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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."
Next step is to find a country where they have too little democracy but a lot of this "seawater" they mention.
Curiously yours, crip.
TFA was points to a 2012 press release, but it contains not much more information. They must need to supply energy to this reaction, but whether this energy is as heat, electricity or something else is unclear.
I see two uses from the point of view of the U.S. navy. One is to put one of these chemical plants in an aircraft carrier, power it with the carrier's reactor, and generate fuel for the aircraft on board. The other is to put the chemical plant on a nuclear powered supply ship, which will then transfer the fuel to non-nuclear surface ships.
From a world energy point of view, this is a way to turn non-fossil fuel power (nuclear, hydro, wind) into hydrocarbon fuel, with the overall process being carbon neutral. Burning fossil fuels to provide the energy for this process would certainly be counter productive in terms of CO2 emission and very likely economically counter productive as you'd be better chemically processing your fossil fuel instead.
By the time you're going to all of this trouble to turn electricity into fuel, it is unlikely that you'd want to run a car on it - you'd rather just have an electric car. For aircraft we really have no good alternative to hydrocarbon fuels, so it could be used here. However, on the road to a low-carbon future, we have decades worth of lower hanging fruit (notably coal power stations) before we really need to care about whether our aircraft fuels are carbon neutral.
Conspicuously missing from the articles is the energy efficiency of this process. Given the $3-$6 per gallon projected jet fuel cost, presumably the efficiency is not too bad. (I notice this number hasn't changed since 2012 which makes me suspicious that it is more guesswork than calculation.)
Quattuor res in hoc mundo sanctae sunt: libri, liberi, libertas et liberalitas.
You do realize that what they're producing here is artificial jet fuel, right? It's not "biofuel" because it isn't produced by bacteria or algae or other direct biological process. No, what they're talking about here is essentially the water gas shift reaction whereby dissolved CO2 in the seawater is combined with water vapor (aka steam) and carbon monoxide (produced via this "bicarbonate" reactant?) to yield carbon monoxide, carbon dioxide and hydrogen which more heat and pressure (steam) in the presence of an iron catalyst converts these products into short chain hydrocarbons (alkenes), probably ethanes (CH3) and propanes (CH4), and from there longer chain hydrocarbons with more heat and pressure until the desired blend is cooked up, jet fuels of CH9 to CH16. However, these processes don't really transition us away from fossil fuels or at least not into something besides a hydrocarbon fuel, whether produced artificially as in this case or refined from naturally occurring crude oil that we've pumped out of the ground.
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.
former navy machinist mate here - theres more available space than most people realize on a carrier. we were exceptionally good space management, so that wouldnt be an issue. the reactors wouldnt have an issue with producing enough energy - the whole powerplant is built with a ton of production headroom. we would often operate with up to 1/3 of our equipment either off or idling and still be well below the energy demands of the ship, even during flight ops in combat zones. there would be a slight reduction in how long the fuel would last, maybe 20 years instead of 25. but, to have onboard aviation fuel production would be very very worth it. stress to the reactors would be minimal, theyre designed to be operated at high capacity for extended amount of time and the navy doesnt come anywhere near running them at their actual capacity - everything is designed with a LOT of headroom! youre right that it isnt a slam dunk, but it is very doable
At sea refueling is trivially easy, all you need is a ship that can carry a lot of fuel, a pump, and a hose.
"Trivially easy"? I think the Navy would disagree strongly with you on that. There are a huge number of non-trivial logistics issues. You have the expense of maintaining a second ship. You have to have that ship transport the fuel to an arbitrary location on the globe. You have to keep the fuel supply safe and ensure that the fuel tender isn't tracked back to the ship it is refueling. You have a ship with a large amount of potentially explosive fuel on board with all the attendant safety hazards that causes. It means your ships are limited in where they can go and how long by their fuel supplies rather than mission parameters.
The fact that they're fairly good at doing it doesn't mean it is something they find easy or useful. Cut of a military's fuel supply and they are effectively helpless. Fuel logistics are a HUGE and expensive problem for the military. It supposedly costs something like $16 to transport $1 worth of fuel. Also bear in mind that a lot of fuel comes from pretty volatile locations that we are likely to engage in hostile action with. There is a reason our military is putting a LOT of money into alternative fuel research. It's a huge cost and a huge tactical/strategic problem for them.
And realistically, when is a carrier or other ship likely to be far from supply lines?
Middle of the Pacific perhaps? Or any other ocean? Or when near hostiles? You don't really want to be refueling anywhere close to the people you are fighting if you can avoid it.