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Navy Creates Fuel From Seawater
New submitter lashicd sends news that the U.S. Naval Research Laboratory has announced a successful proof-of-concept demonstration of converting seawater to liquid hydrocarbon fuel. They used seawater to provide fuel for a small replica plan running a two-stroke internal combustion engine.
"Using an innovative and proprietary NRL electrolytic cation exchange module (E-CEM), both dissolved and bound CO2 are removed from seawater at 92 percent efficiency by re-equilibrating carbonate and bicarbonate to CO2 and simultaneously producing H2. The gases are then converted to liquid hydrocarbons by a metal catalyst in a reactor system. ... NRL has made significant advances in the development of a gas-to-liquids (GTL) synthesis process to convert CO2 and H2 from seawater to a fuel-like fraction of C9-C16 molecules. In the first patented step, an iron-based catalyst has been developed that can achieve CO2 conversion levels up to 60 percent and decrease unwanted methane production in favor of longer-chain unsaturated hydrocarbons (olefins). These value-added hydrocarbons from this process serve as building blocks for the production of industrial chemicals and designer fuels."
There's no doubt that manufacturing fuel on board is desirable from a logistics standpoint. The question is cost, not just monetary but energy. As you're no doubt aware, hydrocarbon fuels are incredibly energy dense which means that an equal amount (and probably more) energy most go into their creation from scratch using the most basic raw materials, H2, CO2 and CO. The question is how much space is available onboard for production scale versions of these reactors and how much steam and electric power will the reactor have to supply to make this work. I don't know, but I would guess lots. This fuel production sounds like an energy hungry process. How much power and steam can be spared from other onboard needs to power fuel production? Would this stress the reactors, possibly reducing service life or requiring more frequent nuclear refuels? There are trade-offs here, it's not a slam dunk.