the 20 minutes piece seems to be in line with this:
http://www.cbc.ca/canada/manitoba/story/2007/03/30/ethanol-emissions.html
I would like to see the methodology of the study. Many times they leave out the fact that corn absorbs CO2 (the primary GHG) just like any other plant. The study above only uses E0 (pure gas) and E10 (10% ethanol). They claim there is no reduction in hydrocarbons, however that would seem to contradict a Gazi University study which showed "The addition of 60% ethanol to the unleaded gasoline caused a 31.45% reduction in HC emissions at the compression ratio of 10:1." (I can get you the study if you want to read it). They also found that "
The addition of 40% ethanol to the unleaded gasoline gave the best results for reduction of CO emissions by about 31.8% at 9:1 compression ratio. The addition of 60% ethanol to the unleaded gasoline caused a decrease in CO emissions by about 19.8% and 22.3% mean average values at 8:1 and 9:1 compression ratio, respectively."
While CO is not a GHG, it is a significant contributor to smog and air pollution. Hydrocarbons on the other hand, are GHGs.
Another study:
A recent Canadian study shows that on a lifecycle basis, 10% ethanol-blended gasoline can lower greenhouse gas emissions by up to 4%. The study tracked greenhouse gas emissions starting at planting and fertilizing fields through to harvest, trucking feedstock to the ethanol plant, production of ethanol, transportation to fuel distributors and retailers and finally to consumption in motorists' vehicles. GHGenius (
www.ghgenius.ca), a Canadian model for lifecycle assessment of transportation fuels, reached similar conclusions about ethanol's impact on greenhouse gas reduction.