Do Bicycles Actually Have a Lower CO2 'Footprint' Than Cars? (Updated)

UPDATE: As mentioned in the original article, the figures I used and the math may not be correct and I asked commenters to offer "corrections," as some have. I put corrections in quotation marks because the correctors can't quite agree how inflated my figures are.

One says -- based on Yahoo Answers, no doubt a highly credible scientific source -- that my figure was 15 times too high. Another says that I was 27 times too high.

When the "correct" figures have a 200% range, I'm not so sure that the corrections are reliable. In any case, a human on a bicycle puts out a non-trivial amount of CO2 that may in fact be on the same order of magnitude as an internal combustion engine.


Transportation Secretary Ray LaHood wants us to ride bikes to work instead of our cars.

One of the reasons he gives is environmental -- what could be greener than riding a bike? Walking perhaps, and actually LaHood wants us to wear out the shoe leather too, but for most people walking to work isn't an option. Riding a bicycle, which can easily hit 20 mph or more, is a viable alternative to driving for many folks.

Not to poke fun, just being observant -- LaHood's physique is not that of an endurance enthusiast. I don't think Ray follows his own advice.

Unlike Secretary LaHood, I know something about bicycles. I've been a serious recreational cyclist for about 16 years and typically ride 2,000 to 4,000 miles a year, using my bike for both transportation and pleasure. When I worked for DuPont, I commuted by bicycle seven months out of the year, about 20 miles a day including the training loop I did on the way home. I've been a staunch advocate for alternative transportation, and I literally have the scars (and a stainless steel plate) to prove it.

But while I'd love to see more bike lanes (and fewer rotaries) and some serious enforcement to make drivers aware of sharing the road, from an environmental standpoint bikes are no panacea.

This may be a surprise to the folks at the EPA, but people produce carbon dioxide. We breathe in air, make use of the oxygen, and exhale carbon dioxide. Breathe in, breathe out. CO2 output at rest is not significant, but at aerobic distances and heart rates, that CO2 expelled becomes a non-trivial amount when compared to an internal combustion engine.

One of LaHood's “recommended actions” to encourage the use of bicycles for transportation is to collect data on biking trips -- though he does not suggest calculating the carbon emissions of your biking vs. a car trip.

This is all quick and dirty, and if my figures are wrong, please provide me with more accurate data or correct my math.