How much wood does an efficient 80,000 kcal hot water generator save in a dyeing unit?

BEE's Solapur report replaces a 22% efficient wood-fired thermic fluid heater with a 70% efficient hot water generator of 80,000 kcal an hour, cutting wood from 104 t to 64 t a year. Cost Rs 2.76 lakh, saving Rs 1.68 lakh at Rs 4.20 a kg, payback 1.64 years (2010).

Why the old heater wastes wood

• Single pass design: flue gas leaves at 350 to 360 C after very little contact with the oil coils.
• Excess air above 100%, against 45 to 50% for good wood firing; grates are not sized for the logs used.
• Measured efficiency about 22%; flue losses of 35 to 40%.
• A typical unit making 1.44 lakh kg of product burns 104 t of wood a year, 8 hours a day for 240 days.

The generator proposed

• 80,000 kcal an hour, water walled wood furnace with fire door, ash door and grate, part of the flue gas recirculated as secondary air.
• Rated 70% efficiency, burning about 33 kg of wood an hour.
• Enough for about 400 kg of dyeing and 400 kg of soaping in an 8 hour day.
• 3 to 4 days to install, which can be timed with holidays.

The sums do not fully agree, so measure

At 33 kg an hour the generator burns about 64 t a year, which is where the report's figure comes from. But if the old heater really ran at 22% and the new one at 70%, wood would fall to about a third, around 33 t. The two efficiency claims and the two wood figures cannot all be right. Weigh wood each day for a week before and after, and judge it on kg of wood per kg of yarn.

Report figures, one unit

• Wood: 33 kg x 8 h x 240 days = 63.4 t, rounded to 64 t
• Saved: 104 less 64 = 40 t, x Rs 4,200 = Rs 1.68 lakh
• Payback: 2.76 / 1.68 = 1.64 years
• Biogenic CO2 avoided: 40 t x 3,200 kcal/kg x 4.1868 = 536 GJ x 112 kg = about 60 t
• The report's 56 t used 1.4 t CO2 a tonne of wood; fossil CO2 does not change

Wood CO2 uses the IPCC 2006 default of 112 kg CO2 a GJ with the report's calorific value of 3,200 kcal a kg. It is biogenic and reported separately, outside Scopes 1 to 3.

What Senseible does here

Senseible reads your electricity bills into records with CO2. It has no factor for wood, so keep wood tonnes from purchase bills as a separate biogenic line; the green loan check shows what a lender asks for on a heater replacement.

• Green loan readiness check
• Hot water generator vs steam boiler
• Economiser on a wood thermic fluid heater
• Efficient chulha for hank dyeing

Sources: BEE, Detailed project report: energy efficient hot water generator, 80,000 kcal an hour, Solapur textile cluster (2010, SAMEEEKSHA), IPCC 2006 Guidelines, Volume 2 Energy, Tables 1.2 and 2.3, 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 2010 prices. Check today's wood price and a current quote.