(From Calera company website)”The heart of the Calera process is the formation of novel, metastable calcium and magnesium carbonate and bicarbonate minerals, similar to those found in the skeletons of marine animals and plants, by capturing carbon dioxide from flue gas and converting the gas to stable solid minerals. We refer to this novel process as Mineralization via Aqueous Precipitation, or MAP for short. In its simplest form MAP involves contacting gas from the power plant with natural waters found in abundance on Earth. Many of the crystallographic forms Calera synthesizes are previously undescribed, or poorly known. These novel ‘polymorphs’ make it possible to produce high reactive cements, and aggregate precursors, with bulk chemistries that would usually be relatively inert.”
Calera estimates that for every ton of cement produced using their method instead of the traditional one, half a ton of CO2 is sequestered.
Traditionally, the production of cement requires heating limestone to 2,640 degrees F. The heating process uses fossil fuels, and releases CO2 previously locked up on a geological time scale. Calera’s process sequesters CO2 instead of releasing it, making it not just carbon neutral, but even carbon negative.