Landfill work face emissions present major methane mitigation opportunity, study finds

In 2022, U.S. landfills released an estimated 119.8M metric tons of methane into the atmosphere, which was 17.1% of the country’s total methane emissions according to the U.S. Environmental Protection Agency (EPA). Attention has increasingly turned to addressing methane emissions as the fastest way to slow the rate of warming in the near term. Landfills present a major mitigation opportunity, both domestically and globally, yet gaps remain in societal understanding of exactly how much landfills are emitting and where these emissions are coming from.

A new study led by Carbon Mapper offers new insights on common sources of methane from landfills based on direct observations — intelligence that can help fill knowledge gaps and guide powerful mitigation action. For the first time, this research attributes methane emissions to specific regions of the landfill, revealing vast mitigation opportunities from the working area of landfills across many U.S. states.

Landfills are dynamic, engineered systems. Within any landfill, multiple methane sources exist, which can be diffuse (where smaller amounts of methane are emitted from multiple sources) or highly concentrated from a single point source (where a large amount of methane is emitted from a single source). Attributing these large emissions to the underlying activities and infrastructure at a landfill can help prioritize methane mitigation efforts and track progress toward abatement targets. 

Key Findings from Carbon Mapper on Landfill Methane Emissions

The Carbon Mapper team and research partners from the EPA and Arizona State University used airborne remote sensing observations collected at 217 landfills across 17 U.S. states in 2023 — attributing these observed emissions to specific sources within the landfill. 

By evaluating this data, they found the following:

• Across all observed landfills, 115 were emitting methane with an average per facility emission rate of 818 kg/hr.  
• Of these 115 emitting landfills, 52 of them had large emissions stemming from the landfill work face. This was far greater than emissions observed from landfill gas control devices, which were only observed at 12 facilities.
• Landfills with work face emissions accounted for less than half of the landfills the team observed emitting methane (52 out of 115), but were responsible for over 75% of the landfill emissions that were quantified, representing a significant mitigation opportunity.
• These 52 landfills only make up 4% of U.S. open landfills by number, but their emissions over a one-year period can account for 15% of methane emissions from U.S. municipal solid waste in 2022.
• As the 217 landfills in this study cover only 17% of open landfills in the U.S., the total mitigation potential is likely greater.

The power of remote sensing technology for landfill methane mitigation

This new research builds on a past study from Carbon Mapper researchers, which revealed the outsized contribution of U.S. landfill point source emissions to overall landfill emissions and highlighted potential gaps in traditional model-based emission accounting methods. Remote sensing tools, including aircraft and satellites, offer unique solutions for monitoring methane at landfills — especially on the work face, which is difficult to monitor via traditional handheld and ground-based sensors. This is because the work face location can shift day-to-day, and there are safety and logistical concerns with on-the-ground measurement approaches due to operator traffic. 

Comprehensive monitoring fills data gaps 

Research using publicly accessible data available on the Carbon Mapper data portal can help inform decision makers, like policymakers and operators, on the most effective methane mitigation solutions available today.

Coordinated studies with state governments, including state reports from California, Colorado and Pennsylvania, have shown that operators often take voluntary action to implement mitigation strategies when guided by these observations. Remote sensing can help operators, municipalities, and governments more comprehensively monitor landfill emissions, including dynamic areas like the work face. This is especially relevant as states like California and Colorado plan to update their landfill rules in the near future.

This methane data can also feed into national inventories. By tying emissions to the activity or process causing emissions at a landfill, decisionmakers can better inform inventories, improving society’s ability to track national progress in methane mitigation. 

The landfill work face as a mitigation opportunity

In addition to highlighting the importance of remote sensing in monitoring emissions at landfills, these findings can help policymakers design policies and operators implement best practices that tackle emission from the landfill work face.

Potential solutions range from early expansion of gas collection systems to using daily cover to minimizing the work face area — as detailed in this report by RMI. Methane can also be tackled before it ever gets to the landfill through organic waste diversion. Additionally, policies are needed to ensure high gas collection efficiency at landfills, including at landfills with renewable natural gas (RNG) facilities. This could benefit both landfills and RNG facilities by ensuring more gas collection and reducing methane emissions.

While the majority of these solutions are currently voluntary in the U.S., policy changes are needed to reinforce best practices. Both operators and policymakers play important roles in bringing mitigation solutions to the table for waste methane.

Learn more about waste methane emissions

• Watch our waste webinar recording
• Read our Landfill quantification study
• Browse waste data on the Carbon Mapper data portal