California Air Resources Board

Municipal solid waste (MSW) landfills are a significant source of methane emissions. Methane is a powerful greenhouse gas (GHG) and is a short-lived climate pollutant, which means it has a relatively short atmospheric lifetime; further, it is a more powerful climate forcer than the GHG carbon dioxide. Emissions of methane are responsible for about 20 percent of the global warming now driving climate change. About 20 percent of the methane emissions in California come from landfills and the remaining methane is from dairies and livestock, oil and natural gas extraction and pipelines, wastewater, agriculture, and other sources. 

California’s Global Warming Solutions Act, Assembly Bill (AB) 32, charged the California Air Resources Board (CARB or Board) with reducing statewide GHG emissions to 1990 levels by 2020. Senate Bill (SB) 32 requires further GHG emissions reductions of 40 percent below 1990 emission levels by 2030. In order to reduce emissions of methane from MSW landfills, the Board approved the Landfill Methane Regulation (LMR), which became effective June 17, 2010. This regulation is a discrete early action GHG emissions reduction measure, meaning that it was one of the first regulations enacted in response to AB 32. 

LMR requires owners and operators of certain landfills to install and optimally operate gas collection and control systems, monitor surface methane concentration and other performance parameters, repair emission exceedances and other performance issues, source test, keep records of these actions and data, and report certain information to CARB or the air districts. LMR allows air districts to voluntarily enter into memoranda of understanding with CARB to implement and enforce the regulation and to assess fees to cover costs. Currently, 22 local air districts are implementing and enforcing LMR.

While implementation of LMR reduces emissions of methane from MSW landfills, production of methane will continue as long as organic waste is disposed at these landfills. For organic waste that is currently landfilled, CalRecycle, in consultation with CARB, is developing the Short-lived Climate Pollutants (SLCP): Organic Waste Reductions Regulations pursuant to the SB 1383 requirement for the State to reduce disposal of organic waste 50 percent by 2020 and 75 percent by 2025.

For information about how the Landfill Methane Regulation is utilized for compliance with U.S. EPA emission guidelines for landfills, visit California State Plan for Compliance with U.S. EPA's Landfill Emission Guidelines.