How does the Bureau of Energy Efficiency (BEE) Tiruppur manual get 220 tonnes of wood saved from recovering heat in hot drained dye water?

BEE's Tiruppur manual takes 62,720 litres a day of dye house drain at 70 degrees Celsius (C), recovers 80% of the heat above 30 degrees C and burns 880 kilograms less wood a day. That is 220 tonnes a year, rupees (Rs) 6.6 lakh (1 lakh = 100,000), for Rs 6 lakh: 11 months.

How the 880 kilograms a day is built

1. Dye per day: 1,400 kilograms (kg) a batch (the table lists six machines and does not say each or total) x 2 batches x 70% use = 1,960 kilograms a day, at a liquor ratio of 8 and 4 hot washes.
2. Hot water drained: 1,960 x 8 x 4 = 62,720 litres a day.
3. Heat in it: 62,720 x (70 minus 30) = 2,508,800 kilocalories (kcal) a day. The manual recovers 80%, 2,007,040 kcal.
4. Wood: 2,007,040 / 0.60 boiler efficiency / 3,800 kcal a kilogram = 880 kilograms a day.
5. Year: 880.28 x 250 days = 220,070 kilograms (the manual prints 880 for the rounded day), 220 tonnes, at Rs 3,000 a tonne = Rs 660,210 (220.07 x 3,000).

Cost and payback

Investment Rs 600,000, so 600,000 / 660,210 = 0.91 years, about 11 months, as printed. The manual's cost table prices heat recovery units at Rs 4.92 lakh for 2 kilolitres an hour and Rs 6.56 lakh for 4 kilolitres an hour, so Rs 6 lakh sits between the two sizes.

Where the report is cautious and where it is not

• The text says water leaves at 90 degrees C, but the table uses 70. At 90 degrees C the heat is 62,720 x 60 = 3,763,200 kcal, and the saving would be about 330 tonnes. The report uses the lower figure, which is the cautious one.
• The daily 1,960 kilograms equals one batch size x 2 x 0.70, though the table lists six machines. Our reading is that 1,400 kilograms is the total of the six; the table does not say.
• The 80% recovery and 60% boiler efficiency are assumptions, not measurements. At 40% recovery the saving halves. Fit two temperature probes and a flow count before you rely on 80%.

What to put on file

• Wood or other fuel bought each month, weighed, from invoices and the stock register.
• Kilograms dyed each month, so fuel per kilogram can be compared before and after.
• Temperatures in and out of the exchanger on a few typical days.

The report's heat sum

• Drain: 1,960 kg x 8 x 4 washes = 62,720 litres a day
• Heat: 62,720 x (70 minus 30) = 2,508,800 kcal; 80% = 2,007,040 kcal
• Wood: 2,007,040 / 0.60 / 3,800 = 880.28 kg a day (printed 880); x 250 days = 220,070 kg = 220 tonnes
• If the drain were 90 degrees C: 62,720 x 60 x 0.8 / 0.6 / 3,800 = about 1,320 kg a day, about 330 tonnes

Figures are the manual's. The 90 degrees C case is our own arithmetic from the manual's text, not a figure it prints.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so the wood bought each month is on file to compare before and after a heat recovery fit. Temperatures and kilograms dyed come from your own logs.

• Surat drain heat recovery reports compared
• Dyehouse hot effluent heat recovery saving
• Tiruppur soft flow dyeing machine report
• Tiruppur manual: payback table in months or years
• Green loan readiness check

Sources: BEE, Manual on Energy Conservation Measures in Textile Cluster, Tirupur (prepared by Winrock International India, via SAMEEEKSHA)

Last reviewed 2026-11-05. Figures are from the manual's study year (around 2010 to 2011), with wood at Rs 3,000 a tonne. Re-run with your own drain flow, temperature and fuel price.