Certainly ethanol works as a biofuel. The greenhouse gas benefits of our current ethanol technology aren't quite there. Lignin cellulosic ethanol is close, but it's not quite there on a commercial scale.
In Europe another one is converting biomass to a natural gas equivalent—synthetic natural gas—putting it into pipelines, and using it as a transportation fuel. If you want to compare it to the price of natural gas, it doesn't work. Natural gas is $7 a gigajoule; it's probably about $14 or $15 a gigajoule for synthetic biogas. In Europe that works, especially for transportation, because gasoline is $25 a gigajoule, so if you were using biogas natural gas for a transportation fuel, that would work.
If you want to talk about studies in Europe that have been done relating to how many kilometres you can get per hectare of agricultural land, if you're interested in that sort of productivity, that works. The problem is that if it's going into a pipeline it won't be competitive with natural gas, and it will increase natural gas demand considerably.