Landfill Gas Calculator
Landfills are significant sources of methane, a potent greenhouse gas produced when organic waste decomposes anaerobically. The EPA LandGEM (Landfill Gas Emissions Model) uses a first-order decay equation to estimate annual landfill gas generation: Q(CH4) = k * Lo * M * e^(-k*t), where k is the first-order decay constant (year^-1), Lo is the methane generation potential (m3/Mg), M is the mass of waste in place (metric tons), and t is the time since waste was placed. This simplified single-cohort version estimates peak-year methane generation from a given mass of waste at a specified age.
LandGEM first-order decay formula
Q(CH4) = k * Lo * M * e^(-k * t) [m3/yr]
Q(total LFG) = Q(CH4) / 0.5 [assuming 50% methane content]
CH4 mass (Mg/yr) = Q(CH4) * 0.000716 [density 0.000716 Mg/m3 at STP]
CO2e (Mg/yr) = CH4 mass (Mg/yr) * 28 [GWP100, IPCC AR6]
This is a simplified single-cohort model. The full LandGEM model sums contributions from each year's waste placement. The CO2e conversion uses a global warming potential (GWP100) of 28 for methane from IPCC AR6 (2021). EPA uses 28 for the US GHG inventory.
Landfill gas and climate
- Landfills are the third largest source of US methane emissions, accounting for about 15 percent of total US methane (EPA 2023 GHG inventory).
- EPA's NSPS (New Source Performance Standards) require large landfills to collect and combust at least 90 percent of generated methane.
- Landfill gas energy projects avoid methane emissions while generating electricity or fuel, providing double environmental benefits.
- The LMOP landfill gas energy database lists all US operational and candidate LFG energy projects with data on energy capacity and waste in place.
- Food waste is the most biodegradable and gas-generating component of MSW, making food waste diversion a high-priority methane reduction strategy.
Frequently asked questions
What is the EPA LandGEM model?
LandGEM (Landfill Gas Emissions Model) is EPA's standard tool for estimating gas generation rates from municipal solid waste (MSW) landfills. It uses a first-order decomposition model where the gas generation rate from each year's waste deposit decays exponentially over time. It is used for Clean Air Act compliance, energy recovery planning, and emissions inventories.
What is the Lo constant?
Lo is the methane generation potential of the waste, expressed in m3 of methane per megagram (metric ton) of waste. EPA's default Lo is 100 m3/Mg for MSW in moderate-precipitation climates. Lo ranges from 100 to 200 m3/Mg depending on waste composition and climate. Drier climates produce less gas.
What is the k decay rate constant?
k is the first-order methane generation rate constant in units of year^-1. EPA's default k is 0.04 year^-1 for arid or semi-arid climates, 0.05 year^-1 for moderate climates, and 0.057 year^-1 for wetter climates. A higher k means faster decomposition and earlier peak gas generation.
How is landfill gas composition divided between methane and CO2?
Landfill gas is typically 50 to 55 percent methane (CH4) and 45 to 50 percent carbon dioxide (CO2) by volume, along with trace amounts of nitrogen, oxygen, and non-methane organic compounds (NMOCs). This calculator estimates total gas as 2x methane volume (assuming 50/50 split).
Can landfill gas be used as energy?
Yes. Landfill gas energy projects capture methane and use it to generate electricity, heat, or vehicle fuel. EPA's Landfill Methane Outreach Program (LMOP) has supported over 600 operational landfill gas energy projects in the US with over 2,200 MW of installed capacity. Methane is about 28 times more potent than CO2 as a greenhouse gas over 100 years.
Official sources
- EPA: LandGEM Landfill Gas Emissions Model.
- EPA: Landfill Methane Outreach Program (LMOP).
- EPA: US GHG Inventory: Sources of Emissions.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.