Biking.
Yesterday, we went and bought Barbara a bicycle. It is what is called a hybrid (meaning a bit of rough terrain and a bit of road riding). It cost about the same as 100 gallons of gas. I told Barbara that she needed to use it for more miles than that.
So, let’s look at the energy equations for biking.
Biking uses somewhere between 135 Calories per hour (for 6 miles per hour riding) and 700 Calories per hour (for 14 miles per hour). This works out to 12.5 Calories per miles and 46 Calories per mile, respectively (after subtracting normal body upkeep).
1 Calorie (kilocalorie) = 3.968 BTUs.
1 Gallon of gas = 125,000 BTUs.
Now we need to know how much fossil fuel goes into each Calorie of food. This depends greatly on where you buy your food and how much it is processed. I have seen numbers as high as 10:1 for the American diet of high processed long distance food. I will assume that 1:1 is the low end of the scale. So, 1 Calorie of food is somewhere between 4 and 40 BTUs of fossil fuel.
So, riding 6 MPH on a local organic diet gets around 2500 Miles per Gallon (of fossil fuel).
While riding 14 MPH on that diet gives around 679 Miles per Gallon.
And riding 6 MPH on an American diet gives around 250 Miles per Gallon.
Finally, riding 14 MPH on that diet gives around 67 Miles per Gallon (not much better than a prius).
— Topher
Midcoast Green Collaborative Forum 
Hi Topher,
Your reasoning works for lean people that need to increase their caloric intake if they want to burn more energy by cycling. The majority that already eat too much just transform the extra calories into increased weight. The resulting raise in basal metabolism then gobbles up the excess calories. In such a case, more cycling does not require more eating. So unlimited miles per Gallon and a healthier body weight to boot.
Comment by Bart Hazes — July 23, 2008 @ 2:46 pm
True enough. However, if you are eating too much that should be your first fix, to becoming more green. None of what I say here should be taken as a reason not to bike, but rather an attempt to present all information, and prompt discussion.
Comment by Topher — July 25, 2008 @ 4:41 pm
Michal Pollan, whom I heard speak last night, gives the low end of the scale (or at least the 1940 US figure) to be 1 calorie of fossil fuel producing 2.3 calories of food (1:2.3). This would make 1 food calorie equal to 1.7 BTUs of fossil fuel, and 5750 MPG on a 1940’s diet (at 6 MPH), and 1560 at 14 MPH.
Comment by Topher — October 28, 2008 @ 12:41 pm