Sure, in that case it is just as bad. But I don't understand how it could ever be worse than gasoline since part of the CO2 in bio-ethanol should at least come from already unbound CO2.
Because the process from growing corn to distilling ethanol requires more energy than it produces. That energy has to come from somewhere, i.e. fossil fuels. It would be cleaner to just burn the fossil fuels than to run the energy through the Rube Goldberg machine of farm subsidies and ethanol.
Not literally true from the energetics point of view, but close enough that when you add in the other carbon releasing side effects (degradation of soil carbon, land clearing) that comes with increased corn production, it is a net carbon producer right now. That's what this study is all about.
Corn in particular is inefficient, burning corn produces less energy than the energy required to grow corn.
Sugarcane is the opposite, it grows easily (too easy in fact, it has tendency to spread in an unwanted way), doesn't require too much diesel to produce, and it makes a fantastic amount of ethanol when pressed.
