Estimation of residual MSW heating value as a function of waste component recycling

Recycling of packaging wastes may be compatible with incineration within integrated waste management systems. To study this, a mathematical model is presented to calculate the fraction composition of residual municipal solid waste (MSW) only as a function of the MSW fraction composition at source and recycling fractions of the different waste materials. The application of the model to the Lisbon region yielded results showing that the residual waste fraction composition depends both on the packaging wastes fraction at source and on the ratio between that fraction and the fraction of the same material, packaging and non-packaging, at source. This behaviour determines the variation of the residual waste LHV. For 100% of paper packaging recycling, LHV reduces 4.2% whereas this reduction is of 14.4% for 100% of packaging plastics recycling. For 100% of food waste recovery, LHV increases 36.8% due to the moisture fraction reduction of the residual waste. Additionally the results evidence that the negative impact of recycling paper and plastic packaging on the LHV may be compensated by recycling food waste and glass and metal packaging. This makes packaging materials recycling and food waste recovery compatible strategies with incineration within integrated waste management systems.     

Flow analysis of metals in a municipal solid waste management system

This study aimed to identify the metal flow in a municipal solid waste (MSW) management system. Outputs of a resource recovery facility, refuse derived fuel (RDF) production facility, carbonization facility, plastics liquefaction facility, composting facility, and bio-gasification facility were analyzed for metal content and leaching concentration. In terms of metal content, bulky and incombustible waste had the highest values. Char from a carbonization facility, which treats household waste, had a higher metal content than MSW incinerator bottom ash. A leaching test revealed that Cd and Pb in char and Pb in RDF production residue exceeded the Japanese regulatory criteria for landfilling, so special attention should be paid to final disposal of these substances. By multiplying metal content and the generation rate of outputs, the metal content of input waste to each facility was estimated. For most metals except Cr, the total contribution ratio of paper/textile/plastics, bulky waste, and incombustible waste was over 80%. Approximately 30% of Cr originated from plastic packaging. Finally, several MSW management scenarios showed that most metals are transferred to landfills and the leaching potential of metals to the environment is quite small.     

The future course of solid waste management in the U.S.

It is postulated that the current “garbage crisis” is due to a shortage of disposal capacity, not to burgeoning amounts of municipal solid waste (MSW). In support of this, trends in the quantity and composition of MSW, methods of waste reduction, recycling and growth of waste-to-energy capacity are examined to gain insight as to the future course of MSW management in the U.S. over about the next 15 plus years. This is the likely time to install new disposal capacity if pending legislative proposals are passed, that would enable states that provide their own disposal to ban wastes from other states.A new term, the “intensity of waste generation”, is proposed and illustrated, analogous to the intensity of mineral usage. The intensity is decreasing, implying that it is unlikely that waste generation will grow at rates projected by extrapolation or simple macroeconomic assumptions. Some other conclusions are: per capita MSW generation was nearly statistically constant from 1970 to 1984; the content of most forms of packaging in MSW are decreasing; packaging decreases the amount of food residues in MSW; and proposed national recycling targets of about 25% or more are not likely to be achieved, in part because of changes in the composition of MSW. Coupled with likely shortages of labor to process separated waste, it is forecast that there will be some future time when people will not think source separation is worth the bother and recycling will decrease. The future growth of waste-to-energy capacity is projected by assuming that a city will install capacity when others have done so, which leads to a simple quantitative model. The likely effects of impending landfill and incineration regulations are addressed.     

The effect of storage and mechanical pretreatment on the biological stability of municipal solid wastes

Modern mechanical–biological waste treatment plants for the stabilization of both the source-separated organic fraction of municipal solid wastes (OFMSW) and the mixed stream of municipal solid wastes (MSW) include a mechanical pretreatment step to separate recyclable materials such as plastics, glass or metals, before biological treatment of the resulting organic material. In this work, the role of storage and mechanical pretreatment steps in the stabilization of organic matter has been studied by means of respiration techniques. Results have shown that a progressive stabilization of organic matter occurs during the pretreatment of the source-separated OFMSW, which is approximately 30% measured by the dynamic respiration index. In the case of mixed MSW, the stabilization occurring during the reception and storage of MSW is compensated by the effect of concentration of organic matter that the pretreatment step provokes on this material. Both results are crucial for the operation of the succeeding biological process. Finally, respiration indices have been shown to be suitable for the monitoring of the pretreatment steps in mechanical–biological waste treatment plants, with a strong positive correlation between the dynamic respiration index and the cumulative respiration index across all samples tested.     

