[svenrufus]

Big issue with this is what is the source of the fuel.
Biodiesel can mean a number of different things.
It can be just a bit of renewably sourced stuff mixed in with conventional petroleum based diesel - as I understand it, up to 85% Petroleum derivatives is acceptable. That is better, but not much, and what are the implications of shipping/production for such a limited supply. Might even end up having a larger carbon footprint.
As for fully organic derivative based fuels, if this is from a crop that is grown specifically for the purpose, then it is taking productive agricultural land out of use, necessitating the importing of food crops from further afield, adding to the carbon footprint through foodmiles.
The only truly sustainable source of fuel is that derived from the waste products of what was already happening - your old chip fat etc. This is a product less and less available as the big players step in and by it all up. A small bus company down here in Brighton has just started up running off waste veg oil, supplied by a small co-operative called Blooming Futures, but otherwise this source of fuel is like gold dust.
It's not clear what source or sort of fuel you are after, but beware the hype. All Biodiesels are not equal, and a lot of this market is driven (opps!) by the desire to kid people into thinking that their lifestyle is fine, just the detail needs to be changed. It isn't the case. If we all chose to drive on exclusively veg oil diesel, we would have to occupy several other planets to be able to garner the solar energy required.
Good for you for thinking this way - I have too - but the reality is, if i isn;t an option for all of us, it isn't an option. Ergo, it is isn't an option.