What is the carbon footprint per kg of an aluminium die casting?
Per kg of good casting, add the alloy ingot's footprint times the kg of metal bought per kg of good casting, plus melting and machine energy per kg. The ingot route decides most of the answer: secondary alloy ingot carries a small fraction of the footprint of primary aluminium.
The formula
Footprint per kg good casting = (kg ingot bought per kg good casting x ingot factor) + (melting fuel emissions + electricity emissions) / kg good castings.
Use a month or a year so stock changes even out.
Count metal bought, not metal melted
Runners, overflows, biscuits and rejected castings go back into the furnace. They pass through the melt many times, so metal melted is often well above the weight of good castings. That remelt costs energy, which the energy term already captures, but it does not add ingot. The ingot term uses only metal that leaves the plant as melt loss, dross or sold scrap, on top of the good castings.
Where the ingot factor comes from
- Best: a footprint or EPD from your ingot supplier for the alloy and batch.
- Secondary alloy ingot made from scrap: much lower than primary, because remelting needs a few percent of the energy of smelting.
- Primary ingot from a coal-powered Indian smelter: high, mostly from smelting power. Ask the producer for its figure.
- Never mix: if you buy both, weight the factor by kg of each.
What a buyer will ask next
Auto buyers usually want cradle to gate per part under ISO 14067: the per kg figure times the part's finished mass, plus machining energy and any heat treatment or coating. State the alloy, the share of recycled content and the year of the energy data.
Worked example: one month, 100 tonnes of good castings
- Ingot bought: 1,04,000 kg for 1,00,000 kg good castings (4,000 kg melt loss and dross)
- Ingot (secondary, illustrative 1.0 kg CO2e per kg): 1,04,000 x 1.0 = 1,04,000 kg CO2e
- Melting PNG: 9,000 scm x 2.05 = 18,450 kg CO2
- Electricity: 1,20,000 kWh x 0.710 = 85,200 kg CO2
- Total: 1,04,000 + 18,450 + 85,200 = 2,07,650 kg; per kg good casting: 2.08 kg CO2e
- Same plant on primary ingot at an illustrative 16 kg CO2e per kg: (16,64,000 + 1,03,650) / 1,00,000 = 17.7 kg CO2e per kg
Both ingot factors are illustrative; use your supplier's figures.
What Senseible does here
Senseible reads melting fuel and power bills into Scope 1 and 2 with the factor on each line; ingot purchases go to the supplier evidence trail by HSN code and kg, where a supplier footprint can be kept with the invoice.
- Why Indian aluminium is carbon intensive
- Check an aluminium supplier's claim
- Product carbon footprint calculator
Sources: ISO 14067:2018, Carbon footprint of products, 2006 IPCC Guidelines, Volume 2 Energy (fuel factors), CEA CO2 Baseline Database
Last reviewed 2026-10-17.