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The environmental cost of flying
Minderbender, a loyal MM reader, asks:
How should we think about the environmental costs of commercial flying? It seems as though the average cost is high, but the marginal cost is quite low. When I fly across the country, it doesn't cause any extra flights, it just makes the one I'm on slightly heavier. Yes, the increased revenues might give the airline an incentive to increase the number of flights, but this effect seems very weak - much lower than the average cost of my flight (the consumption of fuel divided by the number of passengers). Maybe I'm just miscalculating?
I think about this every time I fly. A simple model of route expansion is that higher demand increases the number of total flights by some probability. For the system as a whole, the decisive flying unit has to come somewhere and there is no reason why, on average, it can't be you. In other words, at least in stochastic terms you can't escape the blame.
A second simple model of route expansion is that gates and other airport facilities are scarce and underpriced relative to demand. When demand goes up, supply is not very elastic and mostly they raise price rather than increasing output. Those who feel very guilty should prefer this second model.
The more they cut back on flights, as they have been doing, the more likely the first model is true. The second model is most likely true if you are flying into regulated foreign markets although I believe the Europeans are now opening up for U.S. carriers.
You might ask comparable questions about eating meat and killing cows. If you're worried about your net impact, eat animals from countries with very privileged, monopolized and highly regulated, supply-inelastic livestock sectors.
Posted by Tyler Cowen on June 18, 2008 at 06:57 AM in Economics | Permalink
Comments
I think we also miss that when we fly, we travel less miles. I looked at taking the train from Detroit to NYC once. The ticket cost more than flying, it was not direct, there were severl change overs, and I would have needed to take and extra day off of work.
Posted by: aaron at Jun 18, 2008 8:27:26 AM
I think we also miss that when we fly, we travel less miles.
Unless you make an out of the way connection with a hub or two.
The official DOT statistics on energy use have shown some pretty impressive gains for efficiency by domestic airlines recently, though to my understanding that is mostly from load factor improvements. The industry as a whole has really been filling planes close to full recently.
The Amtrak numbers presumably vary a lot on routes. In addition to load factors, I would assume that long-distance trains with sleeper cars and the like use more energy per passenger and per seat than short-distance trains that pack people in more.
Posted by: John Thacker at Jun 18, 2008 8:38:08 AM
Numbers for driving here. By train. And BTS numbers for energy consumption for travel modes
Driving to Manhattan: 614 miles (google maps) Flying: 501 miles (nwa.com)Passenger Car:
3,527 BTU/Passenger-Mile
Domestic Airliner:
3,297 BTU/Passenger-MileTotal Energy Consumption Passenger Car:
2165578 BTU
Total Energy Domestic Airliner:
1651797 BTUEnergy Savings by flying: 24%
Cost analysis--
Passanger Car: Fuel $135 + Parking $50 + Toll $30 + Time $304 (Median Personal Income/2080Hrs*20hrs travel time)=
$519Air: Ticket $180 + Gas $9 (to/from airport) Parking $24 + Cab/Bus $40 + Time $128(Median Personal Income/2080Hrs*8hrs travel time)=
$381Of course, this assumes a much lower income than for me personally, and for an individual travelling alone, I’d expect the BTU/passenger-mile to be a little higher for a passanger car (though not much, I doubt the average passengers in a car are much more than 1).
Posted by: aaron at Jun 18, 2008 8:39:47 AM
Also, if you're guilty you should at least arguably favor larger planes. One industry shift reversing itself under the higher fuel prices was a move towards more small regional jets.
Most people prefer more frequent service on smaller planes to less frequent service on larger planes. This holds in aggregate even if the former causes more delays; more flights with somewhat more delays still ends up getting more people to their destinations at more convenient times. (Particularly when connections are concerned; fewer flights per day significantly increases the chance of taking another half day or whole day of travel.) Regional jets are more fuel inefficient, though.
Posted by: John Thacker at Jun 18, 2008 8:42:38 AM
Aaron,
Don't forget to add in the BTU's used in driving to and from the the airport. Depending on how far it is, and how congested, that can add 150-200,000 BTU's or more.
Posted by: Bernard Yomtov at Jun 18, 2008 9:37:27 AM
Here are 3 easy steps:
1)Stop whining about increasingly expensive airfares.
2)Be a good homo economicus and respond to those higher fares by adjusting your future travel plans so that you fly less.
3)When you do fly, get on that flight guilt-free
Posted by: ramster at Jun 18, 2008 10:09:16 AM
I included the time, but ignored the added BTUs for drive to the airport. Adding on another 300,000BTU, the plane still comes in under driving.
I also didn't consider making the entire trip on a motorcycle...
Posted by: aaron at Jun 18, 2008 10:39:25 AM
I think the thousands of planes that are junked in the boneyard outside of Phoenix or in Mojave, CA (both wild places to visit if you love airplanes and have the chance) arall a testament to the validity of the first model. Capacity cuts this time around are going to make many airliner types an endangered species.