The Origins Of Municipal Solid Waste: II. Policy Options For Plastics Waste Management

Plastic items in some portions of municipal solid waste (MSW), particularly from households and restaurants, have long been viewed as a disposal problem and a symbol of a "throwaway society". There is no question that the amount of plastics in solid waste is growing. However, this observation alone should not cause an hysteria of public policies for the separate management of the plastics or any other portion of the waste. The amount of plastics, and the contribution of the items discarded, must be viewed holistically in setting a solid waste management policy. This paper questions the basis for some U.S. plastics waste policy proposals by reviewing recent U.S. data on the effect of plastics on waste reduction, and the fate of discarded plastics products. Some alternative future policy directions are also discussed.     

Bio-drying and size sorting of municipal solid waste with high water content for improving energy recovery

Bio-drying can enhance the sortability and heating value of municipal solid waste (MSW), consequently improving energy recovery. Bio-drying followed by size sorting was adopted for MSW with high water content to improve its combustibility and reduce potential environmental pollution during the follow-up incineration. The effects of bio-drying and waste particle size on heating values, acid gas and heavy metal emission potential were investigated. The results show that, the water content of MSW decreased from 73.0% to 48.3% after bio-drying, whereas its lower heating value (LHV) increased by 157%. The heavy metal concentrations increased by around 60% due to the loss of dry materials mainly resulting from biodegradation of food residues. The bio-dried waste fractions with particle size higher than 45 mm were mainly composed of plastics and papers, and were preferable for the production of refuse derived fuel (RDF) in view of higher LHV as well as lower heavy metal concentration and emission. However, due to the higher chlorine content and HCl emission potential, attention should be paid to acid gas and dioxin pollution control. Although LHVs of the waste fractions with size <45 mm increased by around 2× after bio-drying, they were still below the quality standards for RDF and much higher heavy metal pollution potential was observed. Different incineration strategies could be adopted for different particle size fractions of MSW, regarding to their combustibility and pollution property.     

On the effect of MSW moisture content on meeting target recycling rates

A mathematical model to calculate the recycle rates for packaging materials from the municipal solid wastes (MSW) built from the dry mass values that are obtained from the corresponding wet masses and their respective moisture contents is presented in this work. A possible universal methodology is also described to be used with the previous model so that reliable comparisons between indicators for different regions are feasible. Furthermore, this mathematical model demonstrates the effect of the moisture content of packaging materials on their recycling rates and constitutes a fundamental tool for operators and persons responsible for MSW management to define new policies and technical measures viewing the improvement of recycling rates. A theoretical study and the application of the model to the MEMSW of the Lisbon region shows that the moisture content of the mixed wastes plays a dominant role in the recycling rates of packaging materials such as paper, plastics and glass. Moreover, accounting for all relevant masses in the dry basis yields higher recycling rate values: increases of 32.8% for paper, 50% for plastics and 44.6% glass are observed.     

An integrated analytical framework for quantifying the LCOE of waste-to-energy facilities for a range of greenhouse gas emissions policy and technical factors

This study presents a novel integrated method for considering the economics of waste-to-energy (WTE) facilities with priced greenhouse gas (GHG) emissions based upon technical and economic characteristics of the WTE facility, MSW stream, landfill alternative, and GHG emissions policy. The study demonstrates use of the formulation for six different policy scenarios and explores sensitivity of the results to ranges of certain technical parameters as found in existing literature. The study shows that details of the GHG emissions regulations have large impact on the levelized cost of energy (LCOE) of WTE and that GHG regulations can either increase or decrease the LCOE of WTE depending on policy choices regarding biogenic fractions from combusted waste and emissions from landfills. Important policy considerations are the fraction of the carbon emissions that are priced (i.e. all emissions versus only non-biogenic emissions), whether emissions credits are allowed due to reducing fugitive landfill gas emissions, whether biogenic carbon sequestration in landfills is credited against landfill emissions, and the effectiveness of the landfill gas recovery system where waste would otherwise have been buried. The default landfill gas recovery system effectiveness assumed by much of the industry yields GHG offsets that are very close to the direct non-biogenic GHG emissions from a WTE facility, meaning that small changes in the recovery effectiveness cause relatively larger changes in the emissions factor of the WTE facility. Finally, the economics of WTE are dependent on the MSW stream composition, with paper and wood being advantageous, metal and glass being disadvantageous, and plastics, food, and yard waste being either advantageous or disadvantageous depending upon the avoided tipping fee and the GHG emissions price.     

