Me vs my car - who pollutes most?

All these threads cropping up about CO2 pollution, hybrid cars, etc reminded me of a claim Jeremy Clarkson (loved and loathed in equal measure by Brits; presumably unknown elsewhere, but try Google if you care) once made, which is that a person produces more CO2 on the running machine at the gym than their car does driving them to and from the gym. I haven’t included the cite, as he probably made the stat up on the spot. However, I’d be interested to hear if anyone thinks there’s any truth to it.

For reference, my car produces 210g/km of CO2 and does about a 3 mile round trip to the gym (apologies for the mismatched units). I spend about 20mins on the treadmill while I’m at the gym, and cover 4km or so. (And please don’t tell me I could accomplish the same by just running to gym - it’s usually raining here, and there’s a very steep hill.)

Here’s a quick and dirty estimate for you, using the following assumptions;

You car has a catalytic converter and gets 20 mpg and runs on gas
19.4 lbs of CO2 are produced from 1 gallon of gasoline (source EPA)
Your exercise respiratory rate is 42 per minute
Your volume per respiration is 0.5 litres (adult 20-30 y.o. avg)
5% of the volume exhaled is CO2

For a 3 mile round trip to the gym your car produces;

3 mi/20 mpg * 19.4 lbs/gal = 2.91 lbs of CO2

For your 20 minutes on the treadmill you produce;

42 resp/min * 20 minutes * 0.5 litres/resp * 0.05 (% CO2) = 21 litres CO2 = 0.021 cubic meters CO2 = 0.0915 lbs CO2

Someone should check my assumptions and math since I did this quickly, but it looks like there is no contest. The car produces much more.

My thought is that you should try pushing a car if you haven’t before. Compare your efforts to that of the internal combustion engine, and that should tell you who is burning more kilocalories.

Rocket I think your numbers are off for the car. In the OP he says that his car produces 210g/Km of CO2 and does a 3 mile round trip.
converting miles to Km 3 *.6 = 1.8
210g * 1.8 = 378 grams
According to Google that is 0.833347351 pounds

I am not sure about your numbers for a human, but these appear to be correct for the car.

Err… miles to km is *1.6, not /1.6.
3 miles = 5km (roughly). So 210g * 5 = 1050g, or just over a kilogram. Without google, I know that’s about 2.3lb.

Rocket, where did you get the 0.5 l / breath figure from? I believe that’s accurate for someone at rest, but during heavy exercise it goes up dramatically - to about 2 or 3l per breath. That would then be 125l CO2, which works out to 0.5lb, give or take.

Still very heavily (snerk) on the side of the car. Jeremy Clarkson may be a great driver and a very funny TV show host, but I strongly suspect his talent for hyperbole outweighs his scientific accuracy in this particular instance.

Firstly, 210g/km seems pretty high - my 1.6 16v Ford Focus puts out 160g/km. What do you drive? A Hummer? :wink:

Secondly, according to this, each human puts out 1kg CO[sub]2[/sub] per day. So it sounds like Mr Clarkson was indulging in some hyperbole for fun. Wouldn’t be the first time.

Of course it is. I am a :wally
I think my brain is starting to rot.

BTW the thread I read right after this one degenerated into a discussion of cars and gas mileage , anyway there was a link to the smart car
CO2 emissions is 90g/Km
So 90 * 5 = 450g Less than half a kilo
The numbers are closer.