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What is carbon-friendly?
Can this result be true? The guy claims that food production and refrigeration is so energy-expensive that it is more carbon-friendly to drive your car than to walk. Walking requires that you eat more to make up the lost energy, as you can lose only so much weight (what's the relevant margin here? Ten feet of walking? A lifetime of walking?).
It is also claimed that: "Paper bags cause more global warming than plastic." Here is the book, I've ordered it and will report in due time. In the meantime, here is Ezra's coverage.
From Chicagoboyz, here is a good post on whether tangerines from a distance can be more carbon-friendly than local fruit. Here is an earlier MR post on the same.
Posted by Tyler Cowen on August 5, 2007 at 09:12 PM in Science | Permalink
Comments
I can't believe this result. I anticipate your report on this.
Posted by: Samson at Aug 5, 2007 9:46:01 PM
Apparently, it's true if you eat beef and only beef.
mmmm. beeef.
Posted by: lardlad at Aug 5, 2007 9:50:52 PM
I'm skeptical. The calculation presumes that all the calories consumed by walking are replaced by beef (and only beef), which is a notoriously carbon-intensive food source. It is entirely possible, of course, to replace with other, less carbon-intensive foodstuffs. It is also unclear how the author estimates the carbon-intensity of beef production, e.g., whether he includes the transportation cost of getting the food from the farm to the consumer's fridge.
The author's point (which is obvious from reading the post on food at his own website) is not that we should drive more and walk less, but that we should reduce the carbon-intensity of the foods we consume. Again, I am skeptical, not as a matter of principle but because it seems far less important than many other steps we might take to reduce the overall level of greenhouse gas emissions. After all, in the US at least, agriculture is a relatively minor source of greenhouse gas emissions. The power industry, other industries, and transportation all produce between 2.5 and 5 times the emissions of agriculture (according to figures from the US EPA's Inventory of Greenhouse Gas Emissions and Sinks 1990-2005 (April 2007)). And the author provides no reason to believe that the costs of reducing emissions from agriculture would be cheaper than the costs of reducing emissions from the big emitters, especially electric power plants.
Posted by: Dan Cole at Aug 5, 2007 9:59:34 PM
Yeah, it's pretty well known that a vegetarian or vegan diet is much more energy-efficient than an omnivorous one.
Posted by: Nick Tarleton at Aug 5, 2007 10:04:53 PM
It generally takes 10x more energy each time you go up a level on the food chain. Herbivore meat is 10x more energy-intensive than the plants the meat ate while it was an animal. Plug that back-of-the-envelope number into the figures given in the story, and walking beats driving again, by a factor of 2.5 or so.
Posted by: James Grimmelmann at Aug 5, 2007 10:05:06 PM
And does organically grown food (beef or otherwise) use less energy?
Posted by: Nick Tarleton at Aug 5, 2007 10:10:08 PM
I like to say that a vegan taking the elevator is saving more energy than the meat-eater climbing the stairs. (I'm not sure if the numbers here are exact, but not all diets do the same thing to the environment, as noted here.)
Side note about elevators: They're great to take even if you are going up only three flights. By pushing the button it forces you to wait; and so it's a great opportunity to practice your patience. The longer it takes the more meditative you can be.
Posted by: Macneil at Aug 5, 2007 10:11:44 PM
I can see how plastic bags could be better than paper from a carbon standpoint (though, couldn't you also argue that increased demand for paper results in higher value for trees which leads to more trees being planted?), but I don't think the "drive, don't walk" argument makes much sense.
Most people aren't going to walk more than a mile to get somewhere anyway, so the "drive, don't walk" argument would only work in dense urban areas. But walking less than a mile doesn't burn a whole lot of calories, certainly not enough to require a big slab of beef! I am fortunate enough to live in Adams Morgan in DC, where I can and do walk everywhere (in fact, I don't own a car). To use a car, I would have to first purchase a car (stimulating demand in an industry that is quite energy intensive). Then, let's say I wanted to go get groceries. Is this guy saying that instead of walking the half mile to the Safeway, I should get in the car, drive over there, look for a parking spot, then walk probably one-tenth to one-quarter of mile from the nearest parking spot to the store?! Then walk back to the car? And from the car to my apartment, which could be quite a ways considering I never see a whole lot of open parking spaces on my street. Add in the physical stress (faster heart rate, etc.) of driving and trying to park around my neighborhood and I doubt you'd conserve any calories. And, if everyone started doing this (meaning, people without cars bought them and drove them more within the city), there would be fewer parking spots, which would require longer walks from parking spots to destinations.