Municipal solid waste composition determination supporting the integrated solid waste management system in the island of Crete

A one-year survey was conducted in the greater region of Crete (located at the lower region of the Aegean Sea) for the purpose of identifying waste composition (including chemical and physical characterization), as well as any seasonal variation. The investigation was carried out repeatedly at seven landfills and one transfer station in Crete, in four phases. Each sampling phase corresponded to a season (autumn, winter, spring, summer). ASTM D5231-92(2003) standard method and RCRA Waste Sampling Draft Technical Guidance were used. Hand sorting was used for classifying the collected wastes into the following categories: plastics, paper, metals, aluminium, leather-wood-textiles-rubbers, organic wastes, non-combustibles and miscellaneous. Further analysis included proximate and ultimate analysis of combustible materials. Metals such as lead, cadmium and mercury were also investigated. The results show that there has been a significant decrease of organic wastes during the last decade due to the increase of packaging materials, as a result of a change in consumption patterns. Three main waste categories were determined: organic wastes, paper and plastics, which combined represent 76% of the total waste in Crete. Furthermore, a high fraction of glass and a seasonal variation of aluminium indicate a strong correlation of waste composition with certain human activities, such as tourism. There is also a variation between the municipal solid waste (MSW) composition in the region of Crete (2003-2004) and MSW composition suggested in the National Solid Waste Planning (2000) [National Solid Waste Planning, 2000. Completion and particularization of Common Ministerial Act 113944//1944/1997: National Solid Waste Planning, June 2000]. The results of this survey are to be utilized by the regional solid waste authorities in order to establish an integrated waste treatment site, capable of fulfilling the regional waste management demands.     

Precious metals and rare earth elements in municipal solid waste – Sources and fate in a Swiss incineration plant

In Switzerland many kinds of waste, e.g. paper, metals, electrical and electronic equipment are separately collected and recycled to a large extent. The residual amount of municipal solid waste (MSW) has to be thermally treated before final disposal. Efforts to recover valuable metals from incineration residues have recently increased. However, the resource potential of critical elements in the waste input (sources) and their partitioning into recyclable fractions and residues (fate) is unknown. Therefore, a substance flow analysis (SFA) for 31 elements including precious metals (Au, Ag), platinum metal group elements (Pt, Rh) and rare earth elements (La, Ce, etc.) has been conducted in a solid waste incinerator (SWI) with a state-of-the-art bottom ash treatment according to the Thermo-Re® concept. The SFA allowed the determination of the element partitioning in the SWI, as well as the elemental composition of the MSW by indirect analysis. The results show that the waste-input contains substantial quantities of precious metals, such as 0.4 ± 0.2 mg/kg Au and 5.3 ± 0.7 mg/kg Ag. Many of the valuable substances, such as Au and Ag are enriched in specific outputs (e.g. non-ferrous metal fractions) and are therefore recoverable. As the precious metal content in MSW is expected to rise due to its increasing application in complex consumer products, the results of this study are essential for the improvement of resource recovery in the Thermo-Re® process.     

Sampling household waste at source: lessons learnt in Gaborone.

Municipal solid waste (MSW) quantity and composition analysis is fundamental for the planning of municipal waste management services. The purpose of this paper is to report the results and experiences of sampling household waste at the source of generation in Gaborone, Botswana. The average generation rate, in kg capita(-1) day(-1), and percentages of various components of waste in Gaborone were determined using a statistically designed household sampling survey. The survey covered 47 households with different socio-economic characteristics over 21 days with 893 samples obtained. The results showed that the average waste generation rate for Gaborone was 0.33 kg capita(-1) day(-1). Contrary to common belief, the waste generation rate measured as in weight units was found not be directly related to household income. However, the packaging fractions of plastic and paper measured as volume had a direct relationship with household income. Across all income groups, the putrescible waste fraction constituted the highest proportion of the waste stream at approximately 68%. The main general conclusion is on the importance of practical considerations. As much as statistically designed sampling procedures provide a useful means of estimating the quantity and composition of household waste at source of generation, there are some practical issues that should be carefully considered during sampling to improve the accuracy and relevance of the results.     

