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

Canonical: https://senseible.earth/answers/tea-dryer-coal-to-biomass-gasifier-co2

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](https://senseible.earth/green-loan-check)
- [Jorhat tea factories: coal, gas and CO2](https://senseible.earth/answers/jorhat-tea-factories-coal-gas-drying-carbon)
- [Biomass boilers: methane and N2O stay in Scope 1](https://senseible.earth/answers/biomass-boiler-ch4-n2o-still-scope-1)
- [Tea factory footprint per kg](https://senseible.earth/answers/tea-factory-carbon-footprint-per-kg-made-tea)

Sources: [BEE, Detailed project report: biomass gasifier for 250 kW thermal application replacing coal, Jorhat tea cluster (2010, SAMEEEKSHA)](https://sameeeksha.org/pdf/dpr/Jorhat_tea_cluster/01_Biomass_gasifier_for250kW_thermal_application_replacing_coal_Jorhat.pdf), [GHG Protocol Corporate Standard (biogenic CO2 reported separately)](https://ghgprotocol.org/corporate-standard)

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.