These could be things like switch grass, which the president mentioned the year before.

NPR: Budget Breakdown: Defense, Health and Energy

Foody says there are lots of other possible ingredients: corn stocks, fast-growing weeds like switch grass, even municipal waste.

NPR: Canadian Dreams of Ethanol Distilled from Grass

But anybody who grows switch grass, I suppose, is going to be happy, because we're going to spend a lot of money trying to find out how to make an ethanol from it.

NPR: Budget Breakdown: Defense, Health and Energy

"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?

Moya's defeat came after a hard-fought contest but Grosjean won only three games as he struggled to switch from the faster grass surface on which he reached the semi-finals at the All England Club earlier this month.

BBC: Seeds fall in Germany

Was it, as some tacticians argue, a case of India's game being too rooted in natural grass to accommodate an international switch to artificial turf?

WSJ: Social Media