Public Comments on EPA’s Waste Reduction Model (WARM)

Date: 26 Feb 2024 | posted in: Composting, environment, governance, waste - composting | 0 Facebooktwitterredditmail

The E.P.A. is accepting public comments until March 15, 2024, on the Waste Reduction Model (WARM) version 16 and its supporting documentation. In an effort to “improve the usability, integrity, and functionality of WARM,” the EPA intends to use these comments along with findings from an external peer review and data quality assessment to update the current model. 

WARM is a measurement tool to estimate and compare potential greenhouse gas (GHG) emissions, energy savings, and economic impacts of various materials management practices, including source reduction, recycling, composting, anaerobic digestion, combustion (incineration), and landfilling. Emissions, energy units, and economic factors are measured across materials commonly found in municipal solid waste and construction and demolition debris. 

The methodology and assumptions used for WARM’s estimations have significant implications – the tool is used to weigh and compare the benefits and drawbacks of materials management practices relative to each other. These estimates are used in consequential decision-making for policy, regulation, funding, and more, and inaccuracies in measurement assumptions elicit biased results.  

In response to the EPA’s request and to strengthen the measurement model and reduce current biases, the Institute for Local Self-Reliance submitted the comments below. The U.S. Composting Council also developed recommendations to include in public comments.

We urge you to also submit public comments, and we welcome the use of our comments to inform or guide responses or to be copied and pasted directly into your submission.

Public comments can be submitted through March 15, 2024, through docket number EPA-HQ-OLEM-2023-0451 in


Comments on the E.P.A. Waste Reduction Model version 16 (WARM 16) Docket No. EPA-HQ-OLEM-2023-0451

Submitted by the Institute for Local Self-Reliance

Dear Administrator Regan,

Thank you for the opportunity to submit comments on EPA’s Waste Reduction Model version 16 (WARM 16). The Institute for Local Self-Reliance (ILSR) is a national nonprofit research and educational organization that advocates for thriving, diverse, and equitable communities. We respectfully request your consideration of our comments and recommendations outlined in this letter, which have been informed by nearly 50 years of experience providing assistance to communities to reduce and recycle wasted materials. 

ILSR commends the EPA for its continuous efforts to improve and update the measurement tool and for seeking input through public comments. However, WARM 16 continues to have several flaws that hinder progress in mitigating and adapting to climate change. The current form falls short of its goal to allow for an adequate comparison among available solid waste management options. In response, ILSR offers the following recommendations to rectify several shortcomings in the tool that bias results and impede future efforts.

  1. Include decentralized composting systems in emissions factors 
  2. Consider increased soil water retention in composting emissions factors
  3. Update research on compost’s ability to displace synthetic fertilizers, fungicides, and pesticides 
  4. Factor bCOemissions (carbon dioxide emissions from biogenic materials) into emissions calculations
  5. Update methane’s Global Warming Potential (GWP) to 80.8 – 82.5 over 20 years and an atmospheric life of 11.8 years to reflect IPCC’s 2021 Assessment Report (AR 6)
  6. Reconsider utility COemissions in combustion net emissions calculations
  7. Report methane emissions separately from other GHGs

Furthermore, we urge EPA to strongly consider the copious additional benefits of composting not represented through emissions calculations when comparing solid waste management options. Excluding benefits such as improved climate resiliency and living natural systems creates an unfair disadvantage for closed-loop, nature-based solutions like composting. We thank you for your consideration of our recommendations.


Recommendations for Waste Reduction Model (WARM)

1) Include decentralized composting systems in emissions factors

WARM 16 models composting only in central composting facilities with windrow piles, citing a lack of data for small-scale composting and other large-scale operations as the reason. However, decentralized, distributed composting is a quickly growing part of the sector, warranting its inclusion in WARM to represent the field accurately. 90% of composting programs in our 2022 census launched since 2010, with over half launching since 2016. Of 2,987 composting facilities with scale data in a 2017 study, 79% were small-scale composters (composting less than 5,000 tons of feedstock per year). With this increase in decentralized activity, access to data should not be a barrier.

Decentralized solutions, such as composting at home, community gardens, urban and local farms, schools, and local government sites, are managed by local, distributed networks of independent businesses, worker cooperatives, nonprofit organizations, and local governments. Community-based composting operations often make and use compost within the same community where wasted food and other materials are generated. Keeping the processes and products as local as possible keeps benefits and profits local and within the community. Decentralized composting offers abundant co-benefits that protect the climate, build healthy soils, stimulate economic growth, enhance food security, and build more prosperous, equitable, and resilient communities. Omitting decentralized composting operations from WARM 16 has created emissions factor modeling inaccuracies.

