How Much Biogas Do Manure and Other Substrates Produce?
Typical biogas yields by substrate (manure, vinasse, whey, food waste) in m³ per ton of volatile solids, with the calculation method and a worked example.
Biogas yield depends on the volatile solids (VS) each substrate contributes, not on its wet weight. As an order of magnitude, cattle manure yields roughly 0.20–0.30 m³ of biogas per kg of VS, pig manure 0.30–0.45, poultry litter 0.30–0.50, and energy substrates such as cheese whey or food waste reach 0.40–0.60 m³/kg VS. To estimate the real output you convert wet tons into total solids (TS), then into volatile solids (VS), and only then apply the substrate-specific yield.
The method: from wet ton to cubic meters of biogas
Biogas comes from the anaerobic digestion of biodegradable organic matter. That fraction is measured as volatile solids (the part of total solids that burns off at 550 °C). The calculation has three steps:
- Total solids (TS): wet mass × %TS. This is the dry matter of the substrate.
- Volatile solids (VS): TS × %VS/TS. This is the organic fraction that actually degrades.
- Biogas: VS × specific yield (m³ biogas / kg VS) for that substrate.
The compact formula is:
Biogas (m³/day) = Wet mass (kg/day) × %TS × (%VS/TS) × Yield (m³/kg VS)
The specific yield —called biochemical methane potential when expressed as methane only— comes from a lab test (BMP assay) or from the literature. Working with prudent ranges avoids oversizing the plant. Methane (CH₄) content in biogas typically sits between 55% and 65% depending on the substrate; the rest is CO₂ plus traces of H₂S and moisture.
Reference table: biogas yield by substrate
Typical engineering values. Use them as pre-design guidance; the final figure comes from characterizing the actual substrate.
| Substrate | TS (% wet) | VS (% of TS) | Biogas (m³/kg VS) | Typical CH₄ |
|---|---|---|---|---|
| Cattle manure (slurry) | 8–12% | 80% | 0.20–0.30 | 55–60% |
| Pig manure (slurry) | 5–8% | 80% | 0.30–0.45 | 60–65% |
| Poultry litter | 20–30% | 75% | 0.30–0.50 | 60% |
| Vinasse (cane ethanol) | 4–8% | 75–85% | 0.25–0.35 | 55–60% |
| Cheese whey | 6–7% | 85–90% | 0.40–0.60 | 55–60% |
| Food waste / OFMSW | 20–30% | 85–90% | 0.40–0.60 | 60% |
This shows why wet weight is misleading: a pig slurry at 6% TS delivers little dry matter per ton, while whey or food waste —more concentrated and highly biodegradable— yield far more per kilo of VS. That is why co-digestion —blending a base manure with an energy co-substrate— is the standard way to raise output without overloading the reactor.
Worked example: 200-cow dairy + whey
Consider a housed dairy that collects manure from 200 cows and also receives 5 tons/day of whey from a nearby cheesemaker.
Step 1 — Cattle manure
A housed dairy cow generates on the order of 50 kg/day of collectable wet manure. With 200 cows:
- Wet mass: 200 × 50 = 10,000 kg/day
- TS (10%): 10,000 × 0.10 = 1,000 kg TS/day
- VS (80% of TS): 1,000 × 0.80 = 800 kg VS/day
- Biogas (0.25 m³/kg VS): 800 × 0.25 = 200 m³/day
Step 2 — Cheese whey
- Wet mass: 5,000 kg/day
- TS (6.5%): 5,000 × 0.065 = 325 kg TS/day
- VS (88% of TS): 325 × 0.88 = 286 kg VS/day
- Biogas (0.50 m³/kg VS): 286 × 0.50 = 143 m³/day
Step 3 — Total and methane
Total biogas: 200 + 143 = 343 m³/day (≈ 125,000 m³/year). At an average methane content of 58%, available methane is 343 × 0.58 ≈ 199 m³ CH₄/day. That methane is what is later converted into thermal or electric energy. The whey, though only a third of the manure's wet mass, contributes 42% of the biogas: the co-digestion effect.
Factors that move the real yield
- Temperature: a stable mesophilic reactor (35–38 °C) produces more and better gas than a cold or fluctuating one.
- Hydraulic retention time (HRT): too short and not all available VS degrades.
- Organic loading rate: overloading acidifies the reactor and cuts production.
- Inhibitors: excess ammonia (poultry), salts, disinfectants or antibiotics slow the biology.
- C/N ratio: the recommended range is around 20–30; co-digestion helps balance it.
To move from these biogas figures to reactor size, review how to size a farm biodigester, and to understand the full plant, our guide on what an industrial biodigester is. Tech Tank delivers turn-key biogas and biodigester plants: we characterize the substrate, calculate yield with engineering judgment, and size the reactor and gas holder on real data.
If you have a stream of manure, vinasse, whey or food waste and want to know how much biogas and energy you can obtain, send us your substrate data and we will build a technical estimate for your project.
Frequently Asked Questions
Why calculate by volatile solids instead of manure weight?
Because water and minerals produce no gas. Only the biodegradable organic fraction —the volatile solids— turns into biogas. Two manures with the same wet weight but different moisture yield very differently, so the calculation is standardized per kg of VS.
How much biogas does one cow produce per day?
As an order of magnitude, a housed dairy cow contributes about 0.8–1.2 m³ of biogas per day if its manure is well collected. On pasture the figure drops because much of the manure stays in the field and never reaches the reactor.
Which substrate produces the most biogas?
Per kg of volatile solids, concentrated and highly biodegradable substrates such as cheese whey, oils, fats and food waste yield more (0.4–0.6 m³/kg VS or higher). Manure yields less per kilo, but provides the stable biological base and the volume that make co-digestion viable.
Can I mix several substrates in the same digester?
Yes, that is co-digestion and it is usually the most profitable option: a base substrate (manure) combined with energy co-substrates. You must respect loading limits and balance the C/N ratio, but a well-designed mix raises gas output without enlarging the reactor.
Are these yields good enough to size the plant?
They are good for pre-design and for estimating the order of magnitude. For final design the real substrate is characterized (TS, VS, BMP assay) because yield varies with animal diet, dilution and co-substrate quality.