emission reduction

February 23, 2024

Estimating the Effect of Organic Waste Diversion on Methane Recovery and Emissions Reduction at the 2024 Global Waste Management Symposium.


Organic waste diversion legislation enacted in 10 states aims to reduce landfill methane emissions. The success of such legislation should be measured by methane emissions reduction, not just organics diversion from disposal. This will help ensure we prioritize both waste reduction and environmental protection. In October 2023, the US Environmental Protection Agency (EPA) released its estimates of potential emissions reduction from food waste diversion on a national scale in a report titled “Quantifying Methane Emissions from Landfilled Food Waste.”[1] The challenge facing landfill owners and operators today is the noted limitations of direct measurement technologies for surface-level methane concentrations, which are years away from providing accurate annual methane emissions estimates.

Landfills now use EPA’s standardized regulatory landfill gas models (LandGEM or equivalent) to report methane emissions. These tools are easy to run, but their simplicity limits them to producing emissions estimates that are approximate at best. Landfill gas models struggle to accurately estimate methane generation, making them prone to error when defining emissions from organics diverted from disposal.

Alex StegeAlex Stege, SCS’s National Expert on Landfill Gas Modeling, will present at the 2024 Global Waste Management Symposium. His presentation will cover the challenges and uncertainties that landfill gas models face while quantifying methane recovery, emissions, and emissions reduction. Alex is presenting for the 6th consecutive time at this conference, sharing insights from decades of experience in developing and applying landfill gas models and other waste sector GHG emissions models, including the Solid Waste Emissions Estimation Tool (SWEET), to estimate landfill methane utilization potential, methane emissions reduction, and the impacts of organics diversion.

Alex’s presentation will summarize state-level legislation targeting organic waste before zeroing in on Washington’s HB 1799. HB 1799 sets a statewide goal to reduce organic waste disposal by 75 percent from 2015 levels by 2030, which would require a decrease from about 3 million tons in 2023 to 700,000 tons by 2030. Estimates of methane emissions reduction from diverting this waste from Washington’s landfills are prepared by running SCS and Inter-governmental Panel on Climate Change (IPCC) landfill gas models to project methane generation, from which assumed rates of methane collection and oxidation are applied to calculate net emissions. Projected reductions in annual methane emissions increase from about 7,500 metric tons (Mg) in 2030 to 17,000 Mg in 2040 and 21,000 Mg in 2050. Cumulative methane emissions reduction will exceed 157,000 Mg by 2040 and 350,000 Mg by 2050.

Achieving these levels of emissions reductions will depend on efforts by the state’s municipalities to develop or access an organics collection and processing infrastructure, which will be difficult in remote regions. Estimating impacts at the scale of municipalities and landfills requires developing a schedule for reducing organic waste disposal, which is achievable, reflects site-specific historical disposal rates, and accounts for prior progress towards the diversion goal. SCS is assisting municipalities in Washington and other states to meet the requirements of organics diversion legislation. This experience informs our calculations of organics diversion’s effects on methane emissions and our forecasts of methane fuel supply for renewable natural gas projects.


Posted by Diane Samuels at 6:00 am

January 9, 2017

On behalf of the solid waste industry, the NWRA and SWANA  both not-for-profit associations provided comments on the EPA’s proposed Revisions to the Prevention of Significant Deterioration (PSD) and Title V Greenhouse Gas (GHG) Permitting Regulations and Establishment of a Significant Emissions Rate (SER) for GHG Emissions Under the PSD Program (81 FR 68110), which we’ll call the PSD Revisions. The comments were submitted on December 16, 2016.


EPA is proposing a GHG SER of 75,000 tons per year (tpy) Carbon Dioxide equivalent (CO2e) and requesting comment on it as well as two lower levels, specifically 30,000 tpy and 45,000 tpy CO2e, respectively.

The Associations do not believe there is sufficient information to support lowering the GHG SER below the proposed 75,000 tpy CO2e level and provided a table utilizing equivalent criteria pollutants from combustion sources (i.e., NOx, CO) yields CO2 emissions as high as 780,000 tpy CO2.

EPA already concluded in USEPA, Proposed PSD Revisions Rule, 81 FR 68137 that the burdens of regulation at a GHG SER level between 30,000 and 75,000 tpy CO2e would yield a gain of trivial or no value from both a programmatic and individual project-level perspective. Therefore, NWRA and SWANA strongly recommend EPA retain proposed GHG SER of 75,000 CO2e (or higher), and resist pressure to lower the GHG SER.



On the Topic of Biogenic GHG Emissions, the EPA’s final rule requires clarification to remain consistent with previous documentation and research to prevent significant permitting delays and increased costs that will not result in meaningful emission reductions.

The Associations encourage the EPA to ensure that waste-derived biogenic CO2 (e.g., from municipal solid waste (MSW) landfills) is treated as carbon neutral under the final PSD Permitting Revisions Rule to be consistent with prior Agency determinations specified in this memorandum and documents as follows:S. EPA, Memorandum Addressing Biogenic Carbon Dioxide Emissions from Stationary Sources, McCabe, Janet, November 19, 2014.

