Why Napier grass for CBG?
- Dependable supply: multiple cuts a year reduce dependence on seasonal residues
- High biomass yield per acre under irrigated conditions
- Farmer income: contract farming creates rural livelihoods around the plant
- Co-digestion friendly: works well alongside cattle dung and other residues
Napier grass: farm to CBG
- Harvesting
- Twin-screw shearing
- Feeder
- Pretreatment tank
- Digester
- Gas upgrading
- Compression
- CBG
- Harvesting in the fieldA Napier harvester cuts and collects the grass for handling
- Twin-screw shearingMechanical size reduction and fibre disruption
- Controlled feedingTransfer to the pretreatment tank for mixing and conditioning
- Anaerobic digestionPrepared feedstock produces raw biogas
- Upgrading & compressionCleaned, upgraded and compressed into CBG
- Digestate to FOMOrganic manure that can go back to the Napier fields
Napier CBG plant sizing: 5 TPD vs 10 TPD
Indicative design ranges for Napier grass plants with a small share of cattle dung, using CSTR-type mesophilic digestion:
| Parameter | 5 TPD CBG | 10 TPD CBG |
|---|---|---|
| Fresh Napier grass (20–28% solids) | 100–140 TPD | 200–280 TPD |
| Cultivated land (180–200 t/acre/yr) | 175–275 acres | 350–550 acres |
| Raw biogas (55–60% methane) | ≈ 12,000–13,000 Nm³/day | ≈ 24,000–26,000 Nm³/day |
| Digester working volume (≈ 36–40 days retention) | ≈ 10,000 m³ | ≈ 20,000–21,000 m³ (usually 2–3 digesters) |
| Solid FOM | ≈ 12–20 TPD | ≈ 24–40 TPD |
| Liquid fraction (LFOM) | ≈ 80–100 m³/day | ≈ 160–200 m³/day |
| Electricity | ≈ 1.4–1.8 kWh per kg of CBG, i.e. ≈ 7,000–9,000 kWh/day for 5 TPD and ≈ 14,000–18,000 kWh/day for 10 TPD | |
Planning ranges by Biovardhan's engineering team. A rule of thumb: about 2,500 Nm³ of raw biogas and about 2,000 m³ of digester volume per TPD of CBG. Final sizing comes from lab tests on your grass at its harvest age.
Feedstock rules that protect gas yield: harvest at about 60–75 days of growth (older grass turns woody and gives less gas), chop or shear to below about 50 mm, reject grass with soil and stones, and keep 3–4 days of grass at site plus a monsoon buffer of about two weeks (silage or stored grass).
Detailed guides: 5 TPD CBG plant · 10 TPD CBG plant. Check how your own numbers compare with our feedstock-to-CBG calculator.
Planning a Napier-based CBG project
| Planning area | Key questions |
|---|---|
| Cultivation | Own land or contract farming? Variety, irrigation, fertilisation and cutting interval |
| Harvest logistics | Harvesters, transport distance and daily delivery schedule |
| Storage | Silage or fresh feeding to bridge gaps between cuts |
| Pretreatment | Shearing capacity, moisture control and feeding system |
| Process | Retention time, organic loading and co-digestion ratio |
Planning a Napier-based CBG project? Share your land, capacity and location and we'll help you work out the feedstock plan. Related: Biomass pretreatment · Paddy straw CBG plant · CBG DPR
Frequently asked questions
Yes. Napier grass is widely used as an energy crop for CBG and Bio-CNG plants because of its high biomass yield and multiple harvests per year. It is often co-digested with cattle dung.
Hybrid and "super" Napier varieties are popular for their biomass yield. The best variety depends on local climate, irrigation and soil. Gas yield and fibre content should be tested at the cutting stage you plan to harvest.
As a rule of thumb, roughly 35–55 acres of well-irrigated Napier grass per TPD of CBG, assuming 180–200 tonnes of fresh grass per acre per year. A 5 TPD plant needs about 175–275 acres, and a 10 TPD plant about 350–550 acres. The DPR confirms this from local yields and the cutting schedule.
Typically about 200–280 tonnes of fresh Napier grass per day, often with a small share of cattle dung. That is roughly 70,000–95,000 tonnes a year over about 340 operating days.
Napier grass has a compact lignocellulosic fibre structure. Twin-screw shearing disrupts and opens the fibre to make it more accessible to microbes, which supports better mixing, feeding and digestion. Actual benefits depend on grass maturity, moisture and plant conditions.