Our 2050 Roadmap: The 5C Approach
In addition to reducing emissions, carbon neutrality can also be reached through greenhouse gas emissions removal through carbon sinks, as recognised in the European Climate Neutrality Law. Cement and concrete have here a key role to play through a process called re-carbonation, which effectively transforms European cities into carbon sinks.
Re-carbonation is the process whereby concrete re-absorbs some of the CO2 that was released during clinker production. It is a process that occurs naturally in all concrete structures, permanently trapping the CO2. Thanks to recarbonation, cities effectively act as carbon sinks, allowing further reduction of emissions in the full cement and concrete value chain.
How can we reduce emissions from re-carbonation?
Re-carbonation in the built environment
In the built environment, re-carbonation occurs naturally in all concrete infrastructure. According to research by IVL1, 23% of process CO2 emissions of cement used, is being captured annually which equates to a 8% saving of total CO2 emissions for the cement manufactured.
Enhanced re-carbonation of recycled concrete
Re-carbonation increases after demolition of a concrete building. The recycled concrete aggregates have a higher surface area and can absorb more easily CO2 within the concrete paste (cement, water and sand) from the ambient air. Initial research has shown this can be accelerated by using the exhaust gases from a cement kiln which have a higher CO2 content and are also at a higher temperature increasing the CO2 captured up to 50% of process CO2 emissions2. Separating the aggregates from the recycled concrete and grinding the cement paste also enables higher CO2 capture with the added advantage that the resulting material can be used as a clinker replacement in cement or as an additive in concrete.
Carbonation of natural minerals
Natural minerals such as olivine and basalt when crushed can also be re-carbonated when exposed to air or kiln exhaust gases. Up to 20% process CO2 emissions can be absorbed. Once carbonated these materials can be used as clinker substitutes.3
 IVL Research Paper
 Fastcarb Research
 Reco2de Research
How can policy support this transformation?
Re-carbonation has a significant, untapped potential
Concrete absorbs CO2 during its lifetime – the EU should fully use this untapped potential. The re-carbonation of built concrete products over their life cycle should be recognised in CO2 emissions accounting, carbon footprint methodologies, and CO2 certification removal schemes.
Innovation in action
Some examples of research projects aiming to reduce CO2 emissions
Uses a reaction chamber in which exhaust gases from the kiln pass over crushed recycled concrete resulting in up to 50% CO2 capture within the concrete paste.