When we think of reducing one's carbon footprint, riding a bicycle might come to mind. Surely, when it comes to carbon emissions, riding a bike is better than taking a car, isn't it? Well, according to an item in today's Guardian that might depend on what fuel is in the bicycle tank:
...however you ride, the energy has to come from the food you eat and that in turn has a carbon footprint. The good news is that the lower-carbon options are also the ones that make the best cycling fuel. Bananas are brilliant, largely because they are grown in natural sunlight (no hot-housing required) and because they keep well, which means that although they may be grown thousands of miles from the end consumer, they are transported by boats, which is a hundred times better in terms of emissions than air-freighting. As a bonus there is hardly any packaging, if any, because bananas provide their own.
Breakfast cereal is pretty good (let down slightly by the milk). The bacon comes in at around 200g CO2e for a 25g rasher with only enough calories for a mile and a quarter of riding. Two people cycling along using energy from cheeseburgers is equivalent to those same people sharing a ride in an efficient car. At the ridiculous high end of the scale, however, is getting your cycling calories by piling up your plate with asparagus that has been flown by air from the other side of the world. At 2.8kg per mile this is like driving a car that does six miles to the gallon (a shade over a mile per litre). You'd be better off in a Hummer.
yeah, but imagine two person riding in a car while eating a cheeseburger! joking aside, I think this article is missing a few points in theirs calculation.
First, they used the the figure of 50 calories / mile to compare a car driver with a bicycle rider which is roughly equivalent to the rider racing to the city at dangerous speed. An average bicycle rider usually get around 35 calories / mile cruising around the city ( http://auto.howstuffworks.com/question527.htm ).
Second, the author then add a "50g per mile to take into account the emissions that are embedded in the bike itself and all the equipment that is required to ride it safely." but fails to consider the carbon footprint of building a car.
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