Most biofuels are not 'green', researchers show
This is an update on a 2007 study on the "ecobalance of numerous biofuels, including their production chains" with "more extensive data set and up-to-date methods".
Diesel from Tar Sands is "greener" than (Swiss) petrol in the GW and Land Use columns
and much "greener" than corn ethanol in most (the colours represent wide ranges, one would need to look at the full report to make an exact comparison).
Disclaimer: As an Alberta resident I own 0.00005 % of the tar.
(I couldn't find a thread where this was discussed - perhaps our Mergerators can)