Municipal solid waste management in Beijing City

This paper presents an overview of municipal solid waste (MSW) management in Beijing City. Beijing, the capital of China, has a land area of approximately 1368.32 km² with an urban population of about 13.33 million in 2006. Over the past three decades, MSW generation in Beijing City has increased tremendously from 1.04 million tons in 1978 to 4.134 million tons in 2006. The average generation rate of MSW in 2006 was 0.85 kg/capita/day. Food waste comprised 63.39%, followed by paper (11.07%), plastics (12.7%) and dust (5.78%). While all other wastes including tiles, textiles, glass, metals and wood accounted for less than 3%. Currently, 90% of MSW generated in Beijing is landfilled, 8% is incinerated and 2% is composted. Source separation collection, as a waste reduction method, has been carried out in a total of 2255 demonstration residential and commercial areas (covering about 4.7 million people) up to the end of 2007. Demonstration districts should be promoted over a wider range instead of demonstration communities. The capacity of transfer stations and treatment plants is an urgent problem as these sites are seriously overloaded. These problems should first be solved by constructing more sites and converting to new treatment technologies. Improvements in legislation, public education and the management of waste pickers are problematic issues which need to be addressed.     

Recycling of non-metallic fractions from waste electrical and electronic equipment (WEEE): A review

The world’s waste electrical and electronic equipment (WEEE) consumption has increased incredibly in recent decades, which have drawn much attention from the public. However, the major economic driving force for recycling of WEEE is the value of the metallic fractions (MFs). The non-metallic fractions (NMFs), which take up a large proportion of E-wastes, were treated by incineration or landfill in the past. NMFs from WEEE contain heavy metals, brominated flame retardant (BFRs) and other toxic and hazardous substances. Combustion as well as landfill may cause serious environmental problems. Therefore, research on resource reutilization and safe disposal of the NMFs from WEEE has a great significance from the viewpoint of environmental protection. Among the enormous variety of NMFs from WEEE, some of them are quite easy to recycle while others are difficult, such as plastics, glass and NMFs from waste printed circuit boards (WPCBs). In this paper, we mainly focus on the intractable NMFs from WEEE. Methods and technologies of recycling the two types of NMFs from WEEE, plastics, glass are reviewed in this paper. For WEEE plastics, the pyrolysis technology has the lowest energy consumption and the pyrolysis oil could be obtained, but the containing of BFRs makes the pyrolysis recycling process problematic. Supercritical fluids (SCF) and gasification technology have a potentially smaller environmental impact than pyrolysis process, but the energy consumption is higher. With regard to WEEE glass, lead removing is requisite before the reutilization of the cathode ray tube (CRT) funnel glass, and the recycling of liquid crystal display (LCD) glass is economically viable for the containing of precious metals (indium and tin). However, the environmental assessment of the recycling process is essential and important before the industrialized production stage. For example, noise and dust should be evaluated during the glass cutting process. This study could contribute significantly to understanding the recycling methods of NMFs from WEEE and serve as guidance for the future technology research and development.     

Revisiting the elemental composition and the calorific value of the organic fraction of municipal solid wastes

In this work, the elemental content (C, N, H, S, O), the organic matter content and the calorific value of various organic components that are commonly found in the municipal solid waste stream were measured. The objective of this work was to develop an empirical equation to describe the calorific value of the organic fraction of municipal solid waste as a function of its elemental composition. The MSW components were grouped into paper wastes, food wastes, yard wastes and plastics. Sample sizes ranged from 0.2 to 0.5 kg. In addition to the above individual components, commingled municipal solid wastes were sampled from a bio-drying facility located in Crete (sample sizes ranged from 8 to 15 kg) and were analyzed for the same parameters. Based on the results of this work, an improved empirical model was developed that revealed that carbon, hydrogen and oxygen were the only statistically significant predictors of calorific value. Total organic carbon was statistically similar to total carbon for most materials in this work. The carbon to organic matter ratio of 26 municipal solid waste substrates and of 18 organic composts varied from 0.40 to 0.99. An approximate chemical empirical formula calculated for the organic fraction of commingled municipal solid wastes was C₃₂NH₅₅O₁₆.     

