[sacred_numbers]

The reason cement is a major contributor to CO2 emissions is because of how much cement we produce. I don't know the lifetime or effectiveness of this catalyst, but typically you only need a tiny amount of catalyst to start a reaction and the catalyst material can be used over and over for a long time.

[gibolt]

We produce a lot of it, *and* it has high CO2 emissions. The chemical reaction that gives concrete strength releases CO2.