The mill already collects the feedstock.
A sugar mill is the closest thing India has to a purpose-built biogas supply chain that nobody designed as one. Cane arrives on a schedule, the residue lands in one yard, and the growers who supplied the cane are the same people who will buy the fertiliser back.
Three residues, ranked by what they are worth in a digester.
The filter cake left after juice clarification — roughly three to four parts per hundred of cane crushed. Wet, organically rich, already dewatered to a handleable solids content, and dumped in a single yard by the mill's own process. The best-characterised biogas feedstock in Indian agro-industry.
The fraction too small for the boiler. High in lignocellulose and slow to digest on its own, but useful as a structural co-feed that keeps the mix from souring and helps the solid fertiliser hold its form.
Tops and dry leaves left in the field after harvest — the material otherwise burnt. Collected from the command area rather than the mill yard, which makes it a procurement problem before it is a process one.
The mill runs five months. The plant has to run twelve.
A crushing season is roughly 150 to 180 days. A BioCNG plant that only runs during it earns for half a year and carries its capital cost for all of it — which is the single most common reason mill-attached projects fail their own business case. The plant has to be designed from the start as a year-round asset that happens to have a very good five months.
Press mud sets the peak. The catchment carries the trough.
Napier grass and crop residue grown and collected within the mill's own cane catchment fill the off-season, on land and relationships the mill already has. The procurement network does not need to be built twice.
What a mill-attached plant looks like.
| Typical capacity | 10 to 50 TPD BioCNG, sized to press mud availability |
|---|---|
| Primary feed | Press mud at 3–4% of cane crushed |
| Off-season feed | Napier grass and crop residue from the command area |
| Operating days | Designed for 330; crushing season supplies ~165 of them |
| Process | CSTR anaerobic digestion, mesophilic |
| Purification | Water scrubber to SATAT purity, two-stage H₂S removal |
| Fertiliser output | Potash-rich solid manure and liquid concentrate |
| Land requirement | Typically within the existing mill premises |
| Commercial models | Mill-owned with EPC + O&M, or built and operated by us on a long-term feedstock agreement |
Indicative envelope for scoping only. Every figure is re-derived from the mill's own crush data, residue tonnage and moisture in the DPR.
The fertiliser goes back to the people who grow your cane.
This is the part that does not apply to any other sector. A mill's suppliers are a fixed, known, registered set of growers in a fixed command area. Organic carbon returned to that specific soil raises the yield of the specific cane the mill will crush in three years. The loop closes on the mill's own balance sheet.
Press mud stops being a monsoon liability and a disposal line item, and starts being a metered input with a price against it.
Output sells into a contracted offtake framework with a mandated blending obligation behind it, not a spot market.
Solid and liquid organic fertiliser goes back through the mill's existing grower relationships, tested and priced.
Organic carbon restored to command-area soil improves water retention and yield — in the same fields that supply the mill.
Send us last season's crush figures.
Tonnes crushed, press mud generated, and the command area. That is enough for a first sizing and an honest view of the off-season gap.