‘ZeroCAL’ cement production process takes CO2 out of the equation | With 98% less CO2 emissions than traditional methods by decomposing limestone – the key raw material involved in making cement – to access calcium oxide, aka lime, without releasing carbon dioxide in the process.

From the article: [The team](https://pubs.acs.org/doi/10.1021/acssuschemeng.4c03193) is calling this method ZeroCAL, short for zero carbon lime. It’s a big deal because there’s a massive opportunity to reduce global greenhouse gas emissions. Traditionally, heating limestone in a kiln to produce lime results in 1 lb of CO2 emitted for every lb of cement produced.

ZeroCAL skips the aforementioned fossil-fuel powered process of heating limestone. Instead, it starts with dissolving the sedimentary rock feedstock in a water-based solution containing a common industrial acid. Next, calcium is separated via membrane nanofiltration. Finally, an electrochemical process is carried out to produce calcium hydroxide – a zero-carbon precursor for cement and lime production.

That goes beyond just reducing the emissions from processing limestone to just 1.5%. “It addresses the carbon emissions resulting from limestone’s decomposition while providing clean hydrogen and oxygen to heat the cement kiln,” notes team lead Gaurav Sant. “Second, it enables onsite decarbonization while making use of existing kilns and limestone feedstocks without having to build separate carbon-capture and storage facilities.”