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Fly Green

sunplane_legault.jpgGreen cars are easy, at least in comparison to making air travel climate-friendly. In order to fly at the speeds, altitudes and distance to which global travelers have become accustomed, nothing now available works better than jet engines. And, for now, the best fuel for jet engines is kerosene, which comes from petroleum. But kerosene puts out a lot of carbon; a 5,000 mile flight -- roughly a round trip from LA to New York -- puts out a ton and a half of CO2 for every person on the plane. Serious environmentalists are starting to talk about a total ban on air travel as a possible result of carbon overload.

A development by the University of North Dakota may change that. Researchers at UND's Energy and Environmental Research Center have come up with a biofuel that has the characteristics needed for aircraft use -- and in some respects, it's actually better than kerosene:

The last time UND researchers were at Wright-Patterson, Air Force scientists said they were interested in the new biojet fuel because it performed as well as regular JP-8 jet fuel. But they were concerned with its ability to operate in extreme cold temperatures, and it tended to "gum up" after long periods in storage.

Wayne Seams, a UND chemical engineering professor working on the project, said they've been working to improve their product since then. Now, the biojet fuel is able to perform at 60 degrees below Celsius. The Air Force specification is 50 below.

Regular biodiesel fuels tend to gel at around 0 to 6 degrees below.

This fuel potentially costs less than petroleum-based aviation fuel, too.

The real question will be whether farms could keep up with the demand for biofuel feedstock along with the increased food needs of a world heading towards 9 billion people, especially if biofuels take on a leading role as a green car fuel, too. Even assuming that the aviation biofuel can be made from non-nutritive biomass (stalks, leaves and such), and various bio-hacks can make the plants grow faster, it's unlikely that we'll be able to cover all three industries. More likely is that automotive biofuels are transitional, while aviation will rely on biofuels for decades to come.

The bigger question is whether the current air travel paradigm will continue. High fuel prices aren't the only threat: shaky financial performance, fickle consumers, and the rising threat of pandemic could each send the air travel industry crashing. Conversely, alternative models of air travel, including next-generation airships, could make flight cleaner and more like a cruiseship than a sardine can.

(Via Urban Eco)


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» Biojet Business Plan Wins Competition from sustainablog
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Comments (21)


quote/The real question will be whether farms could keep up with the demand for biofuel feedstock along with the increased food needs of a world heading towards 9 billion people, especially if biofuels take on a leading role as a green car fuel, too./

second time today on this topic, might as well:

i posit that vegetarianism/veganism is worldchanging, especially if we're going to need our farmers to grow our transportation as well as our food. it takes upwards of 10 lbs of grain to make one pound of meat.

It would be cool to see some Lovins-style arithmetic on the savings from liberating more fields for human (vs. livestock) food relative to using surplus ag land for growing fuel and material. my understanding is that, unfortunately, economic development is leading to greater meat demand globally...

Note that kerosene is diesel. The biofuels being talked about are biodiesel. Same advantates & disadvantages apply.

So it's great to hear they've made a kind of biodiesel that is still liquid at -60C. This is massive overkill for most auto drivers, but might be handy for those in the arctic wilds of Canada.

Joseph Willemssen:

"a 5,000 mile flight -- roughly a round trip from LA to New York -- puts out a ton and a half of CO2 for every person on the plane."

I think that needs to be put in perspective. The net emissions of CO2 equivalents per person in the US is 46,550 lbs. The CO2 emissions on a 5,000 mile international flight are 2,681 pounds/person.

So, that 5,000 mile flight is the same as 5.8% of the average per capita CO2 equivalent emissions.

The fact of the matter is that only a very small segment of the population logs anywhere near that number of air miles per year. The vast majority of people, even in a wealthy country, probably don't fly even once in an average year.

Reference my recent comments about the potential for PRT-like technology to substitute for over-land air travel, and I think it's a much more promising approach than simply looking for fuel substitution or tweaks in air technology itself. It certainly would have a lot of other benefits beyond that, which are self-evident.

Joseph Willemssen:

Here's a very handy chart showing CO2 output for various fuels:




Thats why they are starting to design and test h2 powered jets.

