A California startup called Brimstone Energy has patented a new process that reduces Portland cement emissions to zero.
Carbon-negative cement
Brimstone Energy switched to another rock, calcium silicate, which produces no carbon dioxide when heated to make lime. It produces only silica, a byproduct that can be used to replace fly ash, a waste product from coal-fired power plants that is another ingredient in typical cement. With the disappearance of coal-fired power plants, the availability of fly ash is getting lower and lower, and it is another source of emissions in standard products.
While some other startups are working to make new types of cement that can also reduce emissions, Brimstone Energy wants to make industry-standard Portland cement with a specific chemical composition.
"Miracle Materials"
Brimstone Energy has not only found a way to eliminate emissions from cement manufacturing, its innovation has created an opportunity for our built environment to become a carbon sink. Says Carmichael Roberts of Breakthrough Energy Ventures, which led Brimstone's $550,000 Series a round last year. Roberts called it "an amazing material" that is vital to social and economic infrastructure. This means that buildings and bridges built with carbon-negative sulphur Portland cement can be part of the climate solution, rather than a thorny liability.
When Brimstone Energy processes calcium silicate, it also ends up with piles of magnesium, a substance that naturally absorbs carbon dioxide from the air. This means that even though cement is now made with fossil fuels, it can still be carbon neutral. If it is made from renewable energy, it "will be highly carbon-negative". The company is currently designing its first pilot plant and will work with existing cement and concrete manufacturers.
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