California is lagging behind Colorado and other states in addressing potent methane from landfills
Methane — a highly potent greenhouse gas — is an unseen driver of the climate crisis and is rising at unprecedented levels globally. Piled high in landfills across the Golden State, organic waste sits rotting in the ground for decades, creating air and water pollution for millions of Californians and spewing unchecked methane and other harmful pollutants into our atmosphere. California ranks second in the nation for estimated methane emissions from municipal solid waste (MSW) landfills, with annual methane emissions estimated at more than 21 million metric tons of CO2 equivalent: about the same as 5 million passenger cars driven for a year. And the negative health impacts from landfills are disproportionately felt by BIPOC communities.
On December 18, 2024, the California Air Resources Board (CARB) held a public workshop on potential improvements to the state’s Landfill Methane Rule, which sets standards for how landfill operators must control for methane. At the workshop, CARB staff presented their ideas for how to update their 15-year-old rules to make them more effective and in line with the latest research and technology. . Unfortunately, Governor Newsom and CARB are not making landfill emissions the top priority it needs to be. Meanwhile, other states have moved ahead, including Oregon, Washington and Maryland. And the state of Colorado is poised to issue a nation-leading draft rule in a few months, well ahead of California. California has long been seen as a leader in climate policy, but when it comes to landfill methane, we are falling behind. It’s time for CARB and Governor Newsom to prioritize strong, enforceable regulations that truly tackle this urgent issue and ensure California leads—not lags—on landfill emissions.
While once the strongest landfill emissions standards in the nation, California’s rules have fallen behind the times, and CARB moving at a glacial pace that does not meet the moment. CARB first put forward potential updates to their standards way back in 2023. Now, nearly two years later, we are still at the concept stage, with a preliminary timeline of issuing a draft rule not until late 2025, as this slide from CARB shows.
The changes CARB stated they are considering miss the mark by failing to incorporate the best and most current technologies and practices to find and capture methane. Here’s a rundown on the positives and the missed opportunities of the concepts CARB presented:
Progress on some important fronts:
Creates a super emitter program, requiring landfills to respond to methane leaks detected by flight or satellite monitoring. This is common sense and would be a game-changer in addressing very large point sources - When a satellite identifies a methane plume from space, the landfill operator should be required to go out and find that leak and fix it, just as those in the oil and gas industry must do. The state of California has pioneered aerial remote monitoring for methane emissions, conducting hundreds of flights for many years, with about half of landfill operators responding on a voluntary basis, as this example from CARB shows - just imagine what would be possible if this technology was scaled statewide!
Lowers methane exceedance threshold from 500 parts per million (ppm) to 200 ppm, along with ensuring a faster corrective action timeline for exceedances, and ensuring that operators determine and address full extent of surface leaks. CARB also proposes requiring digital maps of emissions monitoring results, which is an obvious upgrade as detection technology is already digital. Currently, landfill operators do not have to submit maps and coordinates of where they actually monitored for emissions.
More robust gas collection component leak monitoring and repair. Leaking equipment like pumps or valves can emit a lot of methane and other air toxics.
Limiting gas capture and collection downtime: Obviously, you’re not capturing potent gases if the collection system is down. Closing this loophole is a step in the right direction.
Creates a “Persistent Emissions” standard: This is an interesting approach from CARB, which would specify additional follow-up action, such as increasing monitoring frequency, performing cover integrity/collection analysis, or requiring automated wellhead tuning, when the landfill has a specified number of exceedances. However, it is meaningless if the landfill operator can’t find those issues in the first place. Unfortunately, CARB does not upgrade monitoring practices to ensure that emissions are actually found in the first place.
Addresses some energy project loopholes: CARB suggests clarifying that gas control system owners and operators that receive landfill gas are subject to their landfill methane rule and must ensure 99% methane destruction.
