Subpart HH – Municipal Solid Waste Landfills

This page provides resources for subpart HH reporters, including implementation information as well as supporting documents for relevant rulemakings.

Summary

Subpart HH source category consists of municipal solid waste (MSW) landfills that accepted waste on or after January 1, 1980, and generate methane (CH₄) in amounts equivalent to 25,000 metric tons (tonnes) of carbon dioxide equivalent (CO₂e) or more per year.

Frequently Asked Questions

When is a landfill required to report to subpart HH?

In general, a facility is subject to report to subpart HH of the GHGRP if landfill methane generation is equal to or greater than 25,000 metric tons of carbon dioxide equivalent (CO₂e).

• MSW landfills without a gas collection and control system (GCCS) must use subpart HH Equation HH-5 (modeled methane generation) to calculate methane (CH₄) generation adjusted for soil oxidation. The landfill is subject to reporting to subpart HH if Equation HH-5 yields an adjusted CH₄ generation equal to or greater than 25,000 metric tons of CO₂e per year.
• MSW landfills with a GCCS must use two methods to calculate methane generation, Equation HH-5 (modeled methane generation) and Equation HH-7 (measured methane generation). A landfill with a GCCS is subject to reporting to subpart HH if either Equation HH-5 or Equation HH-7 yields an adjusted CH₄ generation equal to or greater than 25,000 metric tons of CO₂e per year.
• The calculation and reporting requirements for Municipal Solid Waste Landfills can be found under 40 CFR Part 98 subpart HH.

When can a landfill stop reporting to subpart HH?

An MSW landfill that is required to report to the GHGRP must report CH₄ generation and emissions to subpart HH. A landfill can stop reporting under the rule if it emits less than 25,000 metric tons of CO₂e for 5 consecutive years or less than 15,000 metric tons of CO₂e for 3 consecutive years. A landfill cannot stop reporting under the rule simply because it ceases operations (i.e., no longer accepts waste) since methane will continue to generate due to the waste in place even though new waste is not being added. See 40 CFR 98.2(i) for more information on when a facility can stop reporting.

How are MSW facilities with a gas collection and control system (GCCS) required to calculate annual methane emissions?

Under subpart HH of the GHGRP, MSW landfills with active landfill gas collection systems must calculate and report GHG emissions in two ways: using Equation HH-6 and Equation HH-8.

• Equation HH-6 (modeled methane emissions) estimates emissions using the modeled CH₄ generation rate based on the quantity and types of waste historically disposed in the landfill using the first order decay model (see 2006 IPCC Guidelines for National Greenhouse Gas Inventories, Volume 5). Methane generation is then corrected for the measured amount of CH₄ recovered and destroyed. CH₄ generated in excess of the measured CH₄ recovery is corrected to account for CH₄ oxidation in the landfill cover material.
• Equation HH-8 (measured methane emissions) estimates emissions based on the measured quantity of methane that was recovered for destruction and an estimated landfill gas collection efficiency. This “back-calculated” quantity of the uncollected gas is then corrected for methane oxidation near the soil surface. Emissions from the quantity of methane recovered for destruction are estimated based on the destruction efficiency.

If a landfill has a gas collection system, which equation should it use to calculate its total methane emissions?

Facilities report data to EPA using the electronic Greenhouse Gas Reporting Tool (e-GGRT). In e-GGRT, a facility should pick the calculated result of Equation HH-6 (modeled methane emissions) or Equation HH-8 (measured methane emissions) that best represents the emissions from the landfill considering the site-specific conditions. Per 40 CFR 98.346(i)(13), for methane emissions from the landfill (i.e., the subpart HH total methane emissions), the reporter is to "choose the methane emissions from either Equation HH-6 or Equation HH-8 of this subpart that best represents the emissions from the landfill. If the quantity of recovered CH₄ from Equation HH-4 of this subpart is used as the value of GCH₄ in Equation HH-6, use the methane emissions calculated using Equation HH-8 as the methane emissions for the landfill."

If a facility does not select an equation to roll up into their total CO₂ emissions, e-GGRT will automatically select the larger of the two rounded results of Equation HH-6 or Equation HH-8.

Are reported methane emissions from a Municipal Solid Waste (MSW) landfill the net emissions of what is recovered in the landfill gas collection and control system (GCCS)?

For MSW Landfills with a GCCS, the emissions equations in subpart HH of the Greenhouse Gas Reporting Program (GHGRP) calculate net CO₂e emissions. In general, this means for landfills with a GCCS, the annual methane emissions (as observed in FLIGHT, the GHGRP’s Facility Level Information on GreenHouse gases Tool) are the amount of methane generation calculated by the landfill, adjusted for soil oxidation minus the amount of methane collected and destroyed by the gas collected system. The soil oxidation refers to the amount of methane that is converted to carbon dioxide in the landfill’s soil cover and is therefore not released as methane. The amount of methane destroyed in a gas collection system is dependent on a destruction efficiency. This means for any methane that is collected but not destroyed in the system and instead passes through the system, is added back into the emissions equations, and reflected in the total net annual emissions. The calculation and reporting requirements for Municipal Solid Waste Landfills can be found under 40 CFR Part 98 subpart HH.

What do the results of Equation HH-6 (modeled methane emissions) mean?

