Life Cycle Assessment Of The Hydrometallurgical Zinc Production Chain In China

Zinc is a kind of nonferrous metals which is widely used in steel,metallurgy,electric power,transportation,chemical industry;especially it plays a vital role on galvanizing industry.With the rapid development of industrialization and economic growth,China has become the largest producer and consumer of zinc in the world.However,zinc production consumes large amounts of energy and burdens the environment.Heavy metals(e.g.,zinc,copper,and mercury)generated by production processes cause severe soil pollution and damage to human health through biological concentration.Life cycle assessment(LCA),which was an effective environmental management tool,was used to access the environmental burden caused by primary zinc production.In this study,the environmental impacts resulting from hydrometallurgical zinc production were quantitatively evaluated from the whole life cycle perspective.To determine the environmental impact of hydrometallurgical zinc production at the macro level,national and regional statistical data were applied in the current study,which can provide scientific and reasonable data supporting for technical improvement and sustainable development of zinc industry.Life cycle inventory(LCI)of hydrometallurgical zinc production was established on the basis of company's primary data.In addition,references and the Chinese Process-based Life Cycle Inventory database was used to build the national LCI.The ReCiPe method was adopted to evaluate environmental burden generated by primary zinc production.Normalization was conducted to identify the dominant categories which had significant impact on environment.Then,the study determined the key factors(process and substance)which contributing most to the main categories.The sensitivity and uncertainty analysis were conducted to scrutinize the variability and accuracy of the Life cycle impact assessment(LCIA)results.Then evaluating the environmental impact of primary zinc production at the micro level by replacing the dominant data identified with the national statistical values.The results showed that the significant environmental impact categories of hydrometallurgical zinc production were freshwater ecotoxicity,marine ecotoxicity,metal depletion,fossil depletion,human toxicity and climate change.The impact of the remaining categories(e.g.,agriculture land use and ozone depletion)was negligible.The zinc ore mining and energy(i.e.,electricity and natural gas)consumption were the key processes which made the largest contributions to environmental burden.The pollutants of copper and zinc were dominant substances contributing most to marine ecotoxicity and freshwater ecotoxicity.With regard to human toxicity,zinc,mercury,and lead were the dominant contributors.Hard coal and natural gas were the dominant substances that influenced fossil depletion.For metal depletion category,the key substance was lead.Direct carbon dioxide(CO2)and methane emissions were mainly responsible for the climate change category.The total national CO2,sulfur dioxide(SO2),nitrogen oxide(NOx),particulate matter(PM),zinc,and copper emissions generated from zinc production in 2013 was 2.60×107 t,4.29×104 t,6.77×104 t,1.23×104 t,1.38×103 t,and 3.20×102 t,respectively.The CO2,SO2,NOx,and PM generated by the hydrometallurgical zinc industry accounted for 0.25%,0.21%,0.30%and 0.10%of the total national emissions in 2013.The large zinc production density fluxes were observed in Hunan,Shaanxi,and Yunnan provinces,which can be attributed to the distribution of mineral resources.Effective approaches to reduce the overall environmental impact of hydrometallurgical zinc production include improving the efficiencies of electricity,natural gas,and zinc ore consumption;substituting hydropower and clean energy for coal-based electricity production;improving production technology to decrease the electricity consumption and direct emissions of heavy metals;recycling utilization of Zinc-containing wastes to expand the regenerative zinc production scale and reduce the waste of resources,as well as focusing on the sustainable development of the industry.