Still far to spendy right now for main use the air force likes the idea because each galolon of jet fuel they use costs ALOT of transport... but h2 can be generated onsite.


When talking about restrictions on forms of transport it is worth keeping in mind that article 13 of universal declaration of human rights addresses freedom of movement.



I'm with sp0078's comment. IIRC, about 70% of agricultural land is used either for grazing animals or growing animal feedstock. If we could seriously cut back on our meat consumption to say 20% of agricultural land, then feeding everyone on the planet would be no problem, plus huge surpluses for biofuel. Worldchangers need to ask why this hasn't happened already. My take on it is that the rich outbid the poor and the rich like meat and don't like sharing. People are starving due to lack of demand; we need to redistrubute our wealth so that everyone can afford to eat. (I'm using 'demand' in the ecomics sense of the word).

Daniel Johnston:

It has to be kept in mind that CO2 released at high altitudes has TWICE the warming effect as when released on the ground. Which makes the whole industry equation even less credible. I like Joseph's PRT idea. People want the travel, not the flight.
Having said that, if the recent e-coli doctoring can genuinely create plants which grow 5 times as fast, the amount of nutrients available is going to make food produced with that technique next to valueless (witness organic versus conventional in that area) . However if it can reduce the land needed for the production of biofuels by five times, while temporarily sequestering more carbon, then we might have a viable situation.

I've seen hundreds of thousands of acres of farmland go to waste because the government is PAYING the farmers to NOT grow anything on them. I can't remember why, but I've seen it happen all over the country, and they're still doing it. There is no shortage of land, there isn't too much demand.

Besides that, farming is the worst place to get such a high-demand product. Farming, by definition, takes nutrients from the soil and sells them somewhere else. This means we're constantly degrading the land and building it back up to degrade it again and again. Plus it's limited to seasons, and just plain difficult to work with.

A better option would be to build verticle farms where crops are grown in nutrient liquids. Saves land for the ecosystem, can be fully automated, we can grow anything at anytime, and it's cheaper (no pesticides, guranteed full yield, etc). WC has talked about this before, but I don't have the link.

But Wintermane is right--H2 is the answer here, since there's a lot of it, and it can be "harvested" on-site. It's just as powerful and no more dangerous.

Actually, H2 may not be the answer at all: the exhaust you get from burning hydrogen is pure water vapor. That's fine on the ground, but at altitude, water vapor is orders of magnitude more powerful a greenhouse gas than CO2. The numbers aren't all settled -- in part because nobody has actually demonstrated a hydrogen jet plane -- but it looks quite possible that swapping hydrogen for kerosene wouldn't make a climate difference. At best, it would only be a very slight improvement, not worth the enormous amount of money required to replace every plane in the global fleet.

Shifting to a kerosene-engine-compatible biofuel -- which can, in principle, be carbon neutral -- makes a lot more sense.

fun data: i calculate per-mile fuel use per person for air travel is about equal to an efficient car with 4 people in it. a new york to san fran flight on an airbus A320 uses about 32 gallons of fuel per passenger - about 80mpg per person. a loaded bus is much better: 300-500mpg per person.

of course, the flight is much faster than a car so you do it much more often.

Jamais; I had no idea, and never would have guessed. Looks like I'll be doing some research on h-a chemistry, because that's quite bizarre - I wonder what else goes on up there. Thanks!

Joseph Willemssen:

I hadn't considered the angle you're mentioning, Jamais, so I looked around a little bit and found this:

"Emissions of water from a hydrogen-fueled airplane are 2.6 times greater than from a kerosene-fueled plane. The greenhouse effect on the atmosphere coming from steam at altitudes up to 10 km. is practically nil, but at higher altitudes the steam can produce a greenhouse effect. [Hart 1997] There are varying opinions as to how great this would be, but it must be taken into consideration that, while CO2 remains active in all layers of the atmosphere for over 100 years, water vapor will be in the stratosphere for only 6-12 months, and at lower altitudes, only three to four days. Airbus believes that the water droplets from a hydrogen airplane would be larger, fewer, and more transparent than those from a conventional airplane with jet fuel, and therefore contribute less to the greenhouse effect. Several studies will be made by Airbus to map the greenhouse effect of the water vapor emissions. If this seems to be a problem at high altitudes, restrictions on flying altitude can be put into effect to alleviate the problem."