As an add-on to the comment about more planes through RJs, 9/11 forced many airlines to do long-distance flying that was previously done by large aircraft with smaller aircraft - the idea being that you have more flexibility with the number of seats you can put on a route and you can keep your planes full as market demand fluctuates. Of course with Jet A at $7 or $8 a gallon, the airlines are now being forced to reconsider this and start doing long-distance domestic flights with 767s, 777s, etc. In this way, persistent high prices should get some planes out of the sky and cut average emissions.
Posted by: Gabe at Jun 18, 2008 10:56:19 AM
You might ask comparable questions about eating meat and killing cows. If you're worried about your net impact, eat animals from countries with very privileged, monopolized and highly regulated, supply-inelastic livestock sectors.
But won't this only work if there are enough consumers that are not able to switch their consumption away from these same providers?
-Kevin
Posted by: Kevin Postlewaite at Jun 18, 2008 12:34:00 PM
I think Gabe is on the right track regarding the real energy cost factor here. Airlines are not completely stupid and probably have better energy-usage models than we can imagine. The oddball factor here is that if you want to be a complete pedant about travel efficiency you also need to consider the energy cost in creating the vehicle: if airlines are shifting their usage patterns to newer and more efficient planes are they using up more energy for creating the planes (which someone out there is writing off as a capex) to save energy that is used to fly the planes (which is an opex.)
Posted by: evgen at Jun 18, 2008 12:35:11 PM
I still fail to see how using less energy is a moral good, in and of itself. I find the environmental ethic to be profoundly anti-human, anti-progress, and immoral. It's a betrayal of the Enlightenment.
Posted by: jim at Jun 18, 2008 1:39:20 PM
I assume, that to a first approximation, the cash cost of anything is directlyu proportional to the energy used to make it. The producer of any good or service I purchase has to pay for all their direct energy costs, and still make a profit. All the non-energy inputs they use also come from suppliers who must pay for their energy use. Including labor - wages have to be high enough to allow workers to purchase food for themselves, fuel for their cars, heat or air-condition their homes, and buy other stuff. All that requires energy, which they pay for.
I then pick the cheapest way, based on my time requirements, and don't feel any guilt.
Posted by: Anthony at Jun 18, 2008 4:03:54 PM
Interesting that you (TC) brought up vegetarianism in the outro. As I was reading through your response, the same analogy immediately occurred to me. Most likely because it's the most common case I deal with of people arguing about marginal impact on a discrete process (in this case, it manifests as "that cow was going to be butchered whether you buy the meatballs or not"). There's some quirk of human psychology wherein people tend not to believe that the large aggregation of small behaviors creates a highly leveraged output that can dramatically change with small percentage changes in behavior.
Posted by: sidereal at Jun 18, 2008 7:55:05 PM
John Thacker: "Most people prefer more frequent service on smaller planes to less frequent service on larger planes."
I agree that some of the regional jets were purchased to increase frequencies in a few markets. But the biggest use of RJ's was to open up low demand direct markets that had previously been served through hub and spoke networks. Markets such as Knoxville-Dallas or Baton Rouge-Chicago did not enough demand for a 130 passenger jet. The distances were too large for slower turbo-props. RJ's changed the economics for such markets.
High jet fuel prices will eliminate direct jet service for many medium-sized cities. And, as you pointed out, frequencies on some previous RJ markets will be cut.
Posted by: John Dewey at Jun 19, 2008 3:47:49 PM
"if airlines are shifting their usage patterns to newer and more efficient planes are they using up more energy for creating the planes"
Some airlines are continuing to honor contracts to buy new planes. I don't think anyone other than Southwest has the cash flow right now to initiate previously unplanned aircraft purchases. Last I read, even Southwest is considering deferring purchases of some NextGen 737's. The rest of the carriers are fighting for survival, grounding aircraft just to slow the cash bleed. At least for a while, the energy expended to build new jet airliners should be minimized.
Posted by: John Dewey at Jun 19, 2008 3:59:09 PM
aaron: You are not going to get free food or a free place to stay on that 20 hour drive. Those are significant costs too.
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Posted by: machile at May 13, 2009 4:47:05 AM
Re. [Driving to Manhattan: 614 miles (google maps) Flying: 501 miles (nwa.com)], Careful: I think the nominal air mileage is based on "as the crow flies", but AFAIR air routes are not necessarily so straight. They may have to avoid flying over a congested airport en route (Chicago or London), a secure area (Washington DC), a restricted country (North Korea) and also tend to fly along corridors and/or between radio beacons. But since the takeoff (& landing?) uses most fuel, maybe this is not too significant.
Posted by: ggwi at Jun 22, 2009 7:52:57 PM
I like the way you broke this down in terms of statistics. Personally, I am of the mindset that if I only fly once in a while, I really do not have an impact on this equation.
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