What do coal gasification and captive power change in a tea factory's coal and diesel use?

In BEE's Jorhat report, coal falls by 136.8 t a year and the dual fuel DG makes 181,440 kWh, but burns 9,000 litres more diesel. Net CO2 cut is about 339 t a year on today's grid, not the report's 410 t. Cost Rs 18.72 lakh, payback 1.15 years at 2010 prices.

The factory the report starts from

• One drier making 280 kg of made tea an hour, fed by an indirect coal heater burning 238 kg of Upper Assam coal an hour.
• Coal at 4,500 kcal a kg and 45 to 49% volatile matter; the heater system runs at about 25% efficiency.
• 12 hours a day, 300 days: 3,600 hours and 856.8 t of coal a year.
• Power is 70% grid and 30% from a 63 kVA backup DG, which the report prices at Rs 7.45 a kWh on average.

What gets installed

1. A 100 kWe coal gasifier taking 200 kg of coal an hour. Its gas runs the generator; the coke left behind fires the drier heater instead of raw coal.
2. The existing 63 kVA DG converted to dual fuel, so it runs on producer gas with 2.5 litres of diesel an hour as pilot fuel.
3. A heat exchanger on the DG exhaust to preheat drying air. The report credits the whole 38 kg an hour coal saving to this preheat.

Two sums to check in the report

• Project cost: the summary table says Rs 17.85 lakh, but the cost table adds to Rs 18.72 lakh (gasifier 10.30, DG conversion 1.50, civil 3.50, the rest erection, freight, EPC and contingency). The 1.15 year payback is 18.72 / 16.25.
• CO2: the report's 410 t uses a grid factor of 1.03 kg per kWh. On CEA's FY 2025-26 factor of 0.675 the power credit shrinks from 187 t to 122 t.

Before you sign

• Ask the supplier for running data from a tea factory: 200 kg of coal an hour has to give both the drier's heat and 50 kW of power.
• The 181,440 kWh assumes the DG runs at full 50.4 kW for every drying hour. Log what it actually makes for a season.
• The DG now runs 3,600 hours a year instead of only during outages, so plan its maintenance and the diesel bill.

One factory, one year (estimate)

• Coal saved: 38 kg x 3,600 h = 136.8 t x 1.76 = 240.8 t CO2
• Grid power replaced: 181,440 kWh x 0.675 = 122.5 t CO2
• Extra diesel: 9,000 L x 2.645 = 23.8 t CO2 added
• Net cut: 240.8 + 122.5 minus 23.8 = about 339 t CO2
• Money: Rs 13.52 lakh power + Rs 6.16 lakh coal minus Rs 3.42 lakh diesel = Rs 16.25 lakh

Assumes every kWh made replaces grid power. Where it replaces backup DG hours instead, the diesel those hours used is also saved.

What Senseible does here

Senseible reads coal invoices, diesel slips and electricity bills into monthly records with CO2, so the season before and the season after the gasifier sit side by side. Before you take this to a bank, run the green loan check.

• Green loan readiness check
• Tea dryer: coal to biomass gasifier
• Jorhat tea factories: coal and gas drying
• Tea dryer efficient gas burner

Sources: BEE, Detailed project report: coal gasification for thermal and captive generation, Jorhat tea cluster (SAMEEEKSHA), CEA CO2 Baseline Database, version 22.0

Last reviewed 2026-11-01. Report figures are from a BEE SME programme project report; costs and paybacks are at the report year's prices (coal Rs 4.50 a kg, diesel Rs 38 a litre). Check today's prices before you rely on the payback.