Temper enthusiasm for fuel-from-air approach

Stockton-on-Tees, a small city in northeastern England, has only one claim to fame

Stockton-on-Tees, a small city in northeastern England, has only one claim to fame: the first-ever train ran from Stockton to Darlington in 1825. But it might one day have another claim: a locally based start-up company called Air Fuel Synthesis has just produced the first gasoline from air and water.

It isn’t a lot of gasoline — five litres (one gallon) in two months — but Peter Harrison, the company’s chief executive, hopes within two years they will build a larger plant producing a tonne a day. He envisages refinery-scale operations within 15 years.

“We’ve taken carbon dioxide from air and hydrogen from water and turned these elements into gasoline,” Harrison told a conference at the Institution of Mechanical Engineers in London. Since the carbon dioxide that goes into the air when this fuel is burned exactly equals the amount taken out of the air when it was fabricated, it is a carbon-neutral fuel. Provided, of course, the electricity used in the process comes from renewable sources.

No wonder people who worry about global warming are excited about this breakthrough — but chemists have long known how to create a complex hydrocarbon like gasoline from just air and water. The question is how much it costs to do it, compared to just pumping oil out of the ground and refining it.

The answer in the past has been: far too much. Splitting water molecules takes a lot of energy. Carbon dioxide is freely available as the by-product of burning coal, gas or oil but using that CO2 as the feedstock for artificial gasoline only postpones the moment when it gets into the atmosphere.

If you want a truly carbon-neutral fuel, then the carbon dioxide you use must come straight from the air. Prototype machines have been built (by Klaus Lackner of Columbia University and David Keith of the University of Calgary) that can extract CO2 from the air in industrial quantities, but the price per tonne at the moment is about $600.

That’s far too much but as Lackner points out, the cost of any new technology plunges steeply once it goes into volume production. And the cost of getting hydrogen from water may also drop dramatically. Daniel Nocera of the Massachusetts Institute of Technology has developed a catalyst made from cobalt and phosphorus that can split water at room temperature.

Peter Harrison is cagey about his current production cost per litre, but as he told The Independent in a recent interview, “You’re in a marketplace where the only way is up for the price of fossil fuel. At some point there will be a crossover where our fuel becomes cheaper.”

David Keith sees it the same way. “You’re selling this fuel, and they’re burning it, putting carbon in the air but then you’re recapturing the same amount of carbon and selling it to them again. That’s a business model that could conceivably take a whack at the global transportation market, which is the hardest part of the climate problem to attack.”

Maybe Harrison’s process will not win the race to capture that market. Maybe the cheaper option will be to grow green algae in wastewater or salt water, crush it to extract the oil and then refine the oil into gasoline. But one way or another,  the gasoline we put in our vehicles in 25 years’ time will probably not come out of the ground.