# Biogas Output Calculator

> Estimate daily biogas, methane, energy and electricity from an anaerobic digester’s feedstock, solids content and specific biogas yield per kg of volatile solids.

Category: Energy & environment · Applies to: Worldwide · Last updated: 2026-10-29
Interactive calculator: https://calculators.geekmidst.com/calculators/biogas-output-calculator

Biogas comes from the volatile solids (the organic part) of the feedstock. Volatile solids × specific yield gives biogas; its methane share sets the energy content.

Also called: Biogas yield calculator, Anaerobic digestion calculator.

## Inputs
- Fresh feedstock per day (unit t; default 10)
- Total solids (unit % of fresh mass; default 10)
- Volatile solids (unit % of total solids; default 80)
- Specific biogas yield (unit m³ per kg VS; default 0.4)
- Methane content of the biogas (unit %; default 60)
- Electrical efficiency of the engine (CHP) (unit %; default 35)
- Operating days per year (default 365)

## Results
- Biogas per day
- Volatile solids fed per day
- Methane per day
- Fuel energy per day
- Electricity per day
- Electricity per year

## Formula

```
VS (kg) = Feed (t) × 1000 × TS% × VS%;  Biogas = VS × Yield;  CH₄ = Biogas × CH₄%;  Energy (kWh) = CH₄ × 35.8 ÷ 3.6;  Electricity = Energy × Efficiency
```

Where:
- 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
1. Volatile solids: 10 t × 1000 × 10% × 80% = 800 kg a day.
2. Biogas: 800 × 0.4 = 320 m³; methane 320 × 60% = 192 m³.
3. Energy: 192 × 35.8 ÷ 3.6 = 1,909.3 kWh; electricity at 35% = 668.3 kWh a day.

**Result:** 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.

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Source: GM¹X CalcVerse — https://calculators.geekmidst.com/calculators/biogas-output-calculator