U.S. ships could drink the ocean for fuel

U.S. Navy researchers have been working for more than a decade on a way to tap an abundant and relatively inexpensive source of fuel. Earlier this month, the Navy announced it had successfully extracted carbon dioxide and hydrogen from seawater, synthesizing the gases into liquid hydrocarbons that can be refined to produce fuel to power ships, jet aircraft, and virtually anything else that has an engine. The discovery could give the Navy the ability to produce its own fuel while deployed at sea.

“What that translates to for the Navy is freedom of action,” said Heather Willauer, who leads the team of Naval Research Laboratory scientists that developed the technology. Willauer discussed the project in a talk recorded in October. “We don’t have to worry about foreign sources of oil, and we don’t have to worry about the fluctuating prices that we’re dealing with,” she said.

The new technology might eliminate the need to take combat ships off their missions to pull alongside an oiler to refuel—a hazardous maneuver in the best of conditions. It would also give the Navy a degree of security and energy independence.

The basic chemistry is pretty straightforward. Fossil fuels are large molecules of carbon, hydrogen, and oxygen that are refined from petroleum. Seawater has an abundance of all those chemicals, especially carbon dioxide, or CO2. The seawater-to-fuel device uses a catalytic converter and electricity to synthesize the CO2 and hydrogen into designer fuels, such as JP-5 jet fuel and diesel.

“The total CO2 content in seawater is 140 times more concentrated than it is in air on a weight-per-volume basis,” Willauer said. “There’s so much more carbon in seawater than in the air.”

Willauer’s device can capture 92 percent of the carbon dioxide in seawater, which is hugely efficient. But it also captures the hydrogen required for the gas synthesis process in the same unit, which keeps down the amount of outside resources needed to run the equipment.

With increases in efficiency gained through improving and scaling up the technology, Willauer estimated that the delivered cost of the seawater-based fuel would be between $3 and $6 per gallon. It currently costs at least $7 per gallon to deliver fuel at sea.

The seawater-to-fuel process is carbon-neutral, which should make environmentalists happy. The carbon dioxide generated by burning this fuel simply goes back into the environment from which it was extracted.

Listen to Michael Cochrane’s report on seawater-based fuel on The World and Everything in It: