Zero-carbon cement

Concrete is made from four ingredients: gravel, sand, water, and cement. The first three are pretty simple, but the cement is a big problem for the environment. To get cement, you need calcium, which comes from limestone. But when you burn limestone in a furnace, you not only get the calcium you need, but you also get something you don't want: carbon dioxide. Unfortunately, we can't make cement without going through this process. This means that for every ton of cement we make, we also get a ton of carbon dioxide. And since we're not going to stop making cement anytime soon, we need to find ways to deal with this problem.

Some companies are working on ways to reduce emissions from cement. One idea is to capture carbon dioxide from other sources and inject it back into the cement before it's used. This can reduce emissions by up to 33%. Another idea is to make cement using seawater and carbon dioxide captured from power plants. This could cut emissions by more than 70%, but it's still not a zero-carbon solution.

Sine we don't have a viable zero-carbon cement, we need to calculate the green premium for cement using carbon capture as an offset. Unfortunately that comes at an astronomical cost: making the net-zero carbon option for cement 75-140% higher than regular cement.

This means that we need to invest in clean en technology to power these processes. We also need to find ways to use less cement. We can recycle more cement and find ways to reduce the amount of energy needed to recycle it. We can also use repurposed materials to build things, which requires less energy than recycling. Finally, we can design buildings and roads to use less cement, and in some cases, we can use cross-laminated wood instead.

To power these processes, we need to increase the deployment of clean energy technology and develop new methods to generate and store zero-carbon electricity at a lower cost. Electrification is another way to reduce emissions by using electricity instead of fossil fuels in some industrial processes.

Aside from finding ways to create cement with zero emissions, we can also use less of it. Recycling concrete can help, but it won't be enough to completely eliminate greenhouse gas emissions. We should explore ways to reduce the amount of energy needed to recycle concrete and to construct and make things using repurposed materials. Additionally, buildings and roads can be designed to limit the use of cement, and in some cases, cross-laminated wood made of glued layers of timber is strong enough to be a substitute for cement.

Gates, Bill. How to Avoid a Climate Disaster (p. 99-111). Penguin Books Ltd. Kindle Edition.