Rapeseed, Grown for Biofuel Production Mark Walton via Wikimedia
The problem with biofuels is that they can actually cost more in energy to produce than they end up yielding in BTUs, delivering a poor return (sometimes a negative return) on energy investment over the course of a given acre’s life cycle. Then there’s food prices that must be taken into consideration; crops like corn, when used to make ethanol, are removed from the food supply. That can cause price spikes, which tend to cause problems ranging from famine to civil unrest.
PETRO will try to optimize plants for energy capture and conversion, so more energy is absorbed, stored, and converted to final fuel products than is being extracted from current biomass crops. To quote ARPA-E:
ARPA-E seeks to fund technologies that optimize the biochemical processes of energy capture and conversion to develop robust, farm-ready crops that deliver more energy per acre with less processing prior to the pump. If successful, PETRO will create biofuels for half their current cost, finally making them cost-competitive with fuels from oil.
If it works, new breeds of plants (and GM biofuel crops) could help the U.S. meet its mandate to manufacture 36 billion gallons of biofuels by 2022 (up from about a third of that today).
Ref. : http://www.popsci.com/science/article/2011-04/arpa-es-petro-program-plans-create-better-biofuel-crops-cutting-costs-half