To make cement, you cook calcium carbonate at high temperature, producing 4% of the world's carbon dioxide in two ways: through the fuel used to heat the kiln, and through the chemistry of converting calcium carbonate to lime and carbon dioxide.
But as climate skeptics are so fond of telling us, plants love CO2. So Pond Biofuels set up shop next to St. Mary's Cement and feeds gases from its stack to algae taken from the nearby Thames River. The algae grows in its algae condos, sucking up sulphur and CO2 and emitting oxygen.
The algae is then harvested, dewatered and processed. It can be turned into100 litres of biofuel per tonne of algae, or as is being done at St. Mary's right now, fed back into the cement plant to replace coal or coke.
There is something so virtuous about a cycle that turns cement plant exhaust gases into oxygen and biofuel. Pond Biofuels says their process scales; I hope it does very quickly.