For the foreseeable future, we’ll have to count on carbon capture and—if it becomes practical—direct air capture to grab the carbon emitted when we make cement.

effect, we’d find a way to take carbon out of the air (using plants or some other method) and put it into a bottle or other plastic product, where it would stay for decades or centuries, with no additional emissions.

What can we do about the processes that inherently produce greenhouse gas emissions? Remember that making steel and cement emits carbon dioxide—not just from burning fossil fuels, but as a result of the chemical reactions that are essential to their creation.

Just as there are lots of ways to add CO2 to the air, there are lots of ways—potentially—to remove it. A technique known as “enhanced weathering” is a sort of upside-down version of the project I toured at the Hellisheiði Power Station. Instead of injecting CO2 deep into rock, the idea is to bring the rock up to the surface to meet the CO2. Basalt