GWMS 2024

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