Showing papers in "Resources Conservation and Recycling in 1995"

Life cycle analysis: A critique

Abstract: Life cycle analysis (LCA) is an increasingly important tool for environmental policy, and even for industry. Analysts are also interested in forecasting future materials/energy fluxes on regional and global scales, as a function of various economic growth and regulatory scenarios. A fundamental tenet of LCA is that every material product must eventually become a waste. To choose the ‘greener’ of two products or policies it is necessary to take into account its environmental impacts from ‘cradle to grave’. This includes not only indirect inputs to the production process, and associated wastes and emissions, but also the future (downstream) fate of a product. The first stage in the analysis is quantitative comparisons of materials flows and transformations. Energy fluxes are important insofar as they involve materials (e.g., fuels, combustion products). This can be an extremely valuable exercise, if done carefully. However, the data required to accomplish this first step are not normally available from published sources. Theoretical process descriptions from open sources may not correspond to actual practice. Moreover, so-called ‘confidential’ data are unverifiable (by definition) and may well be erroneous. In the absence of a formal materials balance accounting system, such errors may not be detected. A key thesis of this paper is that process data can, in many cases, be synthesized, using models based on the laws of thermodynamics and chemistry. While synthetic but possible data may not fully reflect the actual situation, it is far superior to ‘impossible’ data. Most of the recent literature on LCA focusses on the second stage of the analysis, namely the selection and evaluation of different, non-comparable environmental impacts (‘chalk vs. cheese’). This problem is, indeed, very difficult-and may well be impossible to solve convincingly -even at the conceptual level. However, the only approach that can make progress is one that utilizes monetization to the limits of its applicability, rather than one that seeks to by-pass (or ‘re-invent’) economics. Nevertheless, the evaluation problem is second in priority, for the simple reason that LCA has utility even if the evaluation technique is imperfect. On the other hand, LCA has no (or even negative) utility if the underlying physical data is wrong with respect to critical pollutants.

Life cycle assessment of gasoline and diesel

Abstract: A life cycle assessment (LCA) has been carried out to compare production and use of three different fuel products: regular gasoline, gasoline with MTBE and diesel. The study quantifies energy consumption and emissions through the production chain and assesses the potential impacts to the environment. Some of the methodological problems performing the LCA are discussed. The study indicates that production of gasoline with MTBE has potentially larger environmental impacts than production of regular gasoline, caused by the extra facilities for production of MTBE. The study also shows that the results are highly sensitive to the actual product specifications and assumptions that are made. Different product specifications can therefore lead to other conclusions. The results also indicate that production of diesel leads to significantly lower potential impacts than the gasolines.

Use of ash derived from oil-palm waste incineration as a cement replacement material

Abstract: The production of palm oil creates large quantity of solid waste by-products. Empty oil-palm fruit bunches discharged from the mill are currently being disposed of by burning in an incinerator. After combustion, a substantial amount of highly caustic ash is produced which creates problems of disposal. This study examines the feasibility of using the ash as a cement replacement material. The experimental results indicate that blended cement containing ash derived from oil-palm waste shows satisfactory setting times and soundness test results. Workability of concrete incorporating the ash is categorized as good, and no segregation was observed. The effects of ash addition on concrete densities and water absorption are insignificant. Compressive strength of the concrete decreases with the ash content in the cement. Up to 10% by weight of ash addition, no adverse effect on the strength was observed for the cubes cured for 1 year. The results suggest that the ash could possibly be blended in small amounts with ordinary Portland cement for concrete making without detrimental effects on long-term strength property.

