The New Scientist reports in a short item that with regard to cutting carbon dioxide emissions growing biotech crops is the equivalent of removing 4 million cars from the roads. How does this work? Farmers who plant herbicide resistant biotech crops don't have to plow their fields in order to get rid of weeds which leaves more of organic matter sequestered in the soil. This also means that they burn less fuel.
Naturally, as the article points out, the organic folks pooh-pooh these findings. Evidently they prefer to eliminate weeds the old-fashioned way–peasants using hoes.