Municipal Solid Waste Components Research Articles

Pyrolysis characteristics and kinetics of municipal solid wastes

The large variety in municipal solid waste (MSW) composition and differences in thermal degradation behaviour of MSW components makes modelling, design and operation of thermal conversion systems a challenge. The pyrolysis characteristics of 11 different components, representing the dry cellulosic fraction and plastics of MSW, have been investigated. The aim of this study is to obtain detailed information on the pyrolysis characteristics and chemical kinetics of the most important components in MSW. A thermogravimetric analysis including determination of kinetic parameters are performed at a constant heating rate of 10°C/min in an inert atmosphere. The cellulosic fraction of MSW was modelled by three independent parallel reactions describing the degradation of hemicellulose, cellulose and lignin. The plastics polystyrene, polypropylene, low-density polyethylene and high-density polyethylene were all modelled as single reactions describing the degradation of hydrocarbon polymers. The degradation of PVC was modelled with three parallel reactions describing the release of benzene during dehydrochlorination, dehydrochlorination reaction and degradation of remaining hydrocarbons. Possible interactions between different paper and plastic components in mixtures were also investigated. It was found that the reactivity of cellulosic matter was increased in a mixture with PVC.

Methane Emissions from Domestic Waste Management Facilities in Jordan—Applicability of IPCC Methodology

ABSTRACT In this paper, methane emissions from municipal wastewater treatment plants and municipal solid waste (MSW) landfills in Jordan for 1994 have been estimated using the methodology developed by the Intergovernmental Panel on Climate Change (IPCC). For this purpose, the 14 domestic wastewater treatment plants in the country were surveyed. Generation rates and characterization of MSW components as well as dumping and landfilling practices were surveyed in order to estimate 1994 CH4 emissions from these sites. Locally available waste statistics were used in cases where those of the IPCC guidelines were not representative of Jordan's statistics. Methane emissions from domestic wastewater in Jordan were estimated at 4.66 gigagrams (Gg). Total 1994 CH4 emissions from MSW management facilities in Jordan are estimated at 371.76 Gg—351.12 Gg (94.45%) from sanitary landfills, 19.83 Gg (5.33%) from MSW open dumps, and 0.81 Gg (0.22%) from raw sewage-water dumping ponds. Uncertainties associated with these estimations are presented.

Municipal Solid Waste Recycling Issues

Municipal solid waste (MSW) recycling targets have been set nationally and in many states. Unfortunately, the definitions of recycling, rates of recycling, and the appropriate components of MSW vary. MSW recycling has been found to be costly for most municipalities compared to landfill disposal. MSW recycling policy should be determined by the cost to the community and to society more generally. In particular, recycling is a good policy only if environmental impacts and the resources used to collect, sort, and recycle a material are less than the environmental impacts and resources needed to provide equivalent virgin material plus the resources needed to dispose of the postconsumer material safely. From a review of the existing economic experience with recycling and an analysis of the environmental benefits (including estimation of external social costs), we find that, for most communities, curbside recycling is only justifiable for some postconsumer waste, such as aluminum and other metals. We argue that alternatives to curbside recycling collection should be explored, including product takeback for products with a toxic content (such as batteries) or product redesign to permit more effective product remanufacture.

Production of non-methane organic compounds during refuse decomposition in a laboratory-scale landfill

The presence of non-methane organic compounds (NMOCs) in landfill gas is well documented. However, there is little understanding of the degree to which the production of NMOCs should be attributed to the volatilization of household hazardous waste as opposed to intermediates of the anaerobic decomposition of the major cellulosic components of municipal solid waste. The objectives of this study were: (1) to compare the NMOC yields for decomposed refuse, fresh residential refuse, and a synthetic refuse; and (2) to evaluate the source of NMOCs emitted during refuse decomposition. Replicate 2-1 reactors were filled with shredded residential refuse expected to contain household hazardous waste, synthetic refuse containing no hazardous constituents, and control reactors with decomposed refuse only. Anaerobic decomposition of each refuse was initiated with a seed of decomposed refuse, and the reported methane and NMOC yields were corrected for that attributable to the seed. The NMOC yields from the seed, synthetic refuse, and residential refuse were comparable (0.62 to 1.01 X 10-4 g NMOC (dry g)-1, suggesting that the volatilization of hazardous organic compounds is not the sole source of NMOCs in landfill gas and that anaerobic biodegradation intermediates also contribute to NMOCs.