Is that accurate? Are they missing something?

Honestly, I'm not sure what's missing in that, other than it not entirely matching up with claims I've seen elsewhere; I'll dig up what I can. I do see that it's from 1999, and our understanding of climate mechanisms is definitely better now than 6 or 7 years ago. Still, that's not enough to dismiss it out of hand (nor does the fact that it comes from an aircraft manufacturer's study).

The point that water vapor cycles out much faster than CO2 is spot-on, though, and may be a mitigating factor.

It may well be that hydrogen is a better fuel for aircraft, from a greenhouse perspective. That doesn't mitigate the cost issue, especially given that airliners tend to be very long-term investments (like 20-40 year). If H2 is better than I've read, what we'd likely see is biofuel used as a transition while H2 production and aircraft factories gear up for a very slow change-over.

I'm glad you put this up. I was wondering about hybrid technology and if that could be applied to airplanes?


Biodiesel is not the only alternative fuel for air travel. Scientist/engineer Max Shauck at the Baylor Institute of Air Sciences http://www.baylor.edu/bias/index.php?id=34701 has demonstrated the feasibility of using ethonol in aircraft engines. He and his wife were the first to fly a single-engine plane non-stop across the Atlantic the 80s. Through the efforts of Max's team, several planes commonly used in agriculture have been certified by the FAA to use ethanol. Work on certifying jet engines for ethanol fuel is underway.


Well you WILL see h2 used mostly by the military as its vastly cheaper then transporting other fuels.

It costs them 400 bucks a gallon to transport fuel into combat zones.

Later you will see h2 used IF bio runs into problems with scale and availablity AND hs costs come down.

But no matter what the cost of air travel will likely pentuple in 20 years. That will force alot of casual air travel to halt. Up until very recently they were only paying 50 or so cents a gallon for fuel.. its rising fast and bio is likely to always cost at least 2-3bucks a gallon.

Luis Enrique:

You don't have to worry about whether supplies of biofuel will "keep up" with demand. You are forgetting the price mechanism. If demand for biofuel rises and suppliers cannot keep up, prices will rise and choke off demand. If demand falls because of high prices, that will entail fewer emissions pumping flights and car journeys. Surely good news, for environmentalists.

My worry is that remaining forests get sacrified to grow biofuel feed stock.

Tom Volckhausen:

"You don't have to worry about whether supplies of biofuel will "keep up" with demand. You are forgetting the price mechanism. If demand for biofuel rises and suppliers cannot keep up, prices will rise and choke off demand. "
The problem here is that rich people purchasing air travel will be outbidding poor people purchasing food in competition for agricultural resources.
This is not hypothetical but already occurring with ethanol/sugar and biodiesel/oil, etc.


Oh I do have to worry.. after the tropics ruin thier forests to make biofuel it wont take long before the fields fail and the biofuel will run dry in many places.

Now with luck we will have algil and other forms to keep up the job BUT its not likely to fullfill all our needs. Thus h2 andothers will fill the rest.


There is another possible solution, but it won't happen anytime soon. Some research has been done on flying vehicles powered by a laser or microwave beam fired from the ground. Some forms involve vaporizing a tank of reaction mass, such as water, to produce thrust, or to operate a propellor. But NASA has also tested models propelled by nothing but the direct heating of compressed air in a ramjet or pulsejet. The elimination of the weight of fuel is perhaps the ultimate performance enhancement imaginable for aircraft. They would be faster and safer. By the time we could build the network of lasers, we better be producing electricity in a renewable fashion or flying will be the least of our problems.

Then again, there's the Swiss research into magnetic levitation trains running in tunnels with most of the air pumped out, theoretically making any speed possible. That would be the ultimate in energy conservation, because the train can use regenerative braking, putting electricity back into the "rail" as it is slowed. The problem is the energy cost of the actual tunneling and concreting.


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