Americans generated 254 million tons of municipal solid waste in 2007. We also generated another 250 million tons of other non-hazardous solid waste, such as construction and demolition debris. Private and public sector operations collect and process these materials for recycling, composting or disposal in landfills and waste-to-energy facilities. This provides an essential public health and environmental service.
Yet, even as we seek to do well, we also leave a carbon footprint on the environment. This footprint includes a small amount of greenhouse gases (GHG). According to EPA, total U.S. greenhouse gas emissions were 7150.1 teragrams of carbon dioxide equivalent (TgCO2e) in 2007. Of this, 160.5 TgCO2e, or about 2.25 percent, were produced by the solid waste and recycling industry.
Carbon dioxide comprises 80 percent of all GHG emitted in the United States by human activities. Most of it is created by burning fossil fuels. Our industry produces less than one half of 1 percent of carbon dioxide emissions. These come from waste-to-energy facilities, collection trucks and processing facilities.
At 8 percent, methane is the next most emitted greenhouse gas. “Enteric fermentation,” the digestive process used by ruminant animals such as cows, is the leading source of methane. Landfills are second, with one quarter of the methane emissions. These account for four fifths of our industry's total GHG emissions. Composting produces a very small amount of methane. Along with waste-to-energy facilities, they also produce a very small amount of nitrous oxide, another greenhouse gas.
Our industry has a good track record in reducing emissions and creating environmental benefits. Current methane emissions would have been almost twice as high if landfill gas-to-energy projects did not recover methane as an energy source or sites did not flare off recovered gas. The Nobel Prize-winning Intergovernmental Panel on Climate Change (IPCC) states that landfill gas recovery directly reduces GHG emissions. Oxidation also reduces landfill methane emissions.
Both EPA and the IPCC credit landfills for “sequestering” (storing) carbon due to incomplete degradation of organic materials such as wood products and yard waste. The IPCC estimates that half of the “organic” fraction in a landfill does not degrade because lignin is “recalcitrant” and the cellulosic portion degrades slowly. And, waste-to-energy facilities produce energy that offsets the production of electricity from coal or oil-fired power plants.
Recycling and composting offer another climate change success story. We recycled or composted slightly more than one third of our wastes in 2007, leading to a 2.5 percent reduction in total U.S. GHG emissions. That reduction outpaces the GHG emissions produced by our collection and disposal activities! Recycling paper also increases carbon storage in trees by easing the pressure to cut down our forests.
In fact, researchers determined that between 1974 and 1997, solid waste and recycling GHG emissions declined by 78 percent even while waste generation increased by 70 percent. These gains were a result of increased recycling, composting and waste-to-energy along with better regulation of our landfills.
As Congress debates how to combat climate change, we will be called upon to produce even fewer of these gases. We need to find ways to use less diesel fuel, to recycle and compost more, and to recover more energy from our trash. A tall order perhaps, but our industry can get the job done!
Chaz Miller is state programs director for the Environmental Industry Associations, Washington, D.C.
Opinions in this column do not necessarily reflect those of the National Solid Wastes Management Association or the Environmental Industry Associations. E-mail the author at [email protected].