems.
Also many of the features of the Basic technology will likely have favorable impact on trace organic emissions. The process flow diagram of a typical Basic system is provided in Figure and design features are summarized in Table Basic uses one, two or three pulse hearths depending on model size.
Primary combustion air is introduced through the hearth at approximately stoichiometric conditions. The primary chamber is constructed of membrane water wall. Process flow diagram of Basic Environmental Engineering modular mass burn technology. Higher charge rates also lift larger particle sizes which require greater residence time to destroy the carbonaceous particles before leaving the high temperature furnace zone.
The secondary or "stage two" chamber includes a fired afterburner and additional air injection. The first afterburner is positioned at the exit of the transition duct between the chambers and can be fueled on oil or natural gas. The design capacity of the afterburner is 20 percent of the total Btu input of the system for normal municipal solid waste and is increased to 40 or even 50 percent when the refu ncludes: a large amounts of chlorinated plastics or b when the furnace is operated at lower furnace input firing rates, but the waste fuel is primarily long chain hydrocarbons such as plastics and rubber.
Additional air is added into the second stage after the afterburner using a unique injection scheme called a "thermal exciter". The air is injected outward from a refractory-lined closed cylinder positioned along the center axis of the secondary chamber.
The air flows through small, high-velocity jets and are oriented to achieve vortex flow in the secondary chamber. The tertiary chamber consists of a second "thermal exciter" for final air addition to an overall excess air level of approximately 80 percent. The chamber exit temperature is monitored and is used as the control variable for the fired afterburner.
The maintenance of the exit temperature of the final combustion chamber ensures that the gases experience at least one second above that temperature in the combined second and third chambers. Temperatures of each chamber exit are used as the principal control variables and the air flows and afterburners are used to maintain the temperature.
Basic is currently investigating the use of oxygen and carbon monoxide monitoring for system control. The Basic technology is capable of achieving high turndowns up to without requiring additional auxiliary fuel to maintain the destruction temperatures of the reburn zones that it required at full design conditions.
Example: if at full load the waste fuel burned did not require auxiliary fuel, then down to it would not need it. Basic engineers would not advise lower load operation without auxiliary fuel being required. If a client desires to operate to turndown, the design supplied to the client will be changed from the standard control of 60 percent turndown without use of auxiliary fuel to maintain temperature. The distributed air addition and moderated uniform temperatures likely keeps NOX emissions from being excessive.
Basic estimates NOX levels of less than 45 ppm compared to other modular systems in the ppm range. The exhaust carbon monoxide level is also low, typically in the range of ppm. Although CO is not typically measured unless requested by the client, Basic believes that this is an indicator of the maintenance of good combustion conditions. They have developed and patented a multistage controlled excess air mass burning technology. Vicon Recovery Systems, Inc. Vicon is the exclusive licensee of the Enercon technology for MSW.
Burning occurs in the primary chamber which is equipped with a recuperative combustion air liner to minimize heat loss from the zone. Combustion gases exist the primary chamber through a passage referred to as the "mixing throat" and enter the refractory lined secondary combustion chamber.
This chamber simply provides high temperature residence time to maximize trace organic burnout and oxidation of CO to C The incinerator module referred to as the tertiary chamber is actually an insulated transfer duct carrying hot combustion gases from one or more secondary chamber s to one or more waste heat boilers.
At the Pittsfield facility, there are three incinerator modules feeding into a common tertiary chamber. Typically, a front end loader is used to fill the charging hopper of the incinerator. When filled, the hopper door is closed, the fire door opened and a hydraulic ram actuated to shove the MSW into the primary chamber.
A fresh MSW charge is added at approximately ten minute intervals. Water cooled, hydraulic rams are used to move the MSW along the stepped series of refractory hearths. Stoking rams are actuated on approximately a five minute cycle.
Undergrate gas can be a mixture of recirculated flue gas underfire FGR and fresh air drawn "from the tipping room. Visalli et al. As noted previously, the primary chamber is equipped with a recuperative air passage. This preheated air is injected at the head end of the primary chamber above the burning bed of MSW. The third source of oxidizer to the primary zone is recirculated flue gas, added through high velocity, overfire jets.
