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Greening Air Travel
Alex Steffen, 30 Aug 07
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Air travel seems to be one of the few unsustainable practices for which there is no good fix or substitute. Because of their inefficiency and the high altitudes at which they fly, jet engines are particularly potent greenhouse gas emitters. What's more, there don't really seem to be any super-cool engine technologies waiting in the wings: there's no hybrid-electric car waiting to replace this SUV.

That doesn't mean that a whole bunch of people aren't out there looking for some interim solutions. A whole host of small steps have been proposed: using electric vehicles to taxi; flying directly; using shorter and steeper approaches; shutting down engines during delays; reducing the number of first- and business-class seats;

They probably all have some merit, but they are comparatively minor fixes. Big fixes still await discovery, and finding them has been made more urgent by both the increasingly bad news about climate change, and the large and growing protest movement best symbolized by the Heathrow Climate Camp earlier this month:

For the hundreds of climate-change activists who've camped out by Heathrow Airport...there is just one way to reduce aircrafts' carbon footprint: stop flying. "Aviation is a luxury we can live without," says a protester named Merrick. Air travel, he says, is booming, multiplying greenhouse gases just as the climate-change imperative starts to bite. "It has to be scaled right back."

For obvious reasons, the aviation industry would like to find another solution. For perhaps less obvious reasons, I'd like them to succeed: Cheap travel is an essential aspect of growing a global culture of planetary responsibility. Sending large numbers of young people to far-off places (without rifles in their hands) is one of the best hopes we have for developing a truly global culture. At very least, let me say that my own such travels were absolutely fundamental in making me a person who cares about humanity and the planet as whole.

So, what do we do?

Boeing has launched the 787, which conserves significant fuel (using around one-fifth less) compared to its predecessors. Some sources say that other airplane improvements already on the drawing boards might combine with operational efficiencies to slash another half of the greenhouse gas emissions of the most up-to-date planes within the next three decades.

Unfortunately, the old, jet-fuel-guzzling planes may remain in use for decades -- and the number of people flying is expected to grow to at least four times (some estimate six times) in the same time period. Boeing itself estimates the size of the global airplane fleet will double by 2026.

Some positive impact could be made immediately by including airplane emissions in carbon pricing and regulation schemes (international agreements currently exclude them). That would create financial incentives for change. A modest interdisciplinary effort has been launched to encourage research into greener flying. The chief executive of the International Air Transport Association, Giovanni Bisignani, has called for zero emissions flights...by 2050.

Boeing has partnered with the Brazilian biofuels firm Tecbio and is hot after an algal-based jet biofuel:

"You would have to plant an area the size of Florida with soy beans to provide a 15 percent blend of jet fuel" for the whole U.S. aircraft fleet, said Dave Daggett, who heads energy and emissions research at Boeing Commercial Airplanes' product development unit. "Clearly that's not going to be appropriate."
...It would take a lot of land to produce enough crops like soybeans to propel fuel-hungry jets. The increasing use of crops like corn and soybean to produce ethanol and biodiesel is already stirring a controversy of its own. Some argue these biofuels are creating a negative impact on the environment and on food prices.
The solution could lie in the algae, experts say. These slimy aquatic creatures not only absorb great quantities of carbon dioxide during their lifetime, but they are also the source of energy-rich oil that can be turned into fuel. Lurking in the depths of their ponds, they take a lot less space than horizontal conventional above-ground crops — and they can live in brackish water. A huge algae bio-reactor — a series of chambers or ponds outfitted to boost growth — could supply more fuel in less space than other plants. "Instead of needing all of Florida, you could provide the whole world's fleet with biojet fuel if you had a bio-reactor the size of Maryland," Daggett said.

The obvious problem is that while slime-fuels are still a long way off, the problems of global warming are already here. (And even if a Maryland-sized collection of biotech ponds was certain to be a good idea -- and there are real reasons for skepticism -- there are even more reasons for skepticism about crop-based biofuels, which substitute an unsustainable supply of biofuels created through factory farming and soil mining for an unsustainable supply of fossil fuels... but that's another thread).

