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Options for managing alkaline steel slag leachate: A life cycle assessment

Gomes, Helena I.; Mayes, William M.; Baxter, Helen A.; Jarvis, Adam P.; Burke, Ian T.; Stewart, Douglas I.; Rogerson, Mike

Authors

Helena I. Gomes

Helen A. Baxter

Adam P. Jarvis

Ian T. Burke

Douglas I. Stewart

Abstract

Management of steel slag (a major by-product of the steel industry) includes the treatment of highly alkaline leachate (pH > 11.5) from rainwater infiltration of slag deposits to prevent adverse impact upon surface or ground waters. This study aims to compare different treatment options for steel slag leachate through a life cycle assessment (LCA). Five options were compared: active treatment by acid dosing (A-H2SO4), active treatment by carbon dioxide dosing (A-CO2), active treatment by calcium chloride dosing (A-CaCl2), passive treatment by cascade and reedbeds with pumping (P-P), and passive treatment by cascade and reedbeds in a gravity-driven configuration (P-G). The functional unit was 1 m3 of treated leachate with pH < 9, considering 24 h and 365 days of operating, maintenance operations every year, and service life of 20 years. Inventory data were obtained from project designers, commercial suppliers, laboratory data and field tests. The environmental impacts were calculated in OpenLCA using the ELCD database and ILCD 2011 method, covering twelve impact categories. The A-CaCl2 option scored worse than all other treatments for all considered environmental impact categories. Regarding human toxicity, A-CaCl2 impact was 1260 times higher than the lowest impact option (A-CO2) for carcinogenics and 53 times higher for non-carcinogenics (A-H2SO4). For climate change, the lowest impact was calculated for P-G < P-P < A-H2SO4 < A-CO2 < A-CaCl2, while for particulate matter/respiratory inorganics, the options ranked as follows P-G < P-P < A-CO2 < A-H2SO4 < A-CaCl2. The major contributor to these impact categories was the Solvay process to produce CaCl2. Higher uncertainty was associated with the categories particulate matter formation, climate change and human toxicity, as they are driven by indirect emissions from electricity and chemicals production. Both passive treatment options had better environmental performance than the active treatment options. Potential design measures to enhance environmental performance of the treatments regarding metal removal and recovery are discussed and could inform operational management at active and legacy steel slag disposal sites.

Journal Article Type Article
Publication Date Nov 20, 2018
Print ISSN 0959-6526
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 202
Pages 401-412
Institution Citation Gomes, H. I., Mayes, W. M., Baxter, H. A., Jarvis, A. P., Burke, I. T., Stewart, D. I., & Rogerson, M. (2018). Options for managing alkaline steel slag leachate: A life cycle assessment. Journal of cleaner production, 202, 401-412. https://doi.org/10.1016/j.jclepro.2018.08.163
DOI https://doi.org/10.1016/j.jclepro.2018.08.163
Keywords openLCA; Environmental impacts; Active treatments; Acid dosing; Reedbeds; Passive treatments
Publisher URL https://www.sciencedirect.com/science/article/pii/S095965261832506X?via%3Dihub
Copyright Statement © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

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Copyright Statement
© 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/


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Copyright Statement
© 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND
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