How Much Biogas Does a Treatment Plant Make?

A treatment plant's biogas output is driven by its organic load, not its size: anaerobic digestion typically yields 0.30–0.45 m³ of biogas per kg of COD removed, about 60% of it methane. A plant handling 10,000 kg COD/day therefore produces roughly 3,000–4,500 m³ of biogas daily—scaling directly with the biodegradable load it treats.

The Yield Basis: COD Removed

Biogas comes from the organics that microbes break down, so the honest unit is per kg of COD removed, not per m³ of wastewater. The 0.30–0.45 m³/kg COD band holds across digester types (covered sludge digester, UASB, EGSB). Multiply a plant's daily COD removal by this band and you get its biogas potential.

Per-Person and Per-Flow Scaling

At municipal scale, the organic load tracks population and diet. Sewage contributes on the order of 0.02–0.05 m³ of biogas per person per day from its biodegradable fraction. Industrial or agricultural plants with high-strength streams produce far more per cubic metre of water—which is why food and palm-oil sites dominate total biogas output.

Comparative Data Table: Biogas Output by Basis

Technical Considerations

Real output is below the theoretical band when feeding is unstable, temperature drifts from mesophilic 35–38°C, or the digester is under-loaded. Co-digestion with high-energy feedstock can push yield toward the top of the band. Measuring inlet COD and gas volume continuously is the only way to know actual performance.

Advantages and Limitations

Tying output to COD makes biogas predictable and designable. The limit is that dilute plants simply have less to recover, and that shock loads or toxins can cut yield suddenly. The number is an estimate until measured on the specific stream.

Best Practices / How to Estimate Yours

Start from measured COD removal, apply 0.30–0.45 m³/kg, and model CHP on the steady (not peak) flow. Add co-digestion only with spare capacity and a C:N near 20–30:1. Meter gas continuously so estimates become actuals and you can catch drops early.

A treatment plant makes biogas in proportion to the organics it removes—about 0.30–0.45 m³ per kg of COD, ~60% methane. Per person that is roughly 0.02–0.05 m³/day; per tonne of dewatered sludge, about 90–180 m³. Load, not size, sets the number.

Frequently Asked Questions (FAQ)

Q1: How much biogas does a treatment plant make?
A: It scales with organic load: about 0.30–0.45 m³ of biogas per kg of COD removed, roughly 60% methane—so output tracks COD, not plant footprint.

Q2: What drives the amount?
A: Biodegradable COD removed, stable mesophilic temperature (35–38°C), steady feeding, and digester loading. Shock loads and toxins cut yield.

Q3: How much per person?
A: Municipal sewage yields on the order of 0.02–0.05 m³ of biogas per person per day from its biodegradable fraction; diet and sewer type shift it.

Q4: How much per tonne of sludge?
A: About 90–180 m³ per tonne of dewatered sludge at 20–25% dry solids, depending on volatile-solids content and digestion efficiency.

Q5: Why use COD instead of volume?
A: Biogas comes from organics, not water. Per-kg-COD is the universal, comparable yield basis across plants and digester types.

Q6: Can co-digestion raise output?
A: Yes—adding high-energy feedstock with spare capacity and a C:N near 20–30:1 can push yield toward the top of the 0.30–0.45 m³/kg band.

Project Case Reference

Malaysia Biogas Project  —  Malaysia · 2026

5 GFS Tanks   ·   27,000 m³ Total Volume   ·   22,000 m³ Biogas/Day

A large-scale biogas project in Malaysia featuring 5 Glass-Fused-to-Steel (GFS) tanks. The project achieves approximately 80% digestibility, with each single tank producing about 4,400 m³ of biogas daily, totaling 22,000 m³ per day across all 5 tanks.

Technical Specifications

Single Tank Volume: 5,400 m³ (Ø24.46 × 12 m)

Total Effective Volume: 27,000 m³ (5 tanks)

Daily Biogas Production: 22,000 m³ total

Digestibility: ≈ 80%

Gas Production Rate: 0.45 m³ / kg COD removed

Tank Type: Glass-Fused-to-Steel (GFS)

Water Quality Data