Efficiency of landfill gas collection for methane emission reduction

Abstract

Landfill gas collection seems to be overestimated in many countries with methane emission inventories. When no measurements are available, IPCC guidelines allow a default collection efficiency of 20% can be used for the methane generated on landfills with collection. However many Annex 1 countries estimate landfill gas collection to be much higher than 20%. This article reviews available information on collection efficiency. Collection efficiency depends on the phase of the landfill. During operation, a large part of the methane potential is generated. In the absence of a collection system, most is released to the atmosphere. In many cases, landfill gas collection only starts after closure and in this period collection efficiencies generally increases. High efficiencies are achieved, when the site is capped with an impermeable liner. For estimation of collection efficiencies, different landfill types should be distinguished: (a) closed landfills without gas collection; (b) capped landfills; (c) closed landfills with temporary cover and gas collection; (d) landfills in operation with and (e) landfills in operation without gas collection. For landfills with state of the art liners, collection efficiencies can be 90–100%. For closed landfills, reported efficiencies range from 10–90%. For landfills in operation, efficiencies are 10 to 80%.