Air and water make petrol – or plastics?
By Barry Copping
Posted 7 November 2012
Car use has probably peaked; petrol and plastics can be made from air and water – Correlate and discuss.
There’s been excitement at the news that a small British company has produced the first "petrol from air" using a technology that promises to solve the energy crisis as well as helping to curb global warming by removing carbon dioxide from the atmosphere.
Given that Air Fuel Synthesis of Stockton-on-Tees has synthesised just five litres of petrol since August when it switched on a small refinery that manufactures gasoline from carbon dioxide and water vapour, it’s easy to poke fun at the magnitude of the anti-global warming claims – even given the obvious point that there’s a lot of scale-up work between pilot plant and industrial production.
Sadly, thermodynamics doesn’t favour perpetual motion machines, or holy grails and magic bullets come to that. It takes about twice as much energy to make a given amount of petrol by this method as is produced by burning it efficiently in a car engine. So the economic viability of the process hinges entirely on harnessing renewable energy (photovoltaics, wind, tidal etc.). That’s a whole other story.
But why stop at petrol? It’s easy to write the chemical equation for producing middle-weight alkanes (petrol) from carbon dioxide and water, so polyolefins can’t be far behind. Polyesters and polyurethanes would use proportionally more air and less water in the recipe.
Bayer has been quietly getting on with this for some time. Its Dream Production research initiative has a pilot plant at the group’s Leverkusen site using carbon dioxide supplied by the power generation industry to produce high-quality foams, replacing a proportion of the petroleum usually used as feedstock. Using a prime, concentrated source of CO2 as feedstock rather than collecting it from fresh air makes a big difference to viability.
Now throw into the mix findings that total car use in developed countries such as Britain, Japan and Germany may well have peaked and be on a downward trend, and all sorts of interesting questions emerge:
Could/would the use of synthetic petrol mitigate the environmental impact of a shrinking global car fleet?
Will lightweighting and metal replacement in motor vehicles eventually become wasted effort as the fleet shrinks?
If petrol synthesis and non-petroleum plastics synthesis do become viable, what is the optimum mix of the two?
Readers’ insights on these issues will be gratefully received.
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