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Air + water = gasoline? Not quite...

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October 30, 2012

Is there a future for synthetic gasoline? (Photo: Shutterstock)

Is there a future for synthetic gasoline? (Photo: Shutterstock)

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According to Allen Ginsberg's poetic rewording of the laws of thermodynamics:

    1. You can't win
    2. You can't break even
    3. You can't quit

Air Fuel Synthesis, Ltd. (AFS), a small company in the northern English county of Durham, has recently made headlines for a chemical process that claims to synthesize gasoline from air and water. In essence, AFS is using energy to unburn fuel so that it can be burned as fuel again – a great deal of energy. Sixty kWh of electric energy are used up to store 9 kWh of that energy in a liter of gasoline. When you take into consideration that gasoline vehicles are about 15 percent efficient, a car fueled with synthetic gasoline would use roughly 35 times more energy on a given trip than would an electric vehicle. Not, it would seem, a prescription for a commercially valuable green product.

What is gasoline? Not a single compound, gasoline is largely made of a mixture of saturated hydrocarbons, which are carbon skeletons combined chemically with about two hydrogen atoms per carbon atom. The right mixture of saturated hydrocarbons will burn quietly (if not cleanly) in a standard car's engine.

The history of making synthetic gasoline from other natural materials stretches back almost a century, with the first coal liquefaction plant going into service in Germany in 1919.

Coal liquefaction has remained a niche market, although there are oil-poor areas (e.g. South Africa) where a large fraction of liquid fuels are produced in this manner. But coal liquefaction has a number of annoying technological difficulties, as well as one very large problem for the future of our planet – synthetic gasoline made using coal liquefaction is not a carbon-neutral source of power. Instead, it takes carbon which was removed from the ecosphere in eons past and releases it in the form of carbon dioxide.

The Air Fuel Synthesis, Ltd. synthetic gasoline pilot plant in Northern England

The Air Fuel Synthesis, Ltd. synthetic gasoline pilot plant in Northern England

Rather than mine carbon from the Earth in the form of coal, AFS acquires its carbon from the CO2 in the atmosphere. The result is a process whose only net production of CO2 is related to the power required to drive synthesis of the fuel. The general approach has been suggested by numerous people over the years, but AFS appears to be the first commercial company to work out the details and put together a pilot plant. Admittedly, the pilot plant is only producing about 1 percent of the projected yield per day, but the technological problems can be solved, as they have been in other contexts.

Let's break down the process into the individual steps.

The AFS gasoline synthesis process

The AFS gasoline synthesis process

    The AFS synthetic gasoline process
  • Remove carbon dioxide from air by blowing air through a mist of sodium hydroxide solution, converting CO2 to sodium carbonate;
  • Remove CO2 from sodium carbonate by electrolysis;
  • Make hydrogen gas from water by electrolysis;
  • Convert the carbon dioxide into carbon monoxide using the reverse water gas shift reaction;
  • Convert hydrogen and carbon monoxide into gasoline using the Fischer-Tropsch process.

Again, all of these steps depend on well-known chemical reactions. Indeed, a very closely related process for collecting and converting CO2 and water into hydrocarbon fuels was patented by the US government in 2008.

The remaining issues are not primarily technical, but will be driven instead by economics and public policy. In a world where power supplies are vetted for their global warming damage, nearly all stationary energy users will be better served by some energy source other than liquid hydrocarbon fuels, particularly with a 15 percent energy storage ratio for synthetic gasoline. (The energy storage ratio is the amount of energy generated by burning a fuel divided by the amount of energy required to produce that fuel.)

In the AFS and similar processes, this is made worse in that the highest "grade" of energy (electric power) is being converted into a source of low-grade heat energy. In automobiles, for example, the efficiency for conversion of gasoline's heat energy into motive power is in the neighborhood of 15 percent, compared to an efficiency of about 80 percent for an electric car. This means a synthetic-gasoline-powered car will require about 35 times more electric power from a utility source for a given trip than will an electric car – hard to justify for an upcoming period in which our primary energy supplies will be severely tested. In addition, synthetic gasoline shares the other emissions problems of fossil fuels, particularly including CO2 and nitrogen oxide generation.

To synthesize sufficient gasoline to supply the world's present consumption would require about half of all energy currently being used by civilization in any form – heating, manufacturing, lighting, transportation, and so on. At present, it's estimated that gasoline consumption represents about 6.5 percent of total world energy consumption. Everything considered, it is hard to imagine any situation in which synthetic gasoline can compete with electric power for transportation. To be sure, there are other needs for portable power in which the large energy density of gasoline may be beneficial, but the net sum of these probably still points to what at best will be a minor niche market for synthetic fuels.

Source: Air Fuel Synthesis

About the Author
Brian Dodson From an early age Brian wanted to become a scientist. He did, earning a Ph.D. in physics and embarking on an R&D career which has recently broken the 40th anniversary. What he didn't expect was that along the way he would become a patent agent, a rocket scientist, a gourmet cook, a biotech entrepreneur, an opera tenor and a science writer.   All articles by Brian Dodson
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10 Comments

Not as bad as it is made out:

1. It could work quite for seasonal storage of renewable energy that would otherwise go to waste. I expect as solar panel prices continue to drop, then that situation won't be too far off. e.g. Germany gets up to 50% of energy from solar at times, and that could exceed 100% in a while, to say nothing of the Sahara Solar breeder project, which is pretty much free energy if the system works, but transport difficulties.

