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

Canonical: https://senseible.earth/answers/ipcc-ferroalloy-default-co2-per-tonne-by-alloy

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](https://senseible.earth/calculators)
- [Electrode paste CO2 per tonne of alloy](https://senseible.earth/answers/ferro-alloy-electrode-paste-co2-per-tonne)
- [Silicomanganese carbon per tonne](https://senseible.earth/answers/chhattisgarh-silico-manganese-carbon-per-tonne)
- [Ferrochrome CO2 per tonne for CBAM](https://senseible.earth/answers/ferrochrome-co2-per-tonne-cbam)

Sources: [IPCC 2006 Guidelines, Volume 3 chapter 4: Metal Industry Emissions, section 4.3 (Tables 4.5, 4.7, 4.9)](https://www.ipcc-nggip.iges.or.jp/public/2006gl/pdf/3_Volume3/V3_4_Ch4_Metal_Industry.pdf)

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.