Nonetheless, it's encouraging to see at least some efforts at thinking outside the cockpit.

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Comments

I can only see liquid hydrogen used in blended wing body aircraft as a lasting, sustainable solution to the aviation problem. Clearly there are massive technical hurdles to overcome, especially the energy source for the hydrogen, but we're talking at least 5 decades away anyway.

In the meantime, and in addition to the proposals above, rapid development of airships and WIGs would help reduce intercontinental airfreight's environmental impact (as well as the impact of globetrotters with some time on their hands). For long range intracontinental travel we can greatly improve our train services, although this doesn't come cheaply.


Posted by: Scatter on 30 Aug 07

I'm very excited about appropriate biofuels for aviation, and the FAA has commissioned an alternative fuels program (CAAFI) to study such things. Biofuels are the logical and easiest next step for aviation, as gas turbines will usually digest a variety of carbon-based fuels.


Posted by: c! on 30 Aug 07


What's more, there don't really seem to be any super-cool engine technologies waiting in the wings: there's no hybrid-electric car waiting to replace this SUV.

The only difficult problem with substitution is for flights that must go over water for long distances -- like to Hawaii. The vast majority of flights are over land, or could be made over land, so it can be substituted for with high-speed surface technologies like high speed trains (including maglev) as well as near-horizon technologies like evacuated tube personal transit.

Since those forms of travel use electricity for propulsion, it can easily be made carbon-neutral.

Right now, energy utilization rates per functional passenger-mile (energy per person per unit of distance as the crow flies) for commercial aviation far exceed those of cars and SUVs, and relative to poorly utilized modes like long-distance trains in the US, are far more efficient as well.

Forcing factors for aviation are also indeterminate at this point, as scientific consensus hasn't come close to maturing on it. There's still much to be understood about the dynamics.


Posted by: tt on 30 Aug 07

FYI - the tag after "It has to be scaled right back" needs to be changed to a closing italics tag.


Posted by: tt on 30 Aug 07

I am very interested to see what happens with bio-fuels. Sure, right now the use of land and ROI is far from sustainable, but the technology is still extremely young. There are a lot of companies betting very big on this technology, so the funding should be there for advancement.

Another interesting aspect of bio-fuels is the geographical energy shift it could entail. If successful, this technology has the potential to create an interesting shift of power from traditional energy producing states (the Middle East), to the imperialized agriculture states of Central America, the Caribbean, South America, and Africa.

It's a long way off, and certainly not a sure thing, but could be interesting...


Posted by: Rob Meyer on 30 Aug 07

Don't forget the vacuum tube train. Almost no limit on speed, very high efficiency, no vapor trail. There are plenty of studies of its feasability, and it works. The tube can be under or over ground, and under water.


Posted by: wimbi on 30 Aug 07

I have to admit, of all the greening lifestyle changes I've considered, giving up flight is the hardest to imagine. I bike to work, live in a small climate uncontrolled cooperative house, buy wind power, and subscribe to a CSA farm, but I can't imagine giving up overseas travel. I'd be curious what proportion of flight is for cultural exchange (which I value, and which is hard to do remotely) vs. face-to-face business exchange (which I think will ultimately be done almost exclusively via telepresence of some kind, for economic reasons).

Interestingly, if you take the fuel capacity, passenger capacity, and range of a Boeing 747-400, and optimistically assume no fuel waste, and always full planes, you get about 60 (person*miles)/gallon of fuel... which is better fuel economy than most single-person commuters see these days. The problem of course, is that it only takes one round-trip from LA to India to do an entire year's worth of driving...


Posted by: Zane Selvans on 30 Aug 07

I spent all of my 20's oversees, and I love travel. That was an important and formative for me that added much to my understanding of the world.

I agree with the benifits of "sending large numbers of young people to far-off places (without rifles in their hands)".

Some of my best experiences came from long land trips, taking the trans-Siberian (in the mid 90's, maybe still, the cheepest way to get from Europe to Asia), coaches and trains from India to Egypt, coaches and hitch-hiking back and forth across Europe.

Already, for trips not crossing seas, plenty of choices exist for those who have time, want to save money, and see something on the way.

