Residue stream
Anaerobic digestion needs water, unlike pyrolysis. But only the volatile solids fraction actually digests, so a dilute stream can have excellent yield per kilo of solids and still be uneconomic to haul.
Feedstock characterisation
Literature defaults cap confidence at what the published range supports. Supplying your own lab figures raises it a tier, because the estimate stops depending on someone else's feedstock.
Where the mass goes
Digestible material
Methane
Digestate out
Value by route
Electricity and upgraded biomethane are alternative fates for the same gas — not additive. Avoided disposal and digestate sit alongside either.
| Route | Output | Value / yr |
|---|
Prices
None of these carry a sourced quote — they are order-of-magnitude placeholders. Replace them with your own tariff and offtake figures before this informs a decision.
Why biomethane pricing is the volatile one
Upgraded biomethane sold into a pipeline can carry environmental credits that dominate the commodity value — RIN and LCFS credits in the US, and equivalent schemes elsewhere. Whether your project qualifies depends on feedstock, pathway certification and jurisdiction, and the credit can be worth several times the gas itself. The default here is a bare commodity figure with no credit assumed, which will understate a qualifying project and overstate a non-qualifying one.
Method and sources
How methane and digestate are calculated
Total solids are wet mass times the TS fraction. Volatile solids are total solids times the VS fraction — this is the only part that digests. Methane is volatile solids times the biochemical methane potential, expressed in cubic metres of CH₄ per kilogram of VS. Energy uses 9.97 kWh per cubic metre of methane; electricity assumes 38% CHP electrical efficiency.
Digestate mass is taken as input mass less the volatile solids actually destroyed. Only a small fraction of the input leaves as gas, so digestate volume closely tracks input volume — which is why haulage and land access usually decide whether a project works, not gas yield.
Nutrient content uses published whole-digestate ranges of 2.3–4.2 kg/t nitrogen, 0.2–1.5 kg/t phosphorus and 1.3–5.2 kg/t potassium. Feedstock composition shifts this considerably: high-protein streams such as food waste and poultry manure give nitrogen-rich digestate, cattle manure gives a more balanced NPK profile, and crop residue is lower in all three while contributing more soil organic carbon.
Get the real numbers
This is a range from published coefficients. A feedstock assessment characterises your actual stream, validates the yield, and maps where the digestate goes.