Sunday, October 23, 2005

Energy Efficiency of Bicycles

I recently came across someone claiming that bicycles were less efficient than automobiles if the embedded energy in food the rider ate was included in the calculations. They quoted calculations from a paper on the energy efficiency of electric bikes.

However this claim does not match other data that I have seen.

For example one source claims that:

A bike requires 350 calories per 10 miles (supplied by the rider)
A car requires 18,000 calories per 10 miles

And other sources seem to support these numbers

Now even if you add the embedded energy of the food which according to the paper is 7 additional calories per calorie of food consumed, that is still only:
2,450 calories per mile for bikes
vs. 18,000 calories per mile for vehicles.

And this is still not including the embedded energy of the fuel for the automobile or the embedded energy for manufacturing the automobile (about 10 times that of the bike).