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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16 responses so far

16 Responses to “Navy Process to Make Fuel from Seawater”

  1. ca1879on 14 Apr 2014 at 9:10 am

    Steven,

    Apart from the obvious (except to journalists) limitations of the process, calling it carbon-neutral is a bit of a misdirection on the overall soundness of the idea. Moving dissolved carbon from the oceans, while mitigating the acidification problem, places that carbon exactly where it exacerbates the greenhouse problem. If it replaces oil derived fuels on a one-for-one basis, then it there is an argument to made for it being less harmful, but it’s more likely to drive increased fuel use as every other new source has done.

  2. Kawarthajonon 14 Apr 2014 at 9:11 am

    While I agree with you about biofuels, I do believe that waste cooking oil converted into biodiesel is a growing source of fuel that has not yet been fully exploited. If we could convert more of our waste cooking oil (or all), and probably other kinds of oils, into recycled fuel, I think we’d go a long way to reducing fossil fuel use.

  3. Kawarthajonon 14 Apr 2014 at 9:13 am

    “3 billion gallons of waste cooking oil per year” is generated in the US.

    http://www.epa.gov/region9/waste/biodiesel/questions.html#howmuch

  4. Bruceon 14 Apr 2014 at 9:35 am

    “Moving dissolved carbon from the oceans, while mitigating the acidification problem, places that carbon exactly where it exacerbates the greenhouse problem. ”

    I was thinking the exact same thing, is there a (natural) mechanism in which the carbon in the air is converted back to carbon in the seawater? Does that mechanism work at the same rate as we will be pumping the CO2 out? While that lag (if there is indeed lag) might be better than fozzil fuel carbon emmisions is it significantly better to not contribute to the greenhouse problem?

    Or am I just being dumb?

  5. Steven Novellaon 14 Apr 2014 at 9:54 am

    The question of the net effect of taking CO2 from the ocean and releasing it into the atmosphere is a good one. The carbon cycle is a bit complex, but my understanding is that the extra CO2 would be dissolved back into the ocean. This does take some time, and so there may be a net increase in atmospheric CO2, but this would reach a steady state and would not simply increase, as it does with burning fossil fuel.

    I think we can technically still consider this carbon neutral, if we consider all environmental CO2 particpating in the carbon cycle (not sequestered), but it may shift the balance a bit.

  6. jesse.huebschon 14 Apr 2014 at 8:42 pm

    Kawarthajon,

    While it is nice to use alternative source like cooking oil, it will not be more than a minor impact.
    http://www.eia.gov/tools/faqs/faq.cfm?id=33&t=6
    The use uses 6.89 billion barrels or oil * 42 gallons per barrel = 280 billion gallons per year. The maximum impact of cooking oil is 1% of petroleum, assuming none is used to convert and transport it.

    Accroding to the NOAA
    http://www.pmel.noaa.gov/co2/story/Ocean+Carbon+Uptake
    it takes about a year to equilibriate atmospheric CO2 and upper ocean CO2. This is probably quick enough to be considered a negligible impact.

  7. Bruceon 15 Apr 2014 at 3:05 am

    Thanks Jesse.

  8. BBBlueon 15 Apr 2014 at 12:42 pm

    Fugacity models should be able to do an adequate job of answering the question about how quickly CO2 produced from seawater returns to seawater, but from what I understand, as one scales up this type of GTL synthesis, there would be a significant net increase in atmospheric CO2; depends on how much CO2 is produced and how quickly.

    Scientists expect that the ocean will eventually take up about 85% of anthropogenic CO2, but because the ocean takes ~1000 years to mix, this process will take many hundreds to thousands of years.

    Various human activities, including fossil fuel combustion and forest clearing, emit about eight petagrams (or billion tons) of carbon in the form of CO2 into the atmosphere annually. The global ocean absorbs about two petagrams of CO2, and about a half of that amount is absorbed by the Southern Ocean south of 30°S, thus slowing the rapid accumulation of CO2 in the atmosphere.

    LDEO Surface Ocean CO2 Climatology

  9. ca1879on 15 Apr 2014 at 3:01 pm

    Jesse – equilibration does not mean removal. It means the processes reach a new balance with changed concentrations. Only a one time offsetting change in concentrations of carbon storage would eventually balance out at the previous levels, and you have to assume a simple interaction. The addition of a new continuing unidirectional carbon transport process would not have that result, and when, or if, a new equilibrium was reached, it would be at a higher atmospheric and lower oceanic concentration. It’s “if” because that assumes a constant new load from the process which does not exceed the capacity of the return mechanism. It’s not a problem now, because of the previously noted efficiency issues which are likely to keep it in a fairly small niche. But we are a clever lot, and I’d put my money on us finding a way to make it a lot more practical. We did it for oil sands, deep ocean wells, and pressure recovery methods. Storage of renewable energy is a key problem, and we may be presented with a truly ironic solution.

  10. jesse.huebschon 15 Apr 2014 at 8:55 pm

    ca1879
    I am very aware of what equilibrium means. In the case we are talking about we are using energy to move the air-water system away from its current equilibrium by extracting CO2 from seawater. This both lowers the concentration in the water an raises it in the air. The NOAA site suggested that this would be effectively reversed on the order of a year. With the technology under discussion, the total CO2 in the system remains constant. Equilibrium dynamics is the appropriate way of discussing it.
    In the larger context of climate change, the total CO2 in the system is increasing, which will mean new (higher) equilibrium levels in both air and water, but this technology does not increase it. It also doesn’t generate energy, so it shouldn’t be oversold as anything other than a way of making high density energy storage for applications where other energy storage or generating methods are not practical. Transportation, especially aircraft, comes to mind, as does chemical feedstocks.
    This is also a process that could render peaker (typically gas) electrical plants redundant, by allowing enough baseload power to cover the peak electrical demand, and converting the excess at other times to liquid fuels.