Equation HH-6 calculates methane emissions from a landfill based on the modeled methane generation rate, minus the measured amount of methane recovered (i.e., collected by the gas collection system) and destroyed. In other words, if the facility has an emissions value of 17,000 metric tons of methane for Equation HH-6, this is the estimated amount of methane being emitted from the landfill after subtracting out the amount of methane that has been collected and destroyed by the landfill gas collection and destruction system. Additionally, Equation HH-6 also subtracts out a fraction of the methane in the uncollected landfill gas to account for soil oxidized near the landfill surface. This further reduces the predicted methane emissions beyond the reductions attributed to the gas collection system.

Does EPA require the direct measurement of methane from landfills through new technology, including ground-based monitors and aerial monitoring systems?

In 2023, EPA issued a supplemental proposal to amend specific provisions in the Greenhouse Gas Reporting Rule (GHGRP) (40 CFR Part 98), including subpart HH (Municipal Solid Waste Landfills) to improve the quality of data collected. The EPA sought comment on this proposal on how methane monitoring technologies (e.g., satellite imaging, aerial measurements, vehicle-mounted mobile measurement, continuous sensor networks) might enhance subpart HH emissions estimates. Specifically, the EPA requested comment for examples of methane data collected from available monitoring methodologies and how such data might be incorporated into subpart HH for estimating annual emissions. While EPA sought comment on the availability and possible inclusion of such technologies in the reporting under subpart HH, we did not propose, and therefore did not take final action on any amendments to subpart HH to this effect. We will continue to review the comments received along with other studies and may amend subpart HH to allow the incorporation of additional measurement or monitoring methodologies in the future.

What is EPA doing to improve the accuracy of reporting requirements to estimate landfill methane emissions across the U.S?

On April 3, 2024, the Administrator signed the final amendments to the Greenhouse Gas Reporting Rule (GHGRP) (40 CFR Part 98) to improve the quality of data collected. Finalized revisions to subpart HH include updated factors (degradable organic carbon (DOC) and first order decay rate (k)) used in modeling methane generation from waste disposed at landfills to more accurately model landfill methane generation. Additional revisions to subpart HH include reducing default collection efficiencies and expanding reporting requirements to account for emission events that are not currently well quantified under the GHGRP, including revisions to calculation methodologies in subpart HH to account for emissions from poorly operating gas collection systems and destruction devices. Several of these revisions are a direct result of the EPA’s review of measurement studies similar to those reported by Cusworth, et al. (2024).

Reporter Resources

• Subpart HH Information Sheet
• Subpart HH Monitoring Checklist
• Training Presentations

For more questions, please Browse the Help Center for further information.

Subpart HH Regulatory History

40 CFR Part 98.340

Federal Register Date	Citation	Action	Description	First reporting year impacted
12/09/2016	81 FR 89188	Final Rule	Revises 29 subparts to streamline implementation, improve data quality, provide flexibility, and clarify the rule. Establishes confidentiality determinations for new or substantially revised data elements. Final action in response to a Petition for Reconsideration. Final Preamble and Rule (PDF) (87 pp, 801K) Response to Comments Final Rule Fact Sheet Memo: Table of Final 2015 Revisions to the Greenhouse Gas Reporting Rule Proposed Preamble and Rule (PDF)(91 pp, 890K)	2016
11/29/2013	78 FR 71904	Final Rule	Updates global warming potentials (GWPs) to reflect IPCC AR4 values, and amends 27 subparts to improve and clarify reporting requirements. Establishes confidentiality determinations for new and revised data elements. Final Preamble and Rule (PDF) (79 pp, 935K) Correction Notice (PDF) (2 pp, 248K) Response to Comments Fact Sheet Memo: Table of Final 2013 Revisions to the Greenhouse Gas Reporting Rule Proposed Preamble and Rule (PDF) (77 pp, 909K)	2014
05/26/2011	76 FR 30782	Final Rule	Finalizes confidentiality determinations for 34 subparts for data elements that are not inputs to emissions equations. Finalizes amendments to 40 CFR 2 governing CBI obtained under 40 CFR 98. Final Preamble and Rule (PDF) (37 pp, 330K) Proposed Preamble and Rule (07/07/2010) (PDF)(40 pp, 366K) Correction Notice (PDF) (6 pp, 167K) Response to Comments Proposed Preamble and Rule (07/27/2010) (PDF) (4 pp, 164K) Fact Sheet Memo: Final Data Category Assignments and Confidentiality Determinations for Part 98 Reporting Elements More Information	2010
10/28/2010	75 FR 66434	Final Rule	Corrects technical and editorial errors, and clarifies rule provisions for subparts A, E, H, K, N, O, P, Q, S, V, Z, CC, EE, GG, HH, LL, MM, and NN. Final Preamble and Rule (PDF) (47 pp, 376K) Response to Comments Proposed Preamble and Rule (PDF) (34 pp, 316K) More Information	2010
10/30/2009	74 FR 56260	Final Rule	Finalizes the first 30 subparts of 40 CFR Part 98, comprising subparts A, C, D, E, F, G, H, K, N, O, P, Q, R, S, U, V, X, Y, Z, AA, BB, CC, EE, GG, HH, JJ, LL, MM, NN, OO, and PP. Final Preamble and Rule (PDF) (260 pp, 1.4MB) Proposed Rule Proposed Preamble Response to Comments Technical Support Document: Landfills	2010