# How do I estimate the carbon footprint of a forged crankshaft?

Canonical: https://senseible.earth/answers/crankshaft-carbon-footprint-per-piece

Start with the steel bar mass bought, not the finished weight, since forging flash and machining remove a large share. Multiply by the steel supplier's CO2 per tonne, then add forging furnace fuel, heat treatment and machining electricity per piece.

## Inputs

- Bar weight per piece, from the cut length.
- Steel supplier's CO2 per tonne, with its date.
- Furnace fuel and electricity per piece from monthly bills and output.

## Scrap

Flash and turnings sold as scrap leave with your waste. Do not subtract them from the steel bought unless you follow a stated recycling method.

## Worked example (illustrative figures)

- Bar bought: 20 kg per crankshaft.
- Supplier figure: 2.2 kg CO2 per kg of steel; 20 × 2.2 = 44 kg.
- Forging, heat treatment and machining: 6 kWh × 0.710 = 4.3 kg, plus 1.5 kg from furnace gas.
- Total: about 50 kg CO2 per piece.

## What Senseible does here

Senseible reads your electricity bills, fuel invoices and purchase invoices into dated, fingerprinted records, so a per unit footprint can be traced back to the documents behind it. Estimates are labelled as estimates.

- [Forging footprint per tonne](https://senseible.earth/answers/forging-carbon-footprint-per-tonne)
- [Heat treatment emissions](https://senseible.earth/answers/heat-treatment-emissions-per-tonne)
- [Piston footprint](https://senseible.earth/answers/piston-carbon-footprint-per-piece)

Sources: [GHG Protocol Product Standard](https://ghgprotocol.org/standards), [ISO 14067:2018, Carbon footprint of products (iso.org)](https://www.iso.org), [IPCC 2006 Guidelines, Volume 2 Energy (fuel defaults)](https://www.ipcc-nggip.iges.or.jp/public/2006gl/vol2.html)

Last reviewed 2026-10-22.