Which Intergovernmental Panel on Climate Change coal line fits my coal: other bituminous, sub-bituminous or lignite?

The Intergovernmental Panel on Climate Change (IPCC) defines other bituminous as non-coking bituminous coal above 5,700 kilocalories (kcal) per kilogram gross calorific value (GCV), on an ash-free but moist basis. Sub-bituminous is 4,165 to 5,700 and lignite below 4,165, and both also need over 31% volatile matter. For the same energy, sub-bituminous gives 1.6% more carbon dioxide (CO2), lignite 6.8%.

IPCC's three coal lines for Indian non-coking coal

Grouping these three as the lines for Indian non-coking coal is my reading. IPCC itself calls only other bituminous coal a steam-raising coal.

• Other bituminous coal: used for steam raising, all bituminous coal not coking coal, more than 10 percent volatile matter and less than 90 percent fixed carbon. Its GCV is greater than 23,865 kilojoules (kJ) per kilogram (kg), which is 5,700 kcal per kg, on an ash-free but moist basis.
• Sub-bituminous coal: non-agglomerating coals with a GCV between 17,435 kJ per kg (4,165 kcal per kg) and 23,865 kJ per kg (5,700 kcal per kg), containing more than 31 percent volatile matter on a dry mineral matter free basis.
• Lignite: a non-agglomerating coal with a GCV of less than 17,435 kJ per kg (4,165 kcal per kg), and greater than 31 percent volatile matter on a dry mineral matter free basis.

What each line changes

• Other bituminous: 94,600 kg CO2 per terajoule (TJ) at a net calorific value (NCV) of 25.8 TJ per gigagram.
• Sub-bituminous: 96,100 kg per TJ at 18.9. That is 96,100 / 94,600 = 1.6% more CO2 for the same energy.
• Lignite: 101,000 kg per TJ at 11.9. That is 6.8% more for the same energy, but each tonne carries much less energy.
• Per tonne the NCV changes more than the factor, so the line also changes the answer if you use the IPCC default heat value instead of your own.

The catch with Indian lab reports

• IPCC states the other bituminous threshold on an ash-free but moist basis. A GCV as received from an Indian lab includes the ash, so it reads lower. The same coal can look like a lower line on your report than it would on IPCC's basis. That is my reading, not an IPCC statement.
• The sub-bituminous and lignite lines also depend on volatile matter, which a GCV alone does not show.
• The Indian coal answer on this site uses 94.6 in its example. For a coal near 4,150 kcal per kg the difference between the other bituminous and sub-bituminous lines is 1.6%, small beside the spread in the lab's GCV itself.
• Choose one line per coal source, say which basis you read, and keep it for every year.

100 tonnes of coal at 4,150 kcal per kg GCV as received, three lines

• At 4,150, this coal sits just under the 4,165 lignite threshold on a report basis, and lignite also needs over 31% volatile matter. On IPCC's ash-free moist basis the reading would be higher, so any of the three lines could be argued. All three are shown
• GCV: 4,150 x 4.1868 / 1,000 = 17.375 megajoules (MJ) per kg
• NCV at 5% below GCV: 17.375 x 0.95 = 16.506 MJ per kg
• Energy: 100 x 16.506 = 1,650.6 gigajoules = 1.6506 TJ
• Other bituminous: 1.6506 x 94,600 = 156,151 kg, 156.2 t CO2
• Sub-bituminous: 1.6506 x 96,100 = 158,627 kg, 158.6 t CO2. Gap 2,476 kg, 1.6%
• Lignite: 1.6506 x 101,000 = 166,715 kg, 166.7 t CO2

The 4,150 kcal per kg report is an example. The 5% gross to net step is IPCC's rule of thumb for coal; use a lab net value or the Box 1.1 formula if you have the inputs.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, with the coal tonnes on the invoice. The coal line is a method choice, so write it in your method note beside the lab report.

• Indian coal emissions from GCV
• Gross to net calorific value formula
• Coal as received or air dried
• Imported coal GAR and NAR factors

Sources: IPCC 2006 Guidelines, Volume 2, Chapter 1 (Table 1.1 coal definitions, Tables 1.2 and 1.4)

Last reviewed 2026-11-05. IPCC states the thresholds on its own bases. Ask your buyer or verifier which coal line they expect for Indian non-coking coal.