Impact of food waste disposers on the generation rate and characteristics of municipal solid waste

Field surveys were carried out to ascertain the reduction in the generation rate of municipal solid waste as a result of the use of food waste disposers (FWDs). The generation rate and characteristics of garbage and of the food waste ground by FWDs in households were investigated, and the effect of FWDs was discussed. In a medium-sized village, the amount of garbage collected per collection decreased from 251.2 kg to 114.7 kg as a result of FWD use. The unit loading of ground food waste was estimated to be 111 g/cap·day. In a small village, the amount of garbage collected weekly decreased from 175 kg to 112 kg. The average unit loading of ground food waste was measured and found to be 126 g/cap·day. The reduction rate of garbage varied from 25% to 39% monthly and the average reduction rate was 31% throughout the surveying period. Dramatic variations in the characteristics of the collected garbage were recognized: the ratio of food waste on a dry basis declined by more than half, the moisture content decreased to half or less, the combustible matter content increased approximately 1.7 times or more, and the lower heating value increased approximately 2.0 times or more compared to the case without FWD use.     

Feasibility of energy recovery from municipal solid waste in an integrated municipal energy supply and waste management system.

A decision-support model for determining the feasibility of a planned energy-from-waste (EfW) investment for an integrated waste management and energy supply system is presented. The aim is to present an easy-to-understand, inexpensive and fast-to-use tool to decision-makers for modelling and evaluating different kinds of processes. Special emphasis is put on forming the model and interpretation of the results of the example case. The simple integrated system management (SISMan) model is presented through a practical example of the use of the model. In the example the viability of the described system is studied by comparing five different cases including different waste-derived fuels (WDF), non-segregated municipal solid waste (MSW) being one of the fuel options. The nominal power output of the EfW plant varied in each case according to the WDF classification. The numeric values for two main variables for each WDF type were determined, the WDF price at the gate of the EfW plant and the waste management fee (WMF) according to the 'polluter pays' -principle. Comparison between the five cases was carried out according to two determinants, the WMF related to each case and the recovery rate related to each case. The numeric values for the constants and variables used in the calculations were chosen as realistically as possible using available data related to the issue. In the example of this paper, the mass-incineration solution ('pure' MSW as a fuel) was found to be the most viable solution for the described system according to the calculations. However, the final decision of the decision-makers might differ from this in the real world due to extra 'fuzzy' information that cannot be reliably included in the calculations. This paper shows that certain key values of modelled systems can be calculated using an easy-to-use tool at the very early stages of a larger design process involving municipal and business partners. The use of this kind of tools could significantly decrease the overall design costs of large systems in the long run by cutting out irrational system options at the very beginning of the planning.     

The current municipal solid waste management situation in Tibet

The Tibetan Plateau has an average altitude of more than 4,000 m. The total area of Tibetan Plateau is 2,400,000 km2, which occupies 25% of the area of China. Due to the high altitude, the environment has low atmospheric pressure, low oxygen content, and low temperature, and is also fragile. Investigations concerning MSW generation and characteristics, MSW management, collection and transportation, and treatment and disposal of MSW covered four representative cities, including the urban areas of Lhasa city, Shigatse, Nedong of Lhoka and Bayi of Nyingtri. The results show that MSW generation in the urban areas of Lhasa city and Tibet were 450 t/d and 3,597 t/d, respectively, in 2006. However, accelerated economic development and flourishing tourism caused by the opening of the Qinghai-Tibet Railway (QTR) have greatly increased solid waste generation to a new high. It is predicted that MSW generation in Tibet will reach 4,026 t/d in 2010 and 4,942 t/d in 2020. MSW management and disposal lag behind MSW generation due to a number of factors such as equipment shortage, insufficient maintenance, exhaustion of waste treatment capacity and low recycling efficiency. Still, MSW in most areas is dumped in the open with no controls. Because no appropriate collection and treatment systems for leachate and landfill gas exist, untreated leachate is discharged directly into the environment, causing serious secondary pollution. Some suggestions on improving the MSW management system are presented in this paper.     

