# How much CO2 does acetylene used for cutting and welding emit?

Canonical: https://senseible.earth/answers/acetylene-gas-cylinder-co2

Each kg of acetylene burnt in a cutting or welding torch releases about 3.38 kg CO2, because one molecule of acetylene (C2H2) burns to two molecules of CO2. A cylinder holding 7 cubic metres of gas, about 7.7 kg, gives roughly 26 kg CO2.

## Where the 3.38 figure comes from

Acetylene is C2H2, with a molar mass of 26. Burning it fully gives 2 CO2, with a mass of 88. So 88 / 26 = 3.38 kg CO2 per kg of acetylene. This is a carbon balance, not a database default, so it holds for any supplier as long as the quantity is right.

Acetylene burnt in your own torches is stationary combustion in Scope 1 under the GHG Protocol Corporate Standard.

## Converting the invoice quantity to kg

- Invoice in kg of gas: multiply by 3.38 directly.
- Invoice in cubic metres: multiply by about 1.1 kg per cubic metre (acetylene density near room temperature and normal pressure), then by 3.38. That is about 3.7 kg CO2 per cubic metre.
- Invoice by cylinder count only: ask the supplier for the gas content per cylinder, because sizes differ by supplier. Do not use the cylinder's gross weight; it includes the steel shell, the porous filler and the acetone the gas is dissolved in.

## What not to add

- Oxygen cylinders used with the acetylene: oxygen releases no CO2 at the torch. The electricity used to make it at the gas plant belongs in Scope 3 purchased goods, not Scope 1.
- Acetone in the cylinder: it stays in the cylinder and goes back to the supplier, so it is not burnt.
- LPG used as a cutting fuel instead of acetylene: use the LPG factor, 2.98 kg CO2 per kg, on that line.

## Is it worth counting

For most fabrication shops acetylene is a small line next to grid power and diesel. Count it anyway if your invoices show it, because it is easy and a buyer reviewing your Scope 1 will see the purchases. If it is below 1% of your total, you can note it as immaterial but keep the calculation.

## Worked example: a month of cutting gas

- Acetylene invoices: 12 cylinders of 7 cubic metres = 84 cubic metres
- 84 x 1.1 kg per cubic metre = 92.4 kg acetylene
- 92.4 x 3.38 = 312.3 kg CO2 (Scope 1)
- One 7 cubic metre cylinder: 7.7 kg x 3.38 = 26.0 kg CO2

Cylinder content varies by size and supplier; use the quantity printed on your invoice where there is one.

## What Senseible does here

Senseible reads the gas invoice from an image or PDF, classifies the line by HSN code and multiplies the printed quantity by a published factor. A gas line without a factor in its list shows no figure rather than a guess, so the 3.38 calculation above is the one to record for acetylene.

- [Scope 1 emissions in manufacturing](https://senseible.earth/climate-intelligence/manufacturing-scope-1-emissions-india)
- [HSN codes for fuels in Scope 1](https://senseible.earth/answers/hsn-codes-for-fuels-scope-1)
- [Fuel purchased vs fuel consumed](https://senseible.earth/answers/fuel-purchased-vs-fuel-consumed)

Sources: [GHG Protocol Corporate Standard](https://ghgprotocol.org/corporate-standard), [2006 IPCC Guidelines, Volume 2 Energy](https://www.ipcc-nggip.iges.or.jp/public/2006gl/vol2.html)

Last reviewed 2026-10-17. Acetylene density varies with temperature; where the supplier states kg per cylinder, use that.