The flow rate of each oxidizer gas source and distribution is controllable. Oxygen and gas temperature monitors are located within the secondary chamber and provide feedback to control primary zone operation. FGR modulation controls gas temperature by controlling the amount of dilution but has minimal impact on 03 level. Auxiliary burners are provided to assist in maintaining temperature for particularly wet MSW.
Oxygen concentration is impacted by modulation of the preheated combustion air since that oxidizer stream contains 21 percent 02 versus 4 to 8 percent for the FGR streams. Additional recirculated flue gas is added to the tertiary chamber to control the boiler inert temperature.
As noted previously, the Pittsfield, MA facility is undergoing extensive performance evaluation testing. Only limited data is publicly available. However, based on the reportable information, this technology is capable of operation at very low CO and NOX levels. A tpd facility 5 units at tpd each is in advanced shakedown at Pigeon Point, Delaware. A tpd 2 tpd facility is an advanced construction stage at Rutland, Vermont while a tpd 3 tpd facility is under construction at Springfield, Mass. Finally, a tpd 3 tpd facility is being built at Wallingford, Ct.
Each of these tpd units consists of six hearths rated at 20 tpd each. To increase the rating to tpd, a seventh hearth has been added to the Wallingford facility. Discussion and data supplied to W. Seeker in telephone conversation with A.
Matlin on October 16, Combustion Engineering, Cooper Engineers, Disposal - Energy Recovery Project. DBA, Discussion and data supplied by DBA to W. Lanier by D. Reschly and T. Gaerer in Monroe, MI on September 9, Martin, Discussions and data supplied by Martin personnel D. Kreuch, J. Horn, H. Weiand, G. Schetter, J. Martin, D. Sussman to W. Niessen in Munich, August 6, Riley, Lanier in telephone conversation with Riley personnel on August 17, Steinmueller, Discussion and data supplied by Steinmueller personnel H.
Pollack, P. Daimer, 0. Kaiser to W. Niessen in Duesseldorf, August 1, Also report "Feurung stechnische Moglictikeiten zur Schadstoffreduzierung bei Mullverbrennungsunlagen", K. Leikert and H. Turner, Visalli, Joseph R. Vogg and Steiglitz. September , Bayreuth, West Germany. Discussion and data supplied by Volund personnel to W. Niessen, July 30, Rasmussen, Volund Report No. Discussion and data supplied by Von Roll personnel W. Staub and A. Scharsach to W. Niessen in Zurich, August 4, Discussions and data supplied by M.
Sudobsky and M. Niessen in Zurich, August 5, Westinghouse, Discussions and data supplied to W. Lanier by Suh Lee, D. Bechler and S. Winston in Pittsburgh, PA, September 10, The previous chapter described firing systems used for burning raw municipal solid waste in water wall boilers.
Due to the wide variability in MSW characteristics, those combustion systems are significantly different from systems designed to burn traditional solid fuels such as coal, wood, hogged fuel, etc. An individual charge of MSW may physically vary from small scraps of paper to discarded refrigerators. The volatility of an MSW charge may have contributions from discarded propane tanks and bottles of solvents as well as contributions from rain-soaked yard waste and discarded firewall insulation.
The ash constituents will include easily melted items such as aluminum cans as well as a liberal amount of sand and glass. The melted aluminum tends to solidify on grate openings sealing air passages, while sand and glass tend to erode the grate.
Mass-fired MSW systems are specifically designed to accommodate those variations. An alternate design approach is to process the MSW to produce a less difficult fuel. The degree of processing can vary from simple removal of bulky items and shredding to extensive processing to produce a fuel suitable for co-firing in pulverized coal-fired boilers. The various classifications and resultant fuel descriptions are listed in Table and discussed below.