Aerobic decomposition of organic wastes 2. Value of compost as a fertilizer

Abstract: Pot experiments in 20-1 cylindrical pots and in rectangular plastic containers 40 × 60 cm and a soil depth of 40 cm were used to evaluate different kinds of compost. The results are related to the chemical reactions occurring by decomposition of the organic compounds and to chemical analyses of the compost. A good aeration during decomposition promotes the conversion of carbohydrates into carbon dioxide and water. An incomplete aeration may result in accumulation of acetic acid, thus giving trouble to plant growth if the compost is incorporated into the soil. Surface application of the compost minimized the trouble. Proteins and amino acid are converted to ammonia and microbial protein. When no action is taken to collect the ammonia it will be lost through volatilization. The microbial protein is found in the soil fraction, biomass. The plants cannot utilize the nitrogen in the biomass until it is mineralized into ammonium and nitrate nitrogen. For that proces a propagation of microbes in the soil is necessary and caused a delay in the utilization of nitrogen. A proper relation between available carbon and nitrogen enables a mineralization. If the available content of carbon relative to nitrogen is high, the microbes absorb mineral nitrogen from the soil solution promoting nitrogen deficiency in the plants. That biological nitrogen fixation is probable if acetic acid and other water-soluble compounds are accumulated in the compost. A surface application of compost minimizes the risk of biological nitrogen fixation. The risk of ammonia volatilization in the field is very little as ammonia is converted into biomass during decomposition. The fertilizing value of the phosphorus and potassium content in compost is normally as high as that of fertilizers. However, both the water solubility of phosphate and the fertilizing value decrease if the storage time of the compost continues until nitrate accumulates. Due to a high solubility of most nutrients in compost the fertilizing value of the compost is nearly as good by surface application as by incorporation into the soil. By using compost in moderate quantities on the same soil for 8 years the soil structure was markedly improved, especially when the compost was applied on the soil surface and after sowing of the crop. The surface was thereby protected against the compressing effect of rain drops and a rapid drying up afterwards. Water infiltrated into the soil much faster where the compost protected the soil. This was true even with a thin layer of compost.

Critical Review of Life Cycle Analysis and Assessment Techniques and their Application to Commercial Activities

Abstract: This paper summarises the basic methodology of life cycle analysis, and aims to show that without clear understanding of the technique, life cycle inventories (LCI) can be easily misused to give preferred results, or misunderstood to give erroneous results which could lead to detrimental environmental decisions. It highlights areas where most errors are likely to exist, namely through the definition of system boundaries and the collection of data, and shows through examples how these can drastically affect LCI results. The paper also touches briefly on life cycle assessment techniques, which are aimed at evaluating environmental damage, and concludes with a brief summary of the properties of an ideal LCI which would provide a comprehensive data base for life cycle assessment.

Plastic waste management in construction: technological and institutional issues

Abstract: The main objective of a solid waste management system is to effectively safeguard the public health, safety, and welfare. The various options involved in a waste management process are landfilling, incineration, and recycling wastes into useful products. Plastics recycling, in particular, would not be successful unless the proper infrastructure to collect the waste is being set, the technology to economically reprocess the waste into new products is available, and the establishment of markets for the cost-effective use of recycled products are developed. The development of new construction materials using recycled plastics is important to both the construction and the plastics recycling industries. Extensive research investigated the use of resins based on recycled poly (ethylene terephthalate) (PET) plastic waste for the production of a high performance composite material, namely polyester concrete (PC). Resins using recycled PET offer the possibility of a lower source cost of materials for forming good quality PC. PC products also allow the long-term disposal of PET waste, an important advantage in recycling applications.

Environmental impacts by disposal of plastic from municipal solid waste

Abstract: A steadily increasing demand for recycling of polymers has resulted in a demand for methods making it possible to compare different disposal processes' influence on the environment and on the resources. ‘Ecoprofiles’ can be used for ranking of different disposal processes in an environmentally and resource compatible way. An ecoprofile is an assessment of the environmental and resource impacts for a given disposal process, and those processes influenced by the disposal process. Within the constraints and boundaries imposed by the model, assumptions made, and data utilized, this article describes ecoprofiles for six different ways of disposing the plastic fraction in municipal solid waste. The following disposal processes are studied: (1 and 2) two different material recycling processes that include separation of the plastic waste; (3) material recycling without separation of the plastic waste; (4) pyrolysis; (5) incineration with heat recovery; and (6) landfill.

Two-phase continuous anaerobic digestion of fruit and vegetable wastes

Abstract: Results of a two-phase mesophilic (35°C) anaerobic digestion treatment of fruit and vegetable wastes, carried out at laboratory scale, are presented and discussed. They are contrasted with other results obtained with a similar waste, but digested in a one-phase system. The yields are lower in this simple two-phase system, because of the higher organic loading rate. It is concluded that this two-phase system does not seem appropriate to treat these wastes unless it is equipped with some type of control of the hydrolytic step. A one-phase system is simpler and can yield at least the same yields.

