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Digester Volume Calculator

Work out digester volume instantly with clear inputs, formula shown and shareable results.

About Digester Volume Calculator

Anaerobic digesters are sized on the greater of two criteria: hydraulic retention time, 15-25 days for mesophilic digestion, and volumetric volatile solids loading, generally 1.6-3.2 kg VS/m3/day. Thin sludge is governed by retention time; well-thickened sludge is governed by loading.

Formulas

Retention time basis

Volume = feed volume x retention time

Loading basis

Volume = volatile solids load / maximum volumetric loading

Worked example

With the default values below, Digester Volume Calculator returns Digester Volume Required of 1,200.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Sludge Feed Volumeminimum 0 m3/day
60 m3/day
Hydraulic Retention Timeminimum 0 days
20 days
Volatile Solids Loadminimum 0 kg VS/day
1,800 kg VS/day
Maximum Volumetric Loadingminimum 0 kg VS/m3/day
2 kg VS/m3/day

Results

Digester Volume Required
1,200.00
Volume From Retention Time
1,200.00
Volume From Loading Limit
900.00
Actual Volumetric Loading
1.5000

Step by step

  1. 1Values used
  2. 2Retention time basis
  3. 3Loading basis
  4. 4Digester Volume Required= 1,200.00
  5. 5Volume From Retention Time= 1,200.00
  6. 6Volume From Loading Limit= 900.00
  7. 7Actual Volumetric Loading= 1.5000

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 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.
  • Digester gas is flammable and asphyxiating, and digesters are confined spaces. Design and operation must comply with gas safety and confined space regulations.

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

Digester gas is flammable and asphyxiating, and digesters are confined spaces. Design and operation must comply with gas safety and confined space regulations.

Frequently Asked Questions

Why does thickening the feed help?

It reduces feed volume for the same solids, so the retention time criterion needs less volume. Digesters fed thin sludge waste capacity heating and holding water.

What limits volumetric loading?

Volatile fatty acid accumulation and ammonia inhibition. Overloading drops pH and stalls methanogenesis, which can take weeks to recover.

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