Sheesh. Wouldn't you know it, the "walking is bad for the planet" meme has reared its head yet again, this time in a British newspaper:
Food production is now so energy-intensive that more carbon is emitted providing a person with enough calories to walk ... than a car would emit over the same distance. The climate could benefit if people avoided exercise, ate less and became couch potatoes.
This made its way to the top of Digg over the weekend, and it's little wonder. It's got all the characteristics of a "sticky idea": it's simple, it's memorable, it seems credible, and most of all, it's unexpected -- which makes it perfect for passing around at the water cooler.
Yet it's actually nothing new. Versions of this idea have been circulating since at least the 1980s. I blogged about a similar claim a year ago. Moreover, as I found out when I ran the numbers, there's a good reason this claim is so counterintuitive: it's false!
I won't rehash my year-old calculations here. (Lucky you.) But unless I'm crazy or just badly mistaken, the propagators of the walking-is-worse-than-driving meme are probably skipping a few steps in their math.
First, driving emits more global warming pollution than most people allow for. Burning a gallon of gasoline -- the only thing that some people count when considering the climate impacts of cars -- releases a little under 20 pounds of CO2 per gallon. But refining and transporting petroleum releases an additional 4 to 5 pounds per gallon. Plus, CO2 is emitted in car manufacturing and repair; in building and maintaining roads and parking spaces; and even running car insurance offices. You also have to add in climate-warming NOx emissions from vehicle exhaust. All of those extras add up. (To be fair, the same is true for agriculture. There's a lot of methane and NOx released from cows and rice fields and fertilizers, which might not get captured in an energy analysis.)
Second, walking consumes fewer calories than most exercise hounds think. The right measure isn't how many calories you burn by walking; it's how many you burn walking, minus how many you burn just loafing around. Without that correction, you're likely to overestimate the calorie demands of hoofing it -- and thus underestimate the "miles per gallon" you get from shoe leather.
And third, adding a short walk to your daily routine doesn't necessarily increase your consumption of food, or of food-system energy. Sadly, most of us already eat more than we need, so upping our exercise may just keep us a bit slimmer, rather than encouraging us to eat more. Even if we do eat a bit extra, some of it will likely represent a reduction in food waste (Americans waste something like 1,200 food calories per day!). Plus, things like refrigerators and dishwashers don't consume any more energy if we eat a bite or two of extra food each day. All in all, powering a short walk may not raise food system energy all that much, above and beyond what we use in a typical day.
When I ran the numbers a year ago, I only looked at the first two points above ... and I still found that walking gets more miles per gallon than any car on the market. (The third point is just, er, gravy.) Plus, obviously enough, your personal mileage will vary, depending on what you choose to eat. A vegan locavore pedestrian might be even more fuel efficient than an intercity bus. (There's a sentence you won't read every day.)
Still, there's an important truth at the heart of the walking-is-bad meme: it really does take a lot of energy to put food on the table. But it's not just agriculture itself. According to a University of Michigan study, only about a fifth of total food energy -- or about 2 percent of total energy consumption in the U.S. -- is used for fertilizer, tractor fuel, and other farm inputs. Even "food miles" aren't such a huge deal, at least on average. Perhaps a tenth of food energy -- one percent of the U.S. total for all sectors -- is for long-distance food transport. Most of the rest of the energy in the food system is used for home refrigeration and cooking, food-industry processing and packaging, running restaurants and supermarkets, and driving to the store.
Oh right, driving to the store. That raises a completely separate question. If everyone drives everywhere -- if, "for the good of the planet," every trip requires a car -- then stores have to be surrounded by parking; local commercial districts give way to distant malls; downtowns cede space to suburbs. In that kind of world, where the car is the organizing principle of our lives, we all have to travel much farther to go about our daily business. And that's where the real -- and downright dangerous -- energy inefficiency comes in.
So if you think that walking a mile a day is bad for the planet, think hard about the alternative. It's probably worse.
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Comments
View as Flat
spaceshaper Posted 9:17 am
10 Aug 2007
Using the gasoline energy equivalent of food per corn ethanol as a marker that translates into about 138 mpg and 280 mpg respectively.
The true meaning of life is to plant trees, under whose shade you do not expect to sit.
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thand Posted 9:55 am
10 Aug 2007
my understanding of NOx is that it contributes to smog, breaks down very quickly in sunlight and is not a greenhouse gas.
I wasn't to sure about this so i googled. resulting in:
http://www.jamstec.go.jp/frcgc/eng/akimoto/010502/
limiting NOx emissions without simultaneously limiting CO emissions has a warming impact.
If CO and NOx are both reduced their is a climate benefit
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Delay And Deny Posted 2:19 pm
10 Aug 2007
Forget energy usage.
Walking is more important than driving.
At the very least, the use of our bodies helps the brain, both sides, unite, and makes us calm, focused, intelligent.