The materials flow of mercury in the United States

Abstract: This report describes the materials flow of mercury in the United States. It examines the mining and production of mercury and the manufacturing, uses, and ultimate disposal of mercury. Materials flowcharts were prepared for 1989 and 1990. An effort was made to include estimates for all major anthropogenic sources including fossil fuel combustion, waste incineration, and nonferrous metal mining operations. Mining and mineral processing released about 100 metric tons per year (mt/yr) of mercury to the environment in both 1989 and 1990. The combustion of fossil fuels released 175 mt/yr in the same years. The manufacturing, use, and disposal of products containing mercury accounted for the release of 1037 mt of mercury in 1989 and 938 mt in 1990. The manufacture of chlorine and caustic soda was a major source of recycled mercury, but it was all reused within the industry. Recovery from all waste products accounted for 36% of reported consumption in 1989 and 42% in 1990. The losses from manufacturing and end use have been declining, whereas mercury emitted from combustion sources has not been strictly regulated and will likely become the largest source of mercury releases to the environment.

The benefits and costs of alternative solid waste management policies

Abstract: In the last few years controlling the size and composition of the solid waste flow has moved substantially up the public policy agenda in many countries. With this has come the question of what are the appropriate types of public interventions in the economy to control this flow. The most dramatic of the interventions have involved adoption of high recycling targets for specific fractions of the waste stream and special measures to deal with packaging waste, especially in a number of European countries. Questions are being raised about whether the targets and inventions are warranted on the basis of economic analysis, especially about the costs and benefits of the objectives and the instruments to achieve them. This paper reviews the published and some unpublished literature through the spring of 1993 and generally finds that the conceptual and empirical basis on which to predicate efficient and effective solid waste management policy is still rather incomplete. The only principled basis for public interventions thus far established in the economics literature is that for user fees at the household level. The paper analyzes the role of waste management fees or user charges in rationalizing investment in waste management technology and finds that, while there is wide agreement that the prices are not right in this environmental area, there is little focus on the role that such fees can play in motivation source reduction at the consumer or household level. A number of recommendations are made for using economic instruments for efficient solid waste management.

Automobile recycling in the United States: Energy impacts and waste generation

Abstract: Changes in the trends in the material composition of domestic and imported automobiles and the increasing cost of landfilling the non-recyclable portion of automobiles (automobile shredder residue or ASR) pose questions about the future of automobile recycling in the United States. In response to these challenges, new and innovative approaches to automobile recycling are being developed. This paper presents the findings of a recent study to examine the impacts of these changes on the life cycle energy consumption of automobiles and on the quantity of waste that must be disposed of. Given the recycle status quo, trends in material composition and the viability of recycling the non-metallic components of the typical automobile are of secondary importance when compared to the energy consumed during the life of the automobile. The energy savings resulting from small changes in the fuel efficiency of a vehicle overshadow potential energy losses associated with the adoption of new and possibly non-recyclable materials. Under status quo conditions, the life cycle energy consumed by the typical automobile is projected to decrease from 599 million Btus in 1992 to 565 million Btus in 2000. Energy consumed during the manufacture of the typical car will increase from about 120 to 140 million Btus between 1992 and 2000, while energy used during vehicle operation will decrease from 520 to 480 million Btus. This study projects that energy saved at the recycle step will increase from 41 million Btus in 1992 to 55 million Btus in 2000. This study also investigated the energy impacts of several potential changes to the recycle status quo, including the adoption of technologies to retrieve the heat value of ASR by incineration and the recycle of some or all thermoplastics in the typical automobile. The study estimates that under optimistic conditions —i.e., the recycling of all thermoplastics and the incineration with heat recovery of all remaining ASR —about 8 million Btus could be saved per automobile —i.e., an increase from about 55 to 63 million Btus. In the more realistic scenario —i.e., the recycling of easy-to-remove thermoplastic components (bumper covers and dash-boards) —the potential energy savings are about 1 million Btus per vehicle. It is estimated that the annual quantity of ASR in the United States could be reduced from about 5 billion pounds to as little as 1 billion pounds of ash if all ASR is incinerated. Alternatively, ASR quantity could be reduced to about 4 billion pounds if all thermoplastics in automobiles are recycled. However, in the case of recycling only thermoplastic bumper covers and dashboards, the quantity of ASR would be reduced by only 0.2 billion pounds. A significant reduction or increase in the size of the ASR waste stream will not in itself have a large impact on the solid waste stream in the United States.