  • By excluding decentralized composting, emissions associated with transporting compost are inflated. Centralized composting operations are more likely than community composting operations to be located further away from the community where collection occurs, resulting in further distance traveled and higher transportation energy emissions. WARM 16 also assumes transport by a diesel short-haul truck. However, we are seeing a growth in clean energy modes of transportation in our network; a number of our community composting partners are using electric vehicles and bicycles (pedal and electric-powered) for collection. WARM should address the currently stated limitations that “did not allow for variation in transportation distances.”   
  • Leaving out decentralized operations renders emissions associated with turning equipment inaccurate. 44% of community composters did not use windrows for composting but used alternative methods with different levels of machinery (including manual labor only). Increasingly a number of community composters are powering aeration systems with solar and electric power and not fossil fuel energy. For example, LA Compost is moving toward electric-powered bobcats for their composting operations. Machinery emissions in the current model are likely inflated.

These discrepancies place decentralized composters at a disadvantage when utilizing WARM 16 for reporting and funding opportunities. The current version does not accurately reflect the impacts and benefits of their operations due to these inaccuracies.

2) Consider increased soil water retention in composting emissions factors

WARM 16 acknowledges that “compost use also has been shown to increase soil water retention; moister soil gives a number of ancillary benefits, including reduced irrigation costs and reduced energy used for pumping water.” However, these benefits and avoided emissions are not included in WARM 16. Composting emissions factors should address these energy offsets to represent emissions benefits accurately.

3) Update research on compost’s ability to displace synthetic fertilizers, fungicides, and pesticides

Synthetic fertilizers, fungicides, and pesticides collectively have an enormous greenhouse gas profile and should be accurately reflected in WARM. Outdated or inaccurate assumptions on composting’s ability to displace fertilizer can understate the value of composting and compost application. Only looking at NPK nutrients is insufficient to calculate the offset of fertilizers as the benefits of compost have to do with soil structure and beneficial biology. Applying high-quality compost to agricultural soil as a soil health management practice can be crucial for both rebuilding and protecting soil. Compost as a soil amendment improves soil structure, increases soil fertility, suppresses plant disease, improves nutrient cycling, prevents soil erosion, and increases soil resilience to drought and extreme weather. We know farmers that have stopped using synthetic/fossil fuel fertilizers altogether. Furthermore, not all compost is created equal. For example, vermicompost made from worms is higher in beneficial biology and growth hormones. EPA should take into consideration the use of vermicompost to adequately capture these advantages. This is an important issue that should be given continuous and adequate attention. The EPA should be looking to update WARM 16’s data on this issue, which is now a decade old, and use multiple studies to inform assumptions. EPA should conduct ongoing research to continuously update this information to most accurately reflect the value of composting and compost application.

4) Factor bCO2 emissions (carbon dioxide emissions from biogenic materials) into emissions calculations

We support the excellent research of Energy Justice Network and Global Alliance for Incinerator Alternatives (GAIA) on this topic. As recommended by the Intergovernmental Panel on Climate Change guidelines: “if incineration of waste is used for energy purposes, both fossil and biogenic should be estimated… biogenic CO2 should be reported as an information item…Moreover, if combustion, or any other factor, is causing long term decline in the total carbon embodied in living biomass (e.g., forests), this net release of carbon should be evident in the calculation of CO2 emissions.” 

Excluding bCO2 emissions causes bias in favor of incineration. WARM 16 assumes the carbon dioxide emissions from biogenic organic materials (e.g., paper and wood products, yard trimming, and food discards) do not count. The rationale is that plants and trees regrow, and carbon dioxide emissions return carbon to the atmosphere previously sequestered by photosynthesis and would cycle back eventually under natural conditions due to degradation processes. This assumption can exclude 90% of CO2 emissions from incineration but omits a smaller fraction of GHG emissions from landfill calculations (as the model counts methane but not CO2 emissions). Favoring disposal in an incinerator versus a landfill does not cause additional plant and tree regrowth. It is, therefore, biased to grant a large emissions discount to incinerators that does not equally apply to landfills. Although we promote the diversion of all organic materials from landfills or incinerators, WARM 16 incorrectly assumes incineration is better for the climate than landfilling. Along with its dire climate impacts, incineration has devastating air pollution, health, and environmental justice implications

The exclusion of bCO2 emissions does not account for the time-sensitivity of climate change. WARM 16 assumptions acknowledge that “this approach does not distinguish between the timing of CO2 emissions, provided that they occur in a reasonably short time scale relative to the speed of the processes that affect global climate change. In other words, as long as the biogenic carbon would eventually be released as CO2, whether it is released virtually instantaneously (e.g., from combustion) or over a period of a few decades (e.g., decomposition on the forest floor) is inconsequential.” Human activity – including the release of bCO2 through deforestation, incineration, and more – has already altered the Earth’s climate, and severe impacts are anticipated within a decade. The timeframe of emissions impacts is exceedingly crucial, and the magnitude of GHG reductions in the short-term (by 2030) is increasingly of focus in climate mitigation strategies. Delaying the release of bCO2 for even short periods can help avoid overloading short-term atmospheric loading, which could trigger cascading tipping points in the Earth System. 

