One can make several arguments on the carbon balance of ethanol versus crude oil, and a lot depends on what factors are considered. There is no doubt that ethanol and bio oil are renewable energy sources and that is worth something. This renewable factor will become more important when we reach peak oil. The increased use of biofuels will come along with peak oil, and shows how things such as crops are linked to energy prices.
On the subject of green house gases and carbon balance and emissions its all about what parameters one puts into the calculation. I have yet to see a professor include the carbon dioxide emissions that come from the military use of petroluem to protect the oil supply line. So how much oil was burned or carbon emitted by the airforce, navy and army in securing the oil supply line and reserves? Do the carbon emission calculations include the carbon emission in the war with Iraq, or flying missons over the gulf of Hormuz and elsewhere in the middle east? lots of hidden costs imho.
By the way i dont mean to imply that the war with/in Iraq was about oil, but one has to recognize it was a factor. Of course it was mostly about security and removal of Saadam Hussein, but oil had somethings to do with it. One cant help but wonder if Iraq or Kuwait did not have huge oil reserves if the whole situation would have gone on, with out vigorous intervetion (war). Carbon emissions from war and prevention of war, defense are not trivial. if one wants to do a total carbon emission balance for crude an argument the defense carbon emissions should be included as non trivial. jmho