How do I work out the carbon in my coal or coke from an ash and volatile matter report, the way the Intergovernmental Panel on Climate Change does for ferroalloys?
The Intergovernmental Panel on Climate Change (IPCC) takes fixed carbon as 100% minus ash minus volatiles, then adds volatiles times 0.65 for coal or 0.80 for coke, unless you have other information. An example coal at 25% ash and 20% volatiles carries 0.68 tonnes of carbon, or 2.49 tonnes of carbon dioxide (CO2), per tonne.
The two steps as the guide prints them
The guide notes that most ferroalloy producers analyse only the percentage of ash and volatiles, and calculate fixed carbon % = 100 % minus % ash minus % volatiles.
Carbon content of the reducing agent = fixed carbon fraction + volatile fraction x Cv. Cv is the carbon fraction of volatiles. Unless other information is available, it is 0.65 for coal and 0.80 for coke. Multiply carbon by 44/12 to get CO2.
A note on moisture (ours, not the guide's)
As printed, the formula has no moisture term, so ask your lab which basis its ash and volatile figures are on.
The guide's own CO2 per tonne of reducing agent
- Coal for ferrosilicon and silicon metal: 3.1 tonnes of CO2 per tonne.
- Coke for ferromanganese and silicomanganese: 3.2 to 3.3. Coke for silicon and ferrosilicon: 3.3 to 3.4.
- Prebaked electrodes: 3.54. Electrode paste: 3.4. Petroleum coke: 3.5.
- For coal and coke in other ferroalloys the guide gives no figure. It encourages producer-specific values based on the average blend of coal and coke for each producer.
Where the reductant figure goes
In the guide's mass balance, CO2 is the carbon in reducing agents, ores and slag forming materials, minus the carbon leaving in product and in non-product streams such as slag and dust, all times 44/12. A reductant's CO2 is therefore a gross figure until you take off what stays behind.
A coal and a coke from lab reports (example analyses)
- Coal: ash 25%, volatiles 20%, so fixed carbon 100 minus 25 minus 20 = 55%
- Carbon: 0.55 + 0.20 x 0.65 = 0.68 tonnes per tonne; CO2: 0.68 x 44 / 12 = 2.49 tonnes per tonne of coal
- Coke: ash 15%, volatiles 2%, so fixed carbon 83%
- Carbon: 0.83 + 0.02 x 0.80 = 0.846; CO2: 0.846 x 44 / 12 = 3.10 tonnes per tonne of coke
- 1,000 tonnes of that coke: 3,102 tonnes of CO2, before subtracting carbon that stays in alloy, slag and dust
Ash and volatile percentages are example numbers. Use the figures on your own lab analysis report.
What Senseible does here
Senseible reads fuel invoices and electricity bills into monthly records, so tonnes of coke and coal bought each month sit next to the power bills. The ash and volatile figures come from your supplier's analysis report.
Last reviewed 2026-11-04. Check the basis of your lab's ash and volatile figures before using the formula. The guide's Cv values apply unless you have other information.