Turns out…Yeah, it looks like we can.

Refueling U.S. Navy vessels, at sea and underway, is a costly endeavor in terms of logistics, time, fiscal constraints and threats to national security and sailors at sea.

In Fiscal Year 2011, the U.S. Navy Military Sea Lift Command, the primary supplier of fuel and oil to the U.S. Navy fleet, delivered nearly 600 million gallons of fuel to Navy vessels underway, operating 15 fleet replenishment oilers around the globe.

From Seawater to CO₂

Refueling Navy vessels at sea can prove in many ways to be a costly endeavor. The U.S. Naval Research Laboratory (NRL) is developing the chemistry for producing jet fuel from renewable resources in theater. The process envisioned would catalytically convert CO2 and H2 directly to liquid hydrocarbon fuel used as JP-5. (U.S. Navy Military Sea Lift Command)

Scientists at the U.S. Naval Research Laboratory are developing a process to extract carbon dioxide (CO₂) and produce hydrogen gas (H₂) from seawater, subsequently catalytically converting the CO₂ and H₂ into jet fuel by a gas-to-liquids process.

“The potential payoff is the ability to produce JP-5 fuel stock at sea reducing the logistics tail on fuel delivery with no environmental burden and increasing the Navy’s energy security and independence,” says research chemist, Dr. Heather Willauer.

NRL has successfully developed and demonstrated technologies for the recovery of CO₂ and the production of H₂ from seawater using an electrochemical acidification cell, and the conversion of CO₂ and H₂ to hydrocarbons (organic compounds consisting of hydrogen and carbon) that can be used to produce jet fuel.

“The reduction and hydrogenation of CO₂ to form hydrocarbons is accomplished using a catalyst that is similar to those used for Fischer-Tropsch reduction and hydrogenation of carbon monoxide,” adds Willauer. “By modifying the surface composition of iron catalysts in fixed-bed reactors, NRL has successfully improved CO₂ conversion efficiencies up to 60 percent.”

A Renewable Resource

CO₂ is an abundant carbon (C) resource in the air and in seawater, with the concentration in the ocean about 140 times greater than that in air. Two to three percent of the CO₂ in seawater is dissolved CO₂ gas in the form of carbonic acid, one percent is carbonate, and the remaining 96 to 97 percent is bound in bicarbonate. If processes are developed to take advantage of the higher weight per volume concentration of CO₂ in seawater, coupled with more efficient catalysts for the heterogeneous catalysis of CO₂ and H₂, a viable sea-based synthetic fuel process can be envisioned. “With such a process, the Navy could avoid the uncertainties inherent in procuring fuel from foreign sources and/or maintaining long supply lines,” Willauer said.

NRL has made significant advances developing carbon capture technologies in the laboratory. In the summer of 2009 a standard commercially available chlorine dioxide cell and an electro-deionization cell were modified to function as electrochemical acidification cells. Using the novel cells both dissolved and bound CO₂ were recovered from seawater by re-equilibrating carbonate and bicarbonate to CO₂ gas at a seawater pH below 6. In addition to CO₂, the cells produced H₂at the cathode as a by-product.

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