The effect of moisture on air classification of municipal solid waste

The effect of moisture on the air classification of municipal solid waste (MSW) is analysed using a 2³ factorial design. A synthetic MSW is used in the laboratory to facilitate controlled variation of composition and moisture content. A pilot scale 120 ° zig-zag air classifier is used to perform the classification tests. Ten system response variables are evaluated including six recoveries, two purities and two efficiencies, to elucidate the impacts of (1) increased particle density resulting from moisture absorption and (2) particle adhesion. Results indicate a significant decrease in paper recovery and efficiency with increasing moisture. However, no significant reduction in aluminum and iron recovery is observed. This suggests that adhesion of these particles to extracted combustible materials is not a significant factor in reducing extract purity. Instead, extract purity reduction is a result of paper recovery losses from increasing particle density. The degree of moisture effect for varied MSW composition is greater for feeds with lower fractions of adsorbent materials. A redefination of percent moisture based on the MSW absorbent fraction is suggested in order to account for this varied impact. The new definition, moisture absorbancy ratio, is the weight of the moisture in the MSW divided by the dry weight of the absorbent materials in the MSW.     

The origins of municipal solid waste: The relations between residues from packaging materials and food

Data for the composition of municipal solid waste (MSW) from around the world are used to further examine a previously reported statistical correlation between the fraction of food residues and the fractions of paper and board, metal, glass and plastics residues in MSW. For data from many locations, these correlations are statistically significant; multiple linear regressions are computed. The fraction of food waste decreases as the fractions of waste from paper and board, metals and glass increase.The situation in the U.S.A. is examined further for just packaging waste. Similar correlations are established for the fraction of food residues and the fractions of paper and board and plastics packaging residues for predicted compositions for 1980 to 2000. Similar correlations for the U.K. are not statistically significant. Some reasons for this are postulated.The results of the statistical analyses predict that a strategy for decreasing the fraction of food waste in MSW is to increase the use of food packaging by some amount, especially plastics and metals, contrary to conventional wisdom.     

德国城市生活垃圾管理现状及启示

德国是城市生活垃圾管理最为成功的国家之一。从德国垃圾处理的发展过程、法律法规框架、管理体系、管理措施及实施成果等方面介绍了德国城市生活垃圾的管理现状,从而为解决我国现有的城市垃圾管理问题提供管理思路和方法。     

Techno-economic assessment of municipal solid waste management in Jordan

Mismanagement of solid waste leads to public health risks, adverse environmental impacts and other socio-economic problems. This is obvious in many developing countries around the world. Currently, several countries have realized that the way they manage their solid wastes does not satisfy the objectives of sustainable development. Therefore, these countries, including Jordan, which forms the case study presented here, have decided to move away from traditional solid waste management (SWM) options to more integrated solid waste management approaches. Unfortunately, in many developing countries like Jordan, the lack of adequate resources to implement the necessary changes is posing a serious obstacle. The present paper discusses the various practices and challenges of solid waste management in Jordan from both a technical and economic perspective. An overview of the current practices and their environmental implications in three major cities of the country, which generate more than 70% of the country's solid waste, is presented. Recent literature on solid waste management in Jordan has been reviewed; and data on the total amount of municipal solid waste generated, compositional variations over the last two decades, and future projections are presented. The necessity, importance and needs of solid waste recovery and reuse are identified. The review of the legal frameworks indicated that there is a need for detailed and clear regulations dealing specifically with solid waste. The service cost analysis revealed that none of the municipalities in Jordan sufficiently recover the cost of the services, with more than 50% being subsidized from the municipalities' budgets. The allocation of the available resources was analyzed and service performance indicators assessed. Factors that should be taken into consideration when making the decision to move from a traditional SWM approach to a more integrated approach are highlighted and suggestions for a more smooth transition are recommended.     

An overview of municipal solid waste management in China

Municipal solid waste management (MSWM) in China warrants particular attention as China has become the largest MSW generator in the world and the total amount of MSW it produces continues to increase. In recent years, central and local governments have made great efforts to improve MSWM in China. New regulations and policies have been issued, urban infrastructure has been improved, and commercialization and international cooperation have been encouraged. Considering these developments, an overview is necessary to analyze the current state as well as new opportunities and challenges regarding MSWM in China. This paper shows that since the late 1990s, the amount of MSW collected has been largely decoupled from economic growth and incineration has become an increasingly widespread treatment method for MSW. We identify and discuss four major challenges and barriers related to China’s MSWM, and propose an integrated management framework to improve the overall eco-efficiency of MSWM.     

A historical context of municipal solid waste management in the United States.

