Aviation’s cleaned up its act like few other sectors in recent years, but it still can’t catch a break. Earlier this month, Congress looked into greenhouse-gas emissions from commercial aviation, just as news got out that commercial aviation’s unchecked growth means it will contribute more GHGs than expected. Europe continually and toothlessly threatens to include aviation in its emissions-trading scheme, spooking Euro carriers and angering U.S. airlines.

Dang, that’s a lot of coconuts (Associated Press)

But at the same time, the oil price rise is killing airlines. There’s no way to hedge against high fuel costs when jet kerosene costs $150 a barrel. So what’s the beleaguered airline industry to do?

Unlike cars, airplanes can’t turn to electric power, and hydrogen power is still a pipe dream for planes. So the question for the industry is what kind of biofuel comes closest to regular jet kerosene—and at what cost?

Petroleum Review this week has a big takeout on the industry’s connundrum. Planes need high-density, high-octane fuel that withstands freezing temperatures and which is uniform the world over. Easier said than done, especially with fears over deforestation, rising food prices, and worries over water and arable land. Petroleum Review says:

What’s needed, in other words, is an exact replica of fossil jet kerosene - a so-called ‘drop-in’ replacement - which also emits substantially less carbon. ‘Meeting all these conflicting demands is a very tall order,’ says Dr Mike Farmery, Global Fuel Technical and Quality Manager at Shell Aviation. ‘There are lots of exciting ideas, but it will be hard to achieve quickly.

Some companies have already taken baby steps. Virgin’s much-ballyhood flight from London to Amsterdam used 5% coconut-oil biofuel (the part Sir Richard Branson didn’t drink for the photo-op) to show biofuel could take the high-altitude cold. But the test flight alone used 150,000 coconuts, Petroleum Review says—and at least 3 million would have been needed for a full biofuel flight. Multiply that by world air traffic, and the problem comes into focus.

The other options? Flavor-of-the-month jatropha biofuel would be fine—except aviation would require a land area twice the size of France to grow the stuff. What about natural gas-to-liquids technology? No food worries, but that would increase CO2 emissions by 50%. How about biomass, like bits of wood and useless plants? Well, they still need to grow somewhere—and commercial aviation would need to harvest an area three times the size of Germany.

Sir Branson suggested algae—something oil companies like Shell have started working on as a biofuel panacea. It might do the trick, Petroleum Review says, but don’t get your hopes up. Even harvesting oil from algae would require pond scum filling a space twice as big as Belgium.

As much as aviation needs to cut its fuel bill and emissions footprint, there are no easy answers in the short term. Get braced for more fuel surcharges at the airport.