Cycling is bad for the environment. Fact!
Few people if any would argue with the idea that a cycling holiday on the Norfolk Broads would be far less damaging to the environment than a family trip to Disneyland, complete with long haul flights to Orlando and a gas guzzling SUV hire.
However, does that mean that cycling is always better for the environment? I am reading through my excellent Sustrans guide to Cycling in the UK, which features some superb routes on off-road cycling paths throughout the length and breadth of the country. In the introduction is a note from Alistair McGowan, in which he claims that cycling is ‘carbon free’. It is at this point that I have to stop. Breezing along a canal tow path certainly looks pollution free, when compared to a belching old diesel bus, but it just isn’t as simple as that. Carbon dioxide is of course an invisible pollutant, but it is still a pollutant, and you have to look at the whole life cycle chain.
How is it possible for cycling, or any form of human activity to be carbon free – after all, what are carbohydrates? Now we all need to eat, and for many, a bike ride is a good way of burning off excess calories, but what happens on longer cycle rides, when extra food needs to be consumed to be burned off during the ride?
Now remember that this is a blog post, not a peer reviewed scientific paper, but this was my thought when I read McGowan’s claim:
Some highly processed foods such as cornflakes require up to 50 times as much energy to be produced as they yield to the human consumer. Other foods might be shipped vast distances by air, whereas meat and dairy products require large emissions of methane from cows, which as many airline bosses will tell you, could be a much bigger problem than the emissions from air transport. The very obsession we have with ‘carbon footprints’ forgets that carbon (well, actually carbon dioxide) is only half of the problem.
The human body when considered as a machine is approximately 20% efficient, and many of us, including myself, waste up to 1/3 of all the fresh fruit and vegetables we buy — can you imagine filling up your car and then spraying a couple of gallons over the forecourt?
So, here’s the quick back of the envelope calculation — a 100 kg cyclist and bike at 20 miles an hour should need around 1/40th of the energy to keep moving, compared to a one-ton car and driver at 40 miles an hour. This is based on them having 1/10th of the mass and having 1/4 of the friction (double the speed, quadruple the friction). Cars are also around 20% efficient at converting fuel into kinetic (motion) energy, including the energy needed to refine the fuel and transport it to the petrol station. Therefore, even though the cyclist only has 1/40th of the momentum, he still needs 50 times the energy to produce the food in the first place, so cycling uses 25% more energy than driving, on a per-mile basis.
Mile for mile, the emissions caused by flying are compatible to driving, depending of course on the type of aircraft used, the route and occupancy levels, and also depending on the car journey the flight is compared to, and the number of occupants. If we assume a typical low-cost flight on a 80% full Boeing 737 800 wingtips, the cornflake munching cyclist is again a less efficient machine than the aircraft.
A self-rightous lycra-clad cyclist popping along to his local station thinking ‘aren’t I being wonderfully green today’ may pop his bike in a space which could otherwise seat three passengers – causing similar emmissions to driving a car too.
So even if this argument might be a little tenous, it is equally preposterous to claim that cycling is carbon free, when it clearly isn’t. It is just as bad as claiming that electric trains, nuclear power, wind turbines or battery powered cars are ‘carbon free’ – when none of them are, as all have additional hidden environmental costs.
Cycling is bad for the environment – that is an indesputable fact, in that cycling creates carbon dioxide emmissions, and in that there is a huge knock-on requirement in the food production cycle. However, cycling is still relatively good for the environment, if we are to assume that most trips are using calories which need to be burned off anyway, and that the alternative would be to go by car. Just remember though – there is no such thing as a carbon-free lunch.