Landfills are the third largest source of anthropogenic methane, a potent greenhouse gas, in the United States. As organic waste decomposes, methane is released into the atmosphere. Controlling these methane emissions produces huge benefits, including slowing climate change in the near-term, as well as contributing to improving clean energy adoption and reducing food insecurity. Key mitigation measures for the solid waste sector have an estimated global reduction potential of 29–36 million metric tons of methane per year.¹

As the first state in the United States to regulate methane emissions from the solid waste sector, California has over a decade of experience in this domain. It has established two key approaches to address methane emissions, including (1) diverting organic waste from landfills, and (2) reducing methane emissions from existing landfills. Through a combination of policy, regulations, financial incentives, monitoring, and evaluation, California’s efforts illuminate the successes and challenges to effectively reduce methane emissions in a populous state where waste streams continue to grow. 

California’s successes include:

• Mandatory laws requiring recycling services for solid waste have helped increase the solid waste recycling rate and reduce the amount of organic waste disposed of in landfills. 
• Statewide 2025 edible food recovery target and supported projects have provided an effective method for food waste reduction while at the same time addressing environmental justice and poverty issues.
• Grants have supported the building of new compost and anaerobic digestion facilities that will increase the organic waste processing capacity by approximately 1.85 million tons. 
• Recovered organic waste products markets have been expanded by setting annual mandatory procurement targets for every city and county. 
• Collaboration between the California Air Resources Board and the local air quality management districts streamlined emissions monitoring and reduced the regulatory burden on landfill owners.
• Various financial incentives, including grants for commercial biomethane production, funding for research and pilot projects, equipment loans, and implementation fees, have encouraged landfill gas recovery projects, reduced methane emissions from municipal solid waste landfills, and helped recover the cost of methane regulation implementation.

Remaining challenges include:

• Slow progress in establishing waste collection and recycling services;
• Lack of and insufficient organic waste collection and processing infrastructure to meet anticipated needs;
• Limits to compost and biomethane market expansion;
• Introducing technology to monitor methane emissions from existing landfills; and
• Incentivizing greater reductions in landfill methane emissions.                    

Our new California-China Climate Institute report, produced with colleagues from Lawrence Berkeley National Laboratory, analyzes policies and programs, implementation mechanisms, and lessons-learned from California in reducing methane emissions from the solid waste sector. California’s lessons and experiences provide insights for other regions on best practices that could be adopted, as well as existing challenges and gaps to achieve methane reductions. 

Read the Full Report in English.
Read the Summary for Policymakers in English.
Read the Summary for Policymakers in Mandarin. 

1. UNEP & CCAC, 2021