Boeing Biofuel Analysis
Boeing sees biofuel blends in jet fuels in the medium term horizon. Technical hurdles will have to be overcome. The low temperatures of higher altitudes can cause the biofuel to freeze. And, other stability challenges must be remedied. However, the science is steadily advancing as bio-
jet fuels are beginning to reach minimum freeze requirements. ...
... "The major challenges of using pure biofuels in a commercial aircraft are its propensity to freeze at normal operating cruising temperatures, its poorer high temperature thermal stability characteristics in the engine, and its storage stability over time. " ...Via Boeing: Alternative Aircraft Fuels (PDF)