Not only is the result likely not correct, it's simply not practical.
Posted by: dave at Aug 5, 2007 11:02:19 PM
I meant to say it's not practical to drive instead of walk even if it's true that driving is less energy intensive than walking (though I doubt it).
ALSO, if everyone became a couch potato, I imagine there'd be a noticeable health effect, which may have negative consequences in terms of energy consumption. (Though that could go the other way, too... For instance, if more people died sooner from things like heart disease, consumption may decline)
Posted by: dave at Aug 5, 2007 11:10:15 PM
Another reason for a global carbon tax. It makes being environmentally smug so much more straightforward. No need to rely on all these complicated estimates of what's really better. Just be cheap.
Posted by: Kevin at Aug 5, 2007 11:15:28 PM
I don't know about energy intensity, but I believe that the consumer cost of the extra food is probably higher than the cost of gasoline.
I calculated that I burn about 1000 calories cycling for 25 miles. The way I normally eat, that costs about the same as a gallon of gasoline. And biking is more energy efficient than walking.
The key, though, is that if people drive instead of walk they don't go "the same distance," they go much, much, much farther.
Posted by: ed at Aug 6, 2007 1:25:47 AM
I don't know about energy intensity, but I believe that the consumer cost of the extra food is probably higher than the cost of gasoline.
I calculated that I burn about 1000 calories cycling for 25 miles. The way I normally eat, that costs about the same as a gallon of gasoline. And biking is more energy efficient than walking.
The key, though, is that if people drive instead of walk they don't go "the same distance," they go much, much, much farther.
Posted by: ed at Aug 6, 2007 1:26:00 AM
Depending on how long you use them, paper bags are four times 'worse' for the environment than plastic bags. The best is to take a textile shopping bag that you use for several years, of course, and it seems to me that this is the nub of the problem. We are arguing like shoolkids in the playground about what is better and what is worse, while the solution is staring us in the face.
Agriculture is a relatively minor source of greenhouse gas emissions. But it is a huge user of water - the biggest you've got. It's not *just* about greenhouse gases, it's about living sustainably, which won't happen until your government gets it. Switching to biofuel won't do it; to supply biofuel for 50% (that's half) of the car miles in the USA would require all (that's 100%) of the arable land to be turned over to biofuel production. That might well go wome way towards solving the obesity problem ...
Meanwhile, carry on having these arguments. They don't get us as far as learning how to use less.
Posted by: Peter Warne at Aug 6, 2007 1:51:19 AM
It should also be noted that quite a few ppl have enough body fat so that the cost of walking more wouldn't cause them to eat more.
For that matter the health problems that come along with being overweight cost quite a bit of energy too.
Posted by: Factory at Aug 6, 2007 4:30:14 AM
The assumption here is that more exercise results in great food intake. My experience is that the food intake remains largely similar, but some just choose to burn the calories, instead of storing them in public places...
How much less food do you eat if you burn less calories? Are couch potatoes and car junkies more prone to skip a meal a day? That would make the real difference in this situation.
Posted by: sam at Aug 6, 2007 5:28:58 AM
Imagine if the report said "Driving to the gym uses less carbon than jogging the same distance"
Posted by: ths at Aug 6, 2007 5:53:54 AM
On top of the 'beef is inefficient as energy deliverer': I googled some calorie values for beef, and apparently 180 calories/100 grams, as used in the calculation, is very, very lean beef. Switching to fatter beef, like a steak with a bit of fat attached, or ground beef already raises the figure to 280/100 grams.
On top of that, why not use cycling as alternative to cars? Seems more realistic for 3 mile distances, and it is far more energy efficient. Cycling uses something like 25 calories per mile, if you don't drive at exercise speed.
So, just switching to cycling and eating only ground beef instead of only lean steak already closes the gap with a car.