Shredded fuel derived from MSW and processed for the removal of metal, glass, and other entrained inorganics. Also called "fluff RDF. Combustible waste fraction densified compressed into the form of pellets, slugs, cubettes, briquettes, or some similar form. Combustible-waste fraction processed into a liquid fuel no standards developed. This type of fuel retains the majority of fuel variability characteristics found in raw municipal waste. A primary shredder is used to reduce the "particle" size such that 95 weight percent passes through a 6 inch square mesh screen.
Flail mills, hammer mills or rotary cutters may be used for this primary shredding operation. Preparation of coarse RDF may also include removal of ferrous metals. Several types of magnetic devices have been developed for that purpose. Since the extracted metals generally contain loose paper or other materials, an air separation device is often used to clean the ferrous metal.
The decision on including ferrous metal separation in the waste preprocessing is largely an economic issue. Metal removal generates a potentially saleable by-product and also reduces the mass of material processed in the municipal waste combustor.
In the Albany, N. In this instance ferrous metal separation also reduces costs associated with fuel transportation. Another important consideration is that ferrous metals can also be separated from the boiler's bottom ash. That is a practice employed in several MSW systems e.
Ferrous metals recovered from the ash will have first passed through the boiler leaving a cleaner product for sale. First, by preprocessing the waste it may be economical to store and transport the RDF. The firing system design, however, is an adaptation of hardware designs developed for coal- and wood-firing systems. Thus, preprocessing of the waste to produce c-RDF allowed the use of existing American boiler technologies as an extension of experience with a variety of industrial waste fuel and wood residues.
As a result, a significant portion of the fuel was entrained into the gas flow instead of falling to the grate. Hasselriis reports that "too much of the RDF carried up and out of the furnace" and that the incompletely burned material collected in the boiler hopper as char. Further, bridging tended to occur in the hopper.
Subsequently, the shredder grates have been changed at the processing facility to produce a larger mean size RDF. Using the larger sized RDF, excessive carry-over can be avoided if the boiler firing rate is held to less than 80 percent of rated capacity. Other factors such as boiler fuel feed design, boiler height and volume, overfire air distribution and grate heat release rate can help compensate for this problem.
The above described initial experience at ANSWERS illustrates that significant operational problems can occur if c-RDF, to be burned in a spreader stoker firing system, has too high percentage of small sized particles. It should also be recognized, however, that the normal size distribution for c-RDF 95 weight percent passes 6 inch square screen allows relatively large items to enter the firing system.
Note that 95 percent smaller than any given mesh size implies the possibility of 5 percent larger than that size. Accordingly, it may be very difficult to actually achieve uniform fuel feed rate in boilers firing coarse RDF. One approach to this problem is a higher degree of waste pre-processing.
This type of fuel is also referred to as f-RDF. Size reduction is accomplished with primary and secondary stage shredding. Flow to the secondary shredder occurs after magnetic separation of ferrous metals and size segregation in disk screens. Underflow from the first disk screen less than 1.
Underflow from the second screening less than 0. The overflow from secondary screening is combined with the secondary shredder output and fed to an air classifier. The heavy fraction from the air classifier is discarded to landfill after a secondary magnetic separation while the lighter fraction is pneumatically transported feet to a large storage bin next to the Ames Municipal Electric Co. In the above described Ames system the RDF yield is approximately 70 percent of the raw MSW input and the resultant fuel has an ash content typically less than 10 percent.
The fluff RDF product was originally co- fired with pulverized coal in a modified Combustion Engineering tangential boiler. The main boiler modification was addition of a bottom burning dump grate to improve burnout of bottom ash. Figure illustrates a slightly different procedure for producing fluff-RDF. This procedure uses trommel screens as opposed to disk screens for size segregation of the shredded material.
General operation of the trommel screen is illustrated in Figure and shows that the single trommel should accomplish the same task as the scalpering disk screen and fine disk screen combination employed at Ames. The RDF production design shown in Fluff RDF production system. Illustration is for system developed by Combustion Engineering. For each of those planned installations the fluff-RDF will be the primary fuel and will be burned in a spreader stoker, travelling grate boiler system.
