Decarbonizing cement is a chemistry problem where the majority of emissions come from the breakdown of limestone into clinker, the most carbon-intensive ingredient in cement.

Cement manufacturers have traditionally used supplementary cementitious materials (SCMs), such as fly ash from coal-fired power plants and blast furnace slag from coal-based ironmaking, to partially replace clinker in cement. This reduces emissions through abatement, enhances performance, and extends their supply of cement. As highlighted by the Portland Cement Association, SCMs are a critical lever to reaching net zero.

However, as domestic industries like utilities and steel phase out coal, the availability of traditional SCMs has dwindled significantly, causing North American and European manufacturers to rely on imports from overseas.