Concrete production has quietly doubled in the past 20 years as we are building more and more cities, and with that comes the carbon footprint of cement, which is the glue that binds concrete together. Cement production is 8% of our global GHG emissions, and efforts to “green” the cement-making process have largely been around replacing the cement recipe.

Minus Materials is using air, sunlight, and water, to photosynthetically grow the limestone used to make ordinary portland cement, identical to what is used in the industry. Their special microalgae mineralizes CO2 into limestone, which is a renewable source of limestone compared to the traditional method of blowing up our mountains and surface mining to quarry for the same minerals. Minus’s method can reduce emissions by up to 60%, and even go carbon-negative if combined with other technologies.