Fluidised bed pyrolysis of low density polyethylene to produce petrochemical feedstock

Pyrolysis of plastic waste has been proposed as a tertiary or feedstock recycling route where the plastic waste materials are processed back to produce basic petrochemicals that can be used as feedstock to make virgin plastic or refined fuels. The detailed analysis of the derived products from the pyrolysis of plastics provides data on the suitability of the process and the influence of process conditions on the compatibility of the feedstock produced with the conventional petroleum feedstock. Low density polyethylene (LDPE) is a major component of municipal solid waste and this paper describes the influence of pyrolysis temperature from 500 to 700°C on the yield and composition of the derived products. The main gases produced from the pyrolysis of LDPE were hydrogen, methane, ethane, ethene, propane, propene, butane and butene. There was a dramatic increase in gas yield with increasing temperature of pyrolysis. Analysis of the derived oils and waxes showed that the pyrolysis of LDPE gave a mainly aliphatic composition consisting of a series of alkanes, alkenes and alkadienes which showed a decrease in concentration as the pyrolysis temperature was increased. The oil showed an increase in aromatic composition with increasing temperature of pyrolysis and at 700°C significant concentrations of single ring aromatic compounds and polycyclic aromatic hydrocarbons were detected. The derived oil and wax have great potential to be recycled back into the petrochemicals industry as a feedstock for the production of new plastics or the production of refined fuels.

Carbon storage during biodegradation of municipal solid waste components in laboratory‐scale landfills

The objective of this research was to measure the amount of carbon associated with the major biodegradable components of municipal solid waste (MSW) that remains in long‐term storage after anaerobic decomposition in landfills. Tests were conducted in quadruplicate in 2‐L reactors operated to obtain maximum decomposition. Measured carbon storage factors (CSFs) for grass, leaves, branches, food waste, coated paper, old newsprint, old corrugated containers, office paper, and MSW were 0.32, 0.54, 0.38, 0.08, 0.34, 0.42, 0.26, 0.05, and 0.22 kg C sequestered dry kg−1, respectively. These values were then used to estimate an overall CSF for MSW that varied from 0.274 to 0.302 kg C sequestered wet kg−1 for waste mixtures that exclude and include recycling, respectively. On the basis of an overall CSF for MSW and data on global MSW generation, global carbon sequestration from MSW burial is estimated to be at least 119 million metric tons per year.

Thermal treatment of coated printing and writing paper in MSW: pyrolysis kinetics

The pyrolysis kinetics of cellulosic coated printing and writing paper, a principal component of municipal solid waste (MSW) in Taiwan, were investigated by thermogravimetric analysis in nitrogen over the temperature range 450–900 K at heating rates of 1, 2 and 5 K min −1. The t.g.a. curves indicated two principal reactions, distinguished by significant and distinct mass changes over the experimental range. The pyrolysis of coated paper could be adequately described by a two-reaction model. The corresponding activation energies, pre-exponential factors and reaction orders were determined. The experimental results were satisfactorily fitted by the proposed model.

A review of plastics recycling in the USA with policy recommendations

SummaryPlastics are the fastest-growing component of municipal solid waste in the USA, and over the past decade there has been increasing public demand for plastics recycling. However, the necessity to separate the various plastic resins to make their recycling possible, combined with the low cost of virgin resins, make this technically difficult and expensive.Most sorting of plastic waste is done manually, and this method has been constrained to the diversion of only one or two types of plastics, because human sorters are incapable of distinguishing different plastics. A number of technologies are being developed in order to address this problem. Use of these technologies requires considerable capital investment and this makes many of them economically unfeasible at present. The federal, state, and local governments in the USA have continued to explore demand-side policy measures in an effort to promote market formation and operation. Where they have been successful, in the establishment of markets for recycled polyethylene terepthalate (PET), and high-density polyethylene (HDPE) resins, demand has outpaced supply, highlighting the need to find more effective methods to sort and divert different plastic resins. Even with these supply shortages, and with prices for virgin PET and HDPE at historic highs, however, most plastics recycling remains only marginally profitable. This demonstrates the need for continued policy support for the still-developing plastics recycling industry and recycled-plastics market.An analysis of the factors driving the recycling of PET, HDPE and polypropylene indicates that, as long as manual sorting is used, it would make sense for supply- and demand-side policies to focus on the recycling of particular plastic products that are easy to recognize, rather than resins that are not. Appropriate policies can help make specific products easily recognizable sources of specific resins. Such policies, implemented in conjunction with measures designed to facilitate capital investments and promote the establishment and operation of markets for all resins, are necessary to increase significantly the recycling of plastic waste above present levels.