Missed Opportunities Abound:
Doubles down on a very ineffective manual method to find invisible methane: Unfortunately, CARB continues to rely on human-based, infrequent monitoring for methane leaks. These methods are, by definition, spotty, vulnerable to human error, and pose safety threats to landfill inspectors, causing leaks to go undetected. The White House itself, in its national monitoring strategy, acknowledges that human-based surface emissions measurements alone are insufficient. It’s an exciting time to address landfill methane, as advanced methane sensing technology such as sensors and drones are operational, proven, and catching on. They can comprehensively monitor large areas, with greater frequency and accuracy, to provide California landfill operators and regulators with the missing information they need to find and mitigate methane leaks. CARB is considering establishing its own process to approve alternative technology for leak screening, which could include more effective advanced monitoring technology - but this more effective technology should be mandatory, not optional.
No proposed cover requirements: Despite the ability of effective landfill cover to dramatically reduce emissions, California regulators did not propose any requirements related to the type and timing of landfill cover. This is especially ironic considering CARB sponsored research that determined that the type of cover on a landfill was the most significant factor impacting the flux of emissions.
No requirements to address the largest source of emissions - the active face: The active face, or working face where new trash is placed, is a huge source of methane emissions. For example, a Carbon Mapper and U.S. EPA scientific paper, Investigating Major Sources of Methane Emissions at US Landfills, analyzed findings from 217 open landfills across 17 US states. Across states, they saw large fractions of observed landfills emitting. Landfills with significant work face emissions were consistent across surveyed states, and the largest share of emissions came from the working face. CARB should define acceptable active face sizes relative to the volume of incoming waste and require customized operational plans to be implemented by the operator.
No mention of managing liquids in pipes, which harms gas collection. California should follow the state of Michigan’s lead in implementing requirements to minimize well flooding by addressing drainage issues, particularly in areas prone to water infiltration.
No earlier installation of gas capture and collection systems, allowing unchecked methane to vent: A recent EPA report found that “an estimated 61 percent of methane generated by landfilled food waste is not captured by landfill gas collection systems and is released to the atmosphere. Because food waste decays relatively quickly, its emissions often occur before landfill gas collection systems are installed or expanded.” The report further estimates that fifty percent of the carbon in food waste degrades into landfill gas within just 3.6 years. The U.S. EPA further states in their recent white paper that ”Implementing a shorter time between threshold exceedances or landfill expansions and GCCS installation and operation can result in earlier control of LFG emissions versus the current NSPS/EG requirements.” CARB should ensure that as new trash is dumped at a landfill, gas collection is placed beneath the active waste layer. Horizontal gas collectors and/or bottom-up collectors, or caisson wells are critical to capture methane before it escapes into the atmosphere, including in active cells.
Continues to rely on “dumb” pipes, missed opportunity to upgrade to continuous monitoring to boost gas collection: CARB should ensure the use of monitoring technologies that use wellhead sensors to adjust the gas collection system automatically, particularly for landfills that produce gas-to-energy. These sensors can provide real-time data on gas composition, flow rates, and pressure, greatly optimizing methane capture and improving gas collection rates. As the U.S. EPA noted in their recent white paper, “Automated wellhead tuning has emerged as a solution to address these challenges by dynamically adjusting system parameters like vacuum pressure and flow rates in response to real-time data … Similarly, automated wellhead tuning can assist in remedying damages to the gas capture and collection systems. Damage to the collection system can occur and remain unnoticed until monthly wellhead parameter checks.”
California has the opportunity—and the responsibility—to lead the way in tackling methane emissions from landfills, but the current pace and scope of CARB’s proposed updates fall far short of what’s needed. With other states moving forward with stronger, science-based policies, California must act decisively to close regulatory gaps, adopt modern monitoring technologies, and require more effective methane mitigation practices. Communities living near landfills, already bearing the brunt of pollution, cannot afford further delays. CARB and Governor Newsom must make landfill methane reduction a top priority, ensuring that California reclaims its status as a national leader in climate action and environmental justice. The time to act is now.
