Hard-to-Abate Sectors

Cement and similar industries are hard-to-abate sectors because reducing their greenhouse-gas emissions is technically difficult and often costly. Their emissions arise not only from burning fuel but also from chemical reactions intrinsic to production, called process emissions. Cleaner electricity alone therefore cannot eliminate their emissions.

Why industrial processes release carbon dioxide

Cement production illustrates the distinction between energy-related and process emissions. Its principal intermediate product, clinker, is manufactured by heating limestone and other raw materials in a kiln.

• During calcination, calcium carbonate in limestone decomposes into calcium oxide and carbon dioxide: CaCO3 → CaO + CO2.
• This carbon dioxide comes from the raw material itself, so replacing fossil fuels with renewable energy does not prevent its release.
• Additional emissions arise from burning fuels to heat the kiln and from electricity used in grinding and other operations.
• Similar difficulties occur in lime production and conventional ironmaking, where carbon-containing materials participate directly in chemical reactions rather than merely supplying heat.

What makes deep emissions reductions difficult

These industries combine process emissions with demanding energy requirements and production systems that cannot be transformed simply by changing their electricity supplier.

• Many industrial processes require high-temperature heat, making substitution of fossil fuels more technically demanding than switching electricity generation.
• Alternative materials and production routes must satisfy product-quality, safety and performance requirements before they can replace established processes at scale.
• Kilns and furnaces are long-lived, capital-intensive assets; replacing or substantially modifying them requires investment and can disrupt production.
• Low-emission technologies may depend on additional infrastructure, such as clean hydrogen supply or carbon dioxide transport and storage.
• Higher production costs and competition from conventional products can weaken incentives for firms to adopt cleaner technologies.

How these sectors can be decarbonised

Hard-to-abate does not mean impossible to decarbonise. It means that multiple complementary measures are needed, addressing both energy use and the underlying production process.

• Energy efficiency, waste-heat recovery and low-carbon energy can reduce emissions associated with industrial energy consumption.
• In cement, reducing the clinker-to-cement ratio through suitable supplementary cementitious materials can lower emissions, subject to material availability and performance requirements.
• Material-efficient construction, longer product life and reuse can reduce demand for newly manufactured materials.
• Alternative chemical pathways can reduce process emissions where technically viable; clean hydrogen can replace carbon-based reductants in suitable ironmaking routes.
• Carbon capture and storage can address remaining carbon dioxide emissions, but requires capture equipment, transport infrastructure and secure geological storage.