SciCombinator

Discover the most talked about and latest scientific content & concepts.

Journal: Waste management (New York, N.Y.)

27

A sensor unit was placed online in the particle stream produced by an eddy current separator (ECS) to investigate its functionality in non-ferrous metals recovery. The targeted feed was the 1-6mm size fraction bottom ash from a municipal waste incinerator. The sensor unit was attached to the ECS splitter, where it counted in real-time metal and mineral particles and accurately measured the grade of the stream in the metals product. Influence of segregation (e.g. due to particle size or density) on the metals concentrate were detected and studied using the sensor data collected at different splitter distances. Tests were performed in the laboratory and in a bottom ash processing plant with two different types of ECS and two sources of bottom ash with different moisture content. The measured metal grades matched the manual analyses with errors 0%, 1.5% and 3.1% for moist, dry and very wet feed, respectively. For very wet feed the ECS metals recovery dropped, which was observed from the strongly reduced particle counts and the large changes in cumulative particle properties. The measured sample proved representative for the whole metals concentrate if it is collected at a representative position within the metals particle trajectory fan produced by the ECS. ECS-performance proved sensitively dependent on splitter distance, since a 10mm shift may result in 10% change in metal recovery and 18% change in grade. The main functionalities of the sensor unit are determined as online quality control and facilitation of automatic control over the ECS splitter distance. These functionalities translate in significant improvements in ECS metals recovery which in turn is linked to economic benefits, increased recycling rate of scrap metals and a further reduction of the ecological drawbacks of incinerator bottom ash.

Concepts: Waste management, Chemical engineering, Bottom ash, Recycling, Incinerator bottom ash, Eddy current, Iron, Incineration

27

The consumption of bottled water in Italy began in the 1970s. Since then, this usage has grown considerably, also as a result of changes in habits. The environmental impact as a result of the water production chain is very significant; it would be considered, for example, the use of plastic bottles, the consumption of oil in the production of the bottles, the emission of air from the vehicles that transport the bottles, non-recycled plastic packaging, etc. In this study, considering the comparison between two situations, use of bottled water and use of water kiosk (WK), an environmental and economic impact evaluation has been done. The study considered the production of a WK in a town with 9000 inhabitants, which supplies controlled, still and sparkling water, with an organoleptic quality higher than tap water coming from the aqueduct. In particular, taking into consideration the environmental aspects, specific attention was paid both to CO2 emissions and PET bottle waste reduction. The economic impact evaluation was carried out from the consumer’s point of view. In order to provide a supply service that was economically sustainable, a calculation was done with the aim of determining a specific fee for the supplied water. Moreover, a comparison has been made between quality parameters achieved with the analysis of water from aqueducts with the limits established in the Italian legislation and the parameters of several Italian water brands. The study has the aim at considering the opportunity to follow a different people’s habits, closer to the concept of sustainability, reducing the environmental charge related to the realization, transport and consumption of plastic water bottles without significant reduction of the quality of the service and with convenient and interesting economic implications. In fact the results of the study show that the alternative of WKs is more efficient in economic and environmental terms respect to the use of bottled water.

Concepts: Plastic bottle, Recycling, Bottles, Recyclable materials, Bottled water, Aqueduct, Carbon dioxide, Bottle

27

Most of Israel’s waste is disposed in landfills, threatening scarce land resources and posing environmental and health risks. The aim of this study is to estimate the expected costs of transferring municipalities to solid waste source separation in Israel, aimed at reducing the amount of waste directed to landfills and increasing the efficiency and amount of recycled waste. Information on the expected costs of operating a solid waste source separation system was gathered from 47 municipalities and compiled onto a database, taking into consideration various factors such as costs of equipment, construction adjustments and waste collection and disposal. This database may serve as a model for estimating the costs of entering the waste source separation system for any municipality in Israel, while taking into consideration its specific characteristics, such as size and region. The model was used in Israel for determining municipalities' eligibility to receive a governmental grant for entering an accelerated process of solid waste source separation. This study displays a user-friendly and simple operational tool for assessing municipalities' costs of entering a process of waste source separation, providing policy makers a powerful tool for diverting funds effectively in promoting solid waste source separation.

Concepts: Das Model, Municipality, Policy, Waste picker, Estimator, Recycling, Waste, Waste management

27

This paper surveys decision support models that are commonly used in the solid waste management area. Most models are mainly developed within three decision support frameworks, which are the life-cycle assessment, the cost-benefit analysis and the multi-criteria decision-making. These frameworks are reviewed and their strengths and weaknesses as well as their critical issues are analyzed, while their possible combinations and extensions are also discussed. Furthermore, the paper presents how cooperative and non-cooperative game-theoretic approaches can be used for the purpose of modeling and analyzing decision-making in situations with multiple stakeholders. Specifically, since a waste management model is sustainable when considering not only environmental and economic but also social aspects, the waste management bargaining game is introduced as a specific decision support framework in which future models can be developed.