Selective dissolution of critical metals from diesel and naptha spent hydrodesulphurization catalysts

Abstract: The petroleum refining industry makes extensive use of catalysts, containing critical metals, such as, Mo, Co and Ni, for the desulphurization of various oil fractions. The selective recovery of these metals from two uncrushed and at low temperature calcined industrial hydrodesulphurization (MoCo/Al2O3 and MoNi/Al2O3SiO2) catalysts was studied, applying a two-step alkali-acid procedure. Fundamental kinetic aspects of the process, such as, reaction time, leaching reagents concentration and reaction temperature, were studied. Recoveries up to 97% for Mo and up to 92% for Co or Ni in separate solutions were achieved, using low cost and easily available reagents, such as sodium hydroxide and sulphuric acid.

Urban solid waste management in Tanzania Issues, concepts and challenges

Abstract: Urban solid waste in Tanzania in general and in Dar es Salaam city in particular, is a serious environmental problem. Concurrent with recent socioeconomic development, coupled with liberalization of the economy and rapid population growth, the quantum of solid waste generated has increased at a rapid rate. The manner in which urban solid waste is managed in Dar es Salaam directly affects the metropolitan environment, the appearance of the city and the citizens day-to-day life. Hence, a special priority is attached to Dar es Salaam's solid waste management. The existing critical dimensions in the management of solid waste are scavenging, privatization, arresting environmental effects of waste disposal and institutional capacity building. A conceptual framework based on application of sustainability to waste prevention, utilization and recycling for urban solid waste management is proposed. The most appropriate waste management principles seem to be organized scavenging, followed by biological waste utilization and sanitary landfilling. The paper suggests several urban solid waste management challenges based on issues and principles analyzed and discussed.

Piggery waste treatment by anaerobic digestion and nutrient removal by ionic exchange

Abstract: Piggery wastes must be treated before their disposal. The high solids content and high chemical oxygen demand of piggery wastes indicated that anaerobic biological treatment could be successfully applied as primary treatment. For that reason, a comparison between upflow anaerobic sludge bed reactor (UASB) and anaerobic fixed bed reactor (AFBR) at a similar organic volumetric loading rate of 5 kg DQO/m3 day was carried out. 60% of the piggery waste COD was removed with the AFBR compared to 40% with the UASB, thus showing a better performance of the AFBR. After 1-h sedimentation secondary process, both anaerobic effluents were treated by ionic exchange with natural zeolite due to their high values of ammoniacal nitrogen (NH+4 plus free NH3). The high removal of nutrients reported (90%) shows zeolite to be a good choice as tertiary treatment.

A study on the production of a new material from fly ash and polyethylene

Abstract: Coal combustion fly ash is produced as a byproduct in huge amounts from pulverized coal-fired power plants. Waste plastics from packaging materials and other uses are recovered in large quantities. An investigation has been conducted to produce a new building material from fly ash and polyethylene. The work was carried out with two typical coal fly ashes and polyethylene bags. The tensile strengths and the chemical resistance of the materials, in addition to the effect of temperature were examined. Characterization of these materials was also studied by means of XRD, IR and SEM techniques. The tensile strengths of the materials range from 0.92 to 2.62 kp/mm 2 . When the ratio of fly ash is low, better results were obtained. There was no significant loss in weight in solutions of NaOH (5%), CH 3 COOH (5%), C 2 H 5 OH (95%), H 2 SO 4 (5%) and H 2 O.

