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Carbon Cycle

  • Posted by ruben
  • 7 March 2013

The carbon impact of cycling is dead interesting. Here’s some food for thought.

There’s a lot of nonsense talked about carbon footprinting. I have a friend who believed that owning and feeding a dog was more carbon intensive than owning and fueling a 4x4.

The truth is that depending on where you draw the boundaries you can prove anything with carbon footprinting. So if your 4x4 is super efficient and only drives 6,000 miles a year and if your dog eats loads of meat that has been reared just for it (i.e. not a by-product of other part of the meat industry and not mixed with vegetable/rice feed) then yes you can show that the 4x4 has a bigger footprint.

So I wasn’t that surprised to see that US Republican Ed Orcutt declare that the CO2 emissions from riding a bike are greater than that of driving a car. Clearly Mr Orcutt is deluded. Particularly as he cites the greater expiration of the cyclists as being the cause. We can ignore Mr Orcutt on the grounds of stupidity but the carbon impact of cycling is dead interesting. Here’s some food for thought.

Mike Berners-Lee in “How bad are bananas?” looks at the impact of cycling a mile. Now the interesting thing is that it depends on what you’ve eaten. This is the fuel for the bike. So if you are fueled by cheeseburgers the impact of cycling a mile is 260g of CO2e but if you are fueled by bananas this falls to 60g. These figures take into account the embodied impact of the bike per mile.

The embodied impact of a family car kept for 200,000 miles is 100g per mile plus the impact of burning a mile’s worth of fuel (between 150g and 200g per mile). But this doesn’t take into account the fact that the car driver will also have eaten food but that the calories from this food are not burnt off but accumulated. This in turn has a knock-on potential impact of running a health service to deal with those non-cyclists who become obese (note: not all non-cyclists become obese).

So the impact of driving a mile in a car is the impact of the fuel use, the embodied impact of the car and the impact of the food eaten by the driver. So if the driver eats cheeseburgers this gives a figure twice as large as that of a cheese burger eating cyclist.

Phew, that’s complex. The key thing is to understand is where the boundaries of your study are. My advice to Mr Orcutt is to get his facts straight, trust the science and ride a bike more.

Words and facts by Mark Shayler at tickety boo