[sustran] Are bicycles good for the environment?

[Guevarra, Joselito Lomada]

Got this from my mountaineering org where we all love to run and cycle
to keep fit...interesting read. Cheers!

Jojo

_________________________

Everything good for you is bad for the environment


Tags: Bicycling <http://technorati.com/tag/Bicycling> , Longevity
<http://technorati.com/tag/Longevity> , Carbon emissions
<http://technorati.com/tag/Carbon%20emissions> , Global warming
<http://technorati.com/tag/Global%20warming> , Population
<http://technorati.com/tag/Population> , Public health
<http://technorati.com/tag/Public%20health> , Transportation
<http://technorati.com/tag/Transportation> 

In a working paper entitled "The Environmental Paradox of Bicycling
<http://opim.wharton.upenn.edu/%7Eulrich/documents/ulrich-cycling-enviro
-jul06.pdf> ", Karl Ulrich at the University of Pennslyvania reports
that shifting people from their cars to bicycles offers almost no
benefit to the environment. 

We'll dig into this paradox in just a second, but first a little
background. Ulrich is the man behind TerraPass
<http://www.terrapass.com/ourstory.html> , the Wharton professor who
challenged his students to bulid a viable business around consumer
carbon offsets. Ulrich is also an avid cyclist himself and creator of a
number of human-powered personal transportation products, including the
Xootr Scooter <http://xootr.com/xootr/nscooters.shtml>  and Xootr Swift
<http://xootr.com/xootr/swift/bikes.shtml>  folding bicycle.

Bicycles do have large first-order environmental benefits over cars as a
means of transportation. Ulrich's analysis considers the case in which a
formerly sedentary person begins bicycling 10 km per day, 5 days per
week. In this scenario, about one ton of CO2 is spared every year in the
form of reduced fuel consumption.

This reduction in fuel use is partially offset by the increased food
consumption of a cyclist. Although typically we think of food as carbon
neutral - because the plants at the bottom of our food chain regrow
after we harvest them - this view overlooks the fact that most of us
don't feed ourselves by hunting and gathering. The energy required to
grow, harvest, process, package, and transport food to your nearest
Whole Foods significantly outweighs the actual caloric content of your
meal, by a factor of almost six. In other words, only about 15% of the
energy we consume when we eat is actually in our food. The rest is
contained in the fossil fuels used to bring our food to us.

But increased food consumption is a relatively minor effect when
compared to the overall gas savings of cycling over driving. The real
culprit in Ulrich's analysis is the increased lifespan of people who
ride bikes. Regular exercise helps you live longer, which points to an
unsettling fact. One of the single best things you can do for the planet
is to limit your time here.

Population is one of the primary drivers of energy consumption. And
there are only two ways to increase the rate of global population
growth: bump up the birth rate, or bump down the death rate. In effect,
cycling does the latter. (If we look at the population of individual
countries rather than the entire planet, immigration is a third way to
affect population growth. We've previously discussed some of the energy
implications of immigration
<http://www.terrapass.com/terrablog/posts/000249.html> .)

Ulrich estimates that every year of sustained bicycle use adds about
10.6 days to the average person's lifespan, even accounting for the
increased accident risk that cyclists face.

The result, in Ulrich's analysis, is basically a wash. Each of us,
simply by participating in the economy, uses a significant amount of
energy. Bicycling rather than driving causes a large first-order
decrease in the amount of energy a person uses, but the increased
longevity of that person almost entirely negates the savings.

Interesting. But how well does theory map to reality? Personally, I have
strong doubts about the practical implications of this analysis. The
first issue is that most people who opt to cycle rather than drive cars
are likely to be fairly fit already. These cyclists will see less health
benefits on the margin than the hypothetical sedentary person, and
therefore the first order CO2 reductions will dominate.

The second issue is subtler but possibly far more important. In Ulrich's
analysis, the population effects of cycling occur immediately (which is
mathematically accurate in his hypothetical example). But I strongly
suspect that the actual demographics of bicycle usage mean that the
population bump from improved fitness won't be seen for a number of
years. In effect, riding a bicycle shifts energy consumption from today
to an unspecified point in the future.

In private communication, Ulrich ballparks the delay in the population
bump as maybe ten years, which he points out is an insignificant amount
of time when compared to the climactic changes that are already
underway. True enough, but ten years could be long enough for highly
significant changes to occur in the energy intensity of our lifestyles.
If, for example, in ten years all of our electricity is produced by wind
(yea!) or coal (boo!), shifting our consumption into the future will
have real consequences for our rate of carbon emissions.

My advice: keep cycling, certainly for your health, and for the
environment too.

Update: Ulrich's paper got picked up in Andrew Leonard's How the World
Works <http://www.salon.com/tech/htww/2006/07/18/bikers/index.html>
column in Salon. Fun read, although Leonard's main complaint seems to be
that he doesn't really like the conclusion of the paper.


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