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What does the future hold for landfill methane emissions monitoring and reporting?
By Diane Conroy and Tiffany Medley, PhD

The greenhouse gas (GHG) reporting landscape may be changing, as the federal government is reconsidering the requirements for annual reporting. However, a slew of states have established binding GHG reduction targets by statute and are seeking pathways to meet those commitments. State-implemented GHG reporting programs are being developed to help document emission trends. Some states have also specifically identified fugitive emissions of methane from landfills as a targeted area where improvement in releases of GHGs could occur. Here, we review a sample of state programs leading the way and shed some light on new landfill gas monitoring technologies that may help facilities meet future methane emissions challenges.

Regulators Seeking Accurate Landfill Emission Quantification Methods
Over the last few years, the solid waste industry has seen additional Environmental Protection Agency (EPA) monitoring and enforcement actions related to surface emissions of methane at landfills. Regulatory agencies are increasingly focusing on more accurate, transparent, and verifiable landfill emission quantification methods. However, recent changes give the impression that future annual GHG quantification and reporting may only exist if states require it (see Figure 1).

The states that have rolled out their own GHG Reporting programs, such as California, Massachusetts, Washington, Oregon, Colorado, and recently New York, have emulated some portions of the federal regulations. One state that keeps moving the goal post is California, whose recently revised Landfill Methane Rule emphasizes higher-frequency methane emissions monitoring and corrective actions that will have a significant impact on landfill operations, maintenance practices, and cost (see Figure 2).

State GHG Reporting
In September 2025, the EPA submitted legislation proposing to permanently remove landfills, one of 46 source categories, from the Federal GHG Reporting program. The reporting deadline was extended to October 30, 2026, to give the federal government more time to implement these changes. Most industry experts expect that federal GHG reporting requirements will ultimately be removed.

Despite these changes, some facilities are electing to continue with the development of annual GHG emissions calculations. This may be for consistency to track annual emissions, or so they can use the data for other reporting, for example, emission statements, or company carbon neutral or green initiatives. Meanwhile, GHG reporting requirements are being picked up by some state governments and we anticipate others will follow suit in the future.

New York
Take the example of the New York State Department of Environmental Conservation’s (NYSDEC’s) Mandatory GHG Reporting Rule, finalized in December 2025, which establishes a statewide system for tracking GHG emissions across multiple sectors. The NYS reporting program was developed to support New York’s Climate Leadership and Community Protection Act (CLCPA), which set aggressive emission reduction goals—40 percent reduction by 2030 and 85 percent reduction by 2050. NYS will use this new program to build its own data set and establish a statewide baseline to determine if the state is meeting reduction targets.

The NYS Reporting Rule applies to most fuel suppliers and facilities emitting more than 10,000 metric tons of carbon dioxide equivalent (CO2e) annually, including landfills, wastewater treatment plants, anaerobic digesters, and waste haulers and transporters carrying waste out of state.

The calculation of the 10,000 metric tons (MT) CO2e is important to understand. Not only is this a substantial reduction from the federal reporting regulations (25,000 MT)—which means many more facilities will be subject to the rule—the 10,000 MT threshold will be calculated using the 20-year Global Warming Potential (GWP) values, as opposed to the 100-year GWP values. The 20-year GWP for methane is 84, which is three times higher than the 100-year GWP of 28. This is a significant change—it means any landfill facility calculating its emissions would have to multiply its total methane emissions by 84 to determine if it is subject to the NYS Mandatory GHG Reporting rule.

When you do the math, that breaks down to methane emissions of 119 MT requiring reporting (whereas the federal limit of 25,000 MT equates to approximately 893 MT of methane). So, without factoring in releases of any other GHG (i.e., CO2, N2O), if a New York facility emits more than 119 MT of methane per year, they will be subject to this reporting rule. This program will capture many facilities that were never subject to the federal GHG Reporting Program. In turn, some facilities may not be aware of reporting applicability, deadlines, or have protocols in place to monitor or report emissions.

Within the NYS rule, there is a breakdown that splits the reporting requirements into two categories: standard reporting entities (above the 10,000 MT but below 25,000 MT CO2e), and large emission sources (greater than 25,000 CO2e). Most landfills therefore will be considered large emissions sources, subject to much more cumbersome requirements than those of standard reporting entities.

Spotlight on NYSDEC GHG “Large Emission Sources”
Large emission sources are required to develop a GHG Monitoring Plan, which must include:

• The who, what, and where of emissions calculations data collection.
• A description of the procedures and methods that are used for data collection, quality assurance, maintenance and repair of all continuous emissions monitoring systems, flow meters, and other instrumentation used to provide data.

The GHG Monitoring Plan is intended to be a living document that requires updating to reflect facility changes, and subsequent resubmission to NYSDEC. There is also a clause stating that DEC reserves the right to request all information collected in conformance with the GHG Monitoring Plan for review during an audit—and the information must be maintained for 10 years.