An approach for analysing the potential for material efficiency improvement

Abstract: Material efficiency improvement saves energy and reduces the consumption of primary resources and reduces the volume of waste. In this article an approach for analysing the potential for material efficiency improvement is proposed and discussed. In this approach the product functions performed by the materials and various improvement measures are taken into account. The potential for material saving and associated energy saving is assessed and evaluated economically. In this paper the approach is tested in an analysis of the potential for material efficiency improvement with respect to plastic packaging in the Netherlands. The technical reduction potential is found to be 34 ± 7% (157 ± 30 ktonne virgin plastics). Realization of this potential would improve the energy efficiency of the lifecycle of plastic packaging by 31% (10 PJ in 1988). From our study we conclude that our approach can indeed be used to investigate the potential for material efficiency improvement. However, a reliable technical and particularly an economical assessment of reduction measures cannot be made until more detailed data become available.

Life cycle analysis of a polyester garment

Abstract: The American Fiber Manufacturers Association ( AFMA) is exploring ways to evaluate and improve the overall environmental impact of the fiber manufacturing process and manufactured fiber products. In order to understand the true life cycle consequences, AFMA undertook a life cycle inventory study (LCI, also referred to as an ecobalance or a resource and environmental profile analysis, or BEPA) of a typical manufactured product and process flow -in this case, for a women’s blouse of 100% polyester (poly (ethylene terephthalate) or PET) knit fabric. The polyester blouse LCI was performed by Franklin Associates, Ltd. on the manufacture, use and disposal of the garment. The study uses a comprehensive approach, encompassing all energy requirements, atmospheric emissions, waterborne wastes, and solid wastes (both industrial and postconsumer). Each major processing step, from the extraction of raw materials from the earth to final disposition is included in this cradle-to-grave analysis. Detergent manufacture and home laundering are also examined. The inventory provides energy and emissions data in physical units, such as Btus of energy and pounds of emissions. This should not be confused with risk or impact assessment.

Investigation of flue gas desulphurization by fly ash and calcium hydroxide mixtures

Abstract: The desulphurization activity of sorbents obtained by mixing certain fly ashes with calcium hydroxide is studied. BET surface area and conversion of the sorbent samples are higher than with calcium hydroxide alone. In particular, conversion changes in relation to the mixing conditions (time, temperature, fly ash/calcium hydroxide ratio, amount of water in the slurry), to the SiO2 content of fly ashes and to their particle size. The results of this research are promising for the retrofit of the fly ash recycling in the flue gas desulphurization process.

A mixed-integer linear model for optimal processing and transport of secondary materials

Abstract: In every area of materials recovery management, transportation is an important component of waste management systems. Affordable transportation methods to move material from seller to buyer should be carefully investigated. The current study examines the possibility of installing intermediate processing stations between sellers and buyers. Intermediate processing stations are needed to assure quality of the recycled paper and cardboard and to collect and densify these materials for economical transport by truck or rail. The approach used emphasizes the application of a mixed-integer linear programming model for transportation of recovered paper. The research was focused on expressing the transportation optimization problem as a linear programming problem. Determination of optimal locations for the processing stations is emphasized. For this study, the available modes of transportation to recycling markets included semi-trailer truck and rail. The computerized transportation model presented is a general model applicable to either mode and can be modified to evaluate relevant secondary materials. The result of this research is an optimal transportation system model for the movement of recovered paper from selected sources in the State of Iowa to anticipated markets within the state. In most cases, truck transportation is the most practical mode because of its flexibility in routing and unit hauling capacity.

Resource recovery through recycling of sugar processing by-products and residuals

