biodiesel is the best choice of them all.
And germany already has required DIN specs for the rapeseed bio that is highly available over there. Its the reason manufactures (like VW for example) allow you to run B1-B100 in a TDI. Germany has required standards on the fuel.
US hasnt, it isnt mandated and then we get some crap fuel come into the pumps. So VW limits us to B5 because that would be the lowest risk of something happening to the engine.
How to find high quality bio from a pump? Here yah go.
http://forums.tdiclub.com/showthread.php?t=110004&highlight=biodiesel+pd+tdi