California Air Resources Board

As waste in a municipal solid waste (MSW) landfill decomposes, it breaks down to form landfill gas, which includes the greenhouse gases methane (50 percent) and carbon dioxide (50 percent), as well as non-methane organic compounds (NMOC, <1 percent). NMOCs include precursors to photochemical smog, odorous compounds, and toxics. In 2016, the U.S. Environmental Protection Agency (U.S. EPA) published the U.S. Environmental Protection Agency’s Municipal Solid Waste Landfill Emission Guidelines and Compliance Timelines for Municipal Solid Waste Landfills (Emission Guidelines) to reduce both methane and NMOC emissions from existing MSW landfills. The Emission Guidelines require the installation of a landfill gas collection and control system (GCCS) at MSW landfills that exceed a specified design capacity and NMOC emission threshold.

Many California landfills subject to the Emission Guidelines were already subject to the State’s Landfill Methane Regulation (LMR), and were already required to install and operate a GCCS. Because the Emission Guidelines require that states submit plans that identify how each state intends to meet the federal requirements, and because all the landfills covered by the Emission Guidelines already had GCCSs installed, California utilized the Landfill Methane Regulation for California’s State Plan to implement the Emission Guidelines. This plan was developed by CARB with the assistance of the State’s air districts and other stakeholders through a public process, and approved by the Board in 2017.

In early 2020, U.S. EPA partially approved and partially disapproved California’s State Plan. While LMR’s provisions are equivalent to or more stringent than the Emission Guidelines, U.S. EPA’s partial disapproval concerns the omission of certain provisions related to wellhead monitoring. In May 2021, U.S. EPA finalized a Federal Plan to implement the Emission Guidelines for existing municipal solid waste landfills, which includes specific reporting requirements in addition to those required by CARB under LMR.  For more information about meeting those requirements, visit LMR Reporting page.