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Biogas Plant Sizing Calculator

Work out biogas plant sizing instantly with clear inputs, formula shown and shareable results.

About Biogas Plant Sizing Calculator

Digester volume is daily slurry feed times hydraulic retention time — 30-50 days for mesophilic dung digestion depending on temperature. Slurry volume is dung plus dilution water, and the gas holder is sized at roughly 60% of daily production to buffer between generation and cooking demand.

Formulas

Digester volume

Slurry (m3/day) = dung x (1 + water ratio) / 1000; digester = slurry x retention time

Gas

Gas (m3/day) = dung x gas yield per kg; holder = 60% of daily gas

Worked example

With the default values below, Biogas Plant Sizing Calculator returns Digester Volume Required of 4.000. Change any input above and every figure here is recalculated in your browser.

Inputs used

Fresh Dung Availableminimum 0.1 kg/day
50 kg/day
Dung To Water Ratiominimum 0.1 : 1
1 : 1
Hydraulic Retention Timeminimum 5 days
40 days
Gas Yieldminimum 0.001 m3 per kg dung
0.04 m3 per kg dung

Results

Digester Volume Required
4.000
Daily Slurry Volume
0.1000
Gas Production
2.000
Gas Holder Volume
1.200

Step by step

  1. 1Values used
  2. 2Digester volume
  3. 3Gas
  4. 4Digester Volume Required= 4.000
  5. 5Daily Slurry Volume= 0.1000
  6. 6Gas Production= 2.000
  7. 7Gas Holder Volume= 1.200

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 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Biogas is flammable and asphyxiating, and digesters can accumulate hydrogen sulphide. Never enter a digester without confined-space procedures, and install the plant to the applicable national biogas standard.

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

Biogas is flammable and asphyxiating, and digesters can accumulate hydrogen sulphide. Never enter a digester without confined-space procedures, and install the plant to the applicable national biogas standard.

Frequently Asked Questions

How much dung does one animal give?

A crossbred cow yields 10-15 kg of collectable dung a day, a buffalo 15-20 kg. Two to four cattle typically support a 2 m3 family plant.

What does the gas replace?

One cubic metre of biogas roughly equals 0.4 kg of LPG or about 3.5 kWh of thermal energy — enough to cook for four to five people for a day.

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