The Navy's Seawater-To-Fuel System: Can I Use It In My Car?

Last week, the US Navy flew a model airplane with a small 2-stroke engine. That's not normally news, except for one big detail: the fuel the plane burned was made from seawater via a process the Navy has been working on for years. Let's look a little into what this sorcery is, and if it'll ever power our cars.

Essentially, on a very basic level, what the Navy is doing is extracting CO2 and Hydrogen from the seawater, and then recombining it into hydrocarbon chains, and then liquefying that (via a metal catalyst) into synthetic fuel. The type of synthetic fuel that can be made can vary, but jet fuel (similar to diesel) and petroleum-type fuels, like what was run in that little model plane, and, yes, that same sort of fuel could potentially be run in your normal old gasoline car with minimal or no modifications.

If this seems suspiciously too good to be true, it's not — there is a cost here, and that cost is energy — it does take a lot of energy to do these conversions, which utilize around 23,000 gallons of seawater to make one gallon of fuel. Even so, it's a use of energy that makes a lot of sense — a ship with an onboard nuclear reactor (like, say any aircraft carrier) easily has the capacity to use the process to make fuel for its own aircraft, which solves a vast amount of supply-chain issues.

That's at what the Navy says is 92% efficiency. Here's how they describe the process:

CO2 in the air and in seawater is an abundant carbon resource, but the concentration in the ocean (100 milligrams per liter [mg/L]) is about 140 times greater than that in air, and 1/3 the concentration of CO2 from a stack gas (296 mg/L). 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.

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.

In the second step these olefins can be converted to compounds of a higher molecular using controlled polymerization. The resulting liquid contains hydrocarbon molecules in the carbon range, C9-C16, suitable for use a possible renewable replacement for petroleum based jet fuel.

Also, because the process involves extracting the CO2 from seawater, it's quite carbon-neutral. That CO2 will end up back in there after the fuel is combusted, and the process can begin anew.

The Navy's Seawater-To-Fuel System: Can I Use It In My Car?

The Navy is saying they feel that the system could be commercially viable in 7-10 years or so, and resulting fuel would cost between $3-$6/gallon, which is not bad at all, really — that's essentially on par with current costs for fuels we pull out of the ground.

So how is this likely to play out? A safe guess would be that first the system will go into larger scale land-based stations, and then miniaturized to a degree that a seawater-to-fuel plant could be placed on a nuclear-powered ship, like an aircraft carrier. That, of course, is the Navy's primary goal.

After this development and testing, commercial land-based producers would become viable, and large-scale conversion of seawater to fuel would take place. The environmental impact of creating fuel in such a way could be beneficial, according Naval Research Lab research chemist Heather Wilauer:

"It's a net-zero carbon footprint. So you're taking the carbon, you put it in a fuel, it you burn it, it goes back [in] the atmosphere, but you're not creating anything more. I'm not getting fossil fuel out of the ground and putting more CO2 in the air, I'm actually using the CO2 from the environment."

If this can be scaled up as everyone is hoping, it could mean a drastically reduced dependence on foreign sources of oil and all the associated issues that arise with that. It will also mean we'll need to have the ability to generate all the energy needed to extract and produce the fuels, so we may need to look into new nuclear sources, or wind, solar, or really pretty much everything.

So, let's recap: Is it magic? No, it uses lots of energy and science. Can I use the fuel in my car, someday? Yes, it sure looks that way.

It's an exciting development, absolutely. Now if they can make it work with urine as a feedstock, I can better lobby carmakers for in-car urine-collection-systems.