Running the numbers on a zero-emission way to make cement

"Tallying up the energy to do all this using common techniques, the researchers found that you need to use a little more than double the energy of traditional production from limestone."

"The interesting thing is that, according to thermodynamics, the chemical conversion of basalt minerals to calcium oxide only requires around half as much as the conversion from limestone. The problem is that our techniques to facilitate that chemical conversion are quite inefficient, so we don't get anywhere near what is theoretically possible."

"Even if we're stuck with doubled energy usage, producing Portland cement from basalt would significantly reduce CO2 emissions. That's because the direct liberation of CO2 from limestone is eliminated and because the whole process can run on electricity."

"The other components of the basalt also have value. Iron, magnesium, and aluminum could also be separated and recovered, and leftover silicate material can serve as the additive for Portland cement instead of something like coal ash. So if these things were done together, the process could become more economically feasible."

Producing Portland cement from basalt requires more than double the energy of traditional limestone-based production because multiple steps and chemical recovery reactions add cost and energy use. Thermodynamics indicates converting basalt minerals to calcium oxide needs about half the energy required for limestone conversion, but current techniques are inefficient and do not reach theoretical performance. Known lab methods may improve efficiency if scalable. Even with doubled energy use, CO2 emissions could drop substantially because CO2 liberation from limestone is eliminated and the process can run on electricity. With fossil-fuel-dominated electricity, emissions could fall by nearly 30%, while clean electricity could remove most remaining emissions. Additional value could come from recovering iron, magnesium, and aluminum and using leftover silicate as a cement additive, improving economic feasibility.

Read at Ars Technica