Municipal solid waste management (MSWM) in the United States is a system comprised of regulatory, administrative, market, technology, and social subcomponents, and can only be understood in the context of its historical evolution. American cities lacked organized public works for street cleaning, refuse collection, water treatment, and human waste removal until the early 1800s. Recurrent epidemics forced efforts to improve public health and the environment. The belief in anticontagionism led to the construction of water treatment and sewerage works during the nineteenth century, by sanitary engineers working for regional public health authorities. This infrastructure was capital intensive and required regional institutions to finance and administer it. By the time attention turned to solid waste management in the 1880s, funding was not available for a regional infrastructure. Thus, solid waste management was established as a local responsibility, centred on nearby municipal dumps. George Waring of New York City organized solid waste management around engineering unit operations; including street sweeping, refuse collection, transportation, resource recovery and disposal. This approach was adopted nationwide, and was managed by City Departments of Sanitation. Innovations such as the introduction of trucks, motorized street sweepers, incineration, and sanitary landfill were developed in the following decades. The Resource Conservation and Recovery Act of 1976 (RCRA), is the defining legislation for MSWM practice in America today. It forced the closure of open dumps nationwide, and required regional planning for MSWM. The closure of municipal dumps caused a 'garbage crisis' in the late 1980s and early 1990s. Private companies assumed an expanded role in MSWM through regional facilities that required the transportation of MSW across state lines. These transboundary movements of MSW created the issue of flow control, in which the US Supreme Court affirmed the protection of garbage under the Commerce Clause of the Constitution. Thus MSWM in America today is largely managed by municipalities, and operated by a relatively small number of private companies. It consists of a mixture of landfill, incineration, recycling, and composting, and is regulated under RCRA, the Clean Air Act and other related federal and state laws.     

A comparison of municipal solid waste management in Berlin and Singapore

A comparative analysis of municipal solid waste management (MSWM) in Singapore and Berlin was carried out in order to identify its current status, and highlight the prevailing conditions of MSWM. An overview of the various aspects of MSWM in these two cities is provided, with emphasis on comparing the legal, technical, and managerial aspects of MSW. Collection systems and recycling practiced with respect to the involvement of the government and the private sector, are also presented.Over last two decades, the city of Berlin has made impressive progress with respect to its waste management. The amounts of waste have declined significantly, and at the same time the proportion that could be recovered and recycled has increased. In contrast, although Singapore’s recycling rate has been increasing over the past few years, rapid economic and population growth as well as change in consumption patterns in this city-state has caused waste generation to continue to increase. Landfilling of MSW plays minor role in both cities, one due to geography (Singapore) and the other due to legislative prohibition (Berlin). Consequently, both in Singapore and Berlin, waste is increasingly being used as a valuable resource and great efforts have been made for the development of incineration technology and energy recovery, as well as climate protection.     

Greenhouse gases emission from municipal waste management: The role of separate collection

The municipal solid waste management significantly contributes to the emission in the atmosphere of greenhouse gases (e.g. CO₂, CH₄, N₂O) and therefore the management process from collection to treatment and disposal has to be optimized in order to reduce these emissions. In this paper, starting from the average composition of undifferentiated municipal solid waste in Italy, the effect of separate collection on greenhouse gases emissions from municipal waste management has been assessed. Different combinations of separate collection scenarios and disposal options (i.e. landfilling and incineration) have been considered. The effect of energy recovery from waste both in landfills and incinerators has also been addressed. The results outline how a separate collection approach can have a significant effect on the emission of greenhouse gases and how wise municipal solid waste management, implying the adoption of Best Available Technologies (i.e. biogas recovery and exploitation system in landfills and energy recovery system in Waste to Energy plants), can not only significantly reduce greenhouse gases emissions but, in certain cases, can also make the overall process a carbon sink. Moreover it has been shown that separate collection of plastic is a major issue when dealing with global warming relevant emissions from municipal solid waste management.     

LCA comparison of container systems in municipal solid waste management

The planning and design of integrated municipal solid waste management (MSWM) systems requires accurate environmental impact evaluation of the systems and their components. This research assessed, quantified and compared the environmental impact of the first stage of the most used MSW container systems. The comparison was based on factors such as the volume of the containers, from small bins of 60–80 l to containers of 2400 l, and on the manufactured materials, steel and high-density polyethylene (HDPE). Also, some parameters such as frequency of collections, waste generation, filling percentage and waste container contents, were established to obtain comparable systems. The methodological framework of the analysis was the life cycle assessment (LCA), and the impact assessment method was based on CML 2 baseline 2000. Results indicated that, for the same volume, the collection systems that use HDPE waste containers had more of an impact than those using steel waste containers, in terms of abiotic depletion, global warming, ozone layer depletion, acidification, eutrophication, photochemical oxidation, human toxicity and terrestrial ecotoxicity. Besides, the collection systems using small HDPE bins (60 l or 80 l) had most impact while systems using big steel containers (2400 l) had less impact. Subsequent sensitivity analysis about the parameters established demonstrated that they could change the ultimate environmental impact of each waste container collection system, but that the comparative relationship between systems was similar.     

