The short term influence of atmospheric pressure and long term influence of gas recovery on landfill methane emissions

Landfills are the largest sources of methane (CH4) emissions to the atmosphere in the United States. However, few measurements of whole landfill CH4 emissions have been reported. Here, we present the results of a multi-year study of whole landfill CH4 emissions using atmospheric tracer methods at the Nashua, New Hampshire Municipal landfill in the northeastern United States. Emissions were measured in 1994, before the installation of a gas collection system, and again in 1996 and 1997 subsequent to the installation of a gas collection system. Both preand post-collection system emissions were negatively correlated with surface atmospheric pressure. Emissions decreased approximately 2-fold before gas collection over a pressure range of 1011 to 1028 mbar. The pressure effect was even more striking after the initiation of gas collection when emissions decreased more than 3-fold over a pressure range of 1007 to 1023 mbar. From these data we concluded that, at this site: 1) surface atmospheric pressure changes play a predominant role in determining the magnitude of emissions to the atmosphere, and 2) landfill gas extraction increased the rate of gas production by 40%.