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By Robert Rapier on Apr 16, 2008 with no responses

Fuel from Air?

One thing we seem to have in limitless supply is gullibility. You may have seen the story sweeping through the energy circles of the Web:

Federal Lab Says It Can Harvest Fuel From Air

We love the painless technological solution. “This solves Global Warming AND produces carbon neutral fuel!” I talk to people all the time who say, in reference to our energy and environmental problems, “They will figure something out.” So along comes a story like this, and the layman reads the headlines and breathes a sigh of relief. We can make fuel from thin air. This must be even better than cars that run on water or cold fusion.

So what’s the deal? Here is an explanation from the linked article:

In the category of things that sound so good they have to be checked out more thoroughly (so stay tuned) is this news out of Los Alamos National Laboratory:

Scientists there say they have developed a way to produce truly carbon-neutral fuel and useful organic chemicals at large scale using water and carbon dioxide removed from the air as raw materials. There are plenty of schemes brewing to capture carbon dioxide, both directly from the atmosphere and from the stacks of power plants. All of them, for the moment, are costly or hard to envision at the billion-tons-a-year scale that would be needed to blunt the buildup of carbon dioxide in the atmosphere coming mainly from fuel burning.

I like to think I check things out thoroughly, and I try to approach things realistically. I consider myself to be a realistic optimist. It has nothing to do with being a naysayer, it is all about understanding basic science and engineering and knowing what’s likely, what isn’t, and what simply violates physical laws. So, is this pie-in-the-sky or a serious candidate for an energy solution?

Let’s take a critical look. First, details are sketchy (aren’t they always?). They are supposed to be released next week:

Details on the Los Alamos approach will come next week when Dr. Martin gives a presentation at a government and industry meeting, Alternative Energy Now, in Lake Buena Vista, Fla. The conference, held at a resort for military personnel, is sponsored mainly by the U.S. Air Force.

Let’s be perfectly clear. Could you produce fuel out of carbon dioxide and water? Sure you can – with massive energy inputs. You can’t get around the chemistry. When you burn something like natural gas, oil, coal, or just about anything organic – you get carbon dioxide and water. The amount of energy to turn it back into fuel is greater than the energy that was released in the first place. That is a fundamental law of thermodynamics.

As a simple illustrative example, let’s say I burned a quantity of natural gas and it released 10 BTUs per the following reaction: CH4 + 2 O2 = CO2 + 2 H20. Then to reverse that reaction is going to take more than 10 BTUs, and potentially a lot more. So where is this energy going to come from? Why, nuclear reactors of course:

This plan has a minor hurdle, too; the electricity for driving the chemical processes, according to a white paper describing the overarching concept, would come from nuclear power.

That’s more than a minor hurdle. If the fuel takes more energy to produce than it contains – and the laws of chemistry are against you in this case – then you have to ask whether there is a better use of that energy. If (for instance) I take 20 BTUs of nuclear energy to produce 10 BTUs of liquid fuel – was there a better end use for that nuclear energy? How about putting those 20 BTUs into an electric car, which has a much greater efficiency than an internal combustion engine? That is a much better net than the wasteful route of turning it into liquid fuel.

Make no mistake, technical feasibility is certainly there. Likewise, I can technically run a car off of water, or make fuel out of dirt. I could mine Titan for hydrocarbons. I could even build a colony on the moon or at the bottom of the ocean as a “solution” to overpopulation. These are things that one could technically do. That doesn’t mean any of them make sense.

That’s what I would say about this proposal. Unless they have figured out a way to violate the laws of chemistry, there is no free lunch. If you had vast quantities of cheap electricity, then sure, you could do it. But in that case why not just use the electricity directly?

Conclusion: The proponents have gotten way ahead of themselves, and I have yet to see anyone point out the basic fact regarding the energy balance: It will necessarily be a net consumer of energy, not an energy producer.

One other thing:

As described in a news release by Mr. Martin, it sounds like a possible candidate for Richard Branson’s $25 million carbon-capturing prize:

“Our concept enhances U.S. energy and material security by reducing dependence on imported oil. Initial system and economic analyses indicate that the prices of Green Freedom commodities would be either comparable to the current market or competitive with those of other carbon-neutral, alternative technologies currently being considered.”

First, you would be trading dependence on imported oil for dependence on imported uranium. Again, no free lunch. Second, I know someone else who has a much stronger case for Branson’s prize. ;-)