:edit: Ninja'd... we were talking about energy sources when I started this post.
On the subject of clean energy, Audi's teaming up with a genetic engineering firm to develop some very clean fuel.
http://www.buyyourcar.co.uk/news/article/audi-developing-synthetic-fuels/13010http://www.leftlanenews.com/audi-to-begin-production-of-synthetic-e-fuels-in-2014.htmlPlenty of other articles around the net, the CAR magazine article in which I heard about this was more informative than the above links.
The highlights: they're using genetically modified cyanobacteria to create fuel, I think as some form of ethanol. Basically, sunlight, water and CO2 goes in (the plan being to use waste CO2 from industry), the microbes get nom nomming, and they take their number 2s in the form of fuel (and the water, which is then separated for further use).
Initially they'd be distributing this as ethanol fuel - which most engines can be modified to use, and some are built that way (got a Koenigsegg CCXR down your driveway? You're sorted). But apparently it won't be difficult to implement it into a form of diesel, and eventually as petrol.
I'm not sure if the fuel itself will be any cleaner than the conventional gunk, but obviously the manufacturing process
eats up CO2 rather than producing it or even being neutral, it's a renewable resource, and bypasses the various environmental, political and logistical issues of mining for oil. And unlike hydrogen or electrical charging, the infrastructure's already there.
The catch seems to be that it'll require large amounts of land in areas of extreme sunshine - ie. deserts. If I remember rightly, the magazine article stated that a region the size of Tunisia would produce enough fuel to run every Audi on the planet (the fuel isn't only for Audis, just to clarify). On the plus side, these are desolate and infertile regions, so construction of plants wouldn't destroy natural ecosystems or impinge on food production in the way that vile and evil bio-ethanol farming does. It could also bring fresh wealth into equatorial regions, some of which sorely need it.
They're currently on track to start producing the fuel at an Audi plant in 2014, after which I assume they'll take a view about large scale viability.