"You heard that right. Do you know the mileage on that bicycle?"
The logic goes thus. Everything we eat is produced somewhere, processed somewhere and transported to our supermarket and from there to our homes. It takes energy to do that. A major contribution of the energy needed to produce, process and transport our food comes from fossil fuels (the stuff USA is officially addicted to, since January'06). When you eat that sandwich, you are effectively gulping down gasoline. Every time you ride that bicycle, you are burning some of the same energy which came from the fossil-fuels. Naturally this bears the question, "How many miles can you go on that bicycle for every gallon of gasoline you consume (indirectly... through the food you eat)?". Got it? Good!
Lets go over the answer step by step:
1> How much energy does a gallon of gasoline have?
This is called the calorific value of the fuel. This EPA webpage says that the energy content of gasoline is an average 113,000 BTU/gallon. That translates to 28,476 kcal/gallon. (1 BTU = 0.252 kcal)
2>How many gallons of gasoline do you (indirectly) consume?
This depends on the type of your diet. The table below shows the amount of fossil fuel input for different types of diet. These numbers are from the book, "Food energy and society", by David and Marcia Pimentel . Note that all these numbers are for a 3600 kcal daily diet (remember 1 food Cal. = 1 kcal). It is interesting to note here that average American eats ~1500 Cal. more than the daily requirement of 2100 Cal. I have converted the fossil fuel input number into gallons of fuel using the calorific value given above.
3> How many food Calories do we burn while bicycling?
My search yielded a number of different values. I found this table on howstuffworks.com and a few other websites [this pdf, page 21]. It says that 0.049 Calories are burnt per pound, per minute while cycling at the speed of 15 mph. Another table is given in the Dietary guidelines for America, and can be found on many websites [CDC webpage, also this pdf - page 4]. This says that a person weighing 154 lb, will burn 290 Cal. when bicycling at a speed less than 10 mph, for one hour. Translates to 0.031 Cal. per lb per minute. A person weighing 154 lb, bicycling at 10 mph will have to go 125.7 mile to burn 36oo Cal. daily intake.
|Diet||Fossil fuel input(kcal)||Fossil fuel input(gallon)||Miles to burn 3600 Cal.||Mileage (MPG)|
|Average US (28%)||34,560||1.21||125.7||104|
There goes the answer to the question. Bicycling is fun, it is a good exercise and nothing beats the mileage on that bicycle.
 Pimentel D, Pimentel M. "Food, energy and society". Colorado University Press, 1996.
Technorati Tags: bicycling, food, fossil fuels, diet, vegetarianism
Related posts: Vegetarianism, Greens Eat Greens