Material Insights · Understanding the Material World

Biogas and biomethane: Techniques

Digesters, upgraders and landfill wells compared

What this tab covers The methods used to capture this energy: how each works, and how they compare on efficiency, cost, life-cycle emissions, maturity and scale.

Three routes are covered: digesting manure, food waste and sewage; upgrading the gas to grid-quality biomethane; and capturing gas that landfills produce anyway. World output was just under 50 billion cubic metres of methane equivalent in 2023.

Comparison

MethodEfficiencyCostLife-cycle emissionsMaturityScale
Anaerobic digestion of manure, food waste and sewage3267426-32% to electricity in engines; 40-85% in CHP; average leakage about 6%Biogas USD 2-20/MBtu (2018); electricity USD 60-150/MWh and investment USD 2,574-6,104/kW (2015); household digesters in Africa USD 500-800EU default savings for biogas electricity: manure with closed digestate storage 219-240% (net negative, because manure methane that would have escaped is avoided); maize silage 10-53%; biowaste 14-78%mature About 80% of biogases are used unupgraded, mainly for electricity and heat; about 17,000 biogas CHP plants in the EU28 (2016); 42 million household digesters installed in China by 2015
Upgrading to biomethane5267Methane slip 0.2-10% (European measurements)Average USD 18/GJ (about USD 65/MWh, calculated), 90% of potential at USD 10-30/GJ; upgrading USD 2-4/MBtu, membranes about USD 3/GJEU default savings for biomethane transport fuel (comparator 94 g CO2eq/MJ): manure, closed digestate, off-gas burned 202% (typical 206%, about -100 g CO2eq/MJ, calculated); biowaste, open digestate, no off-gas combustion 20% (typical 43%, about 54 g CO2eq/MJ, calculated)mature About 8-10 bcm in 2023, roughly 0.2% of world gas demand (calculated)
Landfill gas capture168US EPA defaults 50% (daily cover) to 85% (final cap)Below USD 3/MBtu (2018), the cheapest biogasNot given as an EU default valuemature 542 US projects (September 2024): 63% electricity, 17% direct gas use, 20% renewable natural gas

Landfill gas is cheapest because the waste is already collected, but capture is incomplete while cells are open. Digesting manure costs more but gives the largest climate benefit by preventing methane that manure stores would release, which is why EU defaults for manure biomethane exceed 100%. Purpose-grown maize saves far less (17-68%) and uses cropland. Upgrading adds USD 2-4/MBtu and a further leak risk but lets biogas use gas pipelines. At USD 18/GJ biomethane costs far more than natural gas; the IEA finds about 280 bcm could compete at USD 50/tCO2 with best-practice emissions management.

How each method works

Anaerobic digestion of manure, food waste and sewage

Organic material sits for weeks in a sealed, warmed tank without oxygen. Bacteria and archaea break it down in stages, releasing a gas of roughly half methane and half CO2; the leftover digestate is spread as fertiliser.32674

Upgrading to biomethane

CO2, water, hydrogen sulphide and trace gases are stripped out by water scrubbing, membranes or pressure swing adsorption, so the gas can enter the grid or fuel vehicles.5267

Landfill gas capture

Buried waste decays without oxygen, making a gas of about 50% methane. Wells and pipes under suction draw it to a flare, engine or upgrading plant.168

Sources

  1. 40 CFR Part 98 Subpart HH (Municipal Solid Waste Landfills), Table HH-3: landfill gas collection efficiencies US Environmental Protection Agency, Greenhouse Gas Reporting Program (eCFR), 2024
  2. Outlook for Biogas and Biomethane: A global geospatial assessment (World Energy Outlook special report) International Energy Agency, 2025
  3. Biomass for Heat and Power, Technology Brief E05 IEA-ETSAP and IRENA, 2015
  4. Biomass CHP facilities (factsheet) ETIP Bioenergy (European Technology and Innovation Platform)
  5. IEA's 2025 Outlook for Biogas and Biomethane (summary of the IEA report) World Biogas Association, 2025
  6. Outlook for Biogas and Biomethane: Prospects for organic growth International Energy Agency, 2020
  7. Directive (EU) 2018/2001 (Renewable Energy Directive II), Annex VI: typical and default greenhouse gas savings for biogas and biomethane; fossil comparators 183 g CO2eq/MJ (electricity) and 94 (biomethane). Default values not changed by amending Directive (EU) 2023/2413 (RED III); a Commission revision was in draft in 2026 European Union (EUR-Lex), 2018
  8. Basic Information about Landfill Gas (Landfill Methane Outreach Program) US Environmental Protection Agency, 2024