biodiesel in airplanes vs kerosene/jet fuel

[westvandude]

Saw a program on TV today about the growing airline industry in developing nations such as India, China, South America and how air travel being relatively cheap there is getting more and more people in the air who might not have considered air travel previously.

Anyhow, the CEO of Virgin Airlines was saying how he's investing in ethanol in California, etc. How the airlines are moving to carbon fiber and other technologies to reduce fuel consumption.

On that note, was wondering if a jet engine could run biodiesel? I suppose the only limitation is the -45deg C temps at 35,000ft. Would that be a reasonable assumption?

Any thoughts you'd like to add?

I'm just curious.

[Spencnaz]

The two kickers about biodiesel in airplanes is the OAT (outside air temperature) issue and the lower calorific content of biodiesel compared to jet fuel.

Jet fuel is pretty energetic compared with other fuels like diesel fuel. It's pretty much like kerosene and I know others with more A&P experience will chime in on that one.

What I would be most concerned about are the emissions from biodiesel at say 40,000 feet. Jet contrails have been a major concern to many as of late.

[frobozz]

Wouldn't biodiesel emissions be infinitely better than jet fuel emissions?! That's the way it works for internal combustion engines down here on the ground.

A year or two ago I saw someone (may have been Virgin/Boeing?) was talking about testing biodiesel as a jet fuel. Never heard any more about it. I think it would be nothing but good side effects, if they solved the cold gelling issue.

Duncan

[taxmame]

Being a jet engine designer the issues is the temperature and the emissions. Todays engines run at EXTREMELY low emissions and bio D would have higher emissions. NOx is a HUGE FAA emission requirement.

As for running an engine on it... thats no problem at all. A lot of engines that are used for power generation or things like that run on diesel, natural gas, oil, steam, pretty much anything. They will run on almost anything... I'm surprised that someone over seas hasnt wanted us to develope one that runs on camel piss yet...

[FTG-05]

I got this off the Boeing News about a month or so ago:

Aerospace Notebook: Boeing sees a future with biofuel
Jetliner industry aims for a smaller carbon footprint
Seattle Post-Intelligencer 08/29/2007
Author: James Wallace
(Copyright 2007)


Within five to 10 years, Boeing and Airbus jetliners could be flying the friendly green skies with a blend of fuel made from plants rather than petroleum.

"That's a realistic target, barring some obstacle that we don't know about today," said Billy Glover of The Boeing Co. Glover is managing director of environmental strategy for Boeing Commercial Airplanes, which, like rival Airbus and the entire aviation industry, is feeling the heat these days from the global-warming debate over the carbon footprint created by jetliners.

Sometime next year, a Virgin Atlantic 747-400 will be taken out of passenger service and one of its tanks filled with biofuel as part of a series of demonstration test flights by Boeing, the airline and engine maker General Electric to prove the technology.

If you had asked Glover two years ago about using biofuel for passenger jets, he would have shaken his head.

"We were pretty skeptical," he said. "This looked like a long shot."

But an industry meeting in Seattle about a year ago helped change Boeing's thinking.

The conversion turned out to be timely.

Even though the world's jetliner fleet contributes no more than 2 percent to 4 percent of the daily carbon emissions, according to most scientific estimates, the industry has become a huge and inviting target for the green movement, especially in Europe.

Two weeks ago, hundreds of climate-change activists camped out at London's Heathrow Airport to draw attention to the issue of greenhouse gases produced by jetliners.

At the Paris Air Show in mid-June, the verbal sparring between Boeing and Airbus was not nearly as loud as their green talk.

At a news conference early in the show, Airbus sales chief John Leahy, who has called the company's new 525-passenger A380 the "gentle green giant," went so far as to suggest that Airbus was "saving the planet one A380 at a time."

That message, however, was apparently lost on U.K. protesters who recently seized a barge delivering a U.K.-produced wing for the A380. The environmental group "Plane Stupid" said the action was taken because the big Airbus jet, even though it may be more fuel-efficient, will add to the surge in the number of people who fly.

Plane Stupid and other environmental groups argue the solution is not to fly.

The aviation industry is all too aware of the consequences of such talk that flying is immoral.

"The noose is going to tighten around the neck of the industry and drive us to more fuel-efficiencies, and we need to tap the best technology out there," Steve Udvar-Hazy, founder and chief executive of International Lease Finance Corp., said at the Paris Air Show.

ILFC is one of the most important Airbus and Boeing customers, and Hazy one of the industry's most respected executives.

One potential breakthrough technology is biofuel.

Fuel produced from plants, which take carbon dioxide from the atmosphere, would essentially be carbon neutral. Burning the fuel in jet engines would add no net greenhouse gases to the atmosphere. Biofuel would also burn cleaner, which is another benefit.

But there are challenges. A biofuel, for example, tends to freeze at a higher temperature than a petroleum-based fuel.

"When you have fuel in the wings, you want to make sure it does not go solid at altitude," quipped Glover. "You have to change the chemistry of the biofuel and bring the freeze temperature down."

About a year ago, Glover and others at Boeing started asking what Glover calls "critical questions" about biofuel.

The result was an overflow industry conference in Seattle that brought together many experts in the field "to see what they were working on," Glover said. That meeting led to the formation of a commercial aviation alternative fuel initiative.

"People have come together and created some road maps for handling these various issues," Glover said. "We saw an opportunity to accelerate things." One was the timing of a demonstration flight. It was initially thought such flight could not take place for about five years. Instead, it will happen in 2008, using a Virgin Atlantic 747-400 that has been taken out of service for heavy maintenance.

Virgin CEO Richard Branson is a strong supporter of the effort. He recently pledged $3 billion to fight global warming.

"I think the chances of us coming up with (an alternative biofuel) in the next five years are pretty good," Branson told Newsweek in a recent interview. A date for the test flights has not been set.

Virgin Atlantic, Boeing and GE will soon select the biofuel to be used in the 747.

But a future supply of biofuel presents another significant challenge.

In a report on biofuel in October, NASA concluded that to supply only U.S. airlines with a 15 percent blend of bio-jet fuel -- using a biofuel made from soybeans -- would require about as much land as the entire state of Florida.

Glover said one possibility that is being closely studied is a biofuel made from algae.

"You don't need much in the way of land area," he said. "And it does not compete with food."

Last year, the Air Force began testing a 50-50 blend of synthetic fuel and conventional JP8 jet fuel on a B-52. The tests went so well that the Air Force intends to certify its entire airplane fleet to run on a synthetic-fuel blend by 2011.

But that synthetic fuel was produced from natural gas using what's known as the Fischer-Tropsch process, which was invented by German scientists during World War II because of a fuel shortage. The process was later modernized in South Africa during the embargo, when fuel was in short supply.

Turning coal or natural gas into a synthetic fuel for jetliners, however, will not address the issue of global warming.

Finding a suitable biofuel could.

The answer likely will be a blend of biofuel with more conventional fuel.

"What we are aiming for is a fuel blend that will be so close to a conventional fuel that to the operator (of the airplane), it will make no difference," Glover said.

"It means that if you go to the pump and get a biofuel blend one day and the next day you get a more traditional petroleum-blend from another pump, you don't know the difference in terms of how the plane flies or engine maintenance," Glover said.

The industry term for this is a "drop in" replacement fuel.

"It's the key to why we are so enamored with this (biofuel)," Glover said. "It can be used on all planes that are in service today. It does not require modified engines, or new airplane designs. As soon as the fuel is available and commercialized, the uptick can be right away."

[westvandude]

Cool. Thanks for the info. Good reading.