How much energy is in your wastewater?

A simple industrial example

Consider 10,000 litres/day at an assumed COD of 5,000 mg/L. That contains 50 kg of COD. If 70% is destroyed in digestion and 80% of the theoretical methane is recovered, the example produces about 9.8 Nm³ of methane/day, supporting roughly 24 kWh of CHP electricity, or an alternative 1.6 kg of hydrogen.

What is COD?

Chemical oxygen demand is a laboratory measure of organic strength. It helps estimate the energy-bearing load in wastewater. The theoretical methane relationship is about 0.35 Nm³ per kg COD destroyed; practical recovery must be assessed separately. [S3]

Australian experience: Malabar

At Malabar in Sydney, wastewater-derived biogas is upgraded for network injection. The project's 2026 final report shows why gas supply and plant operation must be coordinated: improved upgrader reliability alone did not remove upstream supply constraints. Treat gas availability as a measured input, not a fixed promise. [A6]

Existing treatment matters

Industrial anaerobic treatment, municipal sludge digestion and dilute sewage are different cases. Confirm which material reaches the proposed process, its temperature, treatment needs, dissolved methane and the energy used by the whole treatment plant.

Pair the flow record with organic-strength evidence

Record litres or cubic metres per period, sampling location, COD or suitable solids analysis, measurement date and operating pattern. Distinguish incoming wastewater from the load removed in treatment and gas recovered downstream.

Flow without composition is useful intake information, but cannot establish an energy yield. Record Available or Needed capacity in its original unit and identify current treatment obligations, existing gas use and any uncommitted stream.

Assess the whole treatment boundary

Compare treatment performance and savings alongside heating, pumping, gas capture, cleaning and plant electricity. A gas-production estimate does not establish net export from the whole treatment facility.

Where biogas is already collected, use measured flow, methane content and existing commitments. Biomethane upgrading and CO₂ recovery need separate product specifications and demand; hydrogen needs a further conversion process.

A nearby liquid source is not automatically a co-feedstock

Check concentration, contaminants, transport water and the receiving plant's permitted treatment envelope. Trade-waste arrangements and site-specific acceptance conditions are essential before proposing regional collection.

Retain your measurements privately, compare suitable routes and choose whether to submit a reviewed resource or treatment-demand signal. A shared postcode does not establish treatment capacity, permission or a hub.

Frequently asked questions

Is 10,000 litres enough for a commercial plant?

Volume alone cannot answer that. Organic strength, treatment savings and the selected equipment matter.

Can I enter litres without a laboratory result?

You can save the flow record, but the energy estimate is labelled organic strength required.

Sources and references

US EPA, methane recovery protocol

ARENA, Malabar Biomethane Injection Project final report (2026)

Indicative operating-day examples

Indicative screening example. Actual output depends on feedstock testing, collection, plant design and operating conditions. CHP electricity and heat are one route; hydrogen and BioLNG are alternatives and cannot be added to the CHP or biomethane figures.

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