What default carbon dioxide figure does the Intergovernmental Panel on Climate Change give per tonne of ferrosilicon, ferromanganese, silicomanganese and ferrochromium?

The Intergovernmental Panel on Climate Change (IPCC) 2006 Guidelines give generic carbon dioxide (CO2) factors in tonnes per tonne of alloy: ferrosilicon 2.5 to 4.8 by silicon grade, ferromanganese 1.3 or 1.5, silicomanganese 1.4, silicon metal 5.0, and ferrochromium 1.3, or 1.6 with a sinter plant.

The default factors, tonnes of CO2 per tonne of product

• Ferrosilicon 45% silicon: 2.5. 65%: 3.6. 75%: 4.0. 90%: 4.8.
• Ferromanganese with 7% carbon: 1.3. With 1% carbon: 1.5.
• Silicomanganese: 1.4.
• Silicon metal: 5.0.
• Ferrochromium: 1.3, or 1.6 with a sinter plant.

What the factors assume

• They are based on expert judgement of typical practice for each alloy.
• The guide says that if any bio-carbon is used, the factors cannot be employed, except some woodchips for ferrosilicon and silicon metal.
• The ferrosilicon 90% and silicon metal factors assume fixed carbon use of 110% of the amount needed to reduce silicon dioxide. The other ferrosilicon grades assume 114%.
• The manganese alloy factors assume a mix of oxide ores, carbonate ores and imported manganese sinter.

How far to trust a default

The guide calls Tier 1 very simple and says it may lead to errors because it relies on assumptions, not actual data. For uncertainty it gives two different statements: the text says Tier 1 default factors may be 25 to 50 percent uncertain, and its uncertainty table lists below 25 percent. Treat a default as a starting figure to replace with your own tonnes of coke, coal and electrode paste.

Methane (CH4) from silicon alloys

The same chapter gives methane defaults in kilograms of CH4 per tonne of product: silicon metal 1.2, ferrosilicon 90% 1.1, ferrosilicon 75% 1.0 and ferrosilicon 65% 1.0. It gives no methane default for manganese or chromium alloys.

A plant making ferrosilicon 75% and silicomanganese (example output)

• Ferrosilicon 75%: 10,000 tonnes x 4.0 = 40,000 tonnes of CO2
• Silicomanganese: 6,000 tonnes x 1.4 = 8,400 tonnes of CO2
• Process CO2 at default factors: 48,400 tonnes
• Methane: 10,000 tonnes of ferrosilicon 75% x 1.0 kilogram = 10,000 kilograms, or 10 tonnes of CH4

Output tonnes are example numbers. Furnace electricity and fuel are counted separately, from bills.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so the coke and coal bought and the power the furnaces drew are on file. A default factor is a starting point; you can replace it with your own records.

• Free calculators
• Electrode paste CO2 per tonne of alloy
• Silicomanganese carbon per tonne
• Ferrochrome CO2 per tonne for CBAM

Sources: IPCC 2006 Guidelines, Volume 3 chapter 4: Metal Industry Emissions, section 4.3 (Tables 4.5, 4.7, 4.9)

Last reviewed 2026-11-04. Factors are from the 2006 IPCC Guidelines. Check that your buyer, auditor or scheme accepts them, and whether it wants the plant's own mass balance instead.