Management of packaging waste in Poland--development agenda and accession to the EU.

In recent years the issue of the municipal waste in Poland has become increasingly topical, with a considerable rise in the waste generation, much of which can be attributed to a boom in product packaging (mainly plastic). The annual production of plastics packaging has been constantly increasing over the last 20 to 30 years, and now exceeds 3.7 million tons. Due to a lack of processing technologies and poorly developed selective segregation system, packaging waste is still treated as a part of the municipal solid waste (MSW) stream, most of which is landfilled. As a result of Poland's access to the European Union, previous legal regulations governing municipal waste management have been harmonized with those binding on the member countries. One of the main changes, the most revolutionary one, is to make entrepreneurs liable for environmental risks resulting from the introduction of packaging to the market, and for its recycling. In practice, all entrepreneurs are to ensure recovery, and recycling, of used packaging from products introduced to the market at the required level. In recent year, the required recycling levels were fulfilled for all types of materials but mainly by large institutions using grouped and transport packaging waste for that matter. Household packaging gathered in the selective segregation system at the municipalities was practically left alone. This paper is an attempt to describe the system and assess the first year of functioning of the new, revamped system of packaging waste management in Poland. Recommendations are made relating to those features that need to be included in packaging waste management systems in order to maximize their sustainability and harmonization with the EU legal system.     

Biodegradable municipal solid waste: characterization and potential use as animal feedstuffs

Five different fractions of the biodegradable municipal solid waste (BMSW) were evaluated as potential animal feedstuffs. For each source of waste (meat waste (MW), fish waste (FW), fruit and vegetables waste (FVW), restaurant waste (RW), household waste (HW)), samples were obtained from small shops (butchers, fishmongers, fruit and vegetable shops), restaurants and a MSW treatment plant (household waste). The chemical composition, microbiological characterization, dioxins, furans, PCB's and mineral content were determined for every type of waste fraction. The analysed biodegradable waste presented high moisture content (from 60% to 90%). Some fractions were dense in one nutrient: meat waste in ether extract, fish waste in crude protein, fruit and vegetable waste in nitrogen free extract. The other studied fractions (restaurant fraction and household fraction) presented a more balanced composition, but the presence of toxic concentrations of contaminants such as metals was higher than European legislation permitted values in animal feeding. From a microbiological standpoint, a heat treatment at 65 degrees C for 20 min was sufficient to ensure microbiological quality of the samples. This treatment was also advisable to reduce the moisture content: a lower moisture content facilitates the waste handling and processing and, therefore, the inclusion of these waste fractions in commercial animal diets. This paper presents a potential alternative for the recovery of organic matter content in municipal solid waste. The results obtained in this research and the feedstuffs legislation in force related to animal feed, indicated that some of the studied biodegradable waste fractions (meat waste, fruit and vegetable waste and fish waste) could be considered as alternatives to typical raw materials used in animal feeds.     

Controlled combustion tests and bottom ash analysis using household waste with varying composition

The influence of the co-combustion of household waste with either sewage sludge, shredder fluff, electronic and electrical waste (WEEE) or PVC on the bottom ash quality and content was investigated under controlled laboratory conditions using a pot furnace. This laboratory approach avoids the interpretation problems related to large variations in input waste composition and combustion conditions that are observed in large scale MSW incinerators. The data for metals content, transfer coefficients and leaching values are presented relative to data for a base household waste composition that did not contain any of the added special wastes. The small WEEE invited direct measurement of precious metals content in the ashes, where measurement accuracy is facilitated by using only mobile phone scrap for small WEEE. The analyses were carried out for different particle size ranges that are of relevance to the recyclability of metals and minerals in the ashes. Positive correlations were found between elements content of the input waste and the bottom ashes, and also between increased levels of Cl, Mo and Cu in the input waste and their leaching in the bottom ashes. These correlations indicate that addition of PVC, small WEEE and shredder fluff in input waste can have a negative influence on the quality of the bottom ashes. Enrichment of Au and Ag occurred in the fractions between 0.15 and 6 mm. The precious metals content represents an economically interesting intrinsic value, even when the observed peak values are properly averaged over a larger volume of ashes. Overall, it has been shown that changes in quality and content of bottom ashes may be traced back to the varied input waste composition.     

