Manganese, a versatile metal, finds applications across various industries such as metallurgy (Sun et al., 2022), battery manufacturing (Song et al., 2023), and biomedical fields (Sisakhtnezhad et al., 2023). Currently, the increasing global demand for electric vehicles is driving the demand for power batteries, thereby boosting the demand for manganese metal (Maisel et al., 2023). The 2022 data on China's manganese ore consumption suggests a notable increase in the utilization of manganese in lithium-ion batteries, surpassing the 1 % mark (IMNI, 2023). China not only ranks as the world's fourth-largest producer of manganese ore, following South Africa, Gabon (USGS, 2023), and Australia but also holds the top position as the largest producer of electrolytic manganese metal (EMM) (D.J. He et al., 2021; Li et al., 2023). The current situation is that large-scale EMM production enterprises only exist in China and South Africa. Since 2008, China has consistently contributed to over 98 % of the global production of EMM, establishing itself as the leading producer worldwide (Han and Wu, 2019).
The electrolysis production of manganese metal represents a processing industry characterized by elevated resource and energy consumption, substantial pollution generation, high costs, and relatively low profits (Ning et al., 2010). The majority of EMM production enterprises in China are concentrated in the renowned Manganese Triangle, delineated by Hunan, Guizhou, and Chongqing. However, enterprises in the region lacked environmental awareness, resulting in significant environmental damage and pollution caused by these enterprises (S.C. He et al., 2021). The pollution generated by industrial production of EMM, including electrolytic manganese residue, the release of Mn2+, and ammonia nitrogen, poses a serious threat to ecosystems and human health (Chen et al., 2022). Thus, it is necessary to comprehensively assess the environmental impact of EMM production in the Manganese Triangle region in order to make recommendations for cleaner production.
Life cycle assessment (LCA) stands as a potent tool for environmental analysis, systematically quantifying the environmental impact of products, processes, or activities (ISO 14040, 2006). Widely applied across diverse sectors, including agriculture (van der Werf et al., 2020), construction (Rodrigues et al., 2023), and mining (Tao et al., 2022), LCA provides a comprehensive understanding of environmental implications. For the manganese metal industry, Westfall et al. (2016) collected primary data from 16 manganese alloy producers worldwide and conducted a LCA. The results of the study show that total GWP, AP, and POCP for 1 kg of average manganese alloy was 6 kg CO2eq, 45 g SO2eq, and 3 g C2H4eq, respectively. Ning et al. (2010) conducted a comprehensive material balance and pollutant analysis of the EMM industry in China, revealing the sources and destinations of major pollutants. However, their study did not address the aspect of climate change. Peng et al. (2011) utilized LCA to compare the environmental impacts of EMM production in China and South Africa, focusing solely on the global warming potential and acidification potential. Davourie et al. (2017) conducted a LCA to evaluate particulate matter emissions in manganese alloy production. The results revealed that 66 % of production-related particulate matter emissions occur outside of manganese facilities, with direct or on-site emissions accounting for 34 % of the total PM emissions. However, it only studied particulate matter and did not investigate other pollutants. Farjana et al. (2019) conducted an LCA analysis on manganese ore production based on the Ecoinvent database, but did not cover the subsequent electrolysis part of manganese concentrate. Zhang et al. (2020) conducted a detailed LCA analysis on EMM production in China, but the selected mining and electrolysis data were not sourced from the same enterprise, resulting in spatial discrepancies. Furthermore, the majority of existing studies pertaining to EMM have predominantly focused on the analysis of its pollutants. For example, Zhang et al. (2023) investigated the heavy metal pollution situation of Mn, Zn, Pb, and others in a northern Chinese EMM industrial area and its surrounding environment. Sun et al. (2020) utilized sulfur resource recovery from roasting electrolytic manganese residue and desulfurizing manganese ore for the clean production of electrolytic manganese. Xu et al. (2014) proposed a comprehensive wastewater treatment method for EMM production through a study on the water balance of EMM enterprises. In conclusion, China currently lacks a high-quality, comprehensive LCA study on the environmental impacts of EMM production. To address this, this study selected the most representative electrolytic manganese production company in the Manganese Triangle, the region with the richest manganese deposits in China. A LCA was conducted on electrolytic manganese production from the mining stage to the electrolysis stage.
This study aims to (1) analyze the environmental burden of EMM production in the Manganese Triangle region of China using the LCA method; (2) obtain quantitative results of life cycle impact assessment (LCIA) along with uncertainty information and identify the major impact categories on the environment; (3) identify key processes and substances, conduct sensitivity analysis on key processes, and examine the degree of variation in LCIA results; (4) simulate various energy scenarios, compare their corresponding environmental impacts, and propose optimization strategies for the electrolytic manganese metal production industry in China. After conducting a quantitative LCA, analyze from multiple perspectives, including contribution, uncertainty, and sensitivity, to comprehensively assess the current status and environmental impacts of EMM production technology in China. This analysis aims to optimize resource and energy consumption and reduce pollutant emission intensity. Propose technical measures to achieve clean and efficient EMM production and to build a green and sustainable energy system.