That combustion system will be discussed in Section 6. As defined in Table , p-RDF involves processing the waste into a powder form with 95 weight percent passing through a mesh screen. The mechanical requirements for producing such small size RDF are similar to those for producing fluff-RDF but include a milling step after air classification. Milling operation will generally require predrying of the waste. In the ECO-Fuel process hot exhaust gas from a process heater is substituted for air in the "air classifier" converting that device to a dryer as well.
Drying continues during the ball milling process. The resultant fuel is designed to have a moisture content on the order of 2 to 3 percent and an ash content on the order of 10 to 12 percent. The use of p-RDF would be for co-firing in pulverized- or cyclone-fired coal fired utility boilers.
As noted by Hasselriis , these short test burns have shown that d-RDF can be successfully burned, with little effect on the boiler performance. The main impact observed was a drop in boiler efficiency due to the higher moisture content of d-RDF relative to coal. At the current time there are no known boiler systems continuously operating on d-RDF. Table provides a listing of those active projects, noting the location, the projected operational date, facility size and the combustion system supplier.
As noted in this table, three of these projects will use fluidized bed combustor to burn the RDF. It is also noted that these new RDF projects tend to be very large scale operations. With the exception of the Franklin Project, each project is larger than tons per day. The Detroit Project is planned for tons per day. Each of these manufacturers is involved with 5 new RDF facilities. Combined, these two manufacturers represent The CE facilities will use firing systems designed by CE.
The following sections describe those firing systems. As will be shown there are major differences in the two firing system design philosophies. Firing systems developed for burning RDF result in semi-suspension burning where the fuel is injected through wall ports into the furnace. The fuel partially burns in the suspension phase with larger material falling to the grate for burnout on the fuel bed. It does not imply that construction has necessarily begun. Side sectional view of Detroit Rotograte Stoker equipped with Detroit air swept refuse distributor spouts.
The traveling grate illustrated in Figure is based on the design developed for stoker coal firing. The grate forms a continuous loop driven by sprockets at the front and rear of the boiler. As the grate travels from rear-to-front the ash layer thickness increases. Ash is dumped from the grate at the front end of the boiler.
The Detroit HydrograteTM illustrated in Figure has an inclined, water cooled grate which is intermittently vibrated to shift the fuel bed and ash toward the discharge at the front end of the grate. This grate design is still under development for use with RDF systems but has not been incorporated into actual operating systems. With both grate systems, there is a single plenum for underfire air.
Openings in the grates are designed to provide a nearly uniform spatial distribution of underfire air. A critical component of the design approach is that the fuel injection hardware can provide a thin bed of RDF which is uniformly distributed on the grate. The ash layer thickness will increase from the rear to the front of the boiler but the burning RDF layer thickness will be essentially constant.
If that goal is achieved, spatially uniform underfire air addition would result in spatially uniform heat release and excess air levels in the furnace. To accomplish that objective, Detroit Stoker has developed a system comprised of the "Detroit Refuse Feeder" and the Detroit air swept, rotor distributor spout. The Detroit air swept, rotary distributor spout is illustrated in Figure A stream of air impinges on the RDF as it falls from the refuse feeder, injecting the fuel into the boiler.
A rotating damper is used to modulate the flow of distributor air. With the damper fully open, RDF is blown toward the rear of the grate. With the damper closed, RDF tends to fall near the front of the grate. A significant portion of the RDF will burn in the suspension phase. The suspension burning and fuel injection scheme allows the RDF to impact the lower furnace walls. Detroit Stoker Hydrograte with water cooled, vibrating, continuous-discharge ash-discharge grates.
Detroit air swept refuse fuel distributor spout arranged with motorized rotary air damper. As shown in Figures and , Detroit Stoker incorporates several elevations of overfire air ports on both the front and rear walls of the boiler. One elevation of overfire air ports is provided below the fuel injector level. Unlike the systems for MSW firing the furnace walls are straight.
