Your most expensive effluent is a fuel.
Spent wash is the largest single line on a distillery's environmental budget. It is also the densest organic feedstock in the sector — already liquid, already pumpable, already inside the fence line, with a known load that does not vary by ward or by weather.
Eight to fifteen litres for every litre of alcohol.
Spent wash leaves the distillation column hot, acidic, dark and carrying an organic load an order of magnitude above ordinary industrial effluent. Under zero liquid discharge it cannot be released, so it is concentrated, incinerated or composted — all of which consume energy the distillery buys. Biomethanation sits ahead of every one of those steps and removes most of the load before they run.
The load you are paying to destroy is the yield.
Chemical oxygen demand is the cost driver in the effluent plant and the energy content in the digester. They are the same number read from two sides of the ledger.
Ahead of the evaporator, not instead of it.
Biomethanation does not replace the zero liquid discharge train — it reduces what the train has to handle. Downstream evaporation and incineration run on a materially lighter load, which is where most of the operating saving sits.
What a distillery-attached plant looks like.
| Typical capacity | Sized to daily spent wash volume and measured COD |
|---|---|
| Primary feed | Spent wash, fed continuously from the distillation train |
| Co-feed options | Press mud where a mill sits on the same premises |
| Operating days | Matched to distillery run days; buffer storage covers shutdowns |
| Process | High-rate anaerobic digestion with pH and buffering control |
| Purification | Water scrubber to SATAT purity, two-stage H₂S removal |
| Gas destination | Bottled BioCNG, or captive boiler fuel where offtake is unavailable |
| Residue value | Potash-rich concentrate and ash recovered as fertiliser input |
| Commercial models | Distillery-owned with EPC + O&M, or built and operated by us on a long-term effluent agreement |
Indicative envelope for scoping only. Sizing is re-derived from your own spent wash volume, COD and run calendar in the DPR.
Most distillery biogas is burnt in the boiler. That is the cheapest possible use of it.
Raw biogas fired under a boiler displaces coal or bagasse at fuel value. The same gas, scrubbed to SATAT purity and bottled, sells as transport fuel into a mandated blending obligation. The digester is identical; the difference is the purification and bottling island bolted onto the end of it, and the difference in what the gas earns is not marginal.
Boiler gas is worth the coal it displaces. Bottled BioCNG is worth what transport fuel is worth, under a contracted framework.
The effluent plant stops being purely a compliance expense and starts carrying a saleable output alongside it.
Potassium that would have gone up the incinerator stack or into a compost yard is recovered and priced as fertiliser.
Send us a spent wash analysis.
Daily volume, COD, pH and your run calendar. We will come back with a gas estimate and what it does to your effluent operating cost.