MFA-based analysis of CO2 emissions from typical industry in urban - As a case of steel industry

Industrial metabolism has closely impact on urban economic, resources and environment condition. As an intensively consuming-energy and heavily polluting industry, steel industry has emitted extremely large quantitate of CO2. Presently, there are two typical production processes in steel enterprises, which are the long process and the short process. However, to compensate the insufficient scrap resources, some steel enterprises have taken a great deal of hot iron in the electric arc furnace steelmaking, which only happens in China. This unique process called the “Chinese style” short process. Coupling material flow analysis and emission factor method, the CO2 emissions for these different three production processes are analysed and their different carbon flow networks diagram are built. The flow diagram could provide basements on emissions reduction located. Results show that the CO2 emissions of long process, “Chinese-style” short process and short process are 3.102 t/t-s, 2.994 t/t-s and 1.613 t/t-s, respectively. The focus of CO2 emissions reduction are the blast furnace steelmaking in long process, electric arc furnace steelmaking in “Chinese-style” short process and short process, whose CO2 emissions are 2.079 t/t-s, 2.748 t/t-s and 1.367 t/t-s, respectively. Specially, the reason why the CO2 emissions of “Chinese style” short process are too high is excessive hot iron utility. For lower CO2 emissions, it is suggested that scrap resources should be recycled as many as possible and the short process ought to rationally develop based on the existing environmental strategies.