Bicycle fuel economy

Nearly two years ago when the price of gasoline spiked, I wrote this blog entry comparing my fuel cost of operating a bicycle versus that of operating a car. The point of that blog entry was to demonstrate that bicycling is not the zero-cost cornucopia that many would believe it is, and I quantified it by explaining my estimate that I was saving only about $1 per day on fuel costs despite gasoline being four times that amount for only one gallon.

On the way to that $1-per-day conclusion, I started with an assumption of traveling 126 miles per week and derived burning an additional 3614 kcal of food energy to do it.

Here's another way of looking at it. The rule-of-thumb number I come up with in my Google research is that for each 1 kcal of food energy we Americans ingest, an average of 10 kcal of input energy are used within the agricultural, transportation, and food processing industries to grow that food and bring it to our pantry wrapped in its cheery, colorful packaging. So those 3614 kcal of food energy I burn through to bicycle 126 miles themselves require 36,140 kcal of input energy, and we all know by now that the fuel for that input energy is nearly exclusively fossil fuel. But how much is 36,140 kcal of fossil fuel?

One answer is that it's about 1.2 gallons of gasoline. (A gallon of gasoline contains about 31,000 kcal of energy.) In truth, there's probably not much actual gasoline that goes into the production of the food I eat; rather, it's instead fueled by diesel for farm machinery and trucking and coal and natural gas for electrical generation. But let's suppose for simplicity that any one kcal is the same as any other kcal. In that case, what's my fuel economy on the bicycle?

Answer: about 100 miles per gallon (126 miles / 1.2 gallons).

A fuel economy of 100 mpg is still way better than every mass-produced vehicle we have on the road today, but I suspect the figure is way lower than most people suspect. And hopefully the figure sheds some light on just how deep our energy vulnerability is in this country.

To end on a hopeful note, let's keep in mind that I could buy some land, start a garden, and grow organic sweet potatoes and other calorie-rich foods and greatly reduce my personal 10 kcal input-energy figure by simplifying my food-supply chain. Also, it's worth pointing out that the bicycle has a great advantage over most other vehicles on American roads in that its fuel economy is not “hardwired” into the machine. It is thusly that I think that the bicycle does have a role to play in grassroots, self-adopted protections from our nation's energy vulnerability—even if it's not a cornucopia.