Landfill facilities with emissions greater than 300,000 MT of CO2e are also required to develop an additional Emissions Measurement and Monitoring Plan (EMMP) and report on those results every three years. This 300,000 MT threshold may seem hard to reach, but after applying the GWP methane multiplier of 84, many larger landfills in New York will hit this limit.

Once large emitters submit their annual GHG report, the results must be verified by a qualified, independent third-party verifier that has been reviewed by NYSDEC to ensure there is no conflict of interest. There is an extensive process associated with third-party verification—45 pages of details within the NYS rule to be exact—including a requirement for switching verifiers every six years and a rule stating that a facility cannot go back to a previous verifier for at least three years.

Figure 3 shows some recently updated key dates and a general timeline for the NYS Rule. The NYS GHG reports will be submitted through the NYS GHG Reporting Tool (e-GGRT), which is anticipated to look similar to the Federal e-GGRT interface.

Landfill Methane Rule: California
Because California’s environmental regulations are often mirrored in other states, it is useful to evaluate California’s revised Landfill Methane Rule (LMR) and discuss the potential effects such a framework for landfill methane monitoring and reporting might have on the industry.

California’s LMR was originally implemented in 2010, with the aim of helping to meet the state’s target of reducing methane emissions by 40 percent by 2030. In 2025, the California Air Resources Board (CARB) approved an amendment scheduled to go into effect in January 2027, which introduces stricter monitoring requirements, reporting and recordkeeping, and introduces specific timelines for exceedance response, as well as requiring the development of new standard operating procedures. The rules apply to landfills with 450,000 tons of waste-in-place (WIP). Approximately 188 California municipal solid waste landfills (MSWs) may be subject to the revised LMR.

One interesting element of the new LMR is CARB’s use of remote methane plume sensing through a third-party satellite vendor. The new LMR now requires any owner or operator that receives a notification of a remotely detected emission plume to find the exceedance within five calendar days, complete monitoring and repair and re-monitor within 15 calendar days and submit follow-up monitoring information: a brief mitigation plan and a description of activities that may have contributed to the plume detected within 35 calendar days (see Figure 4).

Other notable requirements are the provisions that operators cannot exclude “unsafe to walk areas” from surface emissions monitoring and can only exclude the working face with waste in place for less than 180 days. CARB expects that operators will instead be able to use an approved alternative technology, for example, lasers, drones, or other robotic devices to monitor surface emissions in areas not readily accessible. In areas of recurring exceedances, the rule also increases surface emissions monitoring frequency from quarterly to monthly.

In addition to the scrutiny on surface emissions, the revised LMR focuses on minimizing gas collection system releases by increasing the frequency of wellfield monitoring from monthly to weekly for wells that have recurring positive pressure or temperature exceedances. The rule requires preparation of a collection system assessment—and if the issue is not corrected, an automated wellhead must be installed at the location (see Figure 5). Several states are monitoring the CA LMR to review its success, and it seems likely that some states may adopt a variant of the rule in the years to come.

Advanced Technologies on the Horizon
Whatever the rules adopted by states to meet methane emissions challenges, there are expected increased operational and capital costs, increased time demands on operators and staff, and an increased likelihood of non-compliance and violations. That makes it more than likely that operators will seek to use emerging advanced technologies to assist with methane monitoring requirements needed to meet more stringent expectations of frequency and documentation. Our top picks include:

• Unmanned aerial vehicles (drones): Mounted sensors on drones provide real-time, high-resolution methane data that can access unsafe areas and quickly locate leaks.
• Satellite and fixed-wing aircraft: Provides remote detection of measurable methane plumes that can be further investigated at ground level.
• Fixed sensor arrays: Onsite sensor networks provide continuous methane emissions monitoring that can document trends.
• Handheld imaging devices: Mobile, laser-based detectors provide safe, scalable surface emissions readings at lower costs.

These new tools (see Figure 6) can support and improve regulatory compliance, improve identification of release locations, reduce the risk of excess fugitive emissions, and provide high resolution data to enhance environmental performance under a modernized monitoring regime. | WA

Diane Conroy is a project manager with more than a decade of experience in solid waste landfill and landfill gas-to-energy compliance and permitting. Her air quality expertise includes preparation of state and federal air quality operating permit applications, annual emissions statements, annual greenhouse gas reporting, and semi-annual monitoring reports. She has worked with facilities in New York, New Jersey, Florida, Texas, Virginia, and Pennsylvania. Diane can be reached at [email protected].

Tiffany Medley, PhD, is the National Manager of Air Quality Services for Tetra Tech’s Solid 91TV East division. Working closely with Title V Operating Permit facilities across the country, she helps facility owners and operators comply with state and federal air pollution requirements and represents their interests for all state Department of Environmental Protection and U.S. Environmental Protection Agency permit or enforcement issues. Tiffany can be reached at [email protected].