Life cycle assessment for optimising the level of separated collection in integrated MSW management systems

This life cycle assessment study analyses material and energy recovery within integrated municipal solid waste (MSW) management systems, and, in particular, the recovery of the source-separated materials (packaging and organic waste) and the energy recovery from the residual waste. The recovery of materials and energy are analysed together, with the final aim to evaluate possible optimum levels of source-separated collection that lead to the most favourable energetic and environmental results; this method allows identification of an optimum configuration of the MSW management system. The results show that the optimum level of source-separated collection is about 60%, when all the materials are recovered with high efficiency; it decreases to about 50%, when the 60% level is reached as a result of a very high recovery efficiency for organic fractions at the expense of the packaging materials, or when this implies an appreciable reduction of the quality of collected materials. The optimum MSW management system is thus characterized by source-separated collection levels as included in the above indicated range, with subsequent recycling of the separated materials and energy recovery of the residual waste in a large-scale incinerator operating in combined heat and power mode.     

Metal distribution in incineration residues of municipal solid waste (MSW) in Japan

This study aimed to identify distribution of metals and the influential factors on metal concentrations in incineration residues. Bottom ash and fly ash were sampled from 19 stoker and seven fluidized bed incinerators, which were selected to have a variety of furnace capacity, furnace temperature, and input waste. In the results, shredded bulky waste in input waste increased the concentration of some metals, such as Cd and Pb, and the effect was confirmed by analysis of shredded bulky waste. During MSW incineration, lithophilic metals such as Fe, Cu, Cr, and Al remained mainly in the bottom ash while Cd volatilized from the furnace and condensed to the fly ash. About two thirds of Pb and Zn was found in the bottom ash despite their high volatility. Finally, based on the results obtained in this study, the amount of metal in incineration residues of MSW was calculated and the loss of metal was estimated in terms of mass and money. A considerable amount of metal was found to be lost as waste material by landfilling of incineration residues.     

Material and energy recovery in integrated waste management systems. An evaluation based on life cycle assessment

This paper reports the environmental results, integrated with those arising from mass and energy balances, of a research project on the comparative analysis of strategies for material and energy recovery from waste, funded by the Italian Ministry of Education, University and Research. The project, involving the cooperation of five University research groups, was devoted to the optimisation of material and energy recovery activities within integrated municipal solid waste (MSW) management systems. Four scenarios of separate collection (overall value of 35%, 50% without the collection of food waste, 50% including the collection of food waste, 65%) were defined for the implementation of energetic, environmental and economic balances. Two sizes of integrated MSW management system (IWMS) were considered: a metropolitan area, with a gross MSW production of 750,000 t/year and an average province, with a gross MSW production of 150,000 t/year. The environmental analysis was conducted using Life Cycle Assessment methodology (LCA), for both material and energy recovery activities. In order to avoid allocation we have used the technique of the expansion of the system boundaries. This means taking into consideration the impact on the environment related to the waste management activities in comparison with the avoided impacts related to the saving of raw materials and primary energy. Under the hypotheses of the study, both for the large and for the small IWMS, the energetic and environmental benefits are higher than the energetic and environmental impacts for all the scenarios analysed in terms of all the indicators considered: the scenario with 50% separate collection in a drop-off scheme excluding food waste shows the most promising perspectives, mainly arising from the highest collection (and recycling) of all the packaging materials, which is the activity giving the biggest energetic and environmental benefits. Main conclusions of the study in the general field of the assessment of the environmental performance of any integrated waste management scheme address the importance of properly defining, beyond the design value assumed for the separate collection as a whole, also the yields of each material recovered; particular significance is finally related to the amount of residues deriving from material recovery activities, resulting on average in the order of 20% of the collected materials.