Quick answer
To produce 1 kg of CBG you typically need about 40–60 kg of fresh cow dung, 20–30 kg of press mud, 20–28 kg of fresh Napier grass or 8–11 kg of air-dry paddy straw. A 5 TPD plant therefore needs roughly 200–300 TPD of cow dung, or about 100–140 TPD of fresh Napier grass.
Indicative feedstock required per kg of CBG
| Feedstock | kg feedstock per kg CBG | For a 5 TPD plant (TPD of feedstock) | Notes |
|---|---|---|---|
| Cattle dung (fresh) | 40–60 | 200–300 | About 15–20% solids; easy digestion but low gas per tonne |
| Press mud (sugar mill) | 20–30 | 100–150 | Seasonal with the crushing season; good gas potential |
| Napier grass (fresh, harvested at 60–75 days) | 20–28 | 100–140 | About 20–25% solids; yield falls if the grass is over-mature and woody |
| Paddy straw (baled, air-dry) | 8–11 | 40–55 | High solids; needs shredding, milling and shearing |
| Wheat / mustard straw (air-dry) | 8–12 | 40–60 | Similar fibre challenges to paddy straw |
| Food & market (mandi) waste | 15–22 | 75–110 | Highly degradable; needs segregation and acidification control |
| Segregated municipal organic waste | 18–30 | 90–150 | Depends heavily on segregation quality and inert content |
Indicative planning ranges by Biovardhan's engineering team, assuming good pretreatment and stable mesophilic digestion. Basis: 1 kg CBG ≈ 1.4 Nm³ methane. Always confirm with lab tests on your own feedstock.
CBG yield calculator
Planning estimate only. Your DPR should be based on laboratory BMP tests of representative, seasonal feedstock samples. Ask us to test your feedstock.
How the numbers are worked out
- Solids: only the organic (volatile) part of the dry matter makes gas, so wet feedstocks like cow dung need many more tonnes than dry straw.
- Methane potential: each tonne of volatile solids gives a characteristic volume of methane, measured in the lab as BMP (biochemical methane potential).
- Conversion: 1 kg of CBG is about 1.4 Nm³ of methane, so feedstock per kg CBG = 1.4 ÷ (methane per kg of fresh feedstock).
- Real-plant factors: pretreatment quality, retention time, temperature stability and upgrading losses decide how much of the lab potential a plant actually captures.
Check any quotation against this: if a supplier's guaranteed CBG output needs more methane than your feedstock quantity can supply, the guarantee will not be met in practice. See our CBG quotation checklist.
Why most plants use a feedstock mix
Co-digestion improves stability and supply security. For example, cattle dung adds buffering and microbes to fibrous Napier grass or straw, and press mud can fill seasonal gaps. The mix ratio must be designed into the pretreatment line and digester loading. See pretreatment routes by feedstock.
Worked example: 10 TPD CBG from Napier grass + cattle dung
- Cattle dung, about 5 TPD: at 40–60 kg per kg CBG it adds only about 0.1 TPD of CBG. Its real job is to supply microbes and buffering for stable digestion.
- Napier grass, about 200–280 TPD fresh: this provides the remaining ~9.9 TPD of CBG, which means roughly 350–550 acres of irrigated Napier.
- Raw biogas, about 24,000–26,000 Nm³/day at 55–60% methane. That's about 14,000 Nm³ of methane a day, which is what 10 TPD of CBG needs.
See full 5 TPD vs 10 TPD Napier plant sizing.
Frequently asked questions
Typically about 40–60 kg of fresh cattle dung per kg of CBG. The exact figure depends on dung freshness, solids content, dilution and how well the digester is run.
Roughly 20–28 kg of fresh Napier grass per kg of CBG, when the grass is harvested young (about 60–75 days) with 20–25% solids. Over-mature, woody grass gives less gas.
Around 8–11 kg of air-dry baled paddy straw per kg of CBG, provided the straw is properly shredded and pretreated before digestion.
One kg of CBG contains about 1.4 Nm³ of methane. With raw biogas at 55–60% methane, that is roughly 2.3–2.6 Nm³ of raw biogas per kg of CBG, before small upgrading losses.
No. They are indicative planning figures. Actual yield must be confirmed by laboratory analysis (total solids, volatile solids and biochemical methane potential) of your own feedstock samples, which is the first step of every Biovardhan DPR.