Cheap, plentiful biofuels could ameliorate a host of global problems: carbon emissions, trade imbalances, the need for agricultural employment in the middle of the country and in emerging nations.

And there is no doubting the demand. The world consumes the equivalent of 1.06 cubic miles of oil globally a year, according to A Cubic Mile of Oil, the new book by Hew Crane, Ed Kinderman and Ripu Malhotra at SRI International. That’s close to 1.1 trillion gallons a year, or more than enough to fill 1,500 sports stadiums. Today, Kior, a company in the Khosla Ventures portfolio, announced it has received $75 million in loans from the state of Mississippi.

The problem is the 'cheap and plentiful' part of the equation. Many current biofuels are expensive and rely on food crops grown on valuable arable land. Thirty percent of the U.S. corn crop goes toward corn ethanol, which only marginally reduces greenhouse gases. Subsidies are mandatory.

The high costs and high risks of the industry are already apparent. While investors flocked to alternative fuels in 2007 and 2008, the subsequent dip in oil prices has sucked a significant portion of the life out of the industry. To survive, biofuel companies now claim they will concentrate on green chemicals, aircraft fuel or even oils for the food industry for the meantime.

Electric cars, meanwhile, have zoomed in popularity.

Nonetheless, a trillion gallons -- the figure represents an almost unfathomable opportunity. So what will it take to get biofuels flowing to the mainstream?

Read more on this topic in a joint effort by General Electric Ecomagination and Greentech Media, and join the conversation here.