[ripTDR]

Originally Posted by Street Pharmacist

The cement industry is one of those "hard to abate" sectors. It's responsible for 8% of all GHG emissions which is more than almost all countries.

To understand why it's so tough to eliminate emissions, you need to know a bit about how cement is made. Concrete is essentially Cement + water +/- aggregate. The cement is the emissions intensive stuff. Cement is made by mixing silicates (a bunch of fairly common rocks) with a product from limestone that's been heated. To make the cement, you need to turn limestone (CaCO3) into Calcium oxide (CaO) by removing a CO2. To do that we heat up a large kiln to 900°F, then 1400°F and the carbon dioxide releases from the limestone. Total emissions from cement production are approximately 50% from the coal used to heat the kiln and 50% from the process of removing the CO2 from the limestone. That means that even if you fully electrified the heating (which many have tried to no success so far), you've only eliminated half of the emissions. On the chemical side, some companies have found ways to add materials like coal ash to decrease CO2 emitted by making the reaction more efficient, but you can only decrease it so much. Some companies have found alternate building materials in place of concrete, but they are expensive and don't have the same properties.

A new company, Sublime Systems, has found a new way to get the Calcium Oxide from non carbonated rocks at room temperature in an electrically powered process. This means you can now completely remove emissions from both sides of the equation. They've made their first production plant and are actively selling cement now, but it's small volume. They have plans to open a megaton production facility by 2026, but that's still 2 years away. The biggest issue with scaling the technology is due to the logistics of the concrete industry. It's very cheap, heavy, voluminous material and therefore financially impossible to ship long distances. That means you have to have these plants located near whatever building needs the concrete. That means you can't just build massive factories to cut down costs, because you need to build lots of smaller factories all over the place. The good news though is that concrete is a very cheap material. That means it's total portion of building costs is very small, so having even a doubling of cement costs doesn't change things much

I recall listening to a stuff you should know podcast where they were essentially saying the sand necessary for the use of concrete is a finite resource and is non renewable.