Keith Weitz

The impact of municipal solid waste management on greenhouse gas emissions in the United States.

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.

Case studies examining LCA streamlining techniques

Pressure is mounting for more streamlined Life Cycle Assessment (LCA) methods that allow for evaluations that are quick and simple, but accurate. As part of an overall research effort to develop and demonstrate streamlined LCA, the U.S. Environmental Protection Agency has funded studies to examine the validity of various streamlining methods. Ten streamlining methods were identified and tested for accuracy against full LCAs. The objective of this effort was to identify streamlining methods that produced conclusions similar to those reached through full LCAs. Results of this evaluation showed that many streamlining methods give incorrect conclusions at least half of the time as compared to full LCAs. Streamlining will always incur the risk of obtaining results that are different than a full LCA. However, if some level of risk is acceptable, there are some general rules that can be used to select a streamlining method that will reduce the risk of serious error.

Life Cycle Management of Municipal Solid Waste

Life-cycle assessment concepts and methods are currently being applied to evaluate integrated municipal solid waste management strategies throughout the world. The Research Triangle Institute and the U.S. Environmental Protection Agency are working to develop a computer-based decision support tool to evaluate integrated municipal solid waste management strategies in the United States. The waste management unit processes included in this tool are waste collection, transfer stations, recovery, compost, combustion, and landfill. Additional unit processes included are electrical energy production, transportation, and remanufacturing. The process models include methodologies for environmental and cost analysis. The environmental methodology calculates life cycle inventory type data for the different unit processes. The cost methodology calculates annualized construction and equipment capital costs and operating costs per ton processed at the facility. The resulting environmental and cost parameters are allocated to individual components of the waste stream by process specific allocation methodologies. All of this information is implemented into the decision support tool to provide a life-cycle management evaluation of integrated municipal solid waste management strategies.

Considerations and a report on the state of practice

Life Cycle Assessment (LCA) is an analytical tool to evaluate the environmental consequences of products and their production systems. A great deal of effort has been devoted to developing methodology and guidelines for conducting LCAs. However, many companies are devising shortcuts to the full LCA model. We conducted discussions with twenty-one LCA practitioners and researchers to investigate techniques being used to simplify or streamline the LCA methodology. We found a wide variety of approaches being used to accomplish the streamlining from convening informal in-house expert panels to identify life cycle issues to developing and applying formal, structured tools.

Life Cycle Assessment of End‐Of‐Life Management Options for Construction and Demolition Debris

A life cycle assessment (LCA) of various end‐of‐life management options for construction and demolition (C&D) debris was conducted using the U.S. Environmental Protection Agencys Municipal Solid Waste Decision Support Tool. A comparative LCA evaluated seven different management scenarios using the annual production of C&D debris in New Hampshire as the functional unit. Each scenario encompassed C&D debris transport, processing, separation, and recycling, as well as varying end‐of‐life management options for the C&D debris (e.g., combustion to generate electricity versus landfilling for the wood debris stream and recycling versus landfilling for the nonwood debris stream) and different bases for the electricity generation offsets (e.g., the northeastern U.S. power grid versus coal‐fired power generation). A sensitivity analysis was also conducted by varying the energy content of the C&D wood debris and by examining the impact of basing the energy offsets on electricity generated from various fossil fuels. The results include impacts for greenhouse gas (GHG) emissions, criteria air pollutants, ancillary solid waste production, and organic and inorganic constituents in water emissions. Scenarios with nonwood C&D debris recycling coupled with combustion of C&D wood debris to generate electricity had lower impacts than other scenarios. The nonwood C&D debris recycling scenarios where C&D wood debris was landfilled resulted in less overall impact than the scenarios where all C&D debris was landfilled. The lowest impact scenario included nonwood C&D debris recycling with local combustion of the C&D wood debris to generate electricity, providing a net gain in energy production of more than 7 trillion British thermal units (BTU) per year and a 130,000 tons per year reduction in GHG emissions. The sensitivity analysis revealed that for energy consumption, the model is sensitive to the energy content of the C&D wood debris but insensitive to the basis for the energy offset, and the opposite is true for GHG emissions.

Applying Industrial Ecology to Industrial Parks: An Economic and Environmental Analysis:

Industrial ecology (IE) is an emerging framework for characterizing relationships between businesses and analyzing their economic and environmental performance. By applying the principles of IE, members of eco-industrial parks (EIPs) pursue improvements in their economic efficiency while reducing the environmental burden of their production activities. This article discusses the potential of EIPs for improving economic and environmental performance and presents a methodology for developing and analyzing potential EIPs. The methodology is applied to a prototype EIP based on companies in Brownsville, Texas, and Matamoros, Mexico. The potential for improved economic performance can be an important draw for public and private developers trying to populate an EIF, and this study shows that these benefits are attainable. We conclude with a discussion of the conditions necessary for successful EIPs in the United States.

