Xiaotian Ma

How much water is required for coal power generation: An analysis of gray and blue water footprints

Although water resource shortage is closely connected with coal-based electricity generation, relevant water footprint analyses remain limited. This study aims to address this limitation by conducting a water footprint analysis of coal-based electricity generation in China for the first time to inform decision-makers about how freshwater consumption and wastewater discharge can be reduced. In China, 1 kWh of electricity supply obtained 1.78 × 10-3 m3 of gray water footprint in 2015, and the value is 1.3 times the blue water footprint score of 1.35 × 10-3 m3/kWh. Although water footprint of 1 kWh of electricity supply decreased, the national total gray water footprint increased significantly from 2006 to 2015 with increase in power generating capacity. An opposite trend was observed for blue water footprint. Indirect processes dominated the influence of gray water footprint, whereas direct freshwater consumption contributed 63.6% to blue water footprint. Ameliorating key processes, including transportation, direct freshwater consumption, direct air emissions, and coal washing could thus bring substantial environmental benefits. Moreover, phosphorus, mercury, hexavalent chromium, arsenic, COD, and BOD5 were key substances of gray water footprint. Results indicated that the combination of railway and water transportation should be prioritized. The targeted transition toward high coal washing rate and pithead power plant development provides a possibility to relieve environmental burdens, but constraints on water resources in coal production sites have to be considered.

Life cycle assessment and water footprint evaluation of crude steel production: A case study in China

China, as the worlds largest crude steel producer, is suffering from water scarcity and pollution. However, only a few systematic analyses on the environmental burdens and improvements of Chinas crude steel production have been conducted. Therefore, it is important for research to be done how Chinas steel industry can be improved in environment management. To help decision-makers understand this, a life cycle water footprint analysis including gray and blue water was performed based on the methodology prescribed in the ISO 14046 standard. A life cycle assessment was also conducted to improve the environmental performance of the steel industry. Results of these assessments revealed that gray water footprint, which is mainly derived from aquatic eutrophication, carcinogens, and non-carcinogens, is higher than blue water footprint. Optimizing indirect processes, including iron ore mining, magnesium oxide production, transportation, and electricity generation, played dominant roles in the reduction of gray water footprint. Furthermore, COD, Cr (VI), phosphate, BOD5, Hg, As, nitrogen oxides, particulates, and sulfur dioxide were the key substances for environmental improvements. The underestimation of direct water footprint showed the importance and urgency of implementing scientific and adequate monitoring indicators. Meanwhile, the environmental burden can be reduced by adopting a reasonable location of the steel industry on the basis of regional water resources and actual transportation status, improving the efficiency of raw material consumption, and optimizing the power structure.

Life cycle assessment of copper production: a case study in China

PurposeChina is the world’s largest producer and consumer of refined and reclaimed copper because of the rapid economic and industrial development of this country. However, only a few studies have analyzed the environmental impact of China’s copper industry. The current study analyzes the life cycle environmental impact of copper production in China.MethodsA life cycle impact assessment using the ReCiPe method was conducted to estimate the environmental impact of refined and reclaimed copper production in China. Uncertainty analysis was also performed based on the Monte-Carlo simulation.Results and discussionThe environmental impact of refined copper was higher than that of reclaimed copper in almost all categories except for human toxicity because of the direct atmospheric arsenic emission during the copper recycling stage. The overall environmental impact for the refined copper production was mainly attributed to metal depletion, freshwater ecotoxicity, marine ecotoxicity, and water depletion potential impact. By contrast, that for the reclaimed copper production was mainly caused by human toxicity impact.ConclusionsResults show that the reclaimed copper scenario had approximately 59 to 99% more environmental benefits than those of the refined copper scenario in most key categories except for human toxicity, in which a similar environmental burden was observed between both scenarios. The key factors that reduce the overall environmental impact for China’s copper industry include decreasing direct heavy metal emissions in air and water, increasing the national recycling rate of copper, improving electricity consumption efficiency, replacing coal with clean energy sources for electricity production, and optimizing the efficiency of copper ore mining and consumption.