The IPCC gives 0.70 tonnes of carbon dioxide per tonne of direct reduced iron. Does that fit a coal fired sponge iron kiln?

Probably not. The Intergovernmental Panel on Climate Change (IPCC) 0.70 tonnes of carbon dioxide (CO2) per tonne of direct reduced iron (DRI) assumes natural gas at 12.5 gigajoules (GJ) a tonne. The guide says nothing about coal kilns, so a coal kiln needs its own carbon figures.

What the 0.70 is built on

• The guide says that for Tier 1 the default fuel for DRI is natural gas, because natural gas based processes account for the vast majority of installed DRI capacity, with 63 percent of that capacity being the MIDREX process.
• MIDREX typically uses 10.5 to 14.5 GJ of natural gas per tonne of solid DRI on 100 percent lump ore. Hot briquetted iron from fines is reported at 12.5 GJ per tonne (FINMET) and 14 GJ (CIRCORED).
• The default takes 12.5 GJ of gas per tonne and 15.3 kilograms (kg) of carbon per GJ: 12.5 x 15.3 = 191.3 kg of carbon, which the guide states as 0.7 tonnes of CO2 per tonne of DRI.

How far gas use moves the figure

My arithmetic from the printed range: 10.5 GJ x 15.3 = 160.7 kg of carbon, x 44/12 = 0.59 tonnes of CO2. At 14.5 GJ it is 221.9 kg of carbon, 0.81 tonnes. So even on gas the default is a point inside a range of about 0.59 to 0.81.

If your kiln burns coal

The Tier 1 table has one DRI line and the guide states its fuel as natural gas. My reading: it does not describe a coal fired rotary kiln, so quoting 0.70 for coal based sponge iron would not be backed by this source.

The guide's Tier 2 equation for DRI sums gas, coke breeze and metallurgical coke, each in GJ times its carbon content in tonnes of carbon per GJ, times 44/12. Its text adds that DRI emissions come from combusting fuel, coke breeze, metallurgical coke or other carbonaceous materials. My suggestion, not the guide's: for coal, start from the carbon in the coal you charged, minus the carbon leaving in the sponge iron and char, using your own lab results. The page on coal based sponge iron sets that out, and the steel by route page has the guide's other iron making defaults.

The default rebuilt, per tonne of DRI

• Gas: 12.5 GJ
• Carbon: 12.5 x 15.3 = 191.25 kg, printed as 191.3
• CO2: 191.25 x 44/12 = 701 kg, printed as 0.7 tonnes
• Range check: 10.5 GJ gives 589 kg, 14.5 GJ gives 813 kg

All inputs are the guide's own printed figures. The range check is my arithmetic.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so the coke, coal, gas and power bought each month are on file. The process carbon in this page comes from your own purchase and lab records, not from the bills.

• Coal based sponge iron CO2 per tonne
• IPCC steel defaults by route
• Are pig iron and sponge iron in the Carbon Border Adjustment Mechanism (CBAM)
• Free calculators

Sources: IPCC, 2006 Guidelines for National Greenhouse Gas Inventories, Volume 3, Chapter 4: Metal Industry Emissions

Last reviewed 2026-11-05. Figures are from the 2006 IPCC Guidelines. Check whether your buyer or reporting scheme asks for a different edition of the IPCC guidance, and use your own plant measurements where you have them.