Ok, here is a study that does factor land use change and transportation, and it is still about a 50% percent reduction. Corn ethanol emits 46% less greenhouse gases than gasoline. The land use changes referenced in the paper you linked seem a lot higher than most other sources I have seen. It makes me question whether they are calculating it accurately. I am no expert on how they should be calculated, but why is there a 30-40g co2 per MJ fuel produced difference in between the different studies? The figures I see in other studies are around ~5g co2 per MJ fuel not 38g.