From my home in Canada I needed to fly to get to the places I was interested in, but had the airlines not been able to externalize so much of their costs, trans-Atlantic liners may have added to my experiences.

We don't need to get rid of airplanes all together, but there needs to be far far fewer.


Posted by: keith bassingthwaighte on 30 Aug 07

I spent all of my 20's oversees, and I love travel. That was an important and formative for me that added much to my understanding of the world.

I agree with the benifits of "sending large numbers of young people to far-off places (without rifles in their hands)".

Some of my best experiences came from long land trips, taking the trans-Siberian (in the mid 90's, maybe still, the cheepest way to get from Europe to Asia), coaches and trains from India to Egypt, coaches and hitch-hiking back and forth across Europe.

Already, for trips not crossing seas, plenty of choices exist for those who have time, want to save money, and see something on the way.

From my home in Canada I needed to fly to get to the places I was interested in, but had the airlines not been able to externalize so much of their costs, trans-Atlantic liners may have added to my experiences.

We don't need to get rid of airplanes all together, but there needs to be far far fewer.


Posted by: keith bassingthwaighte on 30 Aug 07

As noted here about a year ago, contrail formation is a significant factor in the environmental impact of air travel.

Have any studies been done on whether contrail scattering properties can be altered so that they become solar reflectors rather than blankets?


Posted by: Tony Fisk on 30 Aug 07

If anyone's after a *very* quick blast through the non-CO2 aspects of aviation then this presentation skims through the main issues quite neatly:

http://snipurl.com/nonco2in5minutes


Posted by: Scatter on 31 Aug 07

Longer distance flights are a real problem, and the kind the 787 can help with. But, there are more options available when looking at the shorter distance flights. For the US, Argonne National Laboratory put together a proposal that would have replaced many of the shorter, commuter type, flights between major traffic hubs with maglev trains. To cut the costs of laying those tracks, the proposal included building them along existing US interstates. This proposal was done as much as 10 years ago, and included plans to have the airlines partner with the trains, and the trains run from airport to airport.

Also, since business travel is a major source of travel, if businesses could be encouraged to use more web-based meeting systems, there would be less need to fly all over the place.

There are options out there, it is just a matter of getting the public, and businesses, to agree to them.


Posted by: Larry on 31 Aug 07

Ok this article is not being helpful, first of all, modern airplanes are just as efficient a form of transportation as a prius per passanger mile, would you rather see 200 people flying, or driving their SUV's accross the country. Planes are by FAR the better option. Second you can't just stop aviation, it is a HUGE part of our economy, and while I would like to see global warming curbed, and a sustainable lifestyle, you can't just crash the economy, because if the economy is gone, nobody has any money to spend on the environment, and from there we drive older cars, stop regulating, and pollution gets even worse.


Posted by: Brad Godfrey on 31 Aug 07

you can't just crash the economy

A gradual change in the fuel mix and a gradual move towards viable substitutes is going to crash the economy?

because if the economy is gone

The entire economy is going to disappear? How?


Posted by: tt on 31 Aug 07

How is it not being helpful? It acknowledges that aviation isn't going to disappear and discusses how the impact can be lessened. I call that pretty helpful.

Yes aviation has brought some benefits, and if you're simply talking about CO2 emissions, modern designs are comparable with cleaner cars on a per km basis. But long haul flights are far easier and cheaper than long car trips so you can knock out the same CO2 in a single flight as you do in a whole year of driving for a fraction of the cost. This is where the danger lies. We're becoming way too accustomed to cheap aviation.


Posted by: Scatter on 2 Sep 07

Also putting a second person in a car and you halve the car's emissions. Put 4 people in the car and you kick aircraft even further into touch.


Posted by: Scatter on 2 Sep 07

Also putting a second person in a car and you halve the car's emissions. Put 4 people in the car and you kick aircraft even further into touch.

All things being equal, in the US, it's more CO2-friendly (per person) for one passenger flying compared to even two passengers driving.


Posted by: tt on 3 Sep 07

What about converting the nations sewage treatment plants to grow the alge?


Posted by: Mike Felicio on 6 Sep 07



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