I am sure studies have been done on how much it takes to produce a gallon of biofuel with consideration to source material, the scale of production, location, weather, level of certification, and a number of other variables. You're welcome to post such data if you find it and I'll make an attempt to do the same. The accurate final cost of producing synthetics and biofuels cannot be known until large-scale production has been attempted, which so far it hasn't. Another relevant fact to consider is that even knowing some number for the cost per gallon of a particular formulation, much of the market value is dependent upon traditional petroleum production in the world. The latter is a daunting problem full of politics, industry-muddled science, volatile markets and other variables.

As for the engines themselves, it has been said that a turbine can burn anything owing to the wide range of activation energy a turbine can produce. The problem is in the supporting systems like fuel lines, tanks, pumps, valves, switches, filters and so forth, they may not be able to reliably use a particular formation due to problems with viscosity, corrosion, expansion, and volatility. It is known that some existing jet aircraft turbines cannot sustain the reliable use of certain synthetic and biofuel formulations. This is the driving reason for all the testing we are seeing these days. In some cases older designs are being found compatible with biofuel while other manufacturers have opted to develop clean sheet designs such as the Pratt & Whitney PW1000 mentioned earlier. The latter was intended from inception to be compatible (and reliable) burning a wide array of chemical formulations. It is expensive work to develop a new turbine for aircraft use, and at this point it represents an unknown in the cost of renewable fuel adoption for commercial and military air travel.

Qatar Airways, Other Firms Target Green Jet Fuel.

The AP (1/10) reports, "Qatar Airways and other state companies in [United Arab Emirates] say they are targeting the development of alternative jet fuel." Quatar Airways announced Sunday that it would "work with Qatar Petroleum, the Qatar Science & Technology Park and plane maker Airbus to study biofuel strategies with the aim of producing 'sustainable bio jet fuel' that could initially be used by the national airline. ... The companies did not provide a timeframe or details of their financial commitment to the project."

Boeing Planning Ways To Install New 737 Engine.

Flight International (2/4, Ostrower) reported, "Amid increasing industry speculation about the imminent launch of re-engined narrowbodies, Flightglobal has learned how Boeing could engineer the tricky installation of an advanced turbofan under the wing of the 737." Boeing could extend the nose's landing gear to give "additional clearance" for a new engine. That could "yield an approximate 12% improvement in specific fuel consumption, before any other airframe modifications are incorporated says the assessment." Randy Tinseth, vice president of marketing for Boeing Commercial Airplanes, "recently confirmed to Flightglobal that Boeing had completed a successful technical feasibility study into the installation of a new engine on the 737, but that the modification would require 'a lot of work.'"