Landfill Methane Calculator

This calculator uses the IPCC mass-balance (first-order) methodology. Methane generated equals: Waste Deposited × DOC × DOCf × MCF × (16/12), where 16/12 converts carbon mass to methane mass. The result represents the annual potential methane produced from decomposing organic waste under anaerobic conditions.

The MCF reflects how landfill management practices influence methane production. Fully managed, lined anaerobic landfills have an MCF of 1.0, while semi-aerobic designs score 0.5 because oxygen introduction suppresses some methanogenesis. Unmanaged open dumps range from 0.4 (shallow) to 0.8 (deep). The IPCC provides these default values in its Waste sector guidelines.

DOC is the fraction of the waste stream capable of biological degradation. It includes food waste, paper, garden waste, and wood. Typical municipal solid waste has a DOC of 0.12–0.20. Higher DOC values mean more carbon is available to be converted to methane and CO₂ during decomposition.

The GWP converts methane mass into CO₂ equivalent (CO₂e) for comparison with other greenhouse gases. The IPCC AR5 value of 28 (100-year timeframe) is widely used in national inventories and regulatory reporting. Some frameworks use 34 (including climate-carbon feedbacks) or the shorter 20-year GWP of 84, but 28 is the most common standard.

Recovered methane (in tonnes) is converted to cubic meters using methane's density (~0.717 kg/m³), then multiplied by its energy content (~35.8 MJ/m³). Assuming a typical gas-to-electricity conversion efficiency of ~35% for landfill gas engines, the result is expressed in MWh per year. This is a theoretical potential — actual output depends on engine availability and gas quality.

Well-operated landfill gas collection systems in managed landfills typically capture 60–85% of generated gas. The U.S. EPA and LMOP use ~75% as a representative figure for active collection systems. Landfills without collection systems have a 0% recovery rate, meaning all generated methane is emitted to the atmosphere.

When landfill gas is captured and combusted (even flared), methane is converted to CO₂, which has a much lower GWP (1 vs. 28). When used for electricity or heat, it also offsets fossil fuel combustion elsewhere. The net CO₂e result shown in this calculator accounts for this benefit, reflecting the emissions that would reach the atmosphere after recovery.

DOCf is the fraction of degradable organic carbon that actually decomposes under anaerobic conditions. Not all organic carbon mineralises — some is locked in recalcitrant structures. The IPCC default is 0.5, meaning 50% of the theoretical DOC is available for methanogenesis. Unless site-specific data are available, 0.5 is the recommended value.