Finding Methane Leaks

Embracing Modern Technology and Find and Control Methane Leaks

The Problem: Manual Detection Has Failed

The federal surface emissions monitoring (SEM) method that landfills are required to follow, known as Method 21, is labor-intensive, incomplete and prone to human error.

Key failures include: 

  • Large gaps: Under federal regulations, each quarter, a technician walks the landfill using a handheld gas analyzer once per quarter to measure methane escaping from the surface. The technician follows a grid pattern with monitoring paths spaced about 100 feet apart, leaving large sections of the landfill unmonitored

  • Infrequent detection: Quarterly checks can’t capture the dynamic, rapidly-changing nature of landfill emissions.  

  • Widespread human error: EPA’s September 2024 nationwide enforcement alert found “widespread” compliance failures: technicians moving too quickly, excluding areas from monitoring, using expired calibration gases, and failing to fully inspect their work. 

  • No monitoring at place with most emissions: Research shows that 60-79% of all landfill methane comes from the active working face, yet this area is typically exempt from SEM entirely. The means manual SEM can only ever detect up to 40% of total site emissions, even when performed correctly.

Image from an EPA inspection of the LRI Landfill in Graham, Washington. Methane exceedance marked by yellow flags.

The Evidence: Operators aren’t finding their own leaks 

There are unfortunately many examples of problematic emission detection practices at landfills in the U.S. Industrious Labs’ Circular Economy Campaign (now Full Circle Future), analyzed EPA inspection reports from 29 landfills across eight states and found 711 methane exceedances over the legal threshold of 500 parts per million (ppm). There was at least one methane exceedance at 96% of sites where EPA conducted monitoring. Further, at nearly half (48%) of these sites, EPA inspectors found multiple exceedances where landfill operators had previously reported few or no exceedances.

  • LRI 304th Street Landfill near Tacoma, Washington: Inspectors detected explosive concentrations of methane, despite the landfill reporting no exceedances in the previous five years

  • Prairie Hill Landfill in Illinois: EPA inspectors found 51 methane exceedances and noted audible bubbling, strong odors, and leachate seeping out of the landfill. The landfill itself reported few to no exceedances in monthly SEM. 

  • Coffin Butte Landfill in Corvallis, Oregon: Inspectors found 61 exceedances, including 21 above 10,000 ppm. The landfill operators reported no more than six exceedances in previous reports, with some showing zero. 

Beyond Toxics Oregon spent hundreds of hours analyzing 32 Surface Emissions Monitoring (SEM) reports from eight Oregon landfills in 2023 to assess compliance with state methane monitoring rules. Researchers evaluated monitoring coverage, exemptions, and reporting completeness, converting the data into GIS-based maps to identify gaps and unmonitored areas across landfill surfaces.  They found that privately owned landfills excluded an average of 48.6% of their surface area from monitoring. Publicly owned landfills excluded about 10% on average.  One landfill exempted 69% of its surface area from monitoring without explanation. Another landfill claiming vegetation prevented monitoring, despite operators being responsible for maintaining cover.

Closing Monitoring Gaps: Ending Exemptions and Modernizing Surface Emissions Monitoring with Available Technologies

Integrating advanced technologies into SEM, particularly drones equipped with methane sensors, dramatically improves the feasibility, efficiency, and accuracy of enhanced monitoring requirements. Unlike manual walking SEM, which is labor-intensive and exposes personnel to hazards such as steep slopes, heavy equipment operations, construction zones, and unpredictable weather, fixed sensors or drones can rapidly and systematically survey the entire landfill surface. There are dozens of companies that provide equipment and/or services for methane detection at landfills.  Drone-based methane monitoring is already commercially available from providers such as ABB, Aerometrix, Bridger Photonics, Project Canary, Scientific Aviation, SeekOps, and SnifferDrone.  

RMI, with WM as a contributor to the report, provides a comprehensive playbook on how advanced methane detection technologies can be used.

CARB has found that these next-generation technologies outperform traditional monitoring by expanding surface coverage, increasing monitoring frequency, improving worker safety, and reducing operator error—making them better suited for comprehensive methane emissions management. 

Key upgrades to state landfill regulations to ensure proper detection of pollutants include:

  • Exemptions from surface emissions monitoring (SEM) for the working face and areas deemed unsafe to walk must be removed. Allowing broad exemptions for the most emissions-intensive areas of a landfill fundamentally undermines the effectiveness of SEM. Monitoring cannot meaningfully drive emissions reductions if the largest sources are systematically excluded.

