Bio-Fuel and you...
#14
Prime Minister/Moderator

Joined: Jan 2006
Posts: 44,895
Likes: 689
From: Engines Turn or People Swim
I read in at least 1 news article that the freeze point of the jatropha blend is actually colder than that of Jet A. This is another benefit of this formula and appears to be one of the large differences with other biofuels that have a much warmer freeze point. Apparently the freeze point issue has been one of the big stumbling blocks for using biofuels for aviation.

Jet A is -40 C
#15
Hopefully a little additive can help with the freeze point. Jet fuel has a BTU (energy release) of about 132000-135000 per gallon. Biofuel is in the 130000-132000 range, so the energy difference is fairly small. The emissions reduction would be in the 60-80% range, according to Boeing.
Jet fuel is about 6.84 pounds per gallon, give or take due to the specific gravity of each batch made. Biofuel is 7.5 pounds per gallon.
Kudos to CAL for doing this flight.
Jet fuel is about 6.84 pounds per gallon, give or take due to the specific gravity of each batch made. Biofuel is 7.5 pounds per gallon.
Kudos to CAL for doing this flight.
#17
Gets Weekends Off
Joined: Mar 2006
Posts: 3,333
Likes: 0
Wasn't Virgin Atlantic first with bio-fuel? If so, I'd say Kudos to them both...
Now that the gas prices are so much lower I'd actually support an OPEC gas tax which could make alternative fuels feasible... Normally I don't like when the government gets involved because they usually screw up things but this is a no-brainer - OPEC will hit us again sooner rather than later...
Now that the gas prices are so much lower I'd actually support an OPEC gas tax which could make alternative fuels feasible... Normally I don't like when the government gets involved because they usually screw up things but this is a no-brainer - OPEC will hit us again sooner rather than later...
#18
Prime Minister/Moderator

Joined: Jan 2006
Posts: 44,895
Likes: 689
From: Engines Turn or People Swim
Hopefully a little additive can help with the freeze point. Jet fuel has a BTU (energy release) of about 132000-135000 per gallon. Biofuel is in the 130000-132000 range, so the energy difference is fairly small. The emissions reduction would be in the 60-80% range, according to Boeing.
Jet fuel is about 6.84 pounds per gallon, give or take due to the specific gravity of each batch made. Biofuel is 7.5 pounds per gallon.
Kudos to CAL for doing this flight.
Jet fuel is about 6.84 pounds per gallon, give or take due to the specific gravity of each batch made. Biofuel is 7.5 pounds per gallon.
Kudos to CAL for doing this flight.
#19
Gets Weekends Off
Joined: Dec 2008
Posts: 341
Likes: 0
From: E-170 Airbender
Additives will get you a few degrees C unless you add a ridiculous amount...chemistry has it's limits. The freezing point is the biggest hurdle for most bio-fuels...they would simply require a redesign of the fuel system to keep the bulk fuel about 35 C warmer than current systems...$$$$$$$
I remember seeing and reading about a US Air Force, I believe B2 bomber being flown with 1 engine on synthetic fuel and then all engiens on synthetic fuel.
Is this the same fuel we are talking about. This happened 2 years ago
#20
There are a number of "synthetic" fuels being tested, but herein lies the difference...
The USAF is proving that its entrie fleet can be flown using jet-fuel made from converted coal. I can't remember the name of the process. You essentially end up with Jet-A that was made by cracking coal. The US has, I believe, the largest coal reserves in the world.
Virgin flew a 747 (only one engine used the bio-fuel) that was made from coconut oil. It worked, but is for all practical purposes, a publicity stunt. Coconuts grow too slowly and do not produce great enough density (biomass per acre) to be economically viable. And think what would happen to the price of Coppertone if all that coconut oil started going into jet engines...
CAL and Air New Zealand flew jets (again, I think only one engine used biofuel) on Jatropha-based fuel. Jatropha is interesting because it is a weed that will grow just about anywhere. Its density and regeneration are such that it can produce a significant biomass for conversion, and requires almost no cultivation (hands-off farming).
Thawednook, I too read that Jatropha Biofuel (I will call it "Jet-J" from now on) has a lower freeze point than Jet-A. It's an issue on long flights, such as the polar flights from the US to Asia. My one experience with it was in a 747-400, and our fuel got down to 3 degrees above the freeze point--the limit before you have to change course, altitude, or speed.
What isn't addressed is the "lubricity," or effectiveness of fuel's lubricating properties, as the temperature drops. This is important in systems such as fuel pumps. Just because the fuel isn't frozen doesn't mean it still is lubricating the pump. This probably still requires research for Jet-J.
In all these alternatives, proof that it will work doesn't mean it is economically viable. Can't remember exactly, but seems the USAF's cracked-coal (Jet-C?) costs over $50 a gallon to produce, in its current limited quantities. Other biofuels are also currently very expensive.
For the near future (I would estimate 5 years) biofuels will be big news items, but it won't become significant until it is cheaper than petroleum-based fuels.
The USAF is proving that its entrie fleet can be flown using jet-fuel made from converted coal. I can't remember the name of the process. You essentially end up with Jet-A that was made by cracking coal. The US has, I believe, the largest coal reserves in the world.
Virgin flew a 747 (only one engine used the bio-fuel) that was made from coconut oil. It worked, but is for all practical purposes, a publicity stunt. Coconuts grow too slowly and do not produce great enough density (biomass per acre) to be economically viable. And think what would happen to the price of Coppertone if all that coconut oil started going into jet engines...
CAL and Air New Zealand flew jets (again, I think only one engine used biofuel) on Jatropha-based fuel. Jatropha is interesting because it is a weed that will grow just about anywhere. Its density and regeneration are such that it can produce a significant biomass for conversion, and requires almost no cultivation (hands-off farming).
Thawednook, I too read that Jatropha Biofuel (I will call it "Jet-J" from now on) has a lower freeze point than Jet-A. It's an issue on long flights, such as the polar flights from the US to Asia. My one experience with it was in a 747-400, and our fuel got down to 3 degrees above the freeze point--the limit before you have to change course, altitude, or speed.
What isn't addressed is the "lubricity," or effectiveness of fuel's lubricating properties, as the temperature drops. This is important in systems such as fuel pumps. Just because the fuel isn't frozen doesn't mean it still is lubricating the pump. This probably still requires research for Jet-J.
In all these alternatives, proof that it will work doesn't mean it is economically viable. Can't remember exactly, but seems the USAF's cracked-coal (Jet-C?) costs over $50 a gallon to produce, in its current limited quantities. Other biofuels are also currently very expensive.
For the near future (I would estimate 5 years) biofuels will be big news items, but it won't become significant until it is cheaper than petroleum-based fuels.


