(Invited) Membrane Science and Technology for Water-Energy-Food Nexus Applications
Authors: Freeman Benny D. 
Published: February 2020

Around the world, drought inflicts an increasingly unpredictable, frequent and devastating toll on human activities, ranging from, for example, struggling to secure access to sufficient clean water to simply survive, leading to political unrest and instability, increasing the cost of agriculture and manufacturing operations, and damaging the environment, both directly and indirectly. Climate change exacerbates stress on both water supply and demand. Water and energy are inexorably linked, with enormous volumes of water required to generate energy in many cases and large energy inputs required to purify water. In the U.S., thermoelectric power plants account for 41% of total water withdrawals, with nearly all the water requiring some form of purification before use. Horizontal drilling and hydraulic fracturing unleashed a sea of valuable hydrocarbons in the U.S., revitalizing the chemical industry, weakening dependence on foreign energy sources, and reducing oil and gas prices worldwide. However, oil and gas production comes at a substantial price in terms of the amount of water required and the amount of flowback or produced water generated. In many cases, for every barrel of oil produced, 5 or more barrels of water are also produced. This water is contaminated and requires substantial cleanup (i.e., energy input) for any form of beneficial use. An additional indicator of the importance of water is its significance for economic activity. It’s estimated that every million USD of economic activity requires 22,000 m3 of water per year; the faster our economies run, the more clean water we need.
However, the world is not at a loss for water. We have more water than we could ever use. But, 96.5% of it is in the oceans, too contaminated with salt for many anthropogenic uses. Of the 2.5% that is freshwater, nearly 70% of it is locked in glaciers and icecaps, leaving precious little water that is both fresh and available, often not in locations where it is most needed.
Membrane science is alleviating water shortages, weakening the linkage between energy and water, and arresting the environmental damage occurring due to agricultural runoff (e.g., uncontrolled algal blooms), conventional and unconventional oil and gas production, and energy generation based on fossil fuels. A “moonshot for water” has been proposed in the U.S. to reduce the cost of desalination to be comparable to that of conventional drinking water costs. Disruptive, membrane-based technologies will lead the way in bringing about this revolution. Membrane-based seawater desalination is already the least energy intensive way to desalinate seawater, and membranes are increasingly used for wastewater treatment and reuse. Basic and applied science discoveries are paving the way for next generation membranes that will be highly selective, fouling resistant, low energy and highly resilient. Rational control of pore size and pore size distribution in membrane filters is critical to such developments. Discovering and developing the underpinning science to predict ion and water transport across membranes designed to separate ions from water is already providing profound insight regarding molecular strategies to tailor next generation membranes.
This presentation will frame the water/energy nexus challenges and opportunities and provide a glimpse of potential paths forward to supply the world with low energy, abundant access to clean water.