The rush towards biofuels to run your car on keeps going even if the mathematics behind it are possibly dubious. Now an American company has built an ethanol generation system for people to keep at home.
They call it the Efuel100 microfueler, and it is basically a brewery and a distillery in one easy to use package. You feed it a mixture of sugar water and yeast in a 750 litre tank, the yeast then converts the sugar into ethanol, in the same way that the sugar in barley is converted to alcohol when you make beer.
The machine then concentrates the alcohol to about 95% pure by distillation – heating the mixture, causing the alcohol to vapourise more quickly than the water, and condensing it in another tank.
This is still not concentrated enough to run a car on, because the small amount of water stops it mixing with petrol, so the machine pumps the mixture through a special membrane separating the last of the water from the alcohol and collecting the resulting fuel in a 140l tank. Apparently after a party you can also concentrate any unused alcoholic drinks and run your car on them.
It will apparently produce fuel costing about 30p a litre, although of course in this country it would be illegal on several grounds, for both not paying road or alcohol taxes, and it isn't really a green solution as sugar takes almost as much energy to grow and refine as it produces, but they are working on versions that break down cellulose, but they could take a while.