Optimizing resource and energy recovery for municipal solid waste Management

Significant reductions of carbon emissions and air quality impacts can be achieved by optimizing municipal solid waste (MSW) as a resource. Materials and discards management were found to contribute ~40% of overall U.S. greenhouse gas (GHG) emissions as a result of materials extraction, transport, collection, processing, recycling, composting, combustion, and landfilling. Decisions affecting materials management today are generally either fiscally based or based on the presumption of favorable outcomes without an understanding of the environmental tradeoffs. However, there is a growing demand to better understand and quantify the net environmental and energy trade-offs in setting waste management goals and priorities at a state and local level. Please click Additional Files below to see the full abstract

Weitz

ABSTRACT Technological advancements, environmental regulations, and emphasis on resource conservation and recovery have greatly reduced the environmental impacts of municipal solid waste (MSW) management, including emissions of greenhouse gases (GHGs). This study was conducted using a life-cycle methodology to track changes in GHG emissions during the past 25 years from the management of MSW in the United States. For the baseline year of 1974, MSW management consisted of limited recycling, combustion without energy recovery, and landfilling without gas collection or control. This was compared with data for 1980, 1990, and 1997, accounting for changes in MSW quantity, composition, management practices, and technology. Over time, the United States has moved toward increased recycling, composting, combustion (with energy recovery) and landfilling with gas recovery, control, and utilization. These changes were accounted for with historical data on MSW composition, quantities, management practices, and technological changes. Included in the analysis were the benefits of materials recycling and energy recovery to the extent that these displace virgin raw materials and fossil fuel electricity production, respectively. Carbon sinks associated with MSW management also were addressed. The results indicate that the MSW management actions taken by U.S. communities have significantly reduced potential GHG emissions despite an almost 2-fold increase in waste generation. GHG emissions from MSW management were estimated to be 36 million metric tons carbon equivalents (MMTCE) in 1974 and 8 MMTCE in 1997. If MSW were being managed today as it was in 1974, GHG emissions would be ~60 MMTCE. INTRODUCTION Solid waste management deals with the way resources are used as well as with end-of-life deposition of materials in the waste stream. 1 Often complex decisions are made regarding ways to collect, recycle, transport, and dispose of municipal solid waste (MSW) that affect cost and environmental releases. Prior to 1970, sanitary landfills were very rare. Wastes were "dumped" and organic materials in the dumps were burned to reduce volume. Waste incinerators with no pollution controls were common. 1 Today, solid waste management involves technologies that are more energy efficient and protective of human health and the environment. These technological changes and improvements are the result of decisions made by local communities and can impact residents directly. Selection of collection, transportation, recycling, treatment, and disposal systems can determine the number of recycling bins needed, the day people must place their garbage at the curb, the truck routes through residential streets, and the cost of waste services to households. Thus, MSW management can be a significant issue for municipalities. IMPLICATIONS Technology advancements and the movement toward integrated strategies for MSW management have resulted in reduced GHG emissions. GHG emissions from MSW management would be 52 MMTCE higher today if old strategies and technologies were still in use. Integrated strategies involving recycling, composting, waste-to-energy combustion, and landfills with gas collection and energy recovery play a significant role in reducing GHG emissions by recovering materials and energy from the MSW stream

Application of the US decision support tool for materials and waste management

The US Environmental Protection Agency (US EPA) launched the Resource Conservation Challenge (RCC) in 2002 to help reduce waste and move towards more sustainable resource consumption. The objective of the RCC is to help communities, industries, and the public think in terms of materials management rather than waste disposal. Reducing cost, finding more efficient and effective strategies to manage municipal waste, and thinking in terms of materials management requires a holistic approach that considers life-cycle environmental tradeoffs. The US EPA’s National Risk Management Research Laboratory has led the development of a municipal solid waste decision support tool (MSW-DST). The computer software can be used to calculate life-cycle environmental tradeoffs and full costs of different waste management or materials recovery programs. The environmental methodology is based on the use of life-cycle assessment and the cost methodology is based on the use of full-cost accounting. Life-cycle inventory (LCI) environmental impacts and costs are calculated from the point of collection, handling, transport, treatment, and disposal. For any materials that are recovered for recycling, offsets are calculated to reflect potential emissions savings from use of virgin materials. The use of the MSW-DST provides a standardized format and consistent basis to compare alternatives. This paper provides an illustration of how the MSW-DST can be used by evaluating ten management strategies for a hypothetical medium-sized community to compare the life-cycle environmental and cost tradeoffs. The LCI results from the MSW-DST are then used as inputs into another US EPA tool, the Tool for the reduction and assessment of chemical and other environmental impacts, to convert the LCI results into impact indicators. The goal of this paper is to demonstrate how the MSW-DST can be used to identify and balance multiple criteria (costs and environmental impacts) when evaluating options for materials and waste management. This type of approach is needed in identifying strategies that lead to reduced waste and more sustainable resource consumption. This helps to meet the goals established in the US EPA’s Resource Conservation Challenge