Environmental assessment of alternative municipal solid waste management strategies. A Spanish case study

The aim of this study is to compare, from an environmental point of view, different alternatives for the management of municipal solid waste generated in the town of Castellón de la Plana (Spain). This town currently produces 207 ton of waste per day and the waste management system employed today involves the collection of paper/cardboard, glass and light packaging from materials banks and of rest waste at street-side containers.The proposed alternative scenarios were based on a combination of the following elements: selective collection targets to be accomplished by the year 2015 as specified in the Spanish National Waste Plan (assuming they are reached to an extent of 50% and 100%), different collection models implemented nationally, and diverse treatments of both the separated biodegradable fraction and the rest waste to be disposed of on landfills.This resulted in 24 scenarios, whose environmental behaviour was studied by applying the life cycle assessment methodology. In accordance with the ISO 14040-44 (2006) standard, an inventory model was developed for the following stages of the waste management life cycle: pre-collection (bags and containers), collection, transport, pre-treatment (waste separation) and treatment/disposal (recycling, composting, biogasification + composting, landfill with/without energy recovery). Environmental indicators were obtained for different impact categories, which made it possible to identify the key variables in the waste management system and the scenario that offers the best environmental behaviour. Finally, a sensitivity analysis was used to test some of the assumptions made in the initial life cycle inventory model.     

The effect of shredding and test apparatus size on compressibility and strength parameters of degraded municipal solid waste

In many situations, MSW components are processed and shredded before use in laboratory experiments using conventional soil testing apparatus. However, shredding MSW material may affect the target property to be measured. The objective of this study is to contribute to the understanding of the effect of shredding of MSW on the measured compressibility and strength properties. It is hypothesized that measured properties can be correlated to an R-value, the ratio of waste particle size to apparatus size. Results from oedometer tests, conducted on 63.5 mm, 100 mm, 200 mm diameter apparatus, indicated the dependency of the compressibility parameters on R-value. The compressibility parameters are similar for the same R-value even though the apparatus size varies. The results using same apparatus size with variable R-values indicated that shredding of MSW mainly affects initial compression. Creep and biological strain rate of the tested MSW are not significantly affected by R-value. The shear strength is affected by shredding as the light-weight reinforcing materials are shredded into smaller pieces during specimen preparation. For example, the measured friction angles are 32° and 27° for maximum particle sizes of 50 mm and 25 mm, respectively. The larger MSW components in the specimen provide better reinforcing contribution. This conclusion is however dependent on comparing specimen at the same level of degradation since shear strength is also a function of extent of degradation.     

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.     

Optimization of municipal solid waste management in Port Said - Egypt

Optimization of solid waste management systems using operational research methodologies has not yet been applied in any Egyptian governorate. In this paper, a proposed model for a municipal solid waste management system in Port Said, Egypt is presented. It includes the use of the concept of collection stations, which have not yet been used in Egypt. Mixed integer programming is used to model the proposed system and its solution is performed using MPL software V4.2. The results show that the best model would include 27 collection stations of 15-ton daily capacity and 2 collection stations of 10 ton daily capacity. Any transfer of waste between the collection station and the landfill should not occur. Moreover, the flow of the district waste should not be confined to the district collection stations. The cost of the objective function for this solution is 10,122 LE/day (equivalent to 1716 US dollars). After further calculations, the profit generated by the proposed model is 49,655.8 LE/day (equivalent to 8418.23 US dollars).     

A performance-based system for the long-term management of municipal waste landfills

Landfills have been the dominant alternative for disposal of solid waste and there are tens of thousands of closed landfills throughout the world that require a long-term management strategy. In contrast to approaches based on time or target values, this paper describes a performance-based methodology for evaluation of post-closure care (PCC). Using the methodology, critical components of PCC at a landfill, including leachate and gas management, groundwater monitoring and cover integrity, are considered to determine whether a landfill meets defined conditions for functional stability and can transition from regulated PCC to a post-regulatory custodial care program representing de minimus care activities only. The methodology is predicated on understanding the biological, chemical, and physical behavior of a landfill and the presence of sufficient data to verify expected trends in landfill behavior. If an evaluation suggests that a change can be made to PCC, the landfill owner must perform confirmation monitoring and then surveillance monitoring at a decreasing frequency to verify that the change is protective of human health and the environment. A hypothetical case study showed that using the methodology to evaluate site-specific PCC requirements could result in increased environmental protection at comparable cost by spending available funds where they are most needed.