Toward carbon-neutral desalination: Scope 1-3 carbon accounting, technological pathways, circular resource recovery, and future perspectives

초록

Desalination is increasingly essential for addressing global water scarcity, particularly in arid and semiarid regions with limited conventional freshwater resources. However, the process remains energy-intensive, making its environmental sustainability heavily dependent on the carbon intensity of its operational energy supply. As global climate mitigation accelerates, carbon-neutral desalination has emerged as a critical objective to align future water supply systems with net-zero emission targets. This review evaluates recent progress, key challenges, and technological pathways for reducing the carbon footprint of desalination systems. It first examines the main carbon drivers of desalination, identifying operational electricity consumption as the dominant source of greenhouse gas (GHG) emissions, especially in reverse osmosis systems. Furthermore, this review evaluates desalination-related emissions using a Scope 1-3 GHG accounting framework, highlighting the growing importance of indirect life cycle emissions from membranes, chemicals, infrastructure, and brine management. Life cycle assessment (LCA) studies indicate that desalinated water generates approximately 1-3 kg CO2-eq m(-3), depending on the electricity mix, plant efficiency, and system configuration. The review also discusses major carbon-reduction pathways, including renewable energy integration, energy recovery devices (ERDs), advanced membranes, process optimization, digital control, and emerging low-carbon desalination technologies. Solar- and wind-powered desalination systems represent key near-term strategies for reducing operational emissions, while advances in ERDs and membrane materials continue to lower specific energy consumption. Emerging technologies, including membrane distillation, forward osmosis, electrodialysis, and capacitive deionization, can further support low-carbon desalination in applications involving low-grade heat, brackishwater, wastewater reuse, or decentralized treatment. Furthermore, sustainable brine management, zero-liquiddischarge systems, and resource recovery are highlighted as key components of circular desalination. Despite recent progress, carbon-neutral desalination remains constrained by renewable energy intermittency, high capital costs, limited full-scale demonstrations, energy-intensive brine treatment, and the lack of standardized Scope 1-3 carbon-accounting frameworks.

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