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

Gomes, H. I., Mayes, W. M., Baxter, H. A. , Jarvis, A. P., Burke, I. T., Stewart, D. I. and Rogerson, M. (2018) Options for managing alkaline steel slag leachate: a life cycle assessment. Journal of Cleaner Production, 202, 401 - 412. (doi: 10.1016/j.jclepro.2018.08.163)

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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.

Item Type:Articles
Additional Information:This project was funded by the UK Natural Environment Research Council, Economic and Social Research Council and the Department for Environment, Food and Rural Affairs under the Resource Recovery from Waste theme via grant NE/L014211/1.
Keywords:Environmental impacts, openLCA, active treatments, acid dosing, reedbeds, passive treatments.
Glasgow Author(s) Enlighten ID:Baxter, Dr Helen
Authors: Gomes, H. I., Mayes, W. M., Baxter, H. A., Jarvis, A. P., Burke, I. T., Stewart, D. I., and Rogerson, M.
College/School:College of Social Sciences > School of Interdisciplinary Studies
Journal Name:Journal of Cleaner Production
ISSN (Online):1879-1786
Published Online:17 August 2018
Copyright Holders:Copyright © 2018 The Authors
First Published:First published in Journal of Cleaner Production 202: 401-412
Publisher Policy:Reproduced under a Creative Commons License

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