Is converting landfill gas to energy the best option?
10.1021/es803266t
However, LFGTE projects can create a disincentive to diverting new discards and end up generating more uncontrolled greenhouse gases than composting does, says Peter Anderson, executive director of the Center for a Competitive Waste Industry, a SALLY BROWN
The waste industry and the U.S. EPA are urging landfill owners to capture methane and burn it to produce electricity as a winning way to cut greenhouse gas emissions. Experts say this may be a good way to make use of existing waste. But when it comes to new discards, critics say that the hype over landfill-gas-to-energy (LFGTE) projects may have perverse outcomes, such as discouraging the diversion of organic waste from landfills and actually increasing the amount of methane being released. The issue bubbled up on October 23 when the Environmental Defense Fund (EDF), an advocacy group, issued a notice of intent to sue EPA over the agency’s failure to update air pollution standards for landfills. In the notice, EDF suggests that EPA tighten current controls, which require the capture and flaring of landfill gas at sites with more than 2.5 million metric tons of waste, by bringing regulation to smaller landfills and defining LFGTE projects as the best demonstrated technology (BDT). After this redefinition, dump owners would have to keep emissions below levels that can be achieved with the BDT. Landfills are the second largest source of anthropogenic methane emissions in the U.S. The gas is generated by anaerobic decomposition of organic waste such as soiled paper, food scraps, and yard waste. It is potent, with 72 times the warming impact of CO2 over a 10 year period, according to Nora Goldstein, executive editor of BioCycle, a journal devoted to the recycling and reuse of waste. Turning landfill gas into energy would be a double win for the environment, EDF says. “It’s a good thing to capture methane and turn it into electricity or biofuels at landfills with existing waste in place,” Goldstein adds.
This anaerobic digester in Washington state uses organic waste diverted from landfills and captures 100% of the methane, then converts it into energy.
nonprofit research organization. When organics are removed from the waste stream and composted, they do not release methane; rather, small amounts of methane are oxidized to CO2 before they are released into the atmosphere. The airless landfill environment generates large amounts of methane from organic waste. Even with a system to collect the methane, capture rates over a landfill’s lifetime can be as low as 40-50%, notes Sally Brown, a soil scientist at the University of Washington. EPA officials maintain that composting is still preferred to landfilling. LFGTE does not create a disincentive to divert organic waste and has lots of benefits, according to an EPA official. “Defining LFGTE as BDT may remove incentives for diversion of organics to composting, resulting
2009 American Chemical Society
Published on Web 12/10/2008
in an increase in greenhouse gas generation due to the loss of the carbon storage, synthetic fertilizer avoidance, and pesticide avoidance benefits of compost,” adds Jeffrey Morris, an environmental economist with the Seattle consulting firm Sound Resource Management Group, Inc. Organic waste makes up more than two-thirds of conventional solid waste streams, and putting it in a landfill is like throwing away money, Brown says. A recent study published in BioCycle calculated for the first time the “true cost” of waste disposal options by combining operational costs and environmental costs and benefits, according to study author Clarissa Morawski, principal of CM Consulting, a Canadian solid waste consulting firm. For example, Morawski studied a regional government in Ontario and found that composting organic waste had a true cost of $19.60/ ton, whereas LFGTE cost $49.37/ ton. Each region will have its own true costs because the expense of landfilling and composting vary. However, not all LFGTE projects for new discards discourage diversion of organic waste, Goldstein says. She points to publicly owned landfills in Columbus, Ohio, and Burlington County, N.J., that have LFGTE projects in place alongside aggressive waste diversion schemes. Still, in several states the waste industry has sought to increase the amount of organics going into private landfills by lobbying to overturn bans that exclude yard wastes from landfills. The industry argues that LFGTE would eliminate the additional methane emissions generated from the yard waste, Anderson says. However, the companies have a financial incentive to bring in more waste because that means more revenue from tipping fees, he adds. —JANET PELLEY
February 1, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 555
