Biogas From Sludge Calculator

Work out biogas from sludge instantly with clear inputs, formula shown and shareable results.

About Biogas From Sludge Calculator

Digester gas yield is around 0.9-1.1 cubic metres per kilogram of volatile solids destroyed, with destruction of 45-55% at conventional mesophilic retention times. At 60-65% methane, biogas holds about 6 kWh of thermal energy per cubic metre, of which a gas engine converts around 38% to electricity.

Formulas

Biogas yield

Gas = volatile solids fed x destruction % x yield per kg VS destroyed

Energy

Thermal kWh = methane volume x 9.94; electrical = thermal x engine efficiency

Worked example

With the default values below, Biogas From Sludge Calculator returns Biogas Production of 855.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Volatile Solids Fedminimum 0 kg VS/day: 1,800 kg VS/day
Volatile Solids Destructionaccepts 0–100 %: 50 %
Gas Yieldminimum 0 m3 per kg VS destroyed: 0.95 m3 per kg VS destroyed
Methane Contentaccepts 0–100 %: 63 %

Results

Biogas Production: 855.00
Methane Production: 538.65
Thermal Energy Available: 5,354.2
Electrical Generation Potential: 2,034.6

Step by step

1Values used
2Biogas yield
3Energy
4Biogas Production= 855.00
5Methane Production= 538.65
6Thermal Energy Available= 5,354.2
7Electrical Generation Potential= 2,034.6

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Digester gas is explosive in air and contains hydrogen sulphide. Gas systems must comply with the applicable gas safety standard with flame arrestors, relief and detection.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Digester gas is explosive in air and contains hydrogen sulphide. Gas systems must comply with the applicable gas safety standard with flame arrestors, relief and detection.

Frequently Asked Questions

Can gas yield be increased?

Yes — thermal hydrolysis, sludge pretreatment or co-digestion with food waste can raise volatile solids destruction to 60-65% and substantially increase gas. Co-digestion often doubles gas output.

How much of the gas is needed on site?

Digester heating typically consumes 30-50% of the thermal energy in a temperate climate, more in winter. Only the surplus is available for export or additional electricity generation.