Can an anaerobic digester on my food factory's wastewater earn carbon credits?

It can, if the old treatment let methane escape, for example an open anaerobic lagoon, and the digester captures and burns it. AMS-III.H, the CDM small-scale method for methane recovery in wastewater, was written for this. If your old treatment was aerobic, there is little methane to avoid, and only displaced fossil fuel counts.

Where the reductions come from

The baseline decides most of the result. IPCC 2006 Volume 5 gives a methane correction factor of 0.8 for a deep anaerobic lagoon and 0 for a well run aerobic plant, so the same factory can have a large claim or almost none.

• Methane avoided: the methane your old open lagoon or anaerobic pond released, now captured in a closed digester.
• Fuel displaced: furnace oil, coal, LPG or diesel that the biogas replaces in your boiler or generator.
• Deducted: methane leaking from the digester and gas lines, unburnt methane from the flare, and electricity used by pumps and blowers.

Which methodology fits

• CDM AMS-III.H, methane recovery in wastewater treatment: the CDM small-scale method for industrial effluent. Before you plan around it, check Verra's methodology list on verra.org for whether AMS-III.H, and which version, is open to new VCS projects.
• Gold Standard: runs its own rules and approves CDM methods case by case; check its current methodology list on goldstandard.org for wastewater methane.
• India's CCTS offset mechanism: none of BEE's 12 approved methodologies (list updated 7 July 2026) is for industrial wastewater methane. If you upgrade the biogas to CBG and sell it, BM WA03.003 for compressed biogas may apply.

The additionality question

Your consent to operate requires you to meet discharge limits for BOD and COD; it does not usually prescribe an anaerobic digester. A project that goes beyond the legal requirement and needs credit revenue to make sense can be additional. If a rule or your consent order already requires methane capture, or the digester pays for itself on fuel savings alone, a verifier is likely to reject the claim. Keep the board's consent conditions and your financial case in the project file.

Records to keep from the start

• Daily effluent flow and inlet and outlet COD, from a flow meter and lab tests.
• Biogas flow from a calibrated meter and its methane content from an analyser.
• Flare running hours, and gas sent to the boiler or generator.
• Fuel invoices for the year before and after, to prove what the biogas replaced.

Worked example: methane in the old open lagoon (baseline only)

• Effluent: 200 m3 a day x 8 kg COD per m3 = 1,600 kg COD a day
• Per year at 330 operating days: 1,600 x 330 = 5,28,000 kg COD
• Baseline methane, deep anaerobic lagoon: 5,28,000 x 0.25 kg CH4 per kg COD x 0.8 = 1,05,600 kg CH4
• CO2e at GWP 28 (IPCC AR5): 1,05,600 x 28 = 29,56,800 kg, about 2,957 t CO2e a year
• Credits would be this baseline minus project emissions and leakage, worked out with the methodology's own equations

Flow and COD are illustrative. 0.25 kg CH4 per kg COD and 0.8 are IPCC 2006 defaults; a methodology may set its own values and a different GWP.

What Senseible does here

Senseible gives carbon credit eligibility signals and keeps a bill-backed, dated record of the fuel and electricity your plant uses before and after the digester, which supports the fuel displacement and project emission terms.

• Methane from an effluent treatment plant
• Dairy biogas plant carbon credits
• BEE approved CCTS offset methodologies
• What is additionality

Sources: UNFCCC CDM methodology AMS-III.H, Methane recovery in wastewater treatment, Verra VCS Program, eligible methodologies, BEE, approved methodologies under the CCTS offset mechanism (updated 7 July 2026)

Last reviewed 2026-10-18. Checked 20 October 2026: AMS-III.H acceptance for new Verra and Gold Standard projects not confirmed, so the page tells readers to check both lists. CCTS statement checked against BEE's list of 12 approved methodologies (updated 7 July 2026); none covers industrial wastewater methane. Recheck both when BEE or the standards add methods.