2. For seasonal storage, the efficiency could be greatly improved. Rather than gasoline you could make a hydrocarbon better for burning in a fuel cell, or natural gas plant, with 60% efficiency.

3. In this case, you can save energy by recycling the CO2 from the exhaust which is more efficient than extracting it from the air, leading to further improvement.

4. This is a prototype, surely the efficiency can also be improved with better technology.

5. As a complement to a plug-in hybrid car, the gasoline required will be hugely reduced, hence a permanent source of a reasonable amount gasoline no matter what happens to oil.

Thor Russell
30th October, 2012 @ 11:21 pm PDT

would be ok if solar could do it directly

wle

wle
31st October, 2012 @ 01:07 pm PDT

And still they have been able to get their moronic research funded and plenty of media coverage!

PS: indeed, modern non US diesel engines can achieve 30-35% efficiency

ugosugo
31st October, 2012 @ 01:57 pm PDT

While this is a very creative solution to a very real problem it's really just another band aid solution to sustain the life of an antiquated and poorly thought out use of natural resources for energy. Since the dawn of man we have generated energy by burning things. We cut down trees and we burn them, we dig coal out of the ground and we burn it, we pump oil out of the ground and we burn that too. Now with this technology we're just sucking hydrocarbons out of the atmosphere and turning it into gasoline so we can burn that too.

Pete Kratsch
31st October, 2012 @ 02:02 pm PDT

Locate the plant here:-

http://www.gizmag.com/volcano-power-plant/24633/

Burn it in these:-

http://www.gizmag.com/liquidpistol-rotary/24623/

Hey - is there any world problem that GizMag cannot solve ?

christopher
31st October, 2012 @ 06:33 pm PDT

What this is is a way of converting electricity into a motor fuel that can be stored long term, can easily be used to double the range of a vehicle without mass outing, or bulk outing the carrying capacity, and can be used with our current infrastructure.

With just changing of the catalysts the process produce diesel or alcohol as well. (Granted I have never heard of ethanol being produced this way.)

Pikeman
31st October, 2012 @ 06:47 pm PDT

A couple details. Cars are only 7% eff on gasoline, diesels about 8% and hybrids 9-12% depending on type.

EV's are hard pressed to do 75% eff and only then if using a 100% eff source of electricity like solar, wind, hydro, etc as no fuel is burned.

But even from old ineff 30% coal plants EV's are still 20% eff and about 40% eff from the newest NG powerplants.

They could avoid much of their ineff in this process if they let plants, waste biomass, garbage, paper, etc collect the CO2 then at 1500F it turns into syn gas they use to make the gasoline/diesel or just about any hydrocarbon. Coal is bad because it has such nasty chemicals which kill the catalysts raising cost for them and trying to clean the syn gas. Biomass avoids most of that.

Presently they are already using NG to make syn gas which is turned into diesel in new GTL plants in the Persian Gulf states that have plenty of NG. So that part of the process is well understood.

jerryd
31st October, 2012 @ 08:35 pm PDT

Burning fossil fuels puts carbon dioxide into the atmosphere, contributing to global warming. Producing electricity from hydroelectric dams, nuclear power plants, or wind, solar or geothermal power, does not. It's as simple as that: so, for those applications that can't be powered by electricity, this is our only choice. There is no longer any excuse to let global warming continue.

quadibloc
5th February, 2013 @ 08:15 am PST

If you are going to talk about electric automobiles, why not get very efficient and talk about electricity-driven public transportation. ( All of the fun will be taken out of driving anyway.)

Marty Power
9th March, 2013 @ 06:38 pm PST

I would say it's not all about efficiency... basically what you have to look into is also, what infrastructure is there. So if you start just with efficiency, from solar power to kinetic energy of car... for what basically you would use fuel is:

1) Biodiesel- first stage, biomass from solar has efficiency of about 0,8% - and efficiency of car engines is on average around 25%, so in the end you get like 0,2% to the road and this does not include ingratiation, harvesting, pest control and fertilizing. If you include this you would get down to 0.1% easily.

2)AFS - in this case would have efficiency, lets say with PV around 25% solar to electricity and 15% from electricity to fuel and from fuel to road as before around 25% - so round trip efficiency would be in range of 0.1%.

3)H - economy, has efficiency 25% solar to electricity, 50-70% for H2 generation and around 50% in fuel cell in car back to electricity and around 90%, to kinetic energy in car. So round trip efficiency is about 6.7%

4) EV cars - from generation to road, 25% for solar cells, 85% transformation, storage and transportation of electricity, 90% for electro-motor in the car. So round trip is around 19% efficient.

So yes round trip for EV cars is by far most efficient, but what helps you here if you have to by new expensive car... and production of which is just not there. H-economy is also very efficient, but it needs by far most investment, on production side, storage and transportation of H2 is very difficult, since it is the smallest molecule and therefore leaks everywhere. Production of H2 cars is just not there. For biodiesel, you have everything, production side is known, is same as agriculture. And it doesn't need special vehicle. But of course it uses valuable arable land and a lot of water.

So AFS is a good alternative or stepping stone away from fossil fuels without the cost towards arable land and food production and it doesn't need investment on user side (change of vehicles or anything that runs on CH fuels) so much easier transition, less investment then other more efficient systems like H-economy or EV.

Matjaz Potocnik
10th January, 2014 @ 03:27 pm PST
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