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Save the planet - be lazy

Angus McPresley

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I will be participating in Australia's Ride To Work day next week, where they're encouraging people to bike to work instead of drive. It has me wondering, though.

There are implications I've seen that biking (or walking) is completely environmentally friendly, causing no carbon emissions or other greenhouse gases. But the physicist dilettante in me sees something wrong in that.

If we bicycle (or walk) we're burning calories that we otherwise wouldn't. This energy must come from somewhere, and like everything else, it seems that it should be traceable back to some quantity of manufacturing or processing. Bottom line -- I suspect biking or walking is better than driving (and has the side benefit of exercise), but is not completely without ecological impact. It would of course depend on what you eat, but I'd love to see some numbers based on the average diet.

Has anyone ever seen a study which evaluates various methods of transport this way?
 
Usually its calories that a person is going to eat anyways. For calculations like this, those of us who exercise alot and will need extra food to be able to go to work are very minimal.

So there should be no extra calories but less obesity if everything "works out". :D
 
Well, now, let's see. If you weigh 200 lbs (~100kg) and you engage in "general bicycling" (as opposed to "racing" or whatnot), then you'll burn 381 calories in half an hour. This is about 1,595,170.8J, which sounds like a lot but really isn't.

Let's suppose you go about 10mph (fairly brisk, but not flat out) which puts work about 5mi away (that's 16kph, and about 8km). A car with pretty good mileage is going to get about 20mpg in the stop-n-go on the way to work, so you'll burn about 1/4 gallon of gas (14.5km/l, and about 0.5l). A gallon of gas contains about 131,760,000J, so you'll burn about 32,940,000J. So you'd burn 20 times as much energy in gasoline as you will on your bike. That makes sense; the car weighs a lot more than you do.

That's about 1 1/2 Snickers candy bars. :D
 
Yes but how many calories of fuel does it take to grow and process each snickers bar? I believe that bikes cost about 60 mpg.

Or, using the Carbon offset kind of thumbnail, where in the retail values are compared, based on same retail = same impact, the snickers bar cost $1 each, so $1.50, vs gasoline at $.75, so the car is cheaper.

But then, if you grown all of your own food by hand....
 
How much extra fuel is burned around a major city each day by motorists forced to drive in low gear by someone on a bike?

Not to mention the wear on tempers.
 
How much extra fuel is burned around a major city each day by motorists forced to drive in low gear by excessive numbers of cars in their way?

Not to mention the wear on tempers.
 
How many miles are on the car and the bike? You have to amortize the cost of making each one, and add that to the equation too. And don't forget the total energy cost of extracting, refining, and transporting the gas.
 
Angus McPresley said:
I will be participating in Australia's Ride To Work day next week, where they're encouraging people to bike to work instead of drive. It has me wondering, though.

There are implications I've seen that biking (or walking) is completely environmentally friendly, causing no carbon emissions or other greenhouse gases. But the physicist dilettante in me sees something wrong in that.

If we bicycle (or walk) we're burning calories that we otherwise wouldn't. This energy must come from somewhere, and like everything else, it seems that it should be traceable back to some quantity of manufacturing or processing. Bottom line -- I suspect biking or walking is better than driving (and has the side benefit of exercise), but is not completely without ecological impact. It would of course depend on what you eat, but I'd love to see some numbers based on the average diet.

Has anyone ever seen a study which evaluates various methods of transport this way?
Click to expand...
Actually, I did see a study of this. I'll try to dig it up for you, but I remember the conclusions. It makes a big difference where you live. If you live in a developed western country, riding a bike around is actually worse because your food tends to get trucked in over large distances in refrigerated trucks. Nor is it helpful to eat local if greenhouses are involved.

And there's another issue. If you ride a bike around, you might be healthier, which will only keep you living and eating longer, which will add to your carbon footprint.

I'm not advocating that you stop using your bike. I think the way we eat is what has to change.
 
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