There's a chain letter going around exhorting its recipients Don't Guy Gas on May 19th, arguing that the oil supply chain will be thus horked.

I don't know what would happen to the supply chain, but the amount of gas you'd conserve would be minimal. Even assuming that all of the world's gasoline users didn't use any gas for one full day, you'd only be cutting less than a third of a percent off the oil producers' annual revenues.

Presumably, it's the oil producers that this meme's progenitors are targetting, and not, say, the local pumping joint.

In any case this poorly-conceived protest got me to thinking about how much energy I use as a bicycle commuter and whether cycling is an energy-efficient way to get around (putting off the fact that food is renewable while petrol isn't).

The first thing I did was some back-of the envelope calculations about my weight, my speed, the friction of my wheels, and so on, but I couldn't think of a way to estimate the friction.

Success came, however, in the form of a Bicycle Speed-Power Calculator, the sort of thing used by athletes, I suppose.

According to this, if it's flat, I burn about 48 kCal in biking my 4 mile commute each day. If it's a 2% grade, it puts me at 162 kCal.

Inspecting my morning cereal, I see that a cup of that stuff delivers 120 kCal per cup (Grape-Nuts weighs in at a whopping 200 kCal per half cup!).

Further cereal box wisdom leads to the realization that a typical diet might be around 2000 kCal per day. Bicycling every day must represent less than that, eh? Eh? Now how much energy does it take to go a mile in a car?

According to the physics students of Glen Elert, who looked this up in several textbooks (!), gasoline has a fuel density of 45 MJ/gal, and the density of gasoline is about 42.42 lbs/ft^3

As per Google Calculator, that comes to 116 MJ/gal.

Glen Elert's students put the figure at 130 MJ/gal, and this guy, using his Jeep Wrangler, came to the figure of 10^8 J/gal, all pretty close to the same value.

So, if we figure a gallon of gas has 100 MJ/gal and a cyclist can go something like 4 miles on 200 kCal, how far can a cyclist go on the enery in a gallon of gas?

About 550 mi.