Future potential for MSW energy development

This work examines the potential supply of municipal solid waste (MSW) which could be used to support new (not existing or currently planned) energy capacity in the year 2000. The resource we are interested in is MSW which is not recycled or burned; which would be landfilled unless new MSW energy conversion capacity is constructed. A detailed analysis of MSW composition by individual components was used for 1990 and 2000. For each component of MSW we estimated heat content, ethanol yield and recycling efficiencies. From these data, we estimated how much MSW could be diverted from landfills to either new biomass-ethanol or new MSW-electricity plants. We also estimated where these new MSW-energy plants could be located. The impact of the planned growth in the MSW-power industry between 1992 and 1995 and higher material recycling rates have a significant effect on the supply of MSW in the year 2000. The implications of these changes are discussed in the context of the solid waste management industry. Some of the possible changes discussed include: • • declining amounts of MSW available after recycling will increase competition for MSW between and within power producers, recyclers and landfill firms, especially along the Eastern seaboard • • more competition for MSW may lead to lower tipping fees in the future • • as recycling efficiencies increase, MSW-power producers will need to attract MSW from further and further away to maintain capacity, causing transportation costs to rise • • the composition of materials reaching landfills may change if a large amount of MSW is consumed to produce energy, and landfill closures may be rendered moot. • • some areas of the country may not be suitable for building MSW-energy facilities in today, because by the year 2000, these areas may be in short supply of MSW. The analysis revealed that from 15.5 million to 71.7 million tonnes of new MSW power capacity could is be added by 2000, depending on the recycling scenario; if MSW is used for biomass-ethanol production, from 11.6 million to 31.6 million tonnes of MSW ethanol capacity in the year 2000.

Methodology for Modeling the Devolatilization of Refuse-Derived Fuel from Thermogravimetric Analysis of Municipal Solid Waste Components

The capacity of waste-to-energy (WTE) plants in the U.S. is expected to double by the year 2000. Many of these plants will burn refuse-derived fuel (RDF) consisting of municipal solid waste (MSW) components. A large percentage of the mass of RDF is volatile matter, which when combusted, contributes significantly to the boiler heat rate. A methodology is presented for estimating the devolatilization characteristics of RDF based on the premise that RDF can be modeled as some combination of select MSW components. Thermogravimetric analyses of these components provide the input data to the methodology. The outputs from the methodology are calculations of volatile weight loss versus temperature, or calculated thermograms, for the components at userdefined conditions. The hypothesis was made that these thermograms could be summed, given the mix of components in the RDF, to give an accurate description of the devolatilization process for the RDF. This hypothesis was tested by performing thermogravimetric analysi...

Anaerobic Biodegradability of the Organic Components of Municipal Solid Wastes (OFMSW)

The aim of this research was to study the anaerobic conversion efficiency of the organic fraction of municipal solid waste (OFMSW). In order to compare and appraise our techniques and respective conversion efficiencies, primary sewage sludge (PSS) assays were also performed. OFMSW has a high cellulose content (32.9% TS) followed by lignin (12.5% TS), protein (9.61% TS), lipids (5.94% TS) and hemicellulose (5.2% TS). PSS is equally rich in lipids (19.8% TS), protein (18.2% TS) and lignin (19.6% TS), followed by cellulose (13.4% TS) and hemicellulose (5.5% TS). Assays were run in CSTRbiodigesters operated at 35°C and 20 days hydraulic retention time (HRT). Three organic loading rates - 1.0, 2.7 and 3.8 OFMSW g VS/Lr.d (gram of volatile solids per liter of reactor per day) - were studied. PSS was assayed only at 1.0 g VS/Lr.d. Concerning the conversion efficiencies, the most important component for the OFMSW anaerobic digestion is cellulose (74.0 - 77.8% conversion), while lipids (70.0 - 80.6% conversion) are the most important for PSS. The biodegradability of the other organic components are also presented and discussed. Some literature data about OFMSW anaerobic digestion processes are discussed in view of the results presented here. The similarities between our results and those of the so-called dry fermentation processes are also discussed in order to evaluate efficiencies of biogas and CH4 production versus volatile solids removal.

