This is related to some morning coffee talks ages ago, where an ex-colleague of mine was pondering whether bicycling is an efficient way of traveling or not… Well, figures. Kinda tricky to measure and what to compare it to?
Anyway, as I’ve kept some track of my biking for the past year (gps + Endomondo) and even occasionally used garmin forerunner with hrm to see how much Garmin calculated calories differ from the ones approximated with Endomondo – here are some calculations.
So for the past year (July to July), I’ve tracked 2786,87 km and used 5d:16h:25m time as ”Cycling, transport”, which makes average speed 20,43 km/h. That is mostly bicycling to/from work. It includes riding in all kinds of weather conditions and with two kinds of bike (hybrid for ”summer” season and MTB for winter.) It also includes some extra payload for most of the trips (extra clothes, food, parcels from post… you name it.) Disclaimer;  my riding most certainly is not from the most efficient end of the spectrum, more from the comfort end. So there would be plenty of room for improvement in that sense.
Anyway, Endomondo calculated calorie consumption for that travel is 92745 kcal – which on the other hand is 388 045 080 joules. 1 liter of gasoline contains roughly 35 MJ of energy, so one year worth of biking has consumed and amount of energy that equals to 11,08l of gasoline.
So, is it much? If you compare it to driving a car, it’s nothing. If compared to the most efficient gasoline powered vehicles – say ones in Eco-marathon – it’s off the scale, I’m defeated! World record is 0,026388 l/100km whereas I would have consumed 0,4l / 100 km of imaginary fuel with my bike. Oh dear, why did I have to calculate this… 😀
But that cannot be the whole truth. First, Endomondo has quite a bit of overhead. At the time of writing I don’t have my notes on this, but If I remember correctly – Endomondo shows constantly at least 10% more burned calories than what my forerunner shows (and somehow I believe it to be more accurate – as it has the heart rate information available.) I might actually be tempted to re-check this in the next few days. Also – as I do this mostly to keep myself fit – the speed and riding geometry are not efficiency optimized in any sense. If I sometimes get my hands on a good road bike, I might check this again from efficiency point of view.
As I started to write this, I googled for bicycling efficiency and came across this article Human power which has a nice chart of approximated calorie consumption / km / person – in which the cyclist is less than 50kcal/km. Endomondo agrees with that, ~520-540kcal for 13,5km.
According to Wikipedia article on Bicycle performance, energy expenditure when cycling is generally 1.62 kJ/(km∙kg). So to compare to that we would get 388045,08 kJ/(2786,87 km*90kg) = 1,547 kJ / (km*kg). That is approximated rider weight only, if we add 15kg for bike + equipment, the expenditure is 1,326 kJ / (km*kg). Which is at least better than generally used figures!
But my point, compared to any commercially available gasoline powered transport, I think cycling and cyclist wins 🙂