. Since then I’ve had numerous conversations with deep experts on the subject that made me realize that it wasn’t just cost, but regulations that held alternatives back.
Brimstone’s solution is to pick a different rock, a group called calcium silicates. There’s a clue there. When we talk about limestone, that’s it. Limestone is very chemically homogenous. Calcium silicates have all sorts of stuff in them by comparison. Calcium oxide is typically around 55-65% of the rocks. Silicon dioxide is 25-35%. But it usually has 2-5% aluminum oxide, 2-3% iron oxide and smaller amounts of magnesium oxide and other trace elements.
Meanwhile calcium silicates, while still prevalent, cluster in certain geological formation, meaning that if you need cement where calcium silicates aren’t, transportation costs will be higher. Those geological formations are mostly where there was a lot of subterranean heat. Calcium silicates like wollastonite and larnite are metamorphic rocks, one form of rock, including limestone, that’s been exposed to a lot of heat and pressure, into another form of rock.
Then there’s the next cost factor, which is higher process heat. Limestone is advantageous because it decomposes into calcium oxide and carbon dioxide at a lower temperature. Limestone kilns run at 900-1,000° Celsius while calcium oxide kilns run at around 1,450° Celsius. 50% more heat means 50% higher energy costs.
That much waste would probably add 5% disposal fees, to be generous, bringing the total cost of a ton of Brimstone’s cement up to $250 to $290. Right now, as long as the atmosphere is treated as an open sewer and no one cares about climate change, that $20 to $30 per MWH for natural gas isn’t much higher delivered. For electricity, it’s tough to get that low except in places that haven’t privatized everything and have a lot of big, old hydro electricity such as Quebec in Canada. Delivered cost of heat is in the $10 to $40 per MWh range.