Rule Applicability
Why many high-emitting landfills escape basic federal standards to control emissions
The Problem
The U.S. EPA regulates non-methane organic compounds (NMOC) coming from landfills, rather than methane itself. There’s basically a two-step trigger for when a landfill has to install a gas collection and control system (GCCS): first based on how big the landfill is, and then based on NMOC estimates. Per the current NSPS, MSW landfills that were constructed/modified after July 17, 2014 must submit an initial design capacity report to EPA and when a landfill reaches or increases its design capacity to or above 2.5 million metric tons of waste in place, the landfill must start estimating its its NMOC emission rate. If NMOC emissions rise above 34 Mg per year, the landfill is required to design and install a gas capture and collection system (GCCS) within 30 months.
There are several significant flaws with the EPA’s trigger for installing GCCS that mean methane emitting landfills fall through the cracks:
Big landfills with plenty of organic waste can still escape regulation: In practice, even once landfills get big enough to trigger the size threshold, they often still don’t hit the NMOC emissions threshold needed to require basic gas collection and controls. Even when they do, they can still delay GCCS installation if methane monitoring does not show exceedances. Read more about the unreliability of current methane monitoring practices here.
The federal trigger is fundamentally misaligned with when methane is actually generated: Methane generation is driven by the amount of biodegradable waste actually in the landfill, not the permit capacity, as the federal threshold dictates. A landfill can be below the trigger threshold of 2.5 million Mg, while generating methane. This leads to such bizarre outcomes as in 2022, when, of the landfills with the highest reported methane emissions in the entire country, only eight were required to install and operate gas collection systems, while two did not meet current federal thresholds.
The federal trigger is built on the wrong metric. NMOC emissions are highly variable and not tied to methane generation. Yet methane is the dominant climate pollutant emitted from landfills. By tying applicability to NMOC emissions instead of methane generation or measured methane emissions, the rule uses an indirect proxy that means a landfill can be generating plenty of methane emissions, but still fall below the NMOC formula.
The EPA acknowledges that lowering the size threshold would enable landfills to capture methane that would otherwise go uncontrolled, by requiring landfills to start estimating emissions and installing gas collection systems earlier in their lifecycle. This is especially important because food waste, which is increasing in landfills, breaks down quickly and can generate methane before gas collection systems are typically installed.
Recognizing this, a number of states have adjusted applicability of landfill air emissions requirements to better target large methane emitters, substituting in a calculated methane generation rate and actual waste-in-place figures. The methane generation rate is dependent on a number of factors including waste-in-place, age of the waste, type of waste (composition), and how much precipitation the landfill receives.
How States Have Closed Federal Gaps
How Landfill Requirements Scale with Risk
And there’s a difference between a landfill being covered by state landfill emission rules and being required to install a full gas collection system. For example, in Oregon:
Landfills under 200,000 tons of waste-in-place are largely exempt from the full program (but they still must maintain cover to minimize landfill gas emissions).
Once a landfill reaches 200,000 tons WIP, it must begin reporting its waste-in-place and methane generation rates;
Additional requirements only kick in if methane generation crosses specific thresholds. If methane generation reaches 664 metric tons per year, the landfill must either comply with the full control program or conduct regular surface emissions monitoring and prove emissions stay below 200 ppmv.
At 7,755 metric tons of methane emissions per year, full compliance is mandatory
In other words, oversight begins early, but stronger actions are tied to real methane risk. And the truth is, this system only works if landfills accurately report and follow through.
Better Targeting
A number of states have already revised the rule applicability threshold to waste-in-place (WIP), which is the actual waste tonnage at a landfill, which is more representative of landfill emissions.
Rule applicability size thresholds:
California: 450,000 tons, waste-in-place (408,000 Mg)
Oregon: 200,000 tons, waste-in-place (181,000 Mg)
Washington
Open landfills: 450,000 waste-in-place tons (408,000 Mg)
Closed landfills: 750,000 waste-in place tons (680,000 Mg)
Maryland: 450,000 waste-in-place tons (408,000 Mg)
For GCCS installation to be required in leading states, emission rates, LFG heat input capacity, and SEM measurements determine the schedule for GCCS installation and operation.
Emission rate thresholds to require GCCS installation:
California and Washington
Primary threshold:
Heat input capacity ≥ 3.0 MMBtu/hr
(Equivalent to ~492 Mg/year CH₄)
Exemption mechanisms:
SEM < 200 ppmv CH₄ (quarterly)
Oregon and Maryland
Primary threshold:
Methane generation ≥ 732 tons/year
Exemption mechanisms:
SEM < 200 ppmv CH₄ (quarterly)
State Rules are Tailored, not One-Size-Fits-All
State rules that have been updated beyond federal requirements are narrowly tailored and do not apply to landfill categories that are not significant methane sources, including:
Hazardous waste landfills and Superfund (CERCLA) sites, which are already regulated under other federal programs;
Landfills that receive only construction and demolition debris, inert material, or non-decomposable solid waste, which generate little or no methane; and
Municipal solid waste landfills that closed before a certain date (varies by state, but usually in the 1990s), if they are below the federal size and emissions thresholds.
Costs and Benefits
EPA estimates that once landfills hit the rule applicability threshold, design and construction of landfill gas collection and control systems (GCCS) typically cost $1–3 million per site, with annual operation and maintenance costs of $150,000–$400,000, and monitoring/reporting around $60,000 per year.