We need to walk.
It's better than biking.
And driving is anathema.
Sometimes I think that cars and houses, are really just coffins (borrowed from "The Office"). We get to be 18, we drive, we buy a house. And we die.
Who knows...maybe it's meant to be that way. But cars, and houses, should not pollute The Children!
We need to get back to the idea that world is not a plaything for Adults -- but that the Adults are there to protect, and serve, the next gen...
John Bailo
Supratext:
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Biodiversivist Posted 1:42 am
11 Aug 2007
I'm sure he does not advocate that we drive instead of walk. He is trying to sell his book by promoting controversy. He got you to write this article, which got me and hundreds of others to read the article that mentioned his book.
Of course, he does this under the auspice of illustrating the carbon intensity of modern food production. Never mind that his claim will be used by SUV drivers and global warming denialists to make fun of environmentalists in general. A small price to pay to sell a book.
He is using this meme to promote another meme, the purported low energy intensity of a 100 mile diet, which as you point out:
"...about 2 percent of total energy consumption in the U.S. -- is used for fertilizer, tractor fuel, and other farm inputs. Even "food miles" aren't such a huge deal, at least on average. Perhaps a tenth of food energy -- one percent of the U.S. total for all sectors -- is for long-distance food transport. Most of the rest of the energy in the food system is used for home refrigeration and cooking, food-industry processing and packaging, running restaurants and supermarkets, and driving to the store."
Apparently, reducing food transportation energy on average is not a big ticket item and would also be difficult to implement. The idea is to buy time to transition to a world without cheap oil by finding ways to make it last longer (use it up slower).
Promoting the 100 mile diet for its aesthetic values makes sense to me. It will help fund local small farmers with a niche market that may grow into a major market. But propogating bullshit by not bothering to do a reality check on every urban legend that happens to support one's eco-fantasies (energy intensity) just leaves environmentalists open to attack by detractors and casts a bad light on environmentalists in general.
The bottom line is that we owe our very existence to cheap fossil energy. We eat oil. Our population could never have swelled to what it is today without that oil and is unlikely to stay this swollen without it unless we come up with better answers than reducing our 1% food transport energy use down to 0.9% by restructuring our entire agriculture system--assuming that a 100 mile diet would not actually increase net energy use.
The world is heading for a giant population crash if we have not found envrionmentally benign (not agrofuels) solutions when we run out of cheap oil.
In the end, it all comes down to biodiversity. Poison Darts--Protecting the biodiversity of our world
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GonzoDon Posted 5:37 am
11 Aug 2007
Please.
Aside from the energy calculus, which clearly points to the energy-efficiency of walkable neighborhoods, it would be kinda nice to see more people out walking for other, um, 'trivial' reasons, such as:
People would be healthier;
People would be happier;
People would begin to SEE more of their local built environment, and begin to CARE more about whether it is attractive or butt-ugly;
People would actually begin to interact with more of their neighbors, either on the sidewalk or at corner cafes and public spaces;
Just a little bit more of our urban space would be freed up for something besides parking lots, widened avenues, and big-box stores.
Sound too good to be true? Actually, it sounds a bit like many places I have visited (Rome, Parma, Cinque Terre, Paris, Pau, Barcelona, Orange, Quebec City, San Francisco, just to name a few. And, oh yeah: Disneyland).
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nedruod Posted 5:53 pm
11 Aug 2007
Everything has it's limits. Walking is a good way to burn off excess calories, but if we setup power plants powered by human walking I think everyone would agree that would be inefficient and just plain dumb (even if they used bikes).
What might not be so stupid is using the energy from people exercising an hour a day to stay in shape.
Another factor is if everyone spent 3 hours a day walking to work and back, productivity would go down and we'd have a harder time creating more efficient systems. But wait! Many people spend 3 hours a day driving to work and back. Most walkers/bikers spend less time.
In terms of productivity, public transportation is near the top. 10 minute walk/bike ride commutes can compete, but I can read on the bus even if it's 20 or 30 minutes.
It's an odd vision, but I have one idea that maximizes all those concerns. First, get an automated personal transportation system. Second put a bike in each "pod". Then you can read, exercise, generate power and get to work all at once.
Alas, it's a doomed idea because the cyclists will hate it because it won't give the exhilaration of biking, the drivers will be afraid they'll have to bike, and the environmental purists will dislike it because it doesn't require enough personal sacrifice.
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Biodiversivist Posted 12:31 am
12 Aug 2007
Consensus among homo sapiens is lost the instant a second person enters a room.
In the end, it all comes down to biodiversity. Poison Darts--Protecting the biodiversity of our world
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amazingdrx Posted 2:15 am
12 Aug 2007
The next time you see a person who is obviously helping the planet in this way. Sincerely thanks them. But don't tell them why you are thanking them. Shhhhhh...
http://amazngdrx.blogharbor.com/blog
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