Is biofuel a reasonable (and safe) jet fuel alternative?

The most recent high-profile experiments came from Boeing, Lufthansa and Air New Zealand. Boeing reported that these flights occurred with no modifications to the engines or aircraft, and that the tests "demonstrated that biofuel blends meet or exceed all technical parameters for commercial jet aviation fuel, including freezing point, flash point, fuel density and viscosity."

The Air Force and Navy flew fighter jets on biofuels in 2009 and 2010.

What's extraordinary is how quickly this technology moved from the theoretical to the practical stages. As recently as 2008, an article in Scientific American pondered the practicality of running aircraft on renewable fuel.

The race to succeed has been driven by cost. According to the Air Transport Association of America, fuel cost is the biggest chunk of the major airlines' expenses. It makes up about 25 percent of the cost to run an airline, slightly more than payroll. The organization reports that every penny increase in the cost of a gallon of fuel adds an additional $200 million in yearly expenses.

The association showed drastic changes in price for the first 10 months of 2010 -- ranging from 10 percent to 25 percent. Though no one can predict for sure whether biofuels will actually be cheaper than fossil fuels after the complicated farming and refining processes, the chance to stabilize the wild price fluctuations could make it much easier to run an airline.