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Calculating Methane Recovery from Landfills For landfills capturing methane for energy, the EPA assumes a 75`% methane instantaneous capture rate for the year in which the calculation is made. The conversion of methane's impact to carbon's impact (calculated by the EPA to be 21 times the impact of carbon) is based on a 100 year time frame {U.S. EPA Warm Model, November 2008) For our calculations, we reluctantly used the WARM model's default landfill capture rates based on the proportions of landfills with landfill gas control in 2004, because they are widely accepted. Using this national average, the result is a 44% capture rate as a. national average based on EPA calculations. However, several people have pointed out significant problems with these calculations. Ffirst, the landfill gas capture rate should be calculated over a period of time; not an instantaneous rate. Over a ~~ realistic time frame based on the life of a .~ landfill, the methane captured may be as ~~ J low as 20%, not the 75% as stated in the ~-' `- ~. ~. r ,~ ,~ _~ assumptions used by WARM. (U.S. El'A, ~ ' ~` ~~- - ~. 2008) (Anderson, 2006}. This means that ~ ix . :';-~, ~t°" ~~ ~ -~~2~ more methane gas is released from ~ ~ ~ ~ ~ ~'~~' landfills, which are already the largest '~,~.~,, `"_ ,. ~~~,_ ,~~- ~ ,~ ` ;~~b "~ ' source of methane frorn humans even by conservative calculations, than is reported in WARM. Secondly, there is an urgency to reduce our greenhouse gas emissions that is not reflected in the EPA's choice to use a 100- year time frame. Over a 20-year time frame, methane is 71 times as potent as carbon as a green house gas, not 27 tunes as stated in WARM. assumptions. Because methane only stays in the atmosphere for around 12 years, its impacts are far greater in the short term. Over a 100-year time frame, methane is 25 times more potent than CO,. However, methane is 72 times more potent than CO_, over 20 years. The Intergovernmental Panel on Climate Change assesses greenhouse gas emission over three time frames-20, 100, and 500 years. The choice of which time frame to use is a policy-based decision, not one based on science (Platt et al., 2008. pg 7). Calculating methane emissions over 20-years instead of 1Q0-years There is a general consensus among scientists that if we do not reduce the amount of carbon dioxide in our atmosphere to below 350 parts per million by 2.012, we may never be able to reverse the impacts of global ~vanning (350.org, About Us/Science Page). In other words, there is ail urgency of action required to fight the effects of global warming. A 20-year time frame For measuring the impact of methane illustrates the short-terra effect of methane on the environment, which, when. acknowledged highlights the urgent need-and the potential-to reduce methane emission. Dr. Ed J. Dlugokencky, a global methane expert at the NOA..A Earth System 12esea:-ch Laboratory, emphasizes the benefits of reducing emissions. Page 3