What default carbon dioxide figure does the Intergovernmental Panel on Climate Change use per tonne of zinc, and does an electrolytic zinc plant have process carbon dioxide at all?
The Intergovernmental Panel on Climate Change (IPCC) 2006 Tier 1 gives carbon dioxide (CO2) per tonne of zinc of 0.43 for the Imperial Smelting Furnace route and 3.66 for the Waelz kiln, with a 1.72 default weighted 60% and 40%. The electrolytic process has no non-energy CO2 by the guide's account.
The three primary routes and their process CO2
- Electro-thermic distillation: coke in an electric retort furnace reduces zinc oxide, so there is process CO2. The guide says it is used in the United States and Japan, and gives no emission factor.
- Imperial Smelting Furnace: treats lead and zinc concentrates together, so the coke or coal reductant has to be shared between the two metals. A mass based split gives 0.74 tonnes of coke per tonne of zinc.
- Electrolytic: zinc sulphide is calcined to oxide, leached in sulphuric acid and plated out by electrolysis. The guide says it does not result in non-energy CO2.
The Tier 1 factors, tonnes of CO2 per tonne of zinc
- Waelz kiln: 3.66. It concentrates zinc from electric arc furnace dust and similar wastes using metallurgical coke, and the guide's coke input is 400 kilograms per tonne of dust.
- Imperial Smelting Furnace: 0.43. A weighted figure for primary and secondary zinc in Europe.
- Default: 1.72, a weighting of 60% Imperial Smelting Furnace and 40% Waelz kiln (0.6 x 0.43 + 0.4 x 3.66).
- Tier 2 inputs: 0.4 tonnes of coke per tonne of dust consumed, and 1.23 tonnes of dust per tonne of zinc. The guide puts Tier 1 default uncertainty at plus or minus 50%.
What it means for an Indian plant
The 1.72 default is a blend of two furnace routes. A purely electrolytic plant should not use it: by the guide's account its non-energy CO2 is nil, so what remains is the energy side, counted from power and fuel bills. A Waelz kiln belongs on the 3.66 row, not the blend, and its own coke and dust records should replace both.
20,000 tonnes of zinc a year under each factor (example output)
- Imperial Smelting Furnace: 20,000 x 0.43 = 8,600 tonnes of CO2
- Default blend: 20,000 x 1.72 = 34,400 tonnes
- Waelz kiln: 20,000 x 3.66 = 73,200 tonnes
- Electrolytic plant: no non-energy CO2 in the guide; count power and fuel from bills
Output is an example number. The spread shows why you need to know the route before any default is used.
What Senseible does here
Senseible reads fuel invoices and electricity bills into monthly records, so the power, coke and fuel a zinc plant buys are on file month by month. Which furnace route you run decides which factor applies.
Sources: IPCC 2006 Guidelines, Volume 3 chapter 4: Metal Industry Emissions, section 4.7 (Table 4.24)
Last reviewed 2026-11-04. Factors are from the 2006 IPCC Guidelines, which cite 2000 and 2003 sources. Use your own coke and dust records where you have them.