🚀 go-pugleaf

In article <68411@apple.Apple.COM>, ehouse@Apple.COM (Eric House) writes:

> In article <SLAGLE.92Jun8203710@sgi417.msd.lmsc.lockheed.com> slagle@lmsc.lockheed.com writes:
>> [stuff deleted]
>>Can anybody come up with any kind of realistic estimate of the
>>comparable environmental and economic damage that would result
>>from a substitution of human for automotive power on the margin?
>>Can we really say that using a car to get to and from work is
>>really worse for the environment, all inputs and outputs
>>considered, than is riding a bicycle?

> Mark, you ask interesting questions.

> But we can at least begin with the fact that if I drive to work I need to
> accellerate and decelerate several thousand pounds of metal while if I
> go by bike I'm only dealing with my own weight plus 25 lbs.  This difference
> dwarfs the human body's being a "notoriously inefficient converter[] of 
> energy", and is responsible for estimates that a bicyclist, if he could
> run on gas, would get upwards of 1500 miles per gallon.

This is part of the answer, but I think your numbers are a little
off.  Your comparison seems to be based on weight alone, so the
true ratio shouldn't be more than about 10-15 times the mileage.
I would think it should be more around ten, though.  If we assume
that the combination of bike, rider, and briefcase weighs in at
about 200 pounds, then all we need is to find a commuter car that
weighs in under 2000 pounds.  I don't have stats, but that
doesn't seem out of line for some of the econoboxes.  If we use
the ratio of ten, then the bicyclist is getting only the
equivalent of around 300 MPG (assuming the commuter car can get
30 MPG), not 1500.  It makes a big difference.  Of course my
motorcycle only weighs about 400 pounds, and gets better than 40
MPG, so it's clear that we can do better than the old two-ton
monster cars of the sixties.  And the bicyclist is only getting
about 150 MPG.  But the figures are misleading because the bicycle
looks better in this comparison as the motorized mileage improves.

> Cars aren't all that efficient either, BTW.  I have at home a chart showing
> what happens to the potential energy in a gallon of crude oil between the
> time it leaves the ground and the time it is converted into useful motion
> of a car.  Something like 20% is lost to refiniement into gas; by the time
> distribution, mechanical and combustion inefficiencies, aerodynamic drag
> and tire/road friction etc. are accounted for only 5% of the original
> energy gets any useful work done.

My question is not really a matter of energy efficiency, although
that is an interesting topic.  I would bet that you would have a
very tough time getting anywhere near 5% energy efficiency, from
ground to sweat, from the biker fuel cycle, though.

The question I still would like to see answered is about the
environmental impact, on the margin, of substituting a bicycle
for a motor vehicle.  While I will agree that part of the problem
with cars is that a large part of the impact on the environment
is on local air quality, and that part of it is not relocatable.
Much of the impact of the bicycle can at least be removed to
another area.  There is some advantage to this, and this is the
large part of the advantage, if there really is one, of electric
vehicles.  Some have argued that even if the total pollution is
slightly more, it is more important to reduce it in the areas of
concentration than it is to increase it in areas that are
relatively less stressed.

In any case, it still seems that there is a large potential
environmental cost of providing fuel for the bike rider and of
disposing of the wastes.  If we require a higher caloric output
from people, what is the marginal effect on the environment of
this extra energy output?
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Mark E. Slagle                                 PO Box 61059
slagle@lmsc.lockheed.com                       Sunnyvale, CA   94088
408-756-0895                                   USA