The notion of water scarcity is entirely counter-intuitive on an ocean planet like Earth. However, freshwater is considered a scarce resource with only less than 1% availability. It is a resource that humanity and the economies and ecosystems that sustain it critically depend upon. Principally, the pressures of anthropic origin, such as over-abstraction and pollution, make this limited natural supply scarcer. To that end, the unsustainable consumption patterns and system inefficiencies are the oft blamed. Bleak forecasts such as ‘the water demand is to grow by 55%’ and ‘nearly 5.7 billion people will live in water-scarce regions by 2050’ underscore the gravity of this issue and point towards an imminent crisis. Besides managing existing freshwater resources, supply augmentation is required to tackle this issue because improving system efficiencies and relying on the natural hydrological cycle alone to alleviate the impending water crisis seems inadequate. Therefore, supply-side augmentation using backstop sources such as seawater/saline water and technologies such as reverse osmosis (e.g. SWRO) desalination is warranted. Currently, at over 120 million m3/d installed capacity, the desalination industry’s exponential growth indicates an effective resolution of the water crisis. Despite the boundless potential, desalination’s environmental and economic sustainability are fiercely disputed. In a preceding study, the author found that a cubic meter of potable water produced using SWRO—the most energy-efficient, resource-efficient, and widely employed desalination technology at present—appropriates 1.8 kg of abiotic resources, 2,600 kg of water, 30 kg of air and emits about 4.7 kg of greenhouse gasses (GHGs). Further studies show that the direct GHG impact of desalination due to energy appropriation (200 TWhel/a, globally) alone amounts to 120 million t/a of CO2-eq, about 0.2% of the global GHG impact. Another study indicates that the brine discharge—concentrated wastewater of desalination—amounts to about 52 billion m3/a. Given the projected rate of growth of the industry—over 7% year-on-year, the environmental consequences of desalination by mid-century will be prodigious. Resolving the water scarcity issue at the expense of the environment is a classic case of anthropic management failures and a product of the current linear economic model that the solution is based upon. Therefore, this study aimed to identify mechanisms to render desalination a sustainable alternative water supply. It focused on decarbonising desalination, reducing upstream and downstream impacts via resource efficiency, and valorising waste and emissions. The solution is framed within the water-energy-resource nexus concept, leading to the development of an Integrated Infrastructure System (IIS) model for sustainable SWRO, utilising lifecycle thinking and systems modelling. A lifecycle-wide sustainability assessment of SWRO desalination was conducted, establishing the status quo and developing the IIS model. The findings indicate that SWRO, particularly when powered by renewable energy (REN-SWRO), has significant potential for lifecycle-wide impact reduction. The fossil energy decoupling of SWRO improves its overall sustainability performance by 19% compared to conventional SWRO. That includes an 86% reduction in GHG footprint (4.37 kgCO2-eq/m3 of conventional SWRO vs 0.598 kgCO2-eq/m3 of REN-SWRO) and a 45% reduction in the material footprint. Moreover, the IIS model optimises material and energy flows through synergistic metabolic processes. The approach also uncovers multilevel opportunities that enhance social and economic value (regional added value score increases from 1.71 to 5.0), promoting sustainable production and consumption.

Author: Ranahansa Dasanayake

Published in: World Congress on Sustainable Technologies (WCST-2024)

• Date of Conference: 4-6 November 2024
• DOI: 10.20533/WCST.2024.0018
• ISBN: 978-1-913572-77-8
• Conference Location: St Anne’s College, Oxford University, UK