# How much gas does a 200 kg gas-fired pit furnace use in place of coal for brass melting?

Canonical: https://senseible.earth/answers/brass-coal-pit-to-gas-pit-furnace

About 104 Nm3 of gas per tonne of brass instead of 192 kg of coal, in BEE's Jamnagar report: 41,497 Nm3 a year replacing 76.86 t of coal for 400 t melted. Net CO2 falls about 45 t a year, not the report's 69 t. Cost Rs 12.65 lakh, payback 3.61 years (2010).

## The two furnaces in the report

- Coal pit furnace: measured at 9.7% and 12.8% efficiency in two units, 43 to 49 kg of coal for 255 to 295 kg melts, coal at 6,500 kcal a kg.
- Gas pit furnace: 200 kg an hour, burner with air to fuel ratio control, waste heat recovery and automatic temperature control, rated at 17% efficiency.
- Use: 2,000 hours a year, 400 t of brass.
- Melting costs about Rs 28 a kg in a typical unit, around a fifth of its energy bill, and takes 1.2 to 1.5 hours a melt.

## Where the Rs 3.50 lakh comes from

- Coal: 192.16 kg a tonne x Rs 18 = Rs 3,459.
- Gas: 103.74 Nm3 a tonne x Rs 24 = Rs 2,490.
- Fuel saving: Rs 969 a tonne, Rs 3.88 lakh on 400 t.
- Less the 5 HP blower: 7,460 kWh at Rs 5 = Rs 0.37 lakh, leaving Rs 3.50 lakh a year.
- Cost: Rs 11.50 lakh furnace, Rs 1.15 lakh erection. One week of downtime.

## Before you choose a pit over a rotary

The same BEE series has a 250 kg gas rotary furnace using 56.25 Nm3 a tonne, about half the pit furnace's gas, at Rs 8.80 lakh and a 1.27 year payback. The pit report also assumed gas at only 6,880 kcal per Nm3 (8,600 kcal a kg at 0.8 kg a cubic metre). Piped natural gas usually carries more heat than that, so ask your supplier for the calorific value on the bill; real gas use may be lower.

## CBAM does not apply to brass

Copper alloy goods such as brass are not in CBAM's list of goods. The reason to track CO2 here is buyer requests and loan files, not an EU border charge.

## 400 t of brass a year, before and after

- Coal removed: 76.86 t x 1.76 = 135.3 t CO2
- Gas added: 41,497 Nm3 x 2.05 = 85.1 t CO2
- Blower power added: 7,460 kWh x 0.675 = 5.0 t CO2
- Net cut: about 45 t a year, or 113 kg per tonne of brass
- The report's 69 t counted coal at about 2 kg CO2 a kg and left out the blower

Indian coal at our factor of 1.76 kg CO2 a kg, natural gas at 2.05 kg a scm and grid at CEA's FY 2025-26 factor, all estimates.

## What Senseible does here

Senseible reads coal invoices, gas bills and electricity bills into monthly records with CO2 for each, so the before and after per tonne of brass can be shown to a buyer or a lender. The green loan check shows what a lender asks for on a furnace loan.

- [Green loan readiness check](https://senseible.earth/green-loan-check)
- [Brass: coal pit to gas rotary furnace](https://senseible.earth/answers/brass-coal-furnace-to-gas-rotoberatory)
- [Jamnagar brass cluster energy and carbon](https://senseible.earth/answers/jamnagar-brass-cluster-energy-and-carbon-footprint)
- [Brass: efficient oil pit furnace](https://senseible.earth/answers/brass-oil-pit-furnace-efficient-saving)

Sources: [BEE, Detailed project report: energy efficient gas fired pit furnace, 200 kg an hour, Jamnagar brass cluster (2010, SAMEEEKSHA)](https://sameeeksha.org/pdf/Jamnagar_brass_cluster/DPR_on_Energy_Efficient_Gas_Fired_Pit_Furnace_200%20kg.pdf), [BEE, Detailed project report: energy efficient gas fired rotoberatory furnace, 250 kg, Jamnagar brass cluster (2010, SAMEEEKSHA)](https://sameeeksha.org/pdf/Jamnagar_brass_cluster/DPR_Energy_Efficient_Gas_Fired_Rotoberatory_Furnace_250%20kg.pdf), [CEA CO2 Baseline Database, version 22.0](https://cea.nic.in/cdm-co2-baseline-view?mappingId=234&lang=en)

Last reviewed 2026-10-31. Report figures are from a BEE SME programme project report; costs and paybacks are at 2010 prices. Coal and gas prices have moved a lot since; redo the payback with today's prices.