Which Bureau of Energy Efficiency report pays back fastest for a Varanasi brick kiln, zigzag firing, semi-mechanised or fully mechanised, and why do their carbon figures use different factors?

In four Bureau of Energy Efficiency (BEE) Varanasi reports, zigzag firing pays back in 1.09 years, a semi-mechanised line in 1.76 and fully mechanised kilns in 3.42 and 2.84. Over half of the fully mechanised saving is better brick prices, not coal. Their carbon figures also use 1.4 tonnes per tonne of coal, against 2.0 for zigzag.

The four reports side by side

• Zigzag firing, 31 lakh bricks a year: cost rupees (Rs) 7.58 lakh, coal saved 139.5 tonnes (18 down to 13.5 tonnes a lakh bricks), benefit Rs 6.98 lakh a year, payback 1.09 years, internal rate of return 72.42 percent. Printed carbon dioxide (CO2) saving 279 tonnes.
• Semi-mechanised, 62 lakh bricks: cost Rs 10.90 lakh, coal saved 124 tonnes, benefit Rs 6.2 lakh, payback 1.76 years, return 41.34 percent. Printed CO2 175 tonnes.
• Fully mechanised, 150 tonnes a day: cost Rs 505 lakh, coal saved 1,200 tonnes, benefit Rs 147.69 lakh, payback 3.42 years, return 16.92 percent. Printed CO2 1,680 tonnes.
• Fully mechanised, 250 tonnes a day: cost Rs 1,100 lakh, coal saved 2,100 tonnes, benefit Rs 387.80 lakh, payback 34 months (2.84 years), return 22.97 percent. Printed CO2 2,940 tonnes.
• All four value coal at Rs 5,000 a tonne. The reports' energy tables work out to about 21 gigajoules a tonne of coal.

What the fully mechanised saving is made of

Both fully mechanised reports add a quality gain to the coal saving. For the 150 tonne kiln it is Rs 87.69 lakh of extra profit, from a brick that costs Rs 3.10 to make instead of Rs 2.50 but sells at Rs 4.10 instead of Rs 3.13, plus Rs 60 lakh of coal (1,200 x 5,000). For the 250 tonne kiln it is Rs 282.80 lakh plus Rs 105 lakh of coal. So the quality gain is 59 percent and 73 percent of the printed benefit.

On coal alone, our arithmetic gives paybacks of 505 / 60 = 8.4 years and 1,100 / 105 = 10.5 years. The quick paybacks of the zigzag and semi-mechanised reports are coal alone; the fully mechanised ones depend on getting a better price per brick.

Two carbon factors in one cluster

The zigzag report says coal saved translates into emissions cut of roughly 2 tonnes per tonne of coal. The semi-mechanised and fully mechanised reports say roughly 1.4 tonnes. At the reports' own 21 gigajoules a tonne, the Intergovernmental Panel on Climate Change (IPCC) default of 94,600 kilograms of CO2 per terajoule for other bituminous coal gives 1.99 tonnes. The reports do not name the coal grade.

So the 2.0 reports agree with the IPCC default and the 1.4 reports sit about 30 percent below it, which makes their CO2 saving the smaller one. On the IPCC factor, the energy saved is 25.2 terajoules for the 150 tonne kiln, giving 2,384 tonnes against the 1,680 printed; 44.1 for the 250 tonne kiln, giving 4,172 against 2,940; 2.60 for the semi-mechanised line, giving 246 against 175; and 2.915 for zigzag, giving 276 against 279. This is our arithmetic. The live page on Varanasi kilns uses India's own factor of 1.76 tonnes of CO2 per tonne of coal, from its second Biennial Update Report. The IPCC 1.99 here is a cross-check on the reports' figures, not a replacement for it.

Where the reports do not match themselves

• The 250 tonne report's text says the quality saving is Rs 87.69 lakh, the 150 tonne figure, while its table and total use Rs 282.80 lakh.
• The 62 lakh semi-mechanised report's Table 2.1 still shows the 31 lakh case: 31 lakh bricks, 62 tonnes saved, Rs 3,10,000. Its summary and Table 3.1 give 124 tonnes and Rs 6.2 lakh.
• The two fully mechanised reports start from 25 tonnes of coal a lakh bricks and go to 20, while the others start from 18. 5 x 237 lakh is 1,185 tonnes against 1,200 printed, and 5 x 422 is 2,110 against 2,100.

The 150 tonne fully mechanised report, rebuilt

• Brick: made at Rs 2.50 and sold at Rs 3.13 from the old kiln, made at Rs 3.10 and sold at Rs 4.10 from the new; 237 lakh bricks. Profit 741.81 minus 592.50 = Rs 149.31 lakh before and 971.70 minus 734.70 = Rs 237 lakh after, a gain of Rs 87.69 lakh
• Coal: 1,200 tonnes x Rs 5,000 = Rs 60 lakh. Total benefit 87.69 + 60 = Rs 147.69 lakh
• Payback with both: 505 / 147.69 = 3.42 years. On coal alone: 505 / 60 = 8.4 years
• CO2 printed: 1,200 x 1.4 = 1,680 tonnes. At the IPCC factor: 25.2 x 94.6 = 2,384 tonnes

All inputs are the report's own figures except the coal-only payback and the IPCC line, which are our arithmetic.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so a season of coal invoices before a change can be compared once uploaded. Bricks fired and sold come from your kiln registers, which you add.

• Varanasi kilns: coal per kiln and vertical shaft option
• Zigzag kiln conversion and carbon credits
• Brick kiln emissions per 1,000 bricks
• Green loan readiness check

Sources: BEE, Detailed project report: fully mechanised, 150 tonnes a day, Varanasi brick cluster (SAMEEEKSHA), BEE, Detailed project report: fully mechanised, 250 tonnes a day, Varanasi brick cluster (SAMEEEKSHA), BEE, Detailed project report: semi-mechanised, 62 lakh, Varanasi brick cluster (SAMEEEKSHA), BEE, Detailed project report: zigzag firing, 31 lakh, Varanasi brick cluster (SAMEEEKSHA), IPCC 2006 Guidelines, Volume 2 chapter 2: Stationary Combustion (Table 2.3, other bituminous coal)

Last reviewed 2026-11-05. Report figures are from BEE's Small and Medium Enterprises (SME) programme project reports, at the report year's prices and coal at Rs 5,000 a tonne. Check today's coal and brick prices and a current quote before you rely on the payback.