Can CO2-derived building materials deliver climate benefits?

The lower cement input required to manufacture concrete, and thus the lower upstream emissions related to the production of cement, is the major contributor to the lower life-cycle emissions of CO2-cured concrete relative to those of conventionally cured concrete. Another factor is the permanent retention of the carbon in the concrete. To date, the exact emissions reduction potential of CO2-cured concrete compared to conventional concrete remains unclear. CarbonCure reports that the CO2 footprint of concrete can be reduced by around 80%, but these claims have not been verified (CarbonCure, 2019). The net benefits are sensitive to the uptake rate of CO2 during the curing process (Alberici et al., 2017).

What are the regulatory requirements?

Prior to adoption in some applications, it is necessary to demonstrate over a period of multiple years that CO2-cured concrete has a similar or better performance than conventional concrete. The extensive body of standards and codes governing the construction sector may prevent a fast adoption of CO2-cured cement by the market. Compliance with standards and codes is often a function of the material composition, for example based on ordinary Portland cement, rather than their performance. A shift from prescriptive to performance-based standards would facilitate the uptake of novel CO2-derived building materials (IEA, 2019c). Governments and industry need to update standards and codes, which can take up to a decade (ICEF, 2017). Standards and codes may be less stringent for non-structural applications of concrete – such as roads, floors and ditches – for which a high mechanical strength is not necessary. Early-stage adoption could target these market segments.

Table 5. Scaling up to a 10 MtCO2 market for CO2-derived building materials from natural minerals