Why do the Bureau of Energy Efficiency Bhubaneswar reports for 30, 60 and 100 kg brass reheating furnaces show different charcoal savings per kg of brass?

Each Bureau of Energy Efficiency (BEE) Bhubaneswar report lifts the reheating pit to 15% efficiency, but they start from different measured baselines of 1.33, 1.00 and 0.95 kilograms of charcoal per kilogram of brass. Savings are 5,380, 7,880 and 12,421 kilograms a year, payback 1.63, 1.39 and 1.12 years.

The three reports side by side

• 30 kilogram (kg) furnace: 4,320 kg of brass a year, charcoal 5,760 kg down to 380, saving 5,380 kg. Cost rupees (Rs) 1.96 lakh, saving Rs 1.20 lakh a year, payback 1.63 years, net present value (NPV) Rs 2.43 lakh, internal rate of return (IRR) 42.86%.
• 60 kg furnace: 8,640 kg of brass, charcoal 8,640 kg down to 760, saving 7,880 kg. Cost Rs 2.45 lakh, saving Rs 1.76 lakh, payback 1.39 years, NPV Rs 4.00 lakh, IRR 52.36%.
• 100 kg furnace: 14,400 kg of brass, charcoal 13,680 kg down to 1,259, saving 12,421 kg. Cost Rs 3.10 lakh, saving Rs 2.78 lakh, payback 1.12 years, NPV Rs 7.19 lakh, IRR 68.99%.
• All three: 144 batches a year, two days of downtime, charcoal at Rs 22.5 a kg, and a small electric blower replacing a hand-driven one (0.37, 0.75 and 1.00 kilowatts), at Rs 2.3 a kilowatt hour (kWh).

Why the saving per kg of brass differs

• Output is the batch size times 144: 30 x 144 = 4,320, 60 x 144 = 8,640, 100 x 144 = 14,400 kg (my reading of the printed sums).
• Each report uses its own measured old pit. Charcoal per batch is 40 kg for 30 kg of brass, 60 kg for 60 kg and 95 kg for 100 kg, which is 1.33, 1.00 and 0.95 kg per kg. Efficiency works out at 0.99%, 1.32% and 1.38%.
• The new furnace is set at 15% in all three. So the saving is 93.4%, 91.2% and 90.8% of the old charcoal, or 1.25, 0.91 and 0.86 kg per kg of brass, and about Rs 28, Rs 20 and Rs 19 per kg of brass a year.
• The 30 kg pit looks best per kg only because its old pit wasted most charcoal. If your own pit uses 0.95 kg per kg, the 30 kg report's baseline does not describe it.

Printed figures that do not tie

• The 30 kg report prints its yearly saving three ways: Rs 1,20,311 in section 3.2, Rs 1,19,360 in annexure 3 and Rs 1.48 lakh in the cash-flow text. Its own sum, 5,380 x Rs 22.5 = Rs 1,21,050 less Rs 735 of power, is Rs 1,20,315. The 1.63 year payback uses the Rs 1.20 lakh figure.
• The 30 kg annexure 3 prints present efficiency as 0.09%. Annexure 1 works it out as 0.99% (2,570 kilocalories (kcal) needed, 260,000 supplied), so 0.09 looks like a slip.
• The 100 kg report's text says 12,241 kg saved in one place and 12,421 in its table and annexure. Use 12,421.

Carbon dioxide (CO2): the reports treat charcoal differently

The 30 kg report prints 15 tonnes of CO2 a year for the 5,380 kg of charcoal saved. The 60 and 100 kg reports say CO2 from the charcoal saved is not considered for carbon credit purposes because charcoal is biomass made from wood. Do not compare the 15 tonnes with the other two. The only fossil figure each saving carries is the blower: about 0.2, 0.4 and 0.5 tonnes a year at 0.675 kg of CO2 a kilowatt hour (320, 648 and 720 kWh). Report the charcoal separately, as wood-based, beside your fossil total.

The 60 kg furnace, report sums

• Heat needed a batch: 60 kg x 0.112 x (800 minus 35) degrees = about 5,141 kcal. Charcoal 60 kg x 6,500 kcal = 390,000 kcal. Efficiency 1.32%
• At 15%: 5,141 / 0.15 / 6,500 = 5.27 kg a batch x 144 = about 760 kg a year. Saved 8,640 minus 760 = 7,880 kg
• Money: 7,880 x Rs 22.5 = Rs 1,77,300, less 648 kWh x Rs 2.3 = Rs 1,490, gives Rs 1,75,810. Payback Rs 2.45 lakh / Rs 1.76 lakh = 1.39 years

Prices are the reports' own at 2010. The blower CO2 is my estimate at CEA's FY 2025-26 grid factor.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so charcoal bought and power used are on file against what a unit makes. It does not measure furnace efficiency or confirm a fabricator's claim.

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Sources: BEE, Detailed project report: energy efficient reheating furnace, 30 kg, Bhubaneswar brass cluster (SAMEEEKSHA), BEE, Detailed project report: energy efficient reheating furnace, 60 kg, Bhubaneswar brass cluster (SAMEEEKSHA), BEE, Detailed project report: energy efficient reheating furnace, 100 kg, Bhubaneswar brass cluster (SAMEEEKSHA), Central Electricity Authority (CEA), CO2 Baseline Database, version 22.0

Last reviewed 2026-11-06. Report figures are from BEE's Small and Medium Enterprises (SME) programme project reports; costs, charcoal price and paybacks are at the report year's prices. Redo the payback with today's charcoal price and a current quote.