Apr 14 2014

Navy Process to Make Fuel from Seawater

Researchers at the US Naval Research Laboratory (NRL) announced that they have successfully tested a process to convert seawater into jet fuel. They can extract CO2 both dissolved and bound from the water as a source of carbon, and can extract H2 through electrolysis. They then convert the CO2 and hydrogen into long chain hydrocarbons:

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.

They claim that with this process they can mass produce jet fuel for $3-6 per gallon. They tested the fuel on a model airplane, and it appeared to work fine.

The mainstream media is reporting the story this way (from the Huffington Post):

Currently, most of the Navy’s vessels rely entirely on oil-based fuel, with the exception of some aircraft carriers and submarines that use nuclear propulsion, reports the International Business Times. The ability to render fuel from seawater may change that.

No, it won’t. The reason the navy is talking about jet fuel and testing the fuel on model planes, rather than talking about fuel for their ships, is that converting seawater into hydrocarbon fuel requires more energy than you get back. This is not a method for creating fuel, but rather for storing energy as fuel.

If you have a nuclear-powered aircraft carrier, you still need jet fuel for all the jets. If, however, you can use that nuclear power to manufacture jet fuel, then you will be more self-sufficient.

If, however, your ship is fueled by oil, there is no utility to this process except to waste energy. Theoretically you could have solar or wind-power on board that you can then use to make fuel from seawater, but such a source of energy is unlikely to produce a significant amount of fuel at sea.

The Huff Po article acknowledges this limitation, at the end of their article, but somehow fails to recognize that this invalidates that rest of the discussion in the article.

Such a method, if it can be scaled to mass production with high efficiency, would be useful in a zero-carbon economy. A nuclear power plant, for example, could provide the energy for this process in order to mass produce fuel for cars, trucks, jets, and other machines that cannot efficiently run directly off of solar power or some other clean energy.

Such a process would also be carbon neutral – if you are extracting the CO2 from the environment (in this case from sea water), then when you burn the fuel you are simply returning the CO2 back to the environment. This contrasts with burning fossil fuels in which we are releasing CO2 that has been sequestered for millions of years.

Even if we will soon have fully electric cars that can be recharged with solar panels, we will still need jet fuel. I don’t envision solar-powered jets anytime soon.

Of course this technology is only useful if we expand our non-fossil fuel energy production. We have some unused capacity in our current system also. Nuclear power plants can use their off-peak capacity, for example, to make fuel from sea water. In order to displace all fossil fuels with synthetic fuels, however, I suspect we would need to add significant capacity, although I have not seen a detailed analysis taking into considering such fuel production methods.

Biofuels may also play a role, but I am not sure if they will ever be a significant contributor to our energy infrastructure. The main problem is land – growing raw material for conversion to biofuels can displace food production, the demand for which will only get greater. There are potential solutions involving growing raw material in bodies of water or using cellulose from waste plant material or from non-crop land. So I remain open minded about biofuels, but at present they are not a good solution and we just have to wait and see what develops.

The fuel from sea water technology may turn out to be a very useful process. It is disappointing, however, that so many people still don’t get the basic idea that such processes do not create energy, they consume energy. The media reporting on this news story was mostly misleading. Readers would have to read all the way down to the end, and then see for themselves that the last comment invalidates the rest of the article. That is a science-reporting fail.

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