How to use this calculator
- Enter or choose fresh feedstock per day.
- Enter or choose total solids.
- Enter or choose volatile solids.
- Enter or choose specific biogas yield.
- Enter or choose methane content of the biogas.
- The biogas per day updates as you type. Use Copy result or Share to keep it.
Method
VS (kg) = Feed (t) × 1000 × TS% × VS%; Biogas = VS × Yield; CH₄ = Biogas × CH₄%; Energy (kWh) = CH₄ × 35.8 ÷ 3.6; Electricity = Energy × Efficiency
- TS
- dry matter share of the fresh feedstock
- VS
- organic (combustible) share of the dry matter
- Yield
- m³ of biogas per kg VS added
- 35.8 MJ/m³
- approximate lower heating value of methane at 0 °C and 1 atm
Worked example
- Volatile solids: 10 t × 1000 × 10% × 80% = 800 kg a day.
- Biogas: 800 × 0.4 = 320 m³; methane 320 × 60% = 192 m³.
- Energy: 192 × 35.8 ÷ 3.6 = 1,909.3 kWh; electricity at 35% = 668.3 kWh a day.
10 t a day of this feedstock yields about 320 m³ of biogas, enough for roughly 670 kWh of electricity a day.
What the result means
The specific yield dominates the answer and depends on feedstock, temperature and retention time. Use measured or laboratory biochemical methane potential (BMP) data before sizing equipment.
Assumptions and limits
- Steady feeding and stable digestion.
- Gas volumes at normal conditions (0 °C, 1 atm).
- Parasitic load of the plant, flaring and heat use are not deducted.
Questions
How much energy is in a cubic metre of biogas?
About 35.8 MJ (≈ 9.9 kWh) per m³ of methane, so biogas at 60% methane holds roughly 6 kWh per m³.
What are total and volatile solids?
Total solids is the dry matter left after drying; volatile solids is the part of it that burns off at high temperature, roughly the organic matter microbes can digest.