Biogenic carbon in waste can also be stored for long periods. Wood can store significant fractions of biogenic carbon for up to 100 years; compost can trigger enhanced, long-term carbon sequestration in soil, etc. The IPCC acknowledges that 65% (range: 35-95%) of all biogenic carbon in landfills will remain in place for over a century.

5) Update methane’s Global Warming Potential (GWP) to 80.8 82.5 over 20 years and an atmospheric life of 11.8 years to reflect IPCC’s 2021 Assessment Report (AR 6)

WARM 16 severely understates the global warming potential (GWP) of methane. WARM 16 uses the GWP factor from the Intergovernmental Panel on Climate Change (IPCC) 2007 Assessment. As such, WARM 16 calculates methane’s GWP as 25, comparing methane to carbon dioxide on a 100-year basis. However, IPCC’s 2021 Assessment Report (AR 6) identifies methane as a short-lived greenhouse gas with a GWP of 80.8 – 82.5 over 20 years and an atmospheric life of 11.8 years. Methane to carbon dioxide emissions conversions may be a shorthand inventory tool, but WARM is intended for decision-making purposes and should model real-world behavior. WARM 16 assumptions understate the benefits of avoiding methane through organic management practices and are inconsistent with approaches to reduce short-lived GHGs to slow the rate of climate change. Indeed, all climate pollutants and greenhouse gas emissions should be adjusted to a 20-year climate horizon, not 100 years.

6) Reconsider utility CO2 emissions in combustion net emissions calculations 

We support Energy Justice Network‘s excellent research on this topic. WARM 16 assumes that electricity generated by combustion avoids using fossil fuels on the electric grid and, therefore, subtracts avoided fossil fuel emissions in net calculations. However, most incinerators are displacing renewable energy sources, not fossil fuels. At least two-thirds of U.S. trash incinerators that generate electricity operate in states where they are eligible to sell renewable energy credits (RECs) to electric utilities under state renewable energy mandates. Many of these incinerators are selling RECs in these markets, directly competing with actual renewable energy sources (mainly wind, solar, and hydroelectric). If utilities could not buy RECs from trash incinerators to meet state mandates, they would have to buy them from actual renewable energy sources. In these cases, trash incinerators are displacing renewable energy, not fossil fuels. Therefore, subtracting these emissions as avoided from combustion net calculations is inappropriate. 

Additionally, the electric grid is rapidly shifting from coal to wind and solar. ILSR tracks this here. WARM 16 assumptions regarding fossil fuel avoidance are exceedingly outdated for waste planning purposes. Even if modeling with the most recently available data, WARM 16 calculations do not reflect fossil fuel’s share of the electricity grid looking forward. WARM must provide future projections (or a heavy disclaimer) if used to support long-term decisions and investments in waste disposal methods.

7) Report methane emissions separately from other GHGs

We support Global Alliance for Incinerator Alternatives (GAIA)’s excellent research on this topic. Methane, along with other short-lived climate pollutants, is currently the focus of intensive work and investment. For example, the LOW-Methane initiative under the U.S. State Department is dedicated to reducing methane emissions from waste by 100 million tons in the next few years. The EPA’s recent report quantifying methane emissions from landfilled food waste further demonstrates the importance of measuring methane, especially in the waste management industry. The 2023 Global Methane Pledge Ministerial from COP28 states, “Achieving the GMP goal of cutting anthropogenic methane emissions by at least 30% by 2030 from 2020 levels is the fastest way to reduce near-term warming and is essential to keep a 1.5°C temperature limit within reach.” This effort requires accurate tools for both forecasting and monitoring interventions. Unfortunately, in its current version 16, WARM cannot serve these goals. 

Rather than combine fossil CO2 and other GHGs into a single CO2e metric, WARM should follow the example of databases such as eGRID, which reports each gas separately. Separating measurements allows users to distinguish between short- and long-lived GHGs as needed. It also eliminates the need to recalculate CO2e as Global Warming Potentials are updated in reports – a problem that has already rendered many calculations outdated. For those users who prefer to use the single CO2e metric, calculating it from individual gasses can be included as an option.


Julia Spector - Research and Policy Associate
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Julia Spector

Julia Spector is the Research and Policy Associate for the Composting for Community Initiative. She works to amplify the team’s policy and advocacy efforts to advance community composting from the local to the federal level. Julia has dedicated her career to promoting social and racial justice, working at organizations focused on democracy, economic, and youth issues.