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Successful Initial Test of 30% Biofuel Blend in Commercial Jet Engine

The CFM56-7B.

CFM International has successfully carried out an initial test of a CFM56-7B engine using an ester-type biofuel at Snecma’s Villaroche facility near Paris. The CFM56-7B is the exclusive engine for the Boeing Next-Generation Single-aisle airliner: 737-600/-700/-800/-900. Thrust ranges from 18,500 to 27,300 lbs.

The biofuel used for this test is a 30% vegetable oil methyl ester blended with 70% conventional Jet-A1 fuel. This test was designed to check the operation of a jet engine using a fuel made from biomass, without making any technical changes to the engine.

With this type of biofuel, the target is a net reduction of 20 percent in carbon dioxide (CO2) emissions compared with current fuels.

Our goal is to support the industry in identifying replacements for traditional hydrocarbon-based fuels, including synthetic fuels that use a mixture of biofuels and jet fuel.

—Pierre Thouraud, Snecma Vice President, Engineering

CFM is also running engine tests to develop solutions based on mixtures of jet fuel and second-generation biofuels. It is currently focusing on the evaluation of alternative fuels made using biomass which offer properties closer to those of jet fuel than do first-generation fuels such as the methyl ester (i.e., biodiesel), and which also offer better environmental performance.

Along with its parent companies, CFM International is participating in a number of emissions-focused initiatives, including the US CAP (Climate Action Partnership), French Calin, and European Alpha-Bird programs.

For alternative fuels to be used in the aviation industry, there are a number of major technology challenges that must be met, including energy density, thermal stability (avoiding coking at high temperature), use at very low temperatures (freezing) or high temperatures, lubricating effect with materials used, and the availability of mass production facilities worldwide.

More than 500 airlines fly CFM56-7B-powered 737s and, since entering service in the mid-90s, the engines have accumulated more than 50 million flight hours. All CFM56-7B engines delivered beginning in mid-2007 are compliant with CAEP/6 (Committee on Aviation Environmental Protection) environmental requirements.

CFM56 engines are produced by CFM International (CFM), a 50/50 joint company of Snecma (SAFRAN Group) and General Electric Company.



Fischer-Tropsch should be able to make a very close JetA substitute from straw bales etc.


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.


They don't say if they tested this at altitude, and what the gel point of this blend would be. Or whether any crystallization is observed at low temperatures...

Roger Pham

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.


Energy of making LH2 versus the energy saved by having a lighter fuel?

Air transport uses a very small percentage of total fuel needs...considering commercial AND general aviation. You could take all the biofuels out of the Automotive supply chain as of today and probably come pretty close to meeting the needs for air transport on an energy basis [nope, I don't have the numbers off hand but you can find energy use through the Bureau of transportation statistics for commercial air and general aviation and then find biofuel consumption in a year through the DoE...I bet it is pretty close]


For air travel:
BTS Table 4-6: 2009 trillion BTU

For renewable fuels:
EIA Renewable Energy Annual: 296 Trillion BTU (may not include biodiesel) []

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


I've recently attended a lecture on this very subject.

One of the more insurmountable issues is that RME bio deisel causes massive swelling of seals/hoses.

Now given the safety implications of this and the size and life cycle of the existing fleet of aircraft in service world wide you can bet your bottom dollar that any new fuels provided for aviation use will have to meet existing technical specifications.

The conclusion from the industry as presented at the lecture was that coal to liquid is most likely to be the way forward.

Given the US military's interest in this technology I'd say they were dead on.

Also providing aviation fuel volumes is likely to be possible within existing coal production rates without too much difficulty. Unlike road transport fuels.



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


"Since the LH2 fuel is so light, you can reduce the takeoff weight of the plane to 1/2-2/3 depending on range"

But because its density is so low the plane needs massive insulated cylindrical fuel tanks that actually add mass and reduce speed and performance. Aerospace engineers in the rocket industry have known this for decades that why they prefer to use Kerosene/LOX for the first stage of a rocket (LH2/LOX for higher stages because those stages won't experience air drag) Most of all a leak of LH2 is a extreme fired hazard. Maybe a blended wing body plane could handle the loss of space from the fuel tanks.

Roger Pham

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.


Nice calculations Roger especially the ones that shows that using liquid hydrogen instead of fossil jet fuel increases storage volume from 1/9 to 2/9 of the airplane volume while at the same time reduces takeoff weight by 50%.

Storing hydrogen in liquid form using light weight super insulation is not a problem as proved by BMWs 7 series car that uses a combination of an ordinary gas tank and a liquid hydrogen tank to power an ordinary ICB engine. The link on the technology is here As can be read they use only 30 milimeters (1,2 inches) with layers of insulation, aluminums, and glass fiber to store the liquid hydrogen. The super insulation is only a few millimeters but still equals a 17-metre thick layer (56 feet) of styrofoam in its insulating effect! Incredible but nevertheless true. The hydrogen tank can withstand enough pressure so that minor evaporation effect only starts after the vehicle has been parked for at least 17 hours, whereupon the pressure inside the fuel tank will increase to a level requiring boil-off management of the gaseous fuel. If these figures could be made similar for a hydrogen fuelled airplane with much larger tanks it would not be technically necessary to empty the airplane for any residual fuel after flight.

In fact because hydrogen explodes much faster than any other known fuel the jet engine trust will be larger for any given amount of energy. The energy to jet engine trust is much higher for hydrogen than for other fuels. I can’t do the involved math but it would be really interesting if someone who could would try to give a few numbers on this.

What is going to make hydrogen more attractive as a jet engine fuel in the future is the higher prices of jet fuel and a requirement to use CO2 neutral fuels. Hydrogen also has the potential to be cheaper to produce in the future using cheap off peak electricity from wind mills. Hydrogen produced this way is already competitive (or close to be competitive) with jet fuel at today’s prices. The problem is that there are no hydrogen airplanes on the market yet and no infrastructure at the airports to support it. It is about time we start doing something about that. A good start would be a large co2 tax on jet fuel whose revenue (billions of dollars) is used to subsidise the production of hydrogen planes and airport infrastructure.

P Schager

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.


Biofuels are a net neutral CO2 fuel. Made from cellulosic biomass or algae and they don't compete for feeding glutinous overweight first world countries cheap high calorie food. Also the aerospace industry only takes up 7% of the oil industry it would not be nearly as hard to replace fuel for cars (45-55%) and it could be done with far far less (even invisible) infrastructure change, unlike hydrogen.

Roger Pham,

I would still like to see the weight of cryogenic tanks compared to form fitting kerosene tanks. I seriously doubt you can make even semi-form fitting cryogenic tanks, they tried that with Venture Star and failed. Also how to deal with the safety hazards of LH2? Also hydrogen combustion produces much higher temperatures then kerosene and would increase NOx production greatly.

If you really want next generation travel just go with a scram jets (LCH4 though would be better then LH2, again because of volume-drag of LH2)

Roger Pham

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.


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.

Florello C. Gallindo

I think Snecma should try to evaluate coconut methyl ester in lower blends. There are unique characteristics of this oil not found in other vegetable oil derived esters. For one, coconut methyl ester is 92% saturated and therefore will reduce NoX emissions unlike other methyl esters which are highly unsaturated and therefore increases NoX emissions as you blend more of the ester in jet fuel. Additionally, its superior cleaning ability due to the presence of lower carbon chains will ensure turbine components are always kept clean.

Henry Gibson

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

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