Quote:
Manufacturing cement is an energy-intensive process. It requires 3 to 6 million BTUs (British thermal units) of energy and 1.7 tons of raw materials, mostly limestone, to make one ton of clinker. Coal or coke is typically used to fire the kilns that are used to burn the limestone, clay, shale, and other materials; the materials must be heated to 1450 degrees C to form C3S. The process is a significant source of carbon dioxide emissions, in addition to nitrogen oxides, sulfur oxides, and particulate matter. Concrete manufacturing is one of the most significant sources of CO2 emissions from manufacturing sources; production of iron and steel also produce significant CO2 emissions. One ton of CO2 is emitted per one ton of cement produced, about half due to the use of fossil fuels and half from the calcination of limestone.Worldwide, cement production is estimated to produce approximately 5 percent of all carbon dioxide emissions from human sources.