Concepts: Decision support system, Model, Recycling, Critical thinking, Waste management, Waste, Decision theory

27

Municipal solid waste management is a multidisciplinary activity that includes generation, source separation, storage, collection, transfer and transport, processing and recovery, and, last but not least, disposal. The optimization of waste collection, through source separation, is compulsory where a landfill based management must be overcome. In this paper, a few aspects related to the implementation of a Web-GIS based system are analyzed. This approach is critically analyzed referring to the experience of two Italian case studies and two additional extra-European case studies. The first case is one of the best examples of selective collection optimization in Italy. The obtained efficiency is very high: 80% of waste is source separated for recycling purposes. In the second reference case, the local administration is going to be faced with the optimization of waste collection through Web-GIS oriented technologies for the first time. The starting scenario is far from an optimized management of municipal solid waste. The last two case studies concern pilot experiences in China and Malaysia. Each step of the Web-GIS oriented strategy is comparatively discussed referring to typical scenarios of developed and transient economies. The main result is that transient economies are ready to move toward Web oriented tools for MSW management, but this opportunity is not yet well exploited in the sector.

Concepts: Waste-to-energy, Waste collection, Recycling, Waste, Waste management

27

The objective of this study is to discuss the role of networks formed of waste-picker cooperatives in ameliorating problems of final disposal of solid waste in the city of Rio de Janeiro, since the city’s main landfill will soon have to close because of exhausted capacity. However, it is estimated that in the city of Rio de Janeiro there are around five thousand waste-pickers working in poor conditions, with lack of physical infrastructure and training, but contributing significantly by diverting solid waste from landfills. According to the Sustainable Development Indicators (IBGE, 2010a,b) in Brazil, recycling rates hover between 45% and 55%. In the municipality of Rio de Janeiro, only 1% of the waste produced is collected selectively by the government (COMLURB, 2010), demonstrating that recycling is mainly performed by waste-pickers. Furthermore, since the recycling market is an oligopsony that requires economies of scale to negotiate directly with industries, the idea of working in networks of cooperatives meets the demands for joint marketing of recyclable materials. Thus, this work presents a method for creating and structuring a network of recycling cooperatives, with prior training for working in networks, so that the expected synergies and joint efforts can lead to concrete results. We intend to demonstrate that it is first essential to strengthen the waste-pickers' cooperatives in terms of infrastructure, governance and training so that solid waste management can be environmentally, socially and economically sustainable in the city of Rio de Janeiro.

Concepts: Incineration, Waste hierarchy, Waste picker, Sustainability, Landfill, Waste, Waste management, Recycling

27

Volatile sulfur compounds (VSCs) are the main source for malodor from composting plants. In this study, the VSCs generated from composting of 15-80mm municipal solid waste (T0), kitchen waste (T1) and kitchen waste mixed dry cornstalks (T2) were measured in 60L reactors with forced aeration for a period of 30days. The VSCs detected in all treatments were hydrogen sulfide (H(2)S), methyl mercaptan (MM), dimethyl sulfide (DMS), carbon bisulfide (CS(2)) and dimethyl disulfide (DMDS). Over 90% of the VSCs emissions occurred during the first 15days, and reached their peak values at days 4-7. The emission profiles of five VSCs species were significantly correlated with internal materials temperature and outlet O(2) concentration (p<0.05). Total emissions of the VSCs were 216.1, 379.3 and 126.0mgkg(-1) (dry matter) for T0, T1 and T2, respectively. Among the five VSCs, H(2)S was the most abundant compound with 39.0-43.0% of total VSCs released. Composting of kitchen waste from separate collection posed a negative influence on the VSC and leachate production because of its high moisture content. An addition of dry cornstalks at a mixing ratio of 4:1 (wet weight) could significantly reduce the VSCs emissions and avoid leachate. Compared to pure kitchen waste, VSCs were reduced 66.8%.

Concepts: Carbon disulfide, Pyrite, Carbon dioxide, Carbon, Dimethyl sulfide, Sulfide, Hydrogen sulfide, Sulfur

26

Potato peel waste (PPW) as zero value byproduct generated from food processing plant contains a large quantity of starch, non-starch polysaccharide, lignin, protein, and lipid. PPW as one promising carbon source can be managed and utilized to value added bioproducts through a simple fermentation process using undefined mixed cultures inoculated from wastewater treatment plant sludge. A series of non-pH controlled batch fermentations under different conditions such as pretreatment process, enzymatic hydrolysis, temperature, and solids loading were studied. Lactic acid (LA) was the major product, followed by acetic acid (AA) and ethanol under fermentation conditions without the presence of added hydrolytic enzymes. The maximum yields of LA, AA, and ethanol were respectively, 0.22gg(-1), 0.06gg(-1), and 0.05gg(-1). The highest LA concentration of 14.7gL(-1) was obtained from a bioreactor with initial solids loading of 60gL(-1) at 35°C.

