How much coal and CO2 does a 250 kW biomass gasifier save in a tea dryer?

BEE's Jorhat report counts 258 t of coal saved a year, about 453 t of fossil CO2, burning 342 t of garden wood. Only 173 t of that coal is the gasifier; 85 t comes from a better burner on the coal heater, which keeps running. Cost Rs 17.18 lakh, payback 3.70 years at 2010 prices.

The factory in the report

• 225 kg of made tea an hour at 950 kcal per kg; the coal heater runs at 19.81% efficiency and burns 240 kg an hour.
• 12 hours a day, 300 days: 3,600 hours and 863.2 t of coal a year at 4,500 kcal/kg and Rs 4.50 a kg.
• A better burner lifts efficiency to 21.97%: 216 kg an hour, 84.9 t a year less.
• The gasifier makes 250 kW of heat, 215,000 kcal an hour, as producer gas at about 1,000 kcal/m3, replacing 48 kg of coal an hour: 172.8 t a year.
• Wood from the tea gardens at 95 kg an hour, 342 t a year at Rs 1.75 a kg.

Most of the coal stays

After both changes the factory still burns about 605 t of coal a year, 70% of what it burned before. A 250 kW gasifier supplies only part of the dryer's heat. Size it against your full heat demand if you want coal gone.

CO2 counted properly

257.67 t of coal x 1.76 = 453 t of fossil CO2 avoided. CO2 from the wood is biogenic and reported separately. The report's 468.12 t used a higher coal factor. Assam coal often carries more carbon than India's average, so use your supplier's calorific value or a lab analysis if you have one.

One figure to get in writing

The specification table rates the gasifier at 250 kg of wood an hour; the costing uses 95 kg. At 250 kg an hour, wood would cost Rs 15.75 lakh a year against Rs 11.59 lakh of coal saved, and the project would lose money. Ask the supplier to guarantee kg of wood per hour at 250 kW.

One season of 3,600 hours

• Burner: 863.2 t x (1 minus 19.81 / 21.97) = 84.9 t coal
• Gasifier: 48 kg an hour x 3,600 = 172.8 t coal
• Total: 257.7 t coal x 1.76 = 453.5 t CO2 avoided
• Coal still burned: 863.2 minus 257.7 = 605.5 t, about 1,066 t CO2

Coal at our Indian coal factor, an estimate. The report gives no figure for the gasifier's blower power.

What Senseible does here

Senseible reads coal invoices and electricity bills into monthly totals and CO2, each linked to its bill, so the coal a gasifier really saves shows up against the year before. The green loan check shows what a lender will want.

• Green loan readiness check
• Jorhat tea factories: coal, gas and CO2
• Biomass boilers: methane and N2O stay in Scope 1
• Tea factory footprint per kg

Sources: BEE, Detailed project report: biomass gasifier for 250 kW thermal application replacing coal, Jorhat tea cluster (2010, SAMEEEKSHA), GHG Protocol Corporate Standard (biogenic CO2 reported separately)

Last reviewed 2026-10-31. Report figures are from a BEE SME programme project report; costs and paybacks are at the report year's prices. Check today's fuel and power prices before you rely on the payback.