Process Emissions
Process emissions are greenhouse gases released as a direct by-product of industrial or chemical processes, rather than from the combustion of fuel. Examples include CO₂ from the calcination of limestone in cement production and PFCs from aluminium smelting.
What is Process Emissions?
Process emissions are greenhouse gases produced by the physical or chemical transformation of materials during industrial manufacturing. Unlike combustion emissions, which result from burning fuel for energy, process emissions arise from the nature of the industrial process itself — even if no fuel is burned.
The most significant industrial process emission globally is the CO₂ released during cement production. Manufacturing one tonne of clinker (the active component of cement) requires heating limestone (calcium carbonate, CaCO₃) to around 1,450°C, causing it to decompose into calcium oxide (CaO) and CO₂. This process — called calcination — releases approximately 0.5 tonnes of CO₂ per tonne of clinker, entirely independent of the fuel used to heat the kiln. Cement production alone accounts for approximately 8% of global CO₂ emissions, with roughly half coming from calcination (process emissions) and half from fuel combustion.
Other significant process emissions include: CO₂ and N₂O from chemical manufacturing (e.g., nitric acid, adipic acid, ammonia production); PFCs and CO₂ from aluminium smelting (the electrolytic reduction of alumina); SF₆ from magnesium production and casting; CH₄ from metallurgical coke production; and CO₂ from glass manufacturing (decomposition of soda ash).
Under the GHG Protocol, process emissions are classified as Scope 1 direct emissions. They are reported alongside combustion and fugitive emissions. Calculating process emissions typically requires knowledge of the quantities of raw materials processed and process-specific emission factors — for example, tonnes of clinker produced multiplied by the calcination emission factor.
Process emissions are among the hardest to abate because they are inherent to the chemistry of production. Unlike combustion emissions, which can be eliminated by switching to renewable energy, process emissions require fundamental changes in materials or technology — such as carbon capture and storage (CCS), alternative cement chemistries (e.g., geopolymers, LC3), hydrogen-based steelmaking, or use of recycled materials to avoid primary production.
Practical Examples
A cement plant producing 500,000 tonnes of clinker per year releases approximately 250,000 tCO₂ from calcination alone — before any fuel-related emissions from the kiln are counted.
An aluminium smelter reports PFC emissions from anode effects during electrolysis, where carbon anodes react with the alumina electrolyte to produce CF₄ and C₂F₆ — gases with GWPs of 6,500 and 9,200 respectively.
A glass manufacturer reports process CO₂ from the decomposition of soda ash (sodium carbonate) in its furnaces, which is distinct from the CO₂ produced by burning natural gas to heat the furnace.
How Climatise Helps
Climatise supports process emission calculations for key industrial sectors by accepting production data (tonnes of material processed) and applying the appropriate process-specific emission factors, keeping these separate from combustion emissions for transparent Scope 1 reporting.
Book a DemoRelated Terms
Frequently Asked Questions
Need help understanding your carbon data?
Climatise turns complex emissions data into clear, useful reports. Book a call and we'll walk you through it.
Book a Demo