Concepts: Bacteria, Lactic acid, Protein, Metabolism, Adenosine triphosphate, Cellulose, Enzyme, Starch

25

Many methods have been reported and used to include recycling in life cycle assessments (LCAs). This paper evaluates six widely used methods: three substitution methods (i.e. substitution based on equal quality, a correction factor, and alternative material), allocation based on the number of recycling loops, the recycled-content method, and the equal-share method. These six methods were first compared, with an assumed hypothetical 100% recycling rate, for an aluminium can and a disposable polystyrene (PS) cup. The substitution and recycled-content method were next applied with actual rates for recycling, incineration and landfilling for both product systems in selected countries. The six methods differ in their approaches to credit recycling. The three substitution methods stimulate the recyclability of the product and assign credits for the obtained recycled material. The choice to either apply a correction factor, or to account for alternative substituted material has a considerable influence on the LCA results, and is debatable. Nevertheless, we prefer incorporating quality reduction of the recycled material by either a correction factor or an alternative substituted material over simply ignoring quality loss. The allocation-on-number-of-recycling-loops method focusses on the life expectancy of material itself, rather than on a specific separate product. The recycled-content method stimulates the use of recycled material, i.e. credits the use of recycled material in products and ignores the recyclability of the products. The equal-share method is a compromise between the substitution methods and the recycled-content method. The results for the aluminium can follow the underlying philosophies of the methods. The results for the PS cup are additionally influenced by the correction factor or credits for the alternative material accounting for the drop in PS quality, the waste treatment management (recycling rate, incineration rate, landfilling rate), and the source of avoided electricity in case of waste incineration. The results for the PS cup, which are less dominated by production of virgin material than aluminium can, furthermore depend on the environmental impact categories. This stresses the importance to consider other impact categories besides the most commonly used global warming impact. The multitude of available methods complicates the choice of an appropriate method for the LCA practitioner. New guidelines keep appearing and industries also suggest their own preferred method. Unambiguous ISO guidelines, particularly related to sensitivity analysis, would be a great step forward in making more robust LCAs.

Concepts: Waste, Waste treatment technology, Recyclable materials, Incineration, Life cycle assessment, Landfill, Waste management, Recycling

25

The aim of this study was to assess how extending the sorting instructions for plastic packaging would affect the exposure of workers working at materials recovery facility (MRF) to dust, endotoxins, fungi and bacteria, taking into consideration other factors that could have an influence on this exposure. Personal sampling was carried out at four MRFs during six sampling campaigns at each facility, both in sorting rooms and when the workers were involved in “mobile tasks” away from the rooms. The data was analysed by describing the extension of sorting instructions both using a qualitative variable (after vs before) and using data for the pots and trays recycling stream, including or excluding plastic film. Overall, before the extension of the sorting guidelines, the geometric mean of personal exposure levels in sorting rooms was 0.3mg/m(3) for dust, 27.7EU/m(3) for endotoxins, 13,000CFU/m(3) for fungi and 1800CFU/m(3) for bacteria. When workers were involved in mobile tasks away from the rooms, these averages were 0.5mg/m(3), 25.7EU/m(3), 28,000CFU/m(3) and 5100CFU/m(3) respectively.The application by households of instructions to include pots, trays and film with other recyclable plastic packaging led to an increase in exposure to endotoxins, fungi and bacteria at MRFs. For an increase of 0.5kg per inhabitant per year in the pots, trays and film recycling stream, exposure in sorting rooms rose by a factor of 1.4-2.2, depending on the biological agent. Exposure during mobile tasks increased by a factor of 3.0-3.6. The age of the waste amplified the effect of the extension of sorting instructions on exposure to fungi, bacteria and endotoxins. Factors that had a significant influence on the exposure of workers to dust and/or bioaerosols included the presence of paper, newspapers and magazines in the sorted waste, the order in which incoming waste was treated and the quality of the ventilation system in the sorting rooms. The levels of exposure observed in this study highlight the need to implement appropriate preventive measures against bioaerosols at MRFs for dry waste. There are grounds to justify these preventive measures, both inside sorting rooms and for the MRF as a whole, regardless of whether the decision to extend sorting instructions for household plastic waste is adopted.

Concepts: Waste treatment technology, Fungus, Arithmetic mean, Recycling, Materials recovery facility