Unique collaboration leads to new, energy-efficient solution to global freshwater shortage
JP LaBrucherie stands in front of his fields – 70,000 acres of kale, Swiss chard, arugula, carrots, onions and celery. The fields have belonged to his family for generations, but the future is uncertain.
“California is about to run out of water,” he says simply. “We’re going to have to basically stop operating part of our farm.”
California and many of its neighbors depend on the Colorado River to deliver water to 40 million people. Each year, 4.4 million acre-feet of water are sent to Californians, but this year, amid extreme drought and years of overuse, a proposal has been floated to reduce the amount to 2, 7 million. With that little water, farmers can’t farm the same amount of land, says the 2002 Notre Dame law graduate. With less farming, there will be less food. Less food means that available food becomes more expensive. And suddenly, even those far from the west coast are feeling the effects of the drought.
By 2025, it is predicted that two-thirds of the world’s population will be affected by water scarcity. The impact will affect everything from agriculture to manufacturing, from health care to residential access to water. Without drinking water, humanity is in danger.
Tengfei Luo, Dorini Family Professor for Energy Studies at the Faculty of Engineering, has been observing this crisis from his graduate studies. During his postdoc days at MIT, Luo participated in a research project that created Directional Solvent Extraction (DSE), a new way to desalinate water. But when he arrived at Notre Dame in 2012, he thought he could design better materials to create a more efficient system. Then he met Brandon Ashfeld.
Professor Ashfeld is an organic chemist in the Department of Chemistry and Biochemistry who specializes in the design and synthesis of small molecules. For years he designed and studied ionic liquids, which were found to be more effective in desalinating water. Together, as part of an interdisciplinary project between the faculties of science and engineering, Ashfeld and Luo were able to design a system that purifies water using much less energy, about a tenfold reduction, and costs much cheaper than the original DSE methods.
Luo says, “In fact, the only place you can grow your freshwater supply is seawater, which is why desalination is very important. However, current technologies are energy and capital intensive. He explains that there are two typical desalination methods. The first, thermal desalination, widely used in the Middle East, requires boiling water, which requires high temperature thermal energy, usually from fossil fuels, which causes additional environmental problems. The second option is reverse osmosis, also called membrane desalination. It relies on electricity and high-pressure pumps to push salt water through expensive membranes, leaving clean water on one side and salty brine on the other.
The technology made possible by Luo and Ashfeld’s research requires none of that. In their process, the liquids need only reach 45 degrees Celsius (113 degrees Fahrenheit), well below boiling, which can be achieved from simple solar heating or even waste heat from industrial systems such as power plants. It also doesn’t require membranes, just Ashfeld’s ionic liquids — which he notes are usually inexpensive to create.
The other problem with typical desalination is the salty brine that results from these interventions. On average, seawater has a salinity of about 3.5%. Traditional methods can draw fresh water until the original solution reaches around 6%, at which point it is often discharged into the ocean, hoping for gradual dilution. But rising ocean salinity is unsustainable because it strains existing ecosystems, kills marine life and destroys aquatic plants.
Luo and Ashfeld also tackled this. Their method can approach zero liquid rejection, meaning they can draw out all the liquid, leaving only crystallized salt, which can then be collected and reused. It can also be used to remove other highly toxic salts, such as arsenic, from contaminated water sources. The applications, Ashfeld notes, are vast.
“We envision using our ionic liquid directional solvent extraction system to clean industrial wastewater streams so as not to contaminate soil and/or existing water sources,” says Ashfeld. “Given the emphasis on clean water in our homes, the importance of which is hard to underestimate in light of recent high-profile incidences of residential water contamination, we are planning the installation of small scale in homes to remove toxic salt contaminants before they reach the faucet.”
The duo are now working on creating a startup with the goal of bringing this technology first to market and then to homes.
In academia, the push for interdisciplinary research isn’t new, but doing it effectively poses many challenges, says Bob Bernhard, vice president of research. To work together, it is important that scholars from different disciplines learn to talk to each other and set goals so that everyone can grow and be fulfilled. Because of these challenges, Bernhard notes, the pace of interdisciplinary research is sometimes slower, but often ultimately radical.
“That’s how you end up with solutions that engineers would never have found, and you end up with applications that scientists would never have imagined,” Bernhard says. “Sometimes the engineer says, ‘Oh, I didn’t know that was possible’, and the scientist says, ‘I didn’t know that was important. You get that kind of a-ha moment on both sides.
“That’s the kind of magic that happens.”
That’s how you end up with solutions that engineers would never have found, and you end up with applications that scientists would never have imagined.” —Bob Bernhard
Ashfeld agrees. He says, “I think that’s a big selling point here [at Notre Dame] it’s that there are a lot of people collaborating, a lot of collaborative research projects, but what’s important to note is that inter-university collaborations, like ours, are important in addressing global challenges.
Back in California, LaBrucherie notes that this isn’t California’s first drought. He remembers the scares of the past, like when his father ran the farm in 1998, but like then, a big snowfall would eventually fill the dams and rivers. This time, he’s less optimistic that he can rely on precipitation and instead seeks change, perhaps like what Luo and Ashfeld can bring.
“The research conducted at Notre Dame could be transformative for me and other farmers, and also benefit generations to come,” he says.