CCU:A More Feasible and Economic Strategy than CCS for Reducing CO_2 Emissions

A new and promising strategy of CO2 capture and utilization(CCU) based on analysis of the costs and potential geological risks of application of CCS technique was presented.It is believed that,in addition to enormous energy expenditure and costs,application of CCS faces a few geological risks such as leakage of CO2,destruction of saline,ground upheaval and triggering earthquake.CCU,meaning that CO2 being captured and used as raw material to produce high-value chemical products(or related by-products),thereby reducing CO2 emissions with low energy expenditure and costs,is more attractive than CCS as the best currently available technology.This study,for the first time,shows several promising methods to mineralize CO2 and simultaneously produce valuable products,such as employing MgCl2·6H2O to mineralize CO2 and to recover hydrochloric acid and magnesium carbonate,and using phosphogypsum to mineralize CO2 and produce Sulphur-based compound fertilizer and calcium carbonate as well.It is shown that within the scope of human use(about 5 km underground),if 1% of calcium and magnesium ions of the total amount of the earth's crust were used for mineralization of CO2 with a conversion rate of 50%,it could theoretically sequestrate 2.56×106 billion tons of CO2.According to a report by the International Energy Agency,global CO2 emission in 2010 was expected to reach 30.06 billion tons.Potentially,in theory,the natural sources could mineralize as much as 85 thousand years of global CO2 emissions.Besides,if the magnesium ions of approximate 50 million tons of phosphogypsum wastes annually produced in China were used for mineralization,it could theoretically sequestrate 12.5 million tons of CO2 per year.By producing value-added product compensating the costs of handling CO2,the proposed CCU strategy provides a feasible and economic way to fulfill commercial application of techniques for reducing global CO2 emission.