Why aren't we using biodiesel or ethanol?

[svtcobra66]

I was watching a show the other day on discovery science, and there was a guy with an ethanol-powered mooney. Basically its corn alcohol, and while we don't have enough to replace our oil supply for cars, you would think that the private/personal aviation market would benefit from this fuel due to its cheap cost and the fact that the changes needed to the fuel system are minute. Also, I'm aware that there are a few diesel aircraft soon to be certified, and wonder why biodiesel isn't catching on as well. Like I said previously, making enough for mass transportation probably isn't possible, but for small airports I don't see why these cheap enviro-friendly fuels aren't used more. http://www.e85fuel.com/index.php
http://www.findarticles.com/p/articles/mi_m0CYH/is_9_7/ai_102090258

[spinwing]

Think you might find it is because quality of product for use as an aviation fuel cannot be guaranteed!

Ethanol I understand can be very hygroscopic and Biodiesel will wax up filters etc when cold!

Oooooohhh ....... ??? :confused: :eek:

[PPRUNE FAN#1]

Ethanol...biodiesel? Funny you should ask. In the current issue of CAR and DRIVER Magazine, columnist Pat Bedard discusses this issue. Let's distill (if you'll pardon the pun) some of what he says. This is not to say that running cars on ethanol, the alcohol from fermented vegetable matter, is an entirely bad idea... Ethanol packs a large amount of energy into a gallon compared with alternatives such as natural gas, LPG, and hydrogen. It's not as good as gasoline, however; you need about 1.5 gallons of ethanol to drive the same distance as on one gallon of gasoline...This has always been the problem with ethanol. We pilots are always performing our delicate balancing act, trying to bring along enough fuel with the particular payload. Requiring that we carry more fuel is not going to go over well, except for perhaps flight school ships that stay fairly local.Ethanol has other problems, too. To ensure good engine starting, it needs to be mixed with gasoline... Moreover, ethanol can't be shipped in pipelines because it picks up water.Yikes! Will the effect of water in the ethanol be the same as water in the gasoline (i.e. silence from the engine compartment)?

The usually skeptical Bedard hedges a little on biodiesel:However, used restaurant "grease," known in the recycling trade as yellow grease, or any vegetable oil, can be transformed into a substitute for diesel fuel by a chemical process known as transesterification. It's a good substitute, too, much closer to diesel than ethanol is to gasoline.Diesels for airplanes simply have not caught on here in the U.S. But I wonder how biodiesel would work in a turbine engine? It would be interesting to find out.

Of course, whichever alternate fuel we use, we're going to have to have a distribution system for it. You sure wouldn't want to take off on a cross-country in an airplane for which there was limited availability of fuel. You might as well have an aircraft powered by an electric motor with a long, long extension cord.

Right now, it would be pretty hard to replace the current distribution system, or even augment it, which is why gasoline is going to be around for a long time for cars. Whether or not we'llbe able to use car gas in our airplanes is the question, especially if the manufacturers want to stop producing avgas. And you know that there are many airplanes that cannot use auto fuel due to their high compression ratios.

"Alternate fuels" is a great theory. The reality of actually implementing them is a whole 'nother subject.

[svtcobra66]

True, but atleast with biodiesel you could just substitute regular diesel or Jet-A. You wouldn't need to use it all the time, so if you can't find a place with biodiesel its not big deal, there are no changes necessary for a diesel engine to run it, its a straight substitute.

[007helicopter]

True, but atleast with biodiesel you could just substitute regular diesel or Jet-A. You wouldn't need to use it all the time, so if you can't find a place with biodiesel its not big deal, there are no changes necessary for a diesel engine to run it, its a straight substitute.

There can be pitfalls with running biodiesel in engines, it will make normal rubber seals in fuel pumps and fuel hoses swell and eventually fail. Also I do not think it is available at a lower cost than regular diesel ?

[corncrasher]

There is a lot more to the alternative fuels than you get from the media. there is a big push for them for enviromental reasons and foriegn oil , the other reasons are mostly a load of crap. They are not cheaper, easier, or better. For the most part they are not even as good and they have a lot of unique problems. It takes more energy to process corn to get a fuel product out of it than than you end up with, that is a step backwards. The veggie oil/diesel thing works ok but on a very small scale, and I wouldn't run it in a aircraft I'm going to fly.

[ShyTorque]

The vapour pressure of a fuel is also an important issue. For example, MOGAS has a higher vapour pressure than AVGAS (=more likely to vapourise) which can be a definite disadvantage at higher ambient temperature and/or increased altitude because it may form a vapour lock in the fuel system. I believe this would also be an issue with ethanol.

[GLSNightPilot]

All things considered, it takes more energy to make a gallon of ethanol than a gallon of gasoline, and less energy is produced when that gallon is burned. Ethanol is a wonderful substance when burned in the human body, but not so good when burned in an internal combustion engine.