Pretreatment of lignocellulosic municipal solid waste by ammonia fiber explosion (AFEX)

The Ammonia Fiber Explosion (AFEX) process treats lignocellulose with high-pressure liquid ammonia and then explosively releases the pressure. The combined chemical effect (cellulose decrystallization) and physical effect (increased accessible surface area) dramatically increase lignocellulose susceptibility to enzymatic attack. For example, bagasse digestibility is increased 5.5 times and that of kenaf core is increased 11 times using extracellular cellulases fromTrichoderma reesei. In this study, we applied the AFEX process to mixed municipal solid waste (MSW) and individual components (e.g., softwood newspaper, kenaf newspaper, copy paper, paper towels, cereal boxes, paper bags, corrugated boxes, magazines, and waxed paper). Softwood newspaper proved to be the most difficult component to digest because of its high lignin content. A combination of oxidative lignin cleavage and AFEX was required to increase softwood newspaper digestibility substantially, whereas AFEX alone was able to make kenaf newspaper digestible. Because most MSW components have been substantially delignified in the paper-making process, AFEX only marginally increased their digestibility.

Opportunities for Composites from Recycled Wood Based Resources

AbstractA reduction is urgently needed in the quantities of industrial and municipal solid waste materials that are currently being landfilled. Major components of municipal solid waste include waste wood, paper, agriculture wastes, and other biomass fibers. In 1990, there were approximately 80 million tons of 6,000 different paper and paperboard products and 5.8 million tons of wood in the municipal solid waste stream. There are also potential millions of tons of wood fiber in timber thinnings, industrial wood waste, demolition waste, pallets, and pulp mill sludges. These materials offer great opportunities as recycled ingredients in wood-based composites. This paper discusses possibilities for manufacturing selected composites from these materials as well as materials which coexist with the wood-based resources such as plastics, fly ash, and gypsum.

Microbiological degradation of pesticides in yard waste composting

Changes in public opinion and legislation have led to the general recognition that solid waste treatment practices must be changed. Solid-waste disposal by landfill is becoming increasingly expensive and regulated and no longer represents a long-term option in view of limited land space and environmental problems. Yard waste, a significant component of municipal solid waste, has previously not been separated from the municipal solid-waste stream. The treatment of municipal solid waste including yard waste must urgently be addressed because disposal via landfill will be prohibited by legislation. Separation of yard waste from municipal solid waste will be mandated in many localities, thus stressing the importance of scrutinizing current composting practices in treating grass clippings, leaves, and other yard residues. Yard waste poses a potential environmental health problem as a result of the widespread use of pesticides in lawn and tree care and the persistence of the residues of these chemicals in plant tissue. Yard waste containing pesticides may present a problem due to the recalcitrant and toxic nature of the pesticide molecules. Current composting processes are based on various modifications of either window systems or in-vessel systems. Both types of processes are ultimately dependent on microbial bioconversions of organic material to innocuous end products. The critical stage of the composting process is the thermophilic phase. The fate and mechanism of removal of pesticides in composting processes is largely unknown and in need of comprehensive analysis.

New Approach for Estimating Energy Content of Municipal Solid Waste

The estimation of energy content of municipal solid waste (MSW) is normally done by the use of modified Dulong equation (MDE). The MDE requires changing all MSW components to percentages of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and sulfur (S), which is very time-intensive effort. An easier-to-use and more practical new equation is presented, which directly uses the percentages of MSW components. The validity of the new equation is checked against MDE by utilizing MSW component data for 35 countries and 86 international cities. A linear regression coefficient (R2) of 0.97 between energy content values (Btu/lb) for the new equation and MDE indicates an excellent closeness. The new equation energy values are about 1–10% higher than the MDE values. The energy content of developing and underdeveloped countries is a half to one-third of those for the developed and highly industrialized countries. About 50–70% of the energy content of MSW is due to the paper component. The new equation offers a goo...