S. EPA, Memorandum Addressing Biogenic Carbon Dioxide Emissions from Stationary Sources, McCabe, Janet, November 19, 2014. The documents highlight waste-derived, biogenic CO2 as a type of “carbon neutral” feedstock based on the conclusions supported by a variety of technical studies and conclusions of the Agency’s latest draft Framework for Assessing Biogenic Carbon Dioxide for Stationary Sources, which was released with the memo. The Agency memo stated that “the Agency expects to recognize the biogenic CO2 emissions and climate policy benefits of such feedstocks in [the] implementation of the CPP.”

US EPA, Emission Guidelines for EGUs, 80 FR 64855. Both the revised Framework, and the EPA’s Scientific Advisory Board (SAB) peer review of the 2011 Draft Framework, found “that the use of biomass feedstocks derived from the decomposition of biogenic waste in landfills, compost facilities, or anaerobic digesters did not constitute a net contribution of biogenic CO2 emissions to the atmosphere.”

S. EPA, Appendix N. of Revised Framework for Assessing biogenic Carbon Dioxide for Stationary Sources, November 2014, pg. N-25. In Appendix N. of the Framework, entitled Emissions from Waste-Derived Biogenic Feedstocks, EPA calculated negative Biogenic Accounting Factors (BAF) for various examples of treatment of landfill gas via collection and combustion. EPA explains, “Negative BAF values indicate that combustion of collected landfill gas feedstock by a stationary source results in a net CO2e emissions reduction relative to releasing collected gas without treatment.”

US EPA, Carbon Pollution Emission Guidelines for Existing Stationary Sources: Electric Generating Units; Final Rule [Emission Guidelines for EGUs], 80 FR 64885. “[T]he use of some biomass-derived fuels can play a role in controlling increases of [in] CO2 levels in the atmosph The use of some kinds of biomass has the potential to offer a wide range of environmental benefits, including carbon benefits.”

US EPA, Emission Guidelines for EGUs, 80 FR 94855. Types of waste-derived biogenic feedstocks may include: landfill gas generated through decomposition of MSW [municipal solid waste] in a landfill; biogas generated from the decomposition of livestock waste, biogenic MSW, and/or other food waste in an anaerobic digester; biogas generated through the treatment of waste water, due to the anaerobic decomposition of biological materials; livestock waste; and the biogenic fraction of MSW at waste-to-energy facilities.



NWRA and SWANA believe the final PSD Revisions document should follow the approach to waste-derived feedstocks enshrined in the Final Clean Power Plan, and as recommended by the SAB, and ensure that waste-derived biogenic CO2 is treated as carbon neutral. Based on EPA’s own lifecycle assessments for the Renewable Fuels Standard program, its U.S. GHG Inventory, and confirmed by the SAB, EPA has sufficient analysis to support exclusion of selected categories of biogenic emissions from PSD permitting, including those from managing landfill gas and organic components of MSW.

The EPA does not seem to consider the regulatory treatment of biogenic CO2 from stationary sources to be a key issue in the context of the PSD revisions rule, based on a comment found in a Summary of Interagency Working Comments on Draft Language.  Instead, the EPA continues to believe this rulemaking to establish a GHG SER under the PSD program is not the appropriate venue to address the broader concern of the regulatory treatment of biogenic CO2 from stationary sources.

The Associations strongly disagree and are concerned that because EPA remains silent on this important issue, some permitting authorities might improperly require landfills to incorporate biogenic CO2 emissions in the PSD permitting process.  Historically, few landfills triggered PSD because non-methane organics emissions rarely reached the threshold. However, if biogenic CO2 emissions become subject to PSD, many landfill projects, which are “anyway sources” due to renewable energy projects, would also be forced to do BACT analysis for GHG. Biogenic CO2 is emitted from:

  • Methane control devices that convert methane to CO2 and destroy NMOCs per the Landfill NSPS/EG Rules;
  • Engines and turbines that use landfill gas as fuel to produce renewable electricity;
  • Treatment of landfill gas to pipeline quality for use as renewable transportation or facility fuel; and
  • Methane that moves through landfill cover where bacteria converts it to CO2.

From the perspective of developing new renewable transportation fuel or energy projects, subjecting biogenic emissions from landfills to PSD could be an enormous barrier.  The Associations would like the EPA to clarify in its final rule that the emissions of biogenic CO2 from treating or controlling landfill gas does not increase the CO2 levels in the atmosphere, but instead, has positive emission reduction and climate benefits.  Failing to clarify this important point could subject landfills to significant permitting delays and increased costs that will result in no meaningful emission reductions.


Questions? Contact SWANA, NWRA, Patrick Sullivan, or your local SCS office.





Posted by Diane Samuels at 3:00 am