Life-Cycle Assessment of Construction and Demolition Derived Biomass/Wood Waste Management

A life cycle assessment (LCA) of various end‐of‐life management options for construction and demolition (C&D) debris was conducted using the U.S. Environmental Protection Agencys Municipal Solid Waste Decision Support Tool. A comparative LCA evaluated seven different management scenarios using the annual production of C&D debris in New Hampshire as the functional unit. Each scenario encompassed C&D debris transport, processing, separation, and recycling, as well as varying end‐of‐life management options for the C&D debris (e.g., combustion to generate electricity versus landfilling for the wood debris stream and recycling versus landfilling for the nonwood debris stream) and different bases for the electricity generation offsets (e.g., the northeastern U.S. power grid versus coal‐fired power generation). A sensitivity analysis was also conducted by varying the energy content of the C&D wood debris and by examining the impact of basing the energy offsets on electricity generated from various fossil fuels. The results include impacts for greenhouse gas (GHG) emissions, criteria air pollutants, ancillary solid waste production, and organic and inorganic constituents in water emissions. Scenarios with nonwood C&D debris recycling coupled with combustion of C&D wood debris to generate electricity had lower impacts than other scenarios. The nonwood C&D debris recycling scenarios where C&D wood debris was landfilled resulted in less overall impact than the scenarios where all C&D debris was landfilled. The lowest impact scenario included nonwood C&D debris recycling with local combustion of the C&D wood debris to generate electricity, providing a net gain in energy production of more than 7 trillion British thermal units (BTU) per year and a 130,000 tons per year reduction in GHG emissions. The sensitivity analysis revealed that for energy consumption, the model is sensitive to the energy content of the C&D wood debris but insensitive to the basis for the energy offset, and the opposite is true for GHG emissions.

Life-Cycle Assessment of Waste Management Greenhouse Gas Emissions Using Municipal Waste Combustor Data

This paper compares life-cycle greenhouse gas (GHG) emissions from two municipal solid waste (MSW) management options, municipal waste combustion, and landfilling, using a U.S. EPA life-cycle assessment (LCA) model, the MSW Decision Support Tool. Unlike previously reported LCAs, key combustion model inputs—total MSW carbon content and its biogenic/fossil split—are determined not from MSW composition studies, but from measurements taken at operating municipal waste combustors (MWCs). MWC measurement data show U.S. MSW carbon content averages of 30% with a biogenic/fossil split of 66%/34%. The LCA also considers a range of landfilling scenarios which account not only for alternative landfill gas (LFG) management techniques, but also for the variability of landfill methane generation and capture. The LCA found that for the range of inputs and scenarios considered, municipal waste combustion outperforms landfilling in terms of GHG emissions, regardless of the LFG management technique.

Analysis of the “Zero Waste” Management Option Using the Municipal Solid Waste Decision Support Tool

The U.S. Environmental Protection Agency’s Office of Research and Development (US EPA ORD) has developed a “Municipal Solid Waste Decision Support Tool”, or MSW-DST, for local government solid waste managers to use for the life cycle evaluation of integrated solid waste management options. The MSW-DST was developed over a five year period (1994–1999) with the assistance of numerous outside contractors and organizations, including the Research Triangle Institute, North Carolina State University, the University of Wisconsin-Madison, the Environmental Research and Education Foundation, Franklin Associates and Roy F. Weston. The MSW-DST can be used to quantify and evaluate the following impacts for each integrated solid waste management alternative: • Energy consumption, • Air emissions, • Water pollutant discharges, • Solid Waste disposal impacts. Recently, the MSW-DST was used by the U.S. EPA to identify solid waste management strategies that would help to meet the goal of the EPA’s “Resource Conservation Challenge.” In this effort, ten solid waste management strategies were evaluated for a hypothetical, medium-sized U.S. community, with a population of 750,000 and a waste generation rate of approximately 3.5 pounds per person per day. (Table 1). The assumed waste composition was based on national averages. A peer-reviewed paper on this research was published in 2008 by the American Society of Mechanical Engineers (ASME).© 2009 ASME

Using a Carbon Balance to Estimate Greenhouse Gas Emissions and Mitigation From Municipal Solid Waste Management

Municipal solid waste (MSW) management is internationally recognized for its potential to be both a source and mitigation technology for greenhouse gas (GHG) emissions. Historically, GHG emission estimates have relied upon quantitative knowledge of various MSW components and their carbon contents, information normally presented in waste characterization studies. Aside from errors associated with such studies, existing data do not reflect changes over time or from location to location and are therefore limited in their utility for estimating GHG emissions and mitigation due to proposed projects. This paper presents an alternative approach to estimate GHG emissions and mitigation using the concept of a carbon balance, where key carbon quantities are determined from operational measurements at modern municipal waste combustors (MWCs).Copyright