  Citation: Bogacka, M.; Iluk, T.; Piko´ n, K.; ´ Sci ˛ a˙ zko, M.; Stec, M.; Czaplicki, A.; Wajda, A. Life Cycle Assessment (LCA) of the Use of Metallurgical Process Gas for Heat and Electricity, Combined with Salt Removal from Discarded Water. Sustainability 2022, 14, 1205. https://doi.org/10.3390/ su14031205 Academic Editor: Andrius Plepys Received: 29 November 2021 Accepted: 11 January 2022 Published: 21 January 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). sustainability Article Life Cycle Assessment (LCA) of the Use of Metallurgical Process Gas for Heat and Electricity, Combined with Salt Removal from Discarded Water Magdalena Bogacka 1 , Tomasz Iluk 2 , Krzysztof Piko ´ n 1 , Marek ´ Sci ˛ a˙ zko 2 , Marcin Stec 2 , Andrzej Czaplicki 2 and Agata Wajda 1, * 1 Department of Technologies and Installations for Waste Management, Faculty of Energy and Environmental Engineering, Silesian University of Technology, 44-100 Gliwice, Poland; Magdalena.Bogacka@polsl.pl (M.B.); Krzysztof.Pikon@polsl.pl (K.P.) 2 Institute for Chemical Processing of Coal, 41-803 Zabrze, Poland; tiluk@ichpw.pl (T.I.); msciazko@ichpw.pl (M. ´ S.); mstec@ichpw.pl (M.S.); aczaplicki@ichpw.pl (A.C.) * Correspondence: Agata.Wajda@polsl.pl; Tel.: +48-32-237-13-21 Abstract: The subject of the article is the assessment of the environmental impact of the technology concerning the use of low-quality post-process gas for the production of electricity and heat, along with the treatment of post-process wastewater. This assessment was carried out based on the results of the full life cycle assessment (LCA) analysis. The presented technology is based on the energetic use of low-quality process gases in a reciprocating engine for the production of electricity and heat in cogeneration with the use of heat in the wastewater treatment system. The article presents the adopted assumptions and the results of the LCA analysis for the RECLEG technology developed specifically for a zinc smelter. The aim of the analysis was to check whether the developed technology has a positive impact on the environment. The LCA analysis was performed using the ReCiPe methodology, which is one of the most frequently used methodologies in this field due to the possibility of observing the environmental impact in a full range of different environmental aspects. At the same time, the analysis also allows the results to be presented in three general impact categories: human health, ecosystem and natural resources, which are easier to interpret. By converting the waste post-process gas into electricity and heat, it is seen that this has a positive impact on the environment. Especially due to the waste nature of the source, which is the post-process gas. Each reduction of gas is potentially beneficial for the environment and, in addition, a replacement effect can be observed, because the gas was previously burned in a flare, where it additionally emitted exhaust gases, sent directly to the atmosphere. Moreover, the RECLEG technology combines post-process wastewater treatment, which has a positive effect on water management, and makes the process even more environmentally friendly. Keywords: LCA; RECLEG technology; post-process gas; chlorine ions; emission reduction; effective generation 1. Introduction The legal regulations introduced in recent years, as well as the growing concern for the natural environment, have contributed to taking actions aimed at implementing innovative solutions in the industry, as well as optimising existing technological processes. The transformation of the economy towards sustainability has been defined by numerous international documents. Actions in this area are undertaken, among others, by the United Nations, which developed the document The 2030 Agenda for Sustainable Development [1], and the European Union, which is working on a coherent policy with the member states in this area. An example of such action is the guidelines for the implementation of the circular economy in the form of a document [2]. An important issue in this regard is the Sustainability 2022, 14, 1205. https://doi.org/10.3390/su14031205 https://www.mdpi.com/journal/sustainability