"It's not our long-term solution because of the competition with feed, and fuel competition, but it is prompting us to put into place a refueling infrastructure that could be used with cellulosic ethanol, " made from other types of plant material such as timber waste or switch grass.

CNN: Ethanol: Is it friend or foe?

Corn stover, garden waste such as grass clippings, and offcuts from forestry and timber production are better bets, she reckons.

ECONOMIST: Biochar could enrich soils and cut greenhouse gases as well