Answer for: Why do you bike?

#2 Takin' my slice out of carbon emissions  

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gam3 Member (Level 5): 1,295 points   11 months ago

A human puts out about 2 lbs (900 grams) of CO2 per day. Riding a bike is likely to triple that for the time on the bike. However burning a gallon of gasoline creates something close to 22 lbs (10000 grams) of CO2.

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MDAdams Member (Level 6): 6,258 points   11 months ago

That's interesting. A gallon of gas weighs about 6 lbs (iirc), and the carbon is only a subset of that, so therefore the large delta in weight must be the O2 mating up with the carbon atom to form CO2?

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gam3 Member (Level 5): 1,295 points   11 months ago

Here are better numbers:

The Carbon to Hydrogen ratio of gasoline is 1:1.85 by weight that make gasoline 79% Carbon. As a gallon of gas weighs about 6 lbs There are 4.75 lbs of carbon in a gallon of gasoline. An equal number of oxygen atoms weigh 6.32 lbs. Add it all together and you get 17.38 lbs of CO2 (4.75 + 2 * 6.32). So I guessed a bit high.

! gallon of gas creates something like 7500 grams (17 lbs) of CO2.

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MDAdams Member (Level 6): 6,258 points   11 months ago

Out of curiosity I looked up the numbers. According to the EPA, assuming 99% oxidation of carbon:

CO2 emissions from a gallon of gasoline = 2,421 grams x 0.99 x (44/12) = 8,788 grams = 8.8 kg/gallon = 19.4 pounds/gallon

CO2 emissions from a gallon of diesel = 2,778 grams x 0.99 x (44/12) = 10,084 grams = 10.1 kg/gallon = 22.2 pounds/gallon

Your calculations were close... 44/12 being the O2/C ratio by weight.

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