to be a significant power sources without either destroying foodcrops or natural ecologicies
Plenty of cropland is already used for biofuel. If we can do so more efficiently, then more area will be available for food and/or nature.
or get more than about 5% efficiency - less than a solar panel.
Comparing biofuels to solar panels in area efficiency is silly. Solar panels cost hundreds of dollars per sq meter. Cropland does not. The important metric is not watts/area but watts/dollar. Also biofuels are liquid and can be used as transportation fuel in affordable vehicles. Solar electricity cannot.
Keeps everyone hopeful, despite the complete silliness.
TFA is completely devoid of any technical information, so I don't think you don't have enough information to determine if her invention is silly or not.