One of the biggest problems in dealing with carbon dioxide emissions is the making of the key component of cement: lime (calcium oxide). Now, a small company with the cute name Sublime Systems appears to have solved this issue.

The concrete industry is responsible for 8% of global carbon emissions. Ordinary Portland cement (OPC) is about 15% of concrete, and calcium oxide or lime is only 60% of OPC. Yet the making of that lime is the cause of almost all of the emissions: Lime is only 8% of concrete but creates 90% of the problem. About half comes from the “chemical fact of life”—the CO2 emitted in calcination or turning calcium carbonate into calcium oxide. The other half comes from burning coal or fossil gas to make the calcination happen.

We have described the process many times: “The key component of cement is lime, which you get by applying heat to calcium carbonate, basically limestone. CaCO3 + heat > CaO + CO2. You can’t do anything about the chemistry; it is the fundamental nature of the material that makes it emits CO2.”

It may be that you can’t do anything about the chemistry, but there are different ways of separating carbon dioxide from limestone. Sublime Systems co-founders Leah Ellis and Yet-Ming Chang described how their company made lime at room temperature using renewable electricity. They wrote:

Keep reading on treehugger.com

• 
•