Carbon Negative Cement: Turning a Climate Liability into an Asset

BERC-E (BERC Engineers) met this week to discuss a topic lying truly at the heart of engineering: cement. Although usually not associated with climate change, cement production is responsible for 5% of global human-caused CO2 annual emissions. In the U.S., only fossil fuel consumption and the iron and steel industry release more greenhouse gas.

The energy-intensive process of cement production has not changed since the discovery of Portland cement in the early 1800s. Annually, more than 3 billion tons of limestone are heated to 1,400C (2,500F) to break into the desired calcium oxide and its by-product, carbon dioxide. The reaction is therefore harmful to the environment in a twofold manner: it releases CO2 itself and consumes massive amounts of fossil fuels.

This inefficiency brings the opportunity for many technological improvements. Companies around the world propose materials and processes that could replace limestone and decrease the energy intensity of cement production. Novacem, a company originating from the Imperial College of London, championed magnesium silicates from earth-abundant minerals. These do not contain carbon, so no CO2 can be evolved, and the heating temperature is reportedly only half of that required in the case of limestone.

Carbon negative cement could come from several naturally existing minerals. Source:

A California-based company, Calera, wants to make calcium carbonate from seawater or brine mixed with CO2 coming from a power plant. This could replace limestone and lead to an almost neutral carbon cycle. Calix, an Australian company, uses superheated steam to modify the cement particles and make them purer and more chemically reactive. In the process CO2 can be separated, making capture much more feasible.

However, none of these technologies is ready for mass market. In fact, Novacem was bought by Calix and further development of magnesium silicates appears to be halted. The challenge for these rising technologies lies in price and required reliability: nobody wants to build more expensive bridges at risk of collapsing. Without an external push, such as the carbon tax, it is hard to envision a widespread transition away from the two-century-old Portland cement. Nevertheless, one thing remains certain: sooner or later technologies that can do away with 5% of global CO2 emissions will prove necessary.

BERC-E welcomes all those interested in the intersection of science, innovation, and policy. Find us every other Monday at 7pm at La Val’s (on Euclid). For more information check out: