Carbon Footprint of Seawater Desalination Technologies: A Review

As an important and effective way of mitigating water shortages, desalination has steadily and rapidly increased its global capacity over the decades. This raises concern about its environmental impacts, especially its carbon footprint (CF). Although the CF of desalination has been extensively studied, the existing literature lacks reviews exclusively for it. To help fill the research gap, this study presents a comprehensive and up-to-date review of the CF of seawater desalination technologies, including the conventional reverse osmosis (RO), multi-stage flash (MSF), multi-effect distillation (MED), electrodialysis (ED), and mechanical vapor compression (MVC), and the emerging membrane distillation (MD) and humidification-dehumidification (HDH). To our knowledge, this is the first review that focuses on the CF of seawater desalination. A general procedure for assessing the CF of a desalination system is discussed. The CF data of 211 scenarios from 34 studies published from 2004 to 2023 are reviewed and analyzed, with special focuses on the CF of different technologies, the roles of different life-cycle phases and material/energy flows, and the mitigation measures. The results highlight the CF advantage of RO and low-carbon heat-driven MSF, MED, and MD, and emphasize the dominant role of the operational energy consumption (the amount, the form, and especially the source of the energy) in the CF of desalination. This review improves the understanding of the CF of seawater desalination technologies and of the ways to reduce it.