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

China, as the world's largest crude steel producer, is suffering from water scarcity and pollution. However, only a few systematic analyses on the environmental burdens and improvements of China's crude steel production have been conducted. Therefore, it is important for research to be done how China's 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 rare earths recovery from waste fluorescent powders - A case study in China.

Life cycle assessment of recycling rare earths from waste fluorescent powders was conducted, including the uncertainty and sensitivity analyses. Three scenarios were set in this study, namely, recycling with/without final disposal and waste fluorescent powders landfill. Recycling with final disposal presented lower environmental burden than that without final disposal due to the significant reduction of direct emissions. The evident impacts from chemicals and energy production stages were considered the main contributors to the overall environmental burden of recycling with final disposal due to their relatively high emissions of particulates matter, sulfur dioxide, heavy metals, and carbon dioxide as well as the use of fossil fuel. Compared with landfills, rare-earth recycling shows the highest environmental benefits because of the substitution of primary rare earths. To relieve the high demand of rare earths and reduce the overall environmental burden, governments are highly recommended to increase recycle rate, create a complete management system, improve energy consumption and wastewater treatment efficiency, and build an adequate recycle standard.

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.