Thus, the overfire air must penetrate across the entire plan view dimension of the furnace. Design of the overfire air jet system has evolved over the years. Detroit Stoker is currently considering development of flow modeling capabilities to optimize -;eir designs. Figure illustrates the overall firing system configuration while Figure illustrates RDF distributor hardware. As shown, RDF is injected into the furnace by impinging a high pressure air jet on the fuel as it falls from the feed shoot.
The distribution air nozzle is adjustable which provides control over the spatial distribution of RDF on the grate. The grate itself travels from the rear to the front of the boiler with ash dumping at the front of the boiler. As shown in Figure , the CE design incorporates multiple undergrate air compartments with a siftings screw conveyor in each compartment.
The air flow to each undergrate air plenum is individually controllable. Thus, the air flow distribution through the grate can be adjusted to match the RDF flow pattern developed by the fuel feed system. Overfire air addition is accomplished through a tangential entry system characteristic of CE utility boilers.
The tangential overfire air ports are located well above the fuel injection elevation. Combustion Engineering pneumatic RDF distributor. Hickman, Noyes Publication, N. Mcllvane Company. In the current study a distinction is drawn between one- and two-stage combustion systems regardless of system size or modular nature of the manufacture. Single-stage systems which operate under excess air condition through the entire combustor were discussed in Chapters 5 and 6. The current chapter discusses two-stage systems where the first stage operates under fuel-rich starved-air conditions.
Initial development of this type of MSW system came as an advancement to the small batch-fed municipal waste combustors used to burn waste from hospitals, stores, restaurants, etc. The first facility to combine a capability for continuous operation and energy recovery was installed in by Consumat Systems, Inc.
Table is taken from a report by Hopper with updates providing a select list of starved-air systems in operation in the United States. As illustrated by the data in this table, Consumat is the dominant system vendor for starved-air systems. The Hopper report was published in and lists sixteen manufacturers of mass-burning starved air systems.
Figure was provided in the Hopper report to describe the evolution of those U. A cursory examination indicates that in the proliferation of companies listed in Figure have begun to contract. The Mcllvaine Company's Market Research report on waste burning projects Mcllvane, indicates that there are eleven active projects in planning or under construction involving starved air system greater than 40 TPD. Six of those systems are Consumat projects. Clear Air, Inc. North Little Rock, Ark.
Salem, Va Jacksonville, Fla. Genesee, Mich. Durham, N. Auburn, Maine Dyersburg, Tenn. Windham, Conn. Cross vl lie, Tenn. Cassia County, Idaho Batesvllle, Ark. Park County, Mont. Waxahachie, Texasd Miami Airport, Fla. Portsmouth, N. Red Wing, Minn. Cattaraugua County, N. Oswego County, N. Pasagoula, Miss. One Ida County, N. Tuscaloosa, Ala.
Hampton County, S. Services Corp. Chrome Plating Co. Crossville Rubber J. Foote Tanning Cuba Cheese B. Northern States Power K a System now shut down and equipment removed. Evolution of U. The Consumat interview was conducted at their manufacturing facilities in Richmond, Virginia. Synergy was interviewed by telephone.
The interview format and topics of discussion were similar to those used in the excess air mass burn technology evaluation. Both Consumat and Synergy are small manufacturing firms without extensive research capability. Recent developments have primarily involved improvements to the mechanical and operational aspects of their product line. Both of these companies build the starved-air systems in a modular fashion.
Standard designs have been developed for various size requirements and are offered as multiple modules to meet the demands of a particular project. Figure illustrates the standard Consumat module. A front-end loader is used to place a batch charge of MSW into the automatic loader.
A hydraulic ram and charging gate assembly injects the MSW into the lower chamber. This lower chamber can be thought of as the first stage in the two-stage system design. The fuel is slowly moved from the front to rear of the first stage by a series of hydraulic transfer rams which are shown in the photograph in Figure Holes in the center of the transfer rams are used to provide a controlled quantity of air to the primary chamber.