Environmental Sustainability of Municipal Waste Thermochemical Conversion Technologies

Both in USA and EU waste management is evolving towards sustainable materials management, intended as a systemic approach to using and reusing materials more productively over their entire life cycles. A similar Waste Management Hierarchy prioritizes and ranks the various management strategies from most to least environmentally preferred. The hierarchy places emphasis on reducing, reusing, and recycling as key to sustainable materials management. However, for non-recyclable materials, waste-to-energy represents the most preferred option, to save important resources (such as landfill volumes and non-renewable energy), to reduce the contribution to global warming, and to provide an essential contribution to fulfil the goals of a really sustainable waste management. According to EU strategy, the waste disposal to landfills must be considered as the last possibility and limited to pre-treated wastes (not biologically active or not containing easily leachable hazardous substances), confirming that thermochemical treatments of non-recyclable or potentially hazardous solid waste are still necessary. Thus, recent data (Cewep, 2019 ) showed that in Europe, by 2035, 142 million ton of residual waste treatment capacity will be required to comply with the targets imposed by the EU on municipal waste, even if the recycling targets will be achieved for commercial and industrial waste. Current Waste-to-Energy capacity in Europe is 90 million ton and the capacity for co-incineration is around 11 million ton. So still 41 million ton have to find appropriate thermochemical treatments aimed at energy recovery. A conventional waste-to-energy (WtE) facility accepts unprocessed municipal waste which is burned in a large combustion unit to generate electricity or utilized in a combined heat and power system. Other thermochemical waste conversion technologies, such as gasification and pyrolysis, are less established and differ from conventional WtE in that they do not directly combust municipal waste. Instead they convert municipal waste feedstock via partial-oxygen or oxygen-absent thermochemical process. The resulting gases can be combusted to produce electricity or further processed into a liquid fuel or chemical commodity product. In assessing conversion technologies, it is important to understand which municipal waste feedstock(s) can be managed by the technology, what pre-sorting or processing is required, whether minimum quantities of municipal waste must be provided, net energy balance, emissions data, environmental permit requirements, and the types and quantities of solid and hazardous residuals requiring management or disposal. With this in mind, the aim of this work is to understand the environmental and economic sustainability of some thermochemical conversion technologies applied to municipal waste – eventually after appropriate pretreatments – in comparison with conventional WtE. While for conventional WtE facilities decades of environmental and economic performance data are available, less experience is available for gasification and pyrolysis technologies applied to waste and in particular to municipal waste/ municipal derived waste. For this reason, after a review of the available plants in EU and USA based on thermochemical conversion technologies different from conventional WtE, a comparison will be performed by environmental point of view, using Life Cycle Assessment, and economic point of view. Cewep, 2019. Achieved Circular Economy Targets Will Leave 40 Million Tonnes Residual Waste Gap in 2035. Available at http://www.cewep.eu/cewep-capacity-calculations

CCA-Treated wood disposed in landfills and life-cycle trade-offs with waste-to-energy and MSW landfill disposal

Chromated copper arsenate (CCA)-treated wood is a preservative treated wood construction product that grew in use in the 1970s for both residential and industrial applications. Although some countries have banned the use of the product for some applications, others have not, and the product continues to enter the waste stream from construction, demolition and remodeling projects. CCA-treated wood as a solid waste is managed in various ways throughout the world. In the US, CCA-treated wood is disposed primarily within landfills; however some of the wood is combusted in waste-to-energy (WTE) facilities. In other countries, the predominant disposal option for wood, sometimes including CCA-treated wood, is combustion for the production of energy. This paper presents an estimate of the quantity of CCA-treated wood entering the disposal stream in the US, as well as an examination of the trade-offs between landfilling and WTE combustion of CCA-treated wood through a life-cycle assessment and decision support tool (MSW DST). Based upon production statistics, the estimated life span and the phaseout of CCA-treated wood, recent disposal projections estimate the peak US disposal rate to occur in 2008, at 9.7 million m3. CCA-treated wood, when disposed with construction and demolition (C&D) debris and municipal solid waste (MSW), has been found to increase arsenic and chromium concentrations in leachate. For this reason, and because MSW landfills are lined, MSW landfills have been recommended as a preferred disposal option over unlined C&D debris landfills. Between landfilling and WTE for the same mass of CCA-treated wood, WTE is more expensive (nearly twice the cost), but when operated in accordance with US Environmental Protection Agency (US EPA) regulations, it produces energy and does not emit fossil carbon emissions. If the wood is managed via WTE, less landfill area is required, which could be an influential trade-off in some countries. Although metals are concentrated in the ash in the WTE scenario, the MSW landfill scenario releases a greater amount of arsenic from leachate in a more dilute form. The WTE scenario releases more chromium from the ash on an annual basis. The WTE facility and subsequent ash disposal greatly concentrates the chromium, often oxidizing it to the more toxic and mobile Cr(VI) form. Elevated arsenic and chromium concentrations in the ash leachate may increase leachate management costs