The climate solution under your feet

CaCO3 (limestone) + heat → CaO (limestone) + CO2 (carbon dioxide)

Making cement this way requires the release of CO2 – greenhouse gases that are essentially baked into the process.

Solutions

One of the main ways to reduce the weathering effect of cement is to use less lime. You have to be careful when doing this, because you don’t want to end up with cement that isn’t as strong or durable as it needs to be. But mixing in a little filling helps to reduce the lemon you need to use without reducing the performance.

An interesting approach to the mixing method comes from carbon ponding, which adds carbon 2 to the concrete as it mixes. The CO2 reacts with the elements in the mixture and solidifies, a process called mineralization.

You are basically doing the opposite of the cementing process I described above – adding CO2 again. Doing this in a controlled manner will help trap some CO2 and reduce how much lime you have to use in the end. Product. (For more on CO2 mineralization, see our story from last year on a facility that operates a similar process underground).

Last week, CarbonCure announced it was making cement using CO2 pulled directly from the atmosphere, a process known as direct air capture. For the demonstration, CarbonCure added CO2 to some wastewater that would otherwise be too reactive to reuse.

For the demonstration, CarbonCure partnered with a California-based startup called Call. Inheritance It controls carbon dioxide, and the companies say it is the first time carbon dioxide taken from the atmosphere has been used to make cement.

This process is now very small, and there are many questions about whether direct air capture is cheap and efficient. But the Carbon Cure approach could shave off some of the climate pollution that goes into construction and also help clean up emissions in the atmosphere.