He also reports on the continuing food riots, this time in Haiti and Bangladesh.

There's still a bitter argument over whether corn ethanol is actually net positive - or whether it uses more fuel than it produces. The latest consensus seems to be narrowly positive - 1.34 times as much fuel energy out as in.

There are other more efficient approaches - cane sugar biodiesel and cellulose biodiesel are both more efficient, and there's much room for improvement in vehicle efficiency - but they suffer from the fact that there is no massive and well-organised US lobby arguing for them, as there is for corn. Those amber waves of grain don't just grow themselves, you know.