Solar thermal process to produce cement without emitting carbon
Power industry is the largest contributor in the production of greenhouse gas emissions and the second in line is the cement industry, which is always overlooked. Going with figures, cement industry accounts for emitting five to six percent of carbon dioxide. Nine kilograms of carbon is released while producing ten kilograms of cement. Around three trillion kilograms of cement is consumed annually making this industry highly potential for reduction in carbon emissions. Since a long time processes to seize carbon from cement production are being explored, but up till now none has been successful in completely eliminating it. Grabbing the opportunity, a method for producing cement with zero carbon emissions has been developed by a research team of George Washington University in Ashburn, Virginia. It is also estimated that the production process will get cheap as compared to the one used at present in the cement industry.
The process is described as the Solar Thermal Electrochemical Production of cement (STEP) by the scientists and was recently published in their study in an issue of Chemical Communications. As explained by the scientists, during cement production 60 to 70 percent emissions of carbon occurs while converting limestone into lime and the rest is due to the fossil fuels burned during the decarbonation process. In the STEP process, solar thermal energy is used to heat the limestone as well as to assist in electrolysis, producing a different chemical reaction, depending upon temperature, separating limestone into lime and some other combination of oxygen and carbon atoms with no carbon dioxide as a byproduct. If electrolyzed below 800 degrees Celsius, lime, carbon and dioxygen is formed and when electrolyzed above 800 degrees Celsius, lime, carbon monoxide and superoxide is formed by the molten limestone.
As explained by Stuart Licht, Chemistry professor at George Washington University, it is possible to use carbon monoxide byproduct in the higher temperature reaction in other industries for purifying nickel, producing fuels and forming plastics and other hydrocarbons. Apart from its use, the solar thermal electrolytic process is producing it at considerably low market value. Lime, the main product can be easily removed as a slurry is formed by it at the vessels bottom and it doesn’t react with the other byproducts.
It was also added by the scientists that the projected cost of the STEP process will be cheaper than the existing cement industry process. In fact, if the value of carbon monoxide is accounted the cost of producing lime will actually be negative. Apart fromthat it can also be extended in other applications like purifying aluminum and iron, producing paper, glass, sugar etc.