Budget challenges can be mitigated through bonding and by leveraging landfill gas energy. These practices can also save operators money by quickly identifying and remediating issues before they develop into more costly problems.
Exhaustive analysis of Colorado’s Regulation No. 31 found that publicly owned landfills face modest per-acre compliance costs while delivering benefit-to-cost ratios between 4.8 and 5.3, meaning every dollar spent yields nearly five dollars in climate benefits. Installing gas collection and control systems (GCCS) at the 18 landfills that currently lack them is expected to capture and destroy 12.3 million metric tons of CO₂-equivalent emissions. These reductions would also generate major economic benefits by avoiding climate damages. Using a 2.5% discount rate, the avoided climate costs from these emission reductions are estimated to be worth about $1.05 billion. Importantly, Colorado found that many publicly owned landfills were operating below thresholds requiring new gas collection systems, instead requiring monitoring or simple reporting.
In 2025, CARB estimated that needed updates to their regulations would deliver roughly three dollars in climate benefits for every dollar in compliance costs, driven by avoided social costs of methane and co-pollutant reductions. Even under a conservative assumption that 100 percent of compliance costs are passed through to residents, the estimated impact would amount to approximately $0.31 per person per year—a negligible cost relative to the benefits in avoided climate damage and improved air quality. CARB further found that improved methane controls would reduce emissions of toxic air contaminants and ozone-forming pollutants, delivering additional, unquantified public health benefits to nearby communities.
Industry Claim: Expanding landfill emissions rule applicability will impose unmanageable costs on small landfills.
Fact: Experience from hundreds of landfills operating under expanded applicability shows that stronger standards are workable, especially for publicly owned sites.
After adopting the lowest applicability threshold in the country (200,000 tons of waste-in-place), the Oregon Department of Environmental Quality found that 84 percent of locally owned landfills only needed to submit a report. Just three landfills were required to conduct surface methane monitoring, and three were required to install or update an existing gas collection and control system (GCCS)—demonstrating that stronger rules primarily improve verification and accountability, not capital intensity.
This pattern is consistent with outcomes in other states. Close to 400 municipal solid waste landfills across the country are already subject to updated state-level landfill methane requirements, including many of the same elements proposed here—earlier GCCS installation, tighter surface emissions monitoring, and enhanced operational oversight. Roughly 70 percent of these landfills are publicly owned, directly contradicting claims that public operators cannot comply with modern standards.
At the national level, concerns about municipal burden are further undermined by the structure of the landfill industry. The five largest publicly traded waste companies control approximately 61 percent of U.S. landfill volume, while local governments manage about 27 percent, with the remainder held by smaller private operators. As a result, most landfill capacity—and most methane emissions—are controlled by large, well-capitalized private firms, not cities or counties.
These firms operate within a U.S. waste and recycling sector valued at over $100 billion annually, with individual companies reporting billions in yearly revenue and net income. Against this backdrop, the compliance costs associated with modern methane monitoring and control represent a small operational expense, especially compared to the substantial climate, public health, and community benefits of reducing methane and toxic co-pollutant emissions.
Emissions Reductions
EPA’s modeling shows that lowering landfill size threshold across the country could result in a reduction of 538 million metric tons of CO₂-equivalent (Global warming potential - 100 years), by 2060 compared to the current standard. In other words, revising the threshold would deliver on the order of half a billion metric tons of additional climate pollution reductions by mid-century.
A study by Energy Vision found that if new collection systems are installed at all open landfills emitting at least 50,000 MT of CO2e annually, combined with early collection of gas and real-time auto-tuning technology, it would collectively cut annual MSW landfill emissions by 58.9% and total U.S. methane by 8.63% (59.2 million metric tons of CO2 equivalent) based on 2023 emissions (or 8.84% from total U.S. methane in 2020).
Emerging Concepts: Expanding Applicability Beyond Size
Lowering the waste-in-place threshold is one way to capture more methane sooner—but states are also exploring new, performance-based triggers that go beyond size altogether.
Remote Sensing as a Regulatory Trigger
Remote methane detection is an emerging tool for finding and verifying emissions - moving from a needle-in-a-haystack-approach to quickly identifying “super-emitter” sites that might not otherwise be regulated. EPA’s recent white papers highlight this as a key innovation for future landfill oversight.
Colorado and California have now incorporated remote sensing technologies into their landfill rules, allowing satellite, aircraft, or ground-based mobile instruments—certified under EPA’s Methane Super-Emitter Program—to identify big methane plumes.
Future state regulations could use persistent detections as an applicability trigger, requiring GCCS installation or other control measures even if a landfill is below the traditional WIP threshold. This approach transforms methane regulation from a static, size-based system to a dynamic, emissions-based system, ensuring that regulators can directly target the worst-performing sources regardless of size.
Biocover as an Alternative Applicability Pathway
For smaller or closed landfills where traditional gas systems are less cost effective or cannot be deployed due to lower levels of methane, biocovers—engineered soil layers enriched with methanotrophic bacteria—offer a biological control option that effectively substitutes for GCCS.
Under Colorado’s updated landfill rules, Regulation 31, closed or low-flow sites can replace gas control devices with biocovers or biofilters that oxidize methane biologically before release.
These systems must demonstrate surface methane ≤ 25% of the lower explosive limit and maintain conditions that support oxidation.
Once methane levels drop below 10%, ongoing monitoring and corrective action can end.
This represents a tiered compliance model, where smaller or end-of-life sites still reduce emissions meaningfully without the high costs of installing active gas collection.