Decarboninzing Concrete

One of Dave Roberts' most recent Volts podcasts was about decarbonizing cement, and it was one of the most hopeful things I've heard in a while.

Cement manufacturing is estimated to create 8% of the world's carbon emissions — equivalent to the third largest country in the world, if it were a country.

Cement production makes C02 in two ways: indirectly through burning fuels to create the 1400°C needed in the chemical process, and directly in the C02 left as a byproduct after the chemical process.

Roberts interviewed Leah Ellis of the company Sublime Systems, a startup created by a chemist and a materials scientist that has rethought the process to use an electrolyzer instead of heat, so there's no energy burned and no carbon output because the inputs were different to start with. 

The final product also meets all industry standards or — it almost sounded like to me — exceeds them. (If you've ever heard about why Roman cement is better than modern cement, this will sound familiar.)

Sublime's process also could be just as cheap as current methods when scaled up, and it uses cheap and available source materials from the place where the cement is made. Those are (of course!) the final requirements. The source material could even possibly be stuff people pay to get rid of (like old concrete from construction debris), which could make it even cheaper.

The hope is to leapfrog the creation of new cement production infrastructure in India and countries across Africa, so they build with clean technology instead of the old, carbon-dirty process. Sublime is on track to build a "kiloton plant" — part of the scaling-up process — in 2026. After that will be megaton plants, maybe in 2028.

Not surprisingly, the Volts discussion lost me when Ellis explained how the electrolyzer works, but that doesn't matter.

Oh, and I love Ellis's analogy of the "leaky tap" for climate change and how to think of fixing it. We should all use that when explaining the best methods.

Check it out!