  • Remote detection technologies should be required to monitor the entire landfill surface, including the working face and areas historically excluded from SEM. Landfills emit methane continuously—365 days a year—and monitoring frameworks must reflect this reality. Limiting advanced monitoring tools to select portions of a site perpetuates known blind spots and allows substantial emissions to persist undetected.

  • This baseline assessment would provide critical insight into site-specific emissions patterns, identify priority areas for mitigation, and inform appropriate operational and corrective actions. Establishing a robust baseline is essential for tracking improvements over time and ensuring accountability as monitoring requirements become more comprehensive and frequent.

  • Monitoring should be conducted at least every other month rather than quarterly. Landfill emissions fluctuate daily due to operational practices, waste placement, cover conditions, GCCS performance, and meteorological factors. Quarterly inspections provide only a narrow snapshot and routinely miss intermittent or short-lived but high-impact emissions events. Advanced technologies enable more frequent monitoring with less labor intensity, making increased frequency both practical and necessary.

  • All monitoring must occur under normal, representative barometric pressure conditions, with atmospheric pressure recorded and reported. Gas collection and control systems are operated relative to atmospheric pressure, and because vacuum settings are typically adjusted on a monthly basis, short-term pressure changes can significantly affect surface emissions.  Rising pressure suppresses emissions, while falling pressure increases them. Monitoring conducted during atypically high pressure systematically understates emissions and misrepresents system performance. If monitoring results are intended to represent emissions over a day, month, or quarter, they must be collected under average atmospheric conditions for that period.

  • Landfills with a school, health care facility within 1 mile, or with over 5,000 people within 2 miles should install perimeter monitors to identify and minimize the impacts of climate- and health-harming pollution, with action thresholds.

Fenceline monitoring is a method of measuring air pollution using sensors placed around the perimeter (or “fence line”) of a facility, such as a landfill. These monitors continuously or frequently sample the air for gases like methane or hydrogen sulfide to detect emissions escaping the site. When concentrations exceed preset thresholds, the system alerts operators so they can investigate and identify the source of the leak or emission event. Because the monitors sit at the facility boundary, they measure pollution where it leaves the site and may reach nearby communities.

Transparency and Verification is Essential

Amazingly, regulators cannot verify whether monitoring rules are actually followed because the landfill operators do not give them the information needed to do so. Federal requirements have no requirement to provide GPS paths of monitoring surveys. Monitoring data often submitted in non-spatial formats, making verification difficult. And worse, operators are not required to report all monitoring grid results, only exceedances. This makes it impossible for regulators to verify whether monitoring actually occurred as required.

In Beyond Toxics Oregon’s analysis of SEM reports from Oregon landfills, they were not able to locate information on three of Oregon’s 11 large municipal solid waste landfills and whether they even complied with methane monitoring rules in 2023. 

Examples from Leading States

Many landfill operators — both large private companies and municipalities — are already integrating satellite, near-ground, and continuous emissions monitoring into their operations to monitor for areas of elevated methane concentration and inform leak repairs and operational decisions. 

Michigan-based Sniffer Robotics, for example, deploys its technology at more than 150 landfills, and the methodology has been approved by the EPA as an alternative test method for SEM.

Costs and Benefits

Remote methane detection technologies are much more cost-effective than manual SEM, widely available, and already being deployed by leading states and operators to identify and reduce emissions.  Satellite, aircraft, drone, and mobile truck methods range $3,000 to $14,000 per survey, and fixed sensors that take continuous measurements cost between $7,000- $30,000 annually. 

Meanwhile, manual monitoring utilizing Method 21 costs at least $70,000 in equipment costs alone, and conducting the actual monitoring itself walking across a landfill is $73 per acre - for a typical 500 acre landfill, that is over $36,000 per survey. 

Industry Claim: Advanced monitoring technologies are experimental and unproven.


Fact: Remote sensing technologies—such as satellite and aircraft-based methane detection—are already used in multiple industries and have been successfully applied to landfills. These tools can rapidly identify large emission sources and help regulators and operators target mitigation efforts.

Industry Claim: Requiring new monitoring tools would be redundant with existing regulatory requirements.


Fact: New monitoring technologies are complementary, not duplicative. Ground inspections provide detailed point measurements, while aerial and continuous monitoring technologies provide a broader picture of emissions across the site. Together, they allow operators to identify leaks faster and improve gas collection performance.

Emissions Reductions

CARB estimates that improved methane detection and faster repair enabled by enhanced monitoring will reduce landfill methane emissions by approximately 17,000 metric tons of methane per year (about 450,000 metric tons of CO₂-equivalent annually). These reductions are attributed to improved gas capture, more comprehensive surface emissions monitoring, and prompt identification and repair of leaks detected through remote sensing technologies.