Fuel From Thin Air? The skinny on making gasoline from air and water

October 26, 2012 |

By Robert Rapier, Energy Trends Insider

This week a U.K.-based company called Air Fuel Synthesis (AFS) announced that they were producing gasoline from thin air. The raw materials for their process reportedly being literally air and water.

A company spokesman explained: “We haven’t broken the Second Law of Thermodynamics or anything. We take carbon, we combine it with hydrogen, put it in a reactor to make methanol, then we take the methanol and put that in another reactor to make petrol. The processes of making synthetic petrol from carbon are well known and have been around for many, many years. The Germans were doing it during the Second World War. The South Africans were doing it during the apartheid years. But they were taking their carbon source from coal. We’re taking our carbon source from the atmosphere.”

Is such a process viable, in terms of technology?

The company is looking for investors, but given the extraordinary claim a bit of due diligence is in order. In cases like this, the most basic due diligence starts with: If it looks too good to be true, it probably is. This certainly looks too good to be true, so what is the real story?

The first question to ask is “Is such a process technically viable?” The answer is that the process is indeed technically viable. In fact, one could take the same ingredients of air and water and make an incredible variety of things. Those same ingredients could be used to make acetaminophen, insulin, clothing, carpet, or plastics — because all of the required atoms for these materials are contained in air and water.

The economic and energy input challenge

But, there is more to the story than was reported by most media outlets. As the spokesman for Air Fuel Synthesis indicates above, the Germans used and the South Africans continue to use coal as a source of carbon for production of liquid fuels. AFS is using carbon dioxide as their source of carbon to do the same thing, albeit by a very different process.

But what’s the difference between coal and carbon dioxide? Coal is an energy-rich fuel, and carbon dioxide is the product of combusting a fuel. And it will always take more energy to convert carbon dioxide back into a fuel than you will ever get from combusting the fuel. That is a consequence of the Second Law of Thermodynamics mentioned by the AFS spokesman — and it necessarily means that this process consumes more energy than it creates. This is the same sort of reason that it is technically feasible to fuel a car with water, but you will always require external energy inputs to do so.

Imagine for a moment that they could connect the output of their process to the input. They could convert carbon dioxide into gasoline, and then burn the gasoline to produce carbon dioxide which is fed back into the process. The only way such a process can run is to input large sums of energy into the process. To produce 1 BTU of gasoline from carbon dioxide will always require the input of more than 1 BTU of energy, and quite possibly a lot more than 1 BTU.

When and how is CO2 attractive?

Now there are some circumstances in which a process that is essentially an energy sink could be attractive. After all, photosynthesis is an extremely inefficient process, but it is driven by abundant and free solar power. Thus, one might envision using excess solar power at the peak of the day as a process input if the solar power can’t otherwise be used.

It might also be economical to convert very cheap coal or natural gas BTUs into electricity to drive the process. However, even if the process was economical under those circumstances, it would accelerate the depletion of those resources. It would be far more efficient to simply use a fuel like natural gas to directly power a vehicle instead of going through the inefficiencies of converting it into a liquid fuel.

So, while this process is not a perpetual motion machine, it is unlikely to be economical. It is of major scientific interest, to be certain. But the truth is a lot more complex than what you are likely to garner from the press releases. And this is what potential investors in the company need to know.

This article was republished with permission from Consumer Energy Report under a content partnership with Biofuels Digest, and originally appeared in Energy Trends Insider, a free newsletter from Consumer Energy Report focusing on financial and investment issues in the energy industry.

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