At the Yale Environment 360 website, an article by David Biello ("For Greening Aviation, Are Biofuels The Right Stuff?"), presents a summary of what has been done so far in aviation biofuels development, and the practical challenges for large scale production. The article traces the successful test flights of some commercial airlines (Continental , Virgin Atlantic, Air New Zealand, Japan Airlines) using aviation bio-jet-fuel produced from various second generation energy feedstocks (such as oils extracted from jatropha, camelina, coconut, babbasu and microalgae). The environmental appeal of aviation biofuels is reportedly strong, because jet emissions (even if low at 3% of total worldwide greenhouse gas emissions from fossil fuel burning) have a chemical mix that intensifies heat-trapping (global warming) power in the upper troposphere. Preliminary results from the Air New Zealand test flight show that for jatropha-based jet fuel, greenhouse gas emissions were reduced by 60%, and the biofuel blend could save 1.4 metric tons of fuel in a 12-hour flight. Biello mentions that the overwhelming challenge is to produce sufficient jet biofuel to supply the annual aviation fuel demand of about 60 billion gallons. Feedstock choice and supply will be important considerations. Jatropha, camelina and algae are the non-food-based feedstocks that have been used for aviation biofuel feedstock. Of these three, jatropha and camelina may have issues related to land use competition with food crops. The use of microalgae in brackish ponds are said to have some advantages as feedstock potential. The full article can be accessed at the Yale Environment 360 website (URL above)..