Abstract: Various technological options for recycling of sugar processing by-products and residuals are discussed making use of field data from five sugar factories in the State of Veracruz in Mexico and information from the literature. It is emphasized that diversification is urgently required in developing sugar exporting countries but that the feasibility of each technological option has to be assessed within each national and regional scenario. Bagasse is already recycled towards energy generation or sold to paper and pulp industries. It is recommended that the use of this by-product as a fuel should be optimied through various actions in such a way that a large saving of fossil fuel could be achieved. In the case of molasses, a strategy to increase ethanol production in the short, medium and long term is discussed. For the short term, the introduction of highly productive yeast strains and use of well trained personnel is recommended. For the medium and long term, development and adaptation of innovative technologies such as those involving continuous reactors and the use of Zymomonas mobilis are suggested. The strategy could be promoted through a National Programme aimed at increasing ethanol exportations, contributing to the benefit of the imports/exports balance. As stillage is the most important residual due to its high BOD and COD values, a discussion of at least five different alternative technologies for the recovery of the minerals or organic matter contained in it is presented. Such alternatives range from low to medium and high capital costs. Some of their advantages and disadvantages are discussed. Anaerobic digestion seems to be the best option whenever capital is available, although a secondary polishing treatment of the anaerobic effluents is required. In this case, an integrated system with recuperation of a multiproduct microalgae biomass (Spirulina sp.) appears to be a feasible option.

Metals recycling in the United States

Abstract: Twenty-two metals for which secondary recovery is important, in terms of quantity and/or value, were compared and ranked for rate and efficiency of recycling, and availability of recycled metal. In general, their recycling rates trended upward over the period 1970–1993. Iron, aluminum, copper, gold, platinum, and lead accounted for most of the value of all secondary metal produced, while iron and steel dominated in terms of quantity produced and exported. The factors most influential on recycling rates are profitability, public support, organization of infrastructure, sortability, legislative support, and scrap purity. The share of supply accounted for by secondary metals is expected to surpass that of primary metals sometime in the next decade.

Fixed film biomethanation of distillery spentwash using low cost porous media

Abstract: Investigations were conducted using a low cost support media for microbial attachment and growth for the anaerobic treatment of sugarcane molasses based distillery spentwash employing fixed film reactor (FFR) technology. An HRT of 3 d corresponding to an OLR of 22 kg COD m−3d−1 based on reactor liquid volume (VL) (VL = 0.534 Veb, empty bed volume) with COD reduction of 71.8% and gas yield of 0.45 m3 kg−1 COD removed has been achieved in the methane phase. Volatile solids analysis has revealed that about 75% of the biomass is attached to the inert media surface leading to a major contribution in the performance of the methane reactor. Solids retention time (SRT) of 106 d has been calculated at an HRT of 3 d, thereby demonstrating superiority of FFR technology over other conventional anaerobic treatment methods. Further, the waste treatment is affected by the entire media height due to continuous effluent recycling. Comparison with granular activated carbon (GAC) has revealed that the media used in the present study has comparable or even better performance due to larger size of the pores in the media.

Membrane filtration for reuse of wastewater from beverage industry

Abstract: Various treatment technologies are employed for the treatment of wastewater. The selection of technology depends on the influent characteristics and the required quality on the final product, the cost and ease of production. Feasibility studies on using membrane technology for the reuse of bottle-washing wastewater from beverage industry were carried out in the laboratory. The qualities and cost of the final product were compared with city potable water. The study reveals that the reuse of bottle-washing wastewater after ultrafiltration and reverse osmosis membrane filtration treatment systems not only reduce the consumption of potable water but also helps to conserve energy. The payback period of ultrafiltration and reverse osmosis treatment systems are found to be about 2 and 5 years, respectively.

Environmental management in an international consumer goods company

Abstract: Many management processes and tools can provide companies with information to support their environmental decision making. Risk assessment, environmental auditing, life cycle assessment and environmental reporting are but a few examples. Each of these has typically evolved independently as the need for it has arisen. Today, however, this abundance of tools can lead to confusion: What is the exact objective of each tool? How do they differ? Are some ‘better’ than others? Should they be used in parallel, sequentially or in place of each other? More importantly, how do they fit together into a coherent environmental management framework that will ensure sound environmental and economic decision making in a company? This paper seeks to answer these questions. It describes the overall environmental framework that has been developed internally within Procter & Gamble and which allows the company to make coherent economically and environmentally sound decisions, in both the short- and long-term.

