True, in modern society pretty much no activity is truly “carbon neutral” (I never claimed it was). But the extra carbon produced by tractors, combines, trucks, etc. to produce the extra food I need to eat because I’m cycling to work is several orders of magnitude smaller than that that I produce by driving each day. Plus of course this carbon was not considered in the original equation proposed.
I’m pretty sure it will, I think the law of thermodynamics ensure that. You are producing kenetic energy, that needs to come from somewhere. Sure I can stand to lose a pound or two, and my efficiency will improve as I get fitter, but I eventually unless I increase the amount of energy I digest, I will starve to death (fortunately I’m some way from that at the moment).
The only way it wouldn’t be the case is if your extremely active anyway (and so are just replacing “useless” work down the gym, with “useful” work cycling to work), or maybe if your extremely INACTIVE and the extra calories that were getting stored as fat in your body, are now being converted to kenetic energy.
But the point has already been made that if you are going to take this into account, you should also (when calculating motoring costs) take into account the fossil fuel used in obtaining fossil fuel. The industry required to locate, extract, refine and transport fuel is enormous.
From here it looks like a bushel of corn takes 55,164 BTU of energy to produce.
From here, a cup (154g) of corn has 132 calories.
One bushel (56lbs) is 453.6 x 56 = 25401 grams, so each bushel has 21,773 calories.
If our cyclist got all of his calories from corn (let’s say he required an extra 1,000 calories per day, which is probably a factor of 2 too high), then he would be consuming 1/21 of a bushel per day, or 2627 BTU (of energy required to grow the corn).
As a reference, the first cite says that Diesel has 137,202 BTU per gallon, so our cyclist would be creating an energy demand equivalent to .019 gallons of diesel, or 2.45 oz.
My truck gets 15 MPG on Diesel around town, so I could go 1/3 of a mile on the energy the cyclist consumed.
What about the inevitable water and power usage increases from the extra showers you have to take after you arrive to work? Or do you go about your work day stinking from sweat?
Even ignoring the fact that the CO2 from your lungs is entirely carbon neutral, you’re making at least two invalid assumptions
You’ve ignored the fact that you have to breathe while you’re driving your car
You claim that the 43km (just over 25 miles for the heathens) takes 4 hours, and that you’ll be using you V02max for the entire time. Unless you live in the Himalayas, this is very unlikely. Cycling at 10km/hr takes a lot less energy than walking. It’s probably not far off the amount you use sitting down on a couch.
Woah, there. He said round trip of 43 km and round trip time of 127 minutes.
Where I come from, 127 minutes is 2 hrs 7 minutes and gives an average of 20.3km/hr.
Which is slow, but may involve traffic lights. My ride as an example is short and flat but with all the accelerating involved due to starting and stopping for traffic lights its more work than you’d expect.
It’s true that carbon in food comes from the atmosphere, so the food itself is carbon neutral, however, the production, processing, distribution, packaging, retail etc. of that food is not generally carbon neutral - it’s powered significantly by fossil fuels. Consume more food in total and somewhere along the line, more fossil carbon is being released to make that possible.
That said, it seems likely that there is considerable waste in propelling a ton of metal with a seat in it - a car engine may be a more efficient converter of energy than human muscles, but in the car vs bike scenario, more work is being demanded of the car, just in moving itself.
First of all, the amount of extra carbon released because of plant-growing is very small (see my post #25).
Secondly, people are WAY more efficient in converting energy to motion than a car is - cycling is one of the most energy-efficient modes of transportation. This guy calculates it as being equal to 684 MPG.
Sure. There’s also processing, distribution, packaging, retail, etc. although I expect this to be fairly low-impact too, given the amount of extra food being discussed.
That reminds me: I remember reading some years ago that the amount of energy/calories one would burn cycling across the U.S. is about equal to the amount of energy/calories in a gallon of gas, or 3000 MPG. I have no idea where I read it or how to verify it. (Maybe someone with really good Google-fu can dig something up.)
This says that it takes .28 calories/mile/pound, so if you are 150 lbs, and going 3,000 miles, it will take 126,000 calories. This says that a gallon of gasoline has 31,000 calories, so to bicycle across country would consume calories equal to 4 gallons of gas. Still pretty good.