Microbiological degradation of pesticides in yard waste composting.

Changes in public opinion and legislation have led to the general recognition that solid waste treatment practices must be changed. Solid-waste disposal by landfill is becoming increasingly expensive and regulated and no longer represents a long-term option in view of limited land space and environmental problems. Yard waste, a significant component of municipal solid waste, has previously not been separated from the municipal solid-waste stream. The treatment of municipal solid waste including yard waste must urgently be addressed because disposal via landfill will be prohibited by legislation. Separation of yard waste from municipal solid waste will be mandated in many localities, thus stressing the importance of scrutinizing current composting practices in treating grass clippings, leaves, and other yard residues. Yard waste poses a potential environmental health problem as a result of the widespread use of pesticides in lawn and tree care and the persistence of the residues of these chemicals in plant tissue. Yard waste containing pesticides may present a problem due to the recalcitrant and toxic nature of the pesticide molecules. Current composting processes are based on various modifications of either window systems or in-vessel systems. Both types of processes are ultimately dependent on microbial bioconversions of organic material to innocuous end products. The critical stage of the composting process is the thermophilic phase. The fate and mechanism of removal of pesticides in composting processes is largely unknown and in need of comprehensive analysis.

The effect of the neutralizing capacity of cellulosic materials on the kinetics of cellulose dilute acid hydrolysis

The production of ethanol has become a new field of investigation for the satisfactory and economical treatment of municipal solid waste (MSW). Since cellulose is a major component of MSW it may be treated as a resource for fuel, chemical and energy recovery. The key, and the difficult, engineering point of this process is the cellulose hydrolysis step in which the chemically resistant cellulose is converted to sugar (glucose) in the presence of acid as a catalyst. The later fermentation to ethanol by yeast should not be a problem. One of the main problems encountered in determining cellulose acid hydrolysis kinetic parameters is the effect of the neutralization capacity of cellulosic materials on the effective acid concentration. This paper shows how important and influential can be the neutralization capacity of cellulosic materials (sawdust and MSW) and teh effect is subsequently quantified. The use of the pH as a measure of the real effective H 3O + concentration is strongly recommended.

Monitoring the fate of chlorine from MSW sampling through combustion Part I: Analysis of the waste stream for chlorine

The total chlorine and water soluble chlorine contents of the components of municipal solid waste (MSW) have been determined from sampling studies carried out at two sites, Baltimore County, MD, and Brooklyn, NY, for a five-day period. The total chlorine contents of the MSW samples from Baltimore County, MD, and Brooklyn, NY, are 0.45 and 0.89 mass %, respectively.

Revenue and energy aspects of recycling municipal solid waste components — A case study

Composition des dechets urbains des Provinces Atlantiques du Canada. Evaluation des revenus et des economies d'energie potentiels resultant de la recuperation des materiaux recyclables des dechets urbains de Fredericton, capitale du Nouveau-Brunswick

Optimum sampling of municipal solid wastes

Quartering, random sampling, stratified sampling and cluster sampling methods are evaluated for precision and efficiency in the analysis of municipal solid wastes (MSW). The optimum method for sampling MSW is proposed and related to the object of the sampling. The main results are as follows: 1. 1. Based on observations made on the movement of tracers, the mixing stage in the quartering method can be done accurately if the weight of MSW is less than about 50kg. 2. 2. The more separation that is carried out in the quartering, the larger the relative error of the composition. However, the error is smaller if MSW is cut into smaller pieces before quartering. 3. 3. The relative error in the quartering process can be expressed by normal distribution. This probability model gives the relationship between the precision of estimation (relative error) and sample weight. 4. 4. The same relationship is also obtained with random sampling, stratified sampling and cluster sampling. 5. 5. If bulk density is used as a stratified variate, stratified sampling becomes an effective method for estimating the water content, low calorific value and several components of MSW.