  11. BBBlueon 15 Apr 2014 at 11:43 pm

    It takes about one year to equilibrate CO2 in the surface ocean with atmospheric CO2…

    The key word in that sentence is surface.

    Think of carbon in the ocean the same way we do carbon in fossil fuels, only compress the time scale by several orders of magnitude. Instead of liberating carbon accumulated over 100′s of millions of years, we would be liberating carbon that has taken 100′s or 1,000′s of years to accumulate in seawater. As long as we introduce carbon from seawater to the atmosphere faster than it can be absorbed back into the oceans, the concentration of atmospheric CO2 will increase.

    If the amount of this type of fuel burned was trivial, then one could consider it virtually carbon neutral, but if some technological advancement shifted the equation from storing fuel to creating fuel and it was burned on a massive, global scale, then it is likely we would still need to be concerned about its contribution to GHGs.

    On the plus side, if enough carbon from seawater could be harvested, perhaps ocean acidification could be slowed, but the cost may still be increased atmospheric CO2.

  12. Paul Parnellon 16 Apr 2014 at 3:49 pm

    Seriously guys there is no way to remove co2 from the ocean faster than it is added. The ocean absorbs half of the co2 we produce from burning coal, gas and other things. Even a massive effort to produce fuel this way would have no impact and the ocean acidity would still increase.

    Second, even if we could reduce co2 in the ocean this way it would still be better than producing more co2. The ocean and atmosphere are linked.

    And third, there is no reason other than convenience for the naval application to use ocean dissolved co2. You could use co2 from the atmosphere or the output of a steel mill as easily or maybe more easily.

  13. BBBlueon 16 Apr 2014 at 5:44 pm

    Hi Paul,

    Seriously guys there is no way to remove co2 from the ocean faster than it is added.

    “No way”… yet! ☺

    Yes, of course, some profound technological breakthrough would have to occur to make this a significant energy source and contributor to GHGs, but that’s the premise of some of these comments, however unlikely it is. Plenty of qualifiers are in evidence to reflect that.

    The fact remains, as long as we burn carbon-based fuels of some type, atmospheric CO2 needs to be accounted for. Frankly, I’m a nuclear energy fan myself.

    As I deal with climate change policy a bit in my professional life, I do have a serious question for you, though. What data supports your comment that “The ocean absorbs half of the co2 we produce from burning coal, gas and other things”? The number that is thrown around among those I talk to is usually 25%.

  14. Paul Parnellon 17 Apr 2014 at 3:14 pm

    BBBlue

    As stated in the blog post this will never ever ever become a source of energy. That is because there is no energy there. It is a system to which you add energy from other sources, like nuclear, in order to store it.

    Using co2 from the surface of the ocean is probably indistinguishable from using it directly from the atmosphere. Either is better by far than burning new carbon.

    You don’t even actually need to use the carbon from the ocean. It may be convenient for the navy but the rest of us can convert fresh water into far more fizzy carbonated water at a few cents per liter even using homemade equipment. Oceanic carbon was never an issue anyway.

    I’m a nuk fan as well but some applications require liquid fuel. Airplanes for example. I would like to use nuk power to make that fuel using atmospheric carbon. This process does that. Oceanic carbon is a red herring.

  15. BubbleHeadon 18 Apr 2014 at 5:21 am

    Aircraft carriers are also capable of providing fuel to their conventionally powered escort ships. Although your points are well taken, failure to consider this basic fact and its impact on an aircraft carrier’s operational schedule invalidates much of your argument regarding media coverage.

    Although it may not change the fuel requirements for the escort ships, it can change the way fuel is delivered to them at sea. Currently, conventionally powered refueling ships relay back and forth to ports along the way as a carrier battle group advances toward its destination. This fuel is transferred to the escort ships through underway refueling operations. When logistics requires it, the carrier itself can serve as an underway refueling station. Merchant ships providing fuel to warships at sea are much slower than the warships they support. As a result, they limit the speed of advance of the battle group. Either the battle group has to limit its speed of advance so as to not leave the merchant ships behind, or warships have to be left behind to escort them to the next rendezvous point for refueling operations. In a case where the battle group has to make all available speed to react to world events, this is a limiting factor. Having a mobile nuclear reactor generating the power necessary to produce conventional fuel allows the carrier to not only fuel its aircraft, but also to fuel its escorts. Slowing down occasionally to conduct refueling operations is not the same as slowing down to allow the merchant ships to keep up, and impacts operational readiness.

    Many of today’s navy warships use Gas Turbine engines, which are basically jet engines. These types of warships could benefit from this type of fuel. For reasons previously stated, fueling these ships at sea from a mobile fuel generating source enhances operational capability.

  16. BBBlueon 18 Apr 2014 at 12:30 pm

    Way to pour cold seawater on another sci-fi fantasy fuel, Paul. But still, the fact that it is a storage medium for energy rather than a source doesn’t preclude its use as fuel. As you said, we need portable sources of energy. However unlikely, its fun and interesting to consider possibilities and their consequences.

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