The former Navy diver was dismayed by how much energy it takes to desalinate seawater. So he developed a more efficient process
Floating on a tiny rubber boat on his way to defuse underwater mines during Operation Desert Storm in 1991, Robert McGinnis spotted a towering desalination plant on the shores of the Persian Gulf. It was the first he'd ever seen. "I was appalled that you'd burn fuel in order to produce pure water," he says.
Four years later, after leaving the U.S. Navy, McGinnis flipped open his first college chemistry textbook and saw a photo of what looked like the same plant. The next day he drove to the ocean, took a water sample, and started experimenting in his kitchen. By the time he'd graduated, McGinnis had filed three patents.
Commercial desalination is usually done in one of two ways. The first, known as thermal desalination, involves boiling seawater above 212F, then distilling the vapors. The second, called reverse osmosis, uses hydraulic pressure to force water through a membrane that filters out salt. Both require enormous amounts of energy. McGinnis says he's found a method that's at least 10 times more fuel-efficient.
Water molecules naturally want to flow from fresher solutions to saltier ones. Hence the "reverse" in reverse osmosis: It forces water molecules to go against their tendency. McGinnis's method makes use of forward osmosis. He's developed a "draw solution" that's saltier than seawater. Without need for any energy, the water molecules in seawater flow across a porous membrane and into the draw solution, leaving the sea salt behind. McGinnis's solution is as undrinkable as ocean water, but its salt compounds—"essentially just ammonium, carbon dioxide, and some other secret stuff," he says—vaporize at lower temperatures. McGinnis's solution needs only 122F to burn off salts and leave behind pure water, instead of the much higher temperatures required for thermal desalination.
After graduating from Yale with a PhD in environmental engineering in 2009, McGinnis co-founded Boston-based Oasys Water and raised $10 million from three venture capital firms to commercialize the technology, including developing a thin membrane suitable for forward osmosis. Oasys plans to start taking orders in late 2011. "Forward osmosis is on the verge of becoming a buzzword," says Tom Pankratz, director of the International Desalination Assn. "Oasys has a clever approach. ... It could potentially be used not only for seawater desalination but also treating wastewater."
McGinnis didn't plan to dedicate his career to desalination. As an undergraduate he majored in theater and wrote "sci-fi coming-of-age think-piece mini-epics," he says. Even then, he spent three nights a week working on desalination experiments, often after late-night play rehearsals. "I just couldn't accept the idea of trading fuel for water," he says.
Defused mines for the U.S. Navy during the first Gulf War
A desalination method 10 times more efficient than alternatives
Majored in theater and wrote sci-fi "think-piece mini-epics"