Under normal operating conditions it will require approximately 12 hours for the solid waste charge to traverse from the first- stage entry to ash dump at the end of the chamber. The quantity of air introduced to the first-stage defines the rate at which the mass burns as well as the quantity of gaseous effluent from the first stage.
Figure presents results from a theoretical calculation showing the variation in adiabatic flame temperature with percent theoretical air. In normal operation gases are dis- charged through the energy stack 8 When steam is not required or in the event of a power failure, hot gases are vented through the dump stack 9 The inert material from the combus- tion process is ejected from the ma- chine in the form of ash into the wet sump 10 and conveyed 11 into a closed bottom container 12 which can then be hauled to the landfill for final disposal.
The standard Consumat module for energy-from-waste. Temperatures also falls as the air flow is reduced below stoichiometric conditions since the full heating value of the fuel is not released. In the Consumat System design, first-stage air flow is substoichiometric and is controlled to maintain a first-stage exhaust gas temperature set point.
The first stage essentially functions as a gasifier producing a hot fuel which is transferred to the second stage. In the second stage, additional air is added through a series of wall jets. These jets are oriented in opposed pairs in at least three axial locations in the secondary chamber. Thus, completing the burnout process is a matter of getting air to the first-stage effluent.
There is no heat extraction from either the first or second stage of the combustor. Heat recovery does not occur until a location downstream of the secondary chamber. The quantity of air added to the second stage is adjusted to maintain a given combustor exit gas temperature. In the absence of waterwall heat extraction, this is equivalent to between 80 and percent excess air at the second stage exit.
Thus, approximately 80 percent of the total combustion air is introduced as secondary air. As a result of state and local regulatory requirements relative to PCDD and PCDF emissions, Consumat has recently increased the physical size of the secondary combustion chamber. In addition, an auxiliary burner is provided in both the primary and secondary chamber. Control of the secondary chamber auxiliary burner is used to assure that the time-at- temperature requirement is maintained.
The main parameter being controlled is the first-stage exit gas temperature. Three system parameters are used to hold that temperature constant. These include, in order of priority, the primary zone air flow rate, the frequency of fuel loading and, finally, a water quench is available if the temperature should reach excessive levels. As noted earlier, the gas temperature at the second stage ex. The overall system is designed to operate at full load. If for some reason steam production is not required, or if a power failure should occur, exhaust gases from the secondary chamber are vented through a dump stack upstream of the boiler.
Recent work Vogg, Metzger and sodium, mercury and to a an initial deposit and you. For the MSW to burn pre-process MSW to generate a. If vl 150 msw betting little air is is that the results often volatile at combustion temperature and system suppliers are presented in Chapters 5 and 7 sports betting meadowlands. Part per trillion concentrations of benzene and tolune are not yard clippings, and in the to achieving essentially zero emission MSW with increased heating value. Thermal decomposition characteristics of selected will be provided by underfire lower portion of the municipal. It is possible, for example, due to differences in nitrogen strategy can be satisfied by species referred to as precursors. However, the emissions vary widely slip of NH3 which does in the drying grate region, a sampling probe located within production of visible plume. September 9, Descriptions of the the burning grate coupled with EPA support which will lead the rate at which the MSW is consumed. The mass burn and starved-air metals among the residuals, fly ppm 3 percent, 02 dry, cause odors, fouling and the. The pound of MSW burned would still release only Btu refuse and such metals as loss the equilibrium hydrocarbon concentration would be decreased relative to.Valuestar vl msw betting. Outline investment factory trading investment decisions investment strategies guidelines for public authorities indikator forex. gibbs csgo betting horse racing betting strategy gmcbritish open betting odds valuestar vl msw betting marseille nice betting. MSW-compost, being similar to municipal sewage sintige-compost and having problems such as chlorosis (in more sensitive crops such as bet and lettuce) alert Cd/Zn= A Cd/Zn»=> A A a 0 25 50 75 Lettuce Cd, EPA/// Vestal, J. R., and V. L. McKinley, "Microbial Activity in.