I guess this is part of the improvement Airbus were talking about.
Biofuels, composite fuselage and propfans, and you might get close, assuming you are not required to have lower noise or safety levels.
[ And can allow it go a bit slower ]
Might work well for shorter hops, wouldn't like to go to Singapore on one.

Biofuel like biodiesel will likely be in limited quantity, since people have to be fed first. A real test of manhood is to use liquid hydrogen in jet engines. Since the LH2 fuel is so light, you can reduce the takeoff weight of the plane to 1/2-2/3 depending on range, and save energy as the result, since the plane will be a lot lighter.

For air travel:
BTS Table 4-6: 2009 trillion BTU
[http://www.bts.gov/publications/national_transportation_statistics/html/table_04_06.html]

For renewable fuels:
EIA Renewable Energy Annual: 296 Trillion BTU (may not include biodiesel) [http://www.eia.doe.gov/cneaf/solar.renewables/page/trends/table2.html]

So, the current use of biofuels is 10% of what we would need to completely power our air travel.

Well, 15% is much lower than I expected but closer than the 22,000 trillion btus used by land transport [excluding transit & rail]

Ben,
The Space Shuttle uses a humongous LO2 and LH2 combined into one external fuel tank with two internal compartments, that provides energy for the first 7 minutes of launch, and it is jettisoned right afterward. The fuel tank is insulated with foam having very little weight (low density). Aircraft LH2 can use the same foam for insulation. Remember that weight and aerodynamic drag is very critical for the Space Shuttle as well. I believe that the Saturn V moon rocket and other large manned rockets are strictly LH2 and LO2 fueled.

I've calculated that LH2 takes up 3-1/2 times more volume than kerosene, but, because the whole plane can be built up to 1/2 as much gross takeoff weight as before, you would only need 1.7-2 times the fuel volume. Since fuel volume takes up but 1/9th the internal fuselage of an airplane like the Boeing 767, you can see that if the fuel volume increase from 1/9th the internal volume to 2/9th internal volume, the overall increase in volume including insulation foam would be still manageable. Very thick foam is not necessary, since most of the fuel will be consumed within one flight. LH2 boiling off will be consumed by the engine right away. In the ground, boiling off LH2 can be fed to a FC APU to generate electricity that can be fed to the grid. After landing, remaning fuel can be pumped out if no more flights will be scheduled for that plane within the next 24 hrs, though that is highly unlikely.

Since LH2 is not under high pressure, exactly cyclindrical tank is not required. A semi-circular tank on top of the fuselage with rounded off corners and many internal compartments in order to seal off leaking section would take up less void space. To avoid leak, tank can be made self-sealing, like in military aircraft fuel tank that can seal off after being fired by a 0.50 cal. machine gun, or even 20mm cannon.

The Saturn V did use kerosene for its first stage, and LH2 above that. A similar strategy could make good sense for an interim long-range airliner. You would have a portion of the fuel as kerosene (or biodiesel B30, as tested here) and the rest liquid hydrogen, to moderate the fuel volume increase while not impacting the weight spirals for fuel consumption too badly because you would burn off the heavy fuel first, and after that the only fuel you are burning to carry fuel is lightweight LH2. Another reason to do this is to combine tried-and-true kerosene engines, tanks etc. and the advanced LH2 stuff for a good fail-soft pioneering plane. Especially if the LH2 stuff is radical, such as fuel cells.

Eventually you want SOFC fuel cells with turbocompounding and an energy recovery hydrogen expander. Overall efficiency could be 70% and the energy that had been used to liquefy the H2 can also largely be recovered. It's like having about a 100%-efficient engine. This means the energy requirement for the LH2 to carry is less than half as much as the old technology, even before the weight spirals, reducing volume. However economics will dictate that, having cut the gross takeoff weight, you double the payload, and so you're back to needing big tanks for long range.

One possible place to put LH2 is in big wingtip tanks. Easily swapped to adjust size for range. Far from the passengers, and they could be jettisoned if you're going to crash, so you won't be sitting in a fire.

For now we have the B30 (I coulda told you it'd work fine). This should be adequate to restore some demand elasticity to the oil market. Only cheapo elastomers like natural rubber will swell, and I can't imagine they use those on airliners. I assume they have fuel heaters. Soon we'll see de-oxygenated versions of the biofuel like NexBTL and it will be equivalent to kerosene, suitable for long flights. Coal has no advantage unless you're in the coal industry.

BTW liquid natural gas is a pretty good aircraft fuel too, as is (for smaller planes) propane. Both are lighter than kerosene, and both are as practical to make from renewable sources as the fuels that seem to be popular targets.

P Schager,

SOFC is really for stationary application, due to the weight involved. Aerospace engines must have very high power-to-weight ratio, and nothing we have now can compete with the gas turbine engine, with the exception of the detonation jet engine that is still under experimental stage.
It takes ~10x more energy to liquefy H2 than the useful work obtainable from vaporizing LH2 using ambient heat. Thus, the considerable energy used to liquefy LH2 is largely lost, about 30% of the heat value of H2. But, if one is to synthesize liquid fuel from the syngas after gasification of coal or waste biomass, one would also lose a comparable amount of energy in the process.
LNG (liquid Natural Gas) is almost as heavy per unit of energy as kerosene, so offers no overall weight saving.

Ben,

Why would you expect cryogenic tank at low pressure be much heavier than form-fitting kerosene tank, when the insulation is light-weight foam, that, when properly sandwiched between layers of aluminum, can provide significant structural strength to the airframe. Many home-built aircraft are made from foam covered with composite fiberglass layers such as Burt Rutan's earlier designs that are quite light.

The Venture Star is a Single Stage to Orbit (SSTO) vertically launched space vehicle that must have its loaded dry weight merely 10% of total wet weight at launch. This design goal is impossible to meet, even with largely carbon composite structure, since the most efficient airliners have dry weight about 50-60% of gross takeoff wet weight. The enormous composite tank failed because of insufficient material was used. Due to the enormous energy requirement to reach orbital velocity at 17,000mph, (E=1/2MV^2) it is not realistic to use a vertically-launched single stage to orbit vehicle. A more realistic option is to use SCRAMjet using LH2 and atmospheric O2 to achieve hypersonic speed at the edge of space, and then use the rocket engine with LH2 and LOx to blast to orbit after achieving 7000 mph from the scramjet engine. Even then, the airframe may be too heavy. Far more sensible is to use the re-usable SCRAMJet powered first stage that takes off and lands horizontally, with the second stage then blasted off to space without having to carry the excess weight of the SCRAMJet engine and the LH2 primary tank in the first stage.

Safety Hazard of LH2? Just ask BMW who is promoting LH2 in the BMW 7 series. Also, LH2 is being used extensively in space launch vehicles for decades, so its safety is well known. Please note that rocket explosion are far more likely from solid-fuel boosters than the liquid fueled stage. LH2 cannot burn until it's mixed with O2. Once escaped, LH2 vaporizes and quickly flies up and away instead of lingering around to cause explosion. Good ventilation should be built-in in order to prevent accumulation of H2 gas.

No ethanol or other biofuel is zero carbon impact if any fossil fuels have been used in its production. ..HG..