Sorry to resurrect an old topic, but I've been 'hors de combat for a month!
My preference is for bio based fuels
immediately.
What the politicians seem to overlook is that it's already too late. It'll take a decade or 2 to even level off the effects already under way, whatever we do today.
Current energy users are heavily hydrocarbon fuel dependant in one form or another. Technology exists and is reasonably well developed and understood to use hydrocarbon fuels, so the obvious thing is to find a way of providing the fuel in as "green" a way as possible. Currently that's bio.
Bio is purely a political issue, the places in the world where the production would be most efficient aren't generally the places where the fuel would be used, and the "west" are continually striving to gain control over the sources of HC fuels so wouldn't feel comfortable with relying on bio-fuel coming from the tropical band.
After all, bio-HC is simply solar energy in another form, and plants are quite effective at doing the conversion.
It reminds me of a tale about a technical institute tasked with trying to devise a process to convert low grade vegetable matter into high grade foodstuffs for 3rd world applications. After $millions were spent, someone pointed out that cows do it quite well already.
OK, bio isn't the ultimate solution, but it can be done NOW and there are really very few drawbacks and negligible risk. Just do it, and buy a little more time.
...and as a post-script, some years ago when there was the big drive for gas powered electricity power stations (cheap to build, gas was cheap, and relatively little toxicity) I said to everyone that burning gas in power stations was crazy, and now look. Natural gas is just too versatile an energy source to stuff it all into power stations. What's going to come into my kitchen when all the gas is gone (or Russia decide they don't want to supply us)? Electricity, I suppose.
Politicians eh?