Cost-benefit analysis of the municipal solid waste collection system in Yangon, Myanmar

Abstract: A study was conducted on the municipal solid waste management system in the city of Yangon, Myanmar (formerly, Rangoon, Burma.) Special emphasis was given to the commercial and residential areas. The city now produces 1510 tons/day of municipal solid waste (MSW) from which Yangon municipal authority collects 484 tons/day, with a collection efficiency of 32%, the uncollected remainder resulting in acute problems, health hazards, and environmental degradation. Major weaknesses are identified in the MSJW collection system for Yangon. The organizational structure is weak, collection methods are ineffective, vehicles are insufficient, and foreign exchange is limited to imported collection vehicles and spare parts from abroad. An attempt was made to find alternative systems appropriate to the present situations for collection improvement. An economic costing procedure was used to find the least—cost option, and comparison between the proposed and existing systems were studied on the basis of cost—benefit analysis. A proposal of a more efficient collection system is forwarded. The proposed system is estimated to reduce up to 42% of the present total expenditure used on the collection services by the Cleaning Department under the Yangon City Development Committee. In the proposed system, a labor-intensive waste collection system, suitable for a developing country, is introduced. More vehicular force, with the container-hoist handling system, is recommended to increase collection efficiency and to promote labor and vehicular productivity.

Optimal design of municipal solid waste recycling systems

Abstract: This work develops an integer linear programming methodology for the optimal design of municipal solid waste recycling systems. The model considers all costs, in present values, concerning recycling of products, disposal of solid wastes, as well as closure and monitoring of the old landfill, and opening of a new one. Economic benefits include revenues coming from the selling of the recycled goods, and those originating from extending the life of the landfill. The model was applied to the city of Chania for the recycling of paper, glass, aluminum and organic residues (putrescible matter). Recycling brings about a significant reduction in the annual cost of solid waste management, as well as an increase in the life of the landfill. The optimal recycling scheme depends on the characteristics of the areas which the city has been devided into. For the residential and tourist areas the largest possible quantities of aluminum, paper and putrescible matter should be recycled, while for the commercial area only aluminum and paper. The model also allows the investigation of less optimistic scenaria, such as future reduction of recovered materials prices or limited absorption of these materials in the market.

Valorization of fly ash in the cold stabilization of clay materials

Abstract: It is possible to valorize fly ash by using it in clay materials cold stablized by means of a binder (cement or lime) and extrusion shaped. Fly ash is an industrial waste. Its utilisation in manufacturing processes as described here allows, on the one hand, to obtain low cost building materials, like bricks or blocks and, on the other hand, to solve some serious pollution problems of waste elimination. The mechanical properties, water resistance, dimensional stability and accelerated ageing of products containing ash are significantly improved when compared to those of clay-binder mixes. This may be explained as follows: • • a better hydration of the binder of mixes containing ash, • • the filler effect of passive ash grains, • • the pozzolanic effect, a property of silico-aluminous fly ash which is able to fix lime, with water, thus producing hydrated compounds.

Local government household battery collection programs: Costs and benefits☆

Abstract: Nearly three billion dry-cell household batteries are discarded in the municipal waste stream annually. While the mercury content of newer batteries has been reduced, older batteries and the accumulated total of mercury and cadmium, as well as other metals in the newer batteries still constitute a potential health risk. Many communities have initiated collection programs to remove this source of contamination from the municipal waste stream, but most have not. Fourteen states have enacted legislation regulating the disposal of household batteries, while nine states require the collection of rechargeable batteries. This article describes the potential health risks associated with continued disposal and incineration of household dry-cell batteries, reviews a sampling of existing municipal collection programs in US communities, and examines the costs and benefits and program options of collection programs.

The development of material recovery facilities in the United States: status and cost structure analysis

Abstract: The rapidly increasing generation of solid waste, continuous landfill closings, and public reluctance concerning the siting and building of more incinerators have motivated various recycling programs at both the national and local levels in many countries. Material recycling has currently become an essential feature in the integrated solid waste management system. Although Taiwan has set a bold agenda in solid waste recycling for the past 5 years, the inherent uncertainties regarding the economic feasibility and the lack of a comprehensive evaluation of the privatization of centralized material recovery facilities (MRFs) are still impediments in decision making for waste management. Therefore, an understanding of the fast track of MRFs development in the United States, and of the related construction and operating cost structures of these facilities, becomes helpful in creating a valuable solid waste management strategy. The results of this analysis can also be applied to future investment forecasting and policy making in many countries.