Climate change is caused by many activities, including waste disposal. The U.S. Environmental Protection Agency (EPA) issued an important life-cycle assessment of greenhouse gases (GHG) and solid waste management. The document, “Solid Waste Management and Greenhouse Gases — A Life-Cycle Assessment of Emissions and Sinks,” is included in the third edition of EPA’s “Greenhouse Gas Emissions from Management of Selected Materials in Municipal Solid Waste.”
In examining how municipal solid-waste management and climate change are related, the document provides a useful assessment of selected waste materials’ GHG implications at each point in the material’s life cycle.
Solid waste and emissions
Municipal solid waste (MSW) has much to do with GHG emissions. The materials in MSW represent what’s left after many steps have been taken, including the extraction and processing of raw materials, the manufacture of products, the distribution of products to market, the use of these products by consumers, and the management of these materials as waste, as EPA notes in the report.
The waste management phase has particular implications for waste that is buried. Bacteria decomposes much of the organic component of solid waste and, in so doing, produces equal parts carbon dioxide and methane gas. Approximately 18% of the buried carbon remains in the landfill, and the balance is converted into landfill gas consisting of carbon dioxide and methane, according to EPA estimates.
To measure the GHG impacts of MSW, EPA selected 21 single-material waste materials, organized into categories of metal, glass, plastic, paper, wood, food discards, yard trimmings, clay bricks, concrete, fly ash, and tires. These materials represent more than 65% by weight of MSW, according to EPA. EPA then developed a life-cycle inventory for each of the selected materials. The life-cycle inventory is streamlined because it examines GHG emissions only and isn’t a full analysis of all emissions from municipal solid waste management options. A more detailed analysis of EPA’s methodology is described in the report.
Reducing GHG emissions
Based on EPA’s analysis, source reduction represents an opportunity to significantly reduce GHG emissions. For many materials, the reduction in energy-related carbon dioxide emissions from the raw material acquisition and manufacturing process, and the absence of emissions from waste management, combine to reduce GHG emissions more so than other options.
For most materials, EPA believes that recycling represents the second best opportunity to reduce GHG emissions. For these materials, recycling reduces energy-related carbon dioxide emissions in the manufacturing process and avoids emissions from waste management.
EPA also believes that composting is a management option for food discards and yard trimmings. The net GHG emissions from composting are lower than those from landfilling of food discards, and higher than those from landfilling of yard trimmings.
In general, given the uncertainty in EPA’s analysis, the emission factors on which EPA’s analysis relies for composting or combusting these materials are similar.
Finally, EPA’s analysis concludes that the net GHG emissions from combustion of mixed MSW are lower than landfilling mixed MSW. According to the report, “[c]ombustors and landfills manage a mixed waste stream; therefore, net emissions are determined more by technology factors (e.g., the efficiency of landfill gas collection systems and combustion energy conversion) than by material specificity. Material-specific emissions for landfills and combustors provide a basis for comparing these options with source reduction, recycling, and composting.”
Regulatory consideration ahead
The global focus on climate change isn’t about to abate any time soon. EPA’s analysis of the GHG implications of MSW is a useful reminder that virtually every aspect of our lives has GHG implications and that waste management is no exception. The analysis also is useful in that, as climate change issues become more acute, waste management practices could be the subject of enhanced regulatory consideration. The Supreme Court ruled in Massachusetts versus Environmental Protection Agency that EPA is authorized to regulate GHG under existing law, and such gases from landfills are fair game.
Lynn Bergeson, regulatory editor, is managing director of Bergeson & Campbell, P.C., a Washington, D.C.-based law firm that concentrates on chemical industry issues. Contact her at email@example.com. The views expressed herein are solely those of the author. This column is not intended to provide, nor should be construed as, legal advice.