As freshwater aquifers dry up globally, turning the ocean into drinking water has been the obvious solution. The barrier has always been physics: removing salt takes massive amounts of energy.
The reverse osmosis bottleneck
Traditional desalination forces seawater through microscopic filters at extreme pressures. The electricity required makes the water far too expensive for agriculture.
Material science breakthroughs
New generations of graphene membranes are drastically reducing the friction of water passing through. This means lower pressure is required, directly translating to lower electricity consumption.
The brine problem
While the energy problem shrinks, the waste problem remains. Desalination produces highly concentrated toxic brine that is usually dumped back into the ocean, killing marine life.