Landfills

Landfill CH₄ accounts for approximately 1.3 per cent (0.6Gt CO₂-eq yr^–1) of global anthropogenic greenhouse gas emissions relative to total emissions from all sectors of about 49Gt (Monni et al, 2006; US EPA, 2006; Bogner et al, 2007; Rogner et al, 2007). For countries with a history of controlled landfilling, landfills can be one of the larger national sources of anthropogenic CH₄; for example, US landfills are currently the second largest source of anthropogenic CH₄ after ruminant animals (US EPA, 2008). In general, landfill CH₄ emissions are decreasing in developed countries (Deuber et al, 2005; US EPA, 2008). Because CH₄ has both a relatively high GWP and a relatively short atmospheric lifetime of about 12 years (Forster et al, 2007), many countries have targeted reductions in landfill CH₄ emissions as part of a strategy to stabilize and reduce atmospheric CH₄ concentrations. Historically, landfill CH₄ has been commercially recovered and utilized since 1975 in many countries to provide a local source of renewable energy (for example Themelis and Ulloa, 2007). In many developed and developing countries, landfilling and other waste management activities are highly regulated; thus, their associated greenhouse gas emissions have also come under public scrutiny with many existing and evolving regulatory, planning, energy-related and financial mechanisms that impact their activities at the local, regional, national and international levels.