Posted by: marius at Aug 6, 2007 6:09:12 AM
On top of the 'beef is inefficient as energy deliverer': I googled some calorie values for beef, and apparently 180 calories/100 grams, as used in the calculation, is very, very lean beef. Switching to fatter beef, like a steak with a bit of fat attached, or ground beef already raises the figure to 280/100 grams.
On top of that, why not use cycling as alternative to cars? Seems more realistic for 3 mile distances, and it is far more energy efficient. Cycling uses something like 25 calories per mile, if you don't drive at exercise speed.
So, just switching to cycling and eating only ground beef instead of only lean steak already closes the gap with a car.
Posted by: marius at Aug 6, 2007 6:09:20 AM
On top of the 'beef is inefficient as energy deliverer': I googled some calorie values for beef, and apparently 180 calories/100 grams, as used in the calculation, is very, very lean beef. Switching to fatter beef, like a steak with a bit of fat attached, or ground beef already raises the figure to 280/100 grams.
On top of that, why not use cycling as alternative to cars? Seems more realistic for 3 mile distances, and it is far more energy efficient. Cycling uses something like 25 calories per mile, if you don't drive at exercise speed.
So, just switching to cycling and eating only ground beef instead of only lean steak already closes the gap with a car.
Posted by: marius at Aug 6, 2007 6:09:27 AM
Is it really necessary to subordinate everything to the holy grail of a low-carbon life? I would think that your health matters too. Then I would walk more, drive less by car, and not worry too much about my carbon footprint. These environmentalists are really getting annoying.
Posted by: ivan at Aug 6, 2007 7:42:02 AM
Nick, I'm not an expert by any means but my intuition is that organically grown beef is less energy efficient, since it's less cost-efficient. But I could be totally wrong.
But all this discussion misses the point - environmentalism, like almost everything else in the world, is about tradeoffs. What's good for global warming may be bad for water quality - say if all those hybrid car batteries are improperly disposed and leak toxins into our groundwater. What's good for air quality may be bad for waste management, etc. I once met a businessman whose company cut down large swaths of rainforest in Malaysia/Indonesia for lumber, who argued that by capturing the carbon in the lumber, he was actually helping with global warming because young, replanted forests capture carbon from the atmosphere at a much faster rate than mature forests. This is true, but doesn't address the deforestation/species diversity arguments against cutting down rainforests, and it assumes that he's telling the truth about replanting trees (I didn't believe him, for what it's worth).
But global warming is only one problem - anyone who has been to China can argue that China has more pressing environmental issues than just reducing greenhouse gases. Smog and water quality are terrible. I'm sure they have an acid rain problem, too, with the amount of electricity they produce from coal. Not to mention the environmental devastation of the flooding from the Three Gorges Dam (which will release greenhouse gases from decaying vegetation for decades).
Posted by: Shane at Aug 6, 2007 8:17:19 AM
Oh and also - when I was in Malaysia it seemed that one of the highest priority environmental issues that the locals cared about was reducing one's detergent footprint, since much of it washes into the sea and ruins the coral reef (which the locals cared about because their tourist-dependent economy included lots of scuba/snorkeling shops). Granted, I was there for scuba, so my sample might be heavily biased, but still.
Posted by: Shane at Aug 6, 2007 8:22:27 AM
I first heard this idea from Michael Bluejay; he claims that walking can be more or less fuel-efficient than driving depending on the walker's diet, but cycling is essentially always more fuel-efficient.
What he doesn't factor in -- and I'm not sure how one would even do this! -- is that in a society where lots of people are walking or cycling, population is probably denser and distances traveled are shorter. (A thirty-mile driving commute is fairly common. A thirty-mile biking commute would be insane.)
Posted by: Isabel at Aug 6, 2007 10:39:58 AM
"Is it really necessary to subordinate everything to the holy grail of a low-carbon"
"But global warming is only one problem"
"These environmentalists are really getting annoying."
And nuclear war is just one among many kinds of security problems...duh!
Posted by: aaron_m at Aug 6, 2007 10:50:24 AM
I reported about a month ago that the carbon footprint of the average day's driving was about the same as that in the production of a couple of cheeseburgers, so I'm not surprised by this sort of result at all.
Posted by: David Tufte at Aug 6, 2007 10:53:26 AM
