Carbon Dioxide and the Farmer's Market

Something about “tons of carbon” has always bothered me:

From my high school chemistry: Carbon weighs about 12 grams per mole (6.022*10^23 atoms). Average gasoline has 8 carbons per molecule and a mole of molecules per litre. Therefore each litre of gasoline has eight moles of carbon or 96 grams of carbon. Since people like to speak in tons (I’ll lave out the math steps, but) you must burn just under 9500 litres of gas to produce a ton of carbo
Now, unless my math/science is WAY off it would take me nearly eight years of daily driving to produce a ton of carbon (because I burn a little less than 100 litres of fuel per month). Conventional wisdom would indicate I am grossly wrong in my calculation.

Another way to look at this is: **Your carbon cannot outweigh your fuel.** Carbon, in fact, must be less than the weight of the fuel since none is added from the atmosphere. How much does a tank of gas weigh? A ton of gasoline is 231 gallons. How far can you drive on that? At 30 mpg you’ll get over six thousand miles. With gasoline I’d produce a ton of carbon (max) per year, and with diesel it’s less.

Anyway, again this disagrees with conventional wisdom.

Another way of looking at this is to look at the ratio of carbon to hydrogen (there’s only those two things in gas), multiply each by their atomic weight, assign that much of the weight of gas to each element and work it out. Again, it will not agree with conventional wisdom.

I just don’t know how they come up with our tonnage numbers.

It turns out there’s about 320 gallons per ton of gasoline — that means I wouldn’t produce a ton of carbon per year under normal daily driving. Anyway, either conventional wisdom is wrong or I am, but how can the carbon weigh more than the fuel? Impossible!

You didn’t reap savings right away in moving, because you spent carbon to move, plus it might do well to compare not just your driving but your utility usage. I’m not sure what else is liable to differ. If you lived off locally produced, processed and packaged food in one place almost exclusively and not at all in the other, or did a lot of canning and root cellar storage in one place but only bought and refrigerated in the other, perhaps those would be other big ticket carbon items? Nationally, those lifestyle choices certainly matter, but for an individual, I don’t know how high they stack up versus the CO2 you put out with your car or by air conditioning your poorly insulated ranch-style home.

Peter, do those figures include CO2 from the production and shipping of the gas too?

Commute solutions makes a very good point. When we figure the “cost* of driving, I wonder if we should figure the cost of the war in Iraq.

Pete: “100 litres of fuel per month is 26.4 gallons (US) of fuel per month, is 517.7 pounds of C02 emitted per month (26.4 x 19.6 = 517.7).”

How? How can the carbon content of a gallon of gas actually weigh more than the gas? I mean really; if I’m wrong about this I would really like to know why because carbon emission figures have been irrational (to me) for years now — they just don’t make sense because:

If gas is 6.2** pounds / gallon (which is the best figure I can find), then the carbon in 26.4 gallons of gas cannot exceed 164 pounds; it’s total weight (at STP). **(avg, gasoline varies *a lot* with temperature)

I think I know the reference for the conversion number you’re using but I just don’t believe it, I think when experts issue a number like this they are obliged to explain it *in detail* and I haven’t seen that as yet.

A factor on the plus side is that at the Farmer’s Market you have purchased locally produced food which would cost less carbon than food shipped in to Sobeys or Superstore from California, Mexico, New Zealand, etc.

Thanks Pete. There’s the answer -=- and I was looking for it.

Anyway, I guess I should learn to not take anyone literally — not even scientists. When I hear a scientist use a phrase like, “carbon emission”, or “tons of carbon” I assume they mean C, not CO2. Anyway, I guess it’s legit to measure the carbon dioxide emissions AS LONG AS carbon monoxide does not combine with anything other than oxygen to produce another greenhouse gas. If that were the case then it would be more appropriate to 1) count the carbon only and 2) drastically reduce the units that are considered safe for the environment, or to say that another way: to set appropriate benchmarks based on elemental carbon.

Methane has carbon and it’s a potent greenhouse gas. But “complete” combustion (as well as complete or metabolism) gives you C02, because thermodynamically it’s the most stable compound in which to combine earthly atoms in earthly abundances at earthly temperatures, pressures, etc. So arguably it’s a natural currency, although I wouldn’t be surprised if scientists talk about the mass of carbon alone too, because some atoms will go into methane and other organic molecules important to the atmosphere or the carbon cycle.

Experts (and journalists) should choose accuracy over cadence; but alas ‘tis often not the case… Anyway, C or CO2, it matters not as long as it is explicit which term is being used. It’s like hearing a politician or journalist talking about an expenditure in dollars but they leave out the “per”; as in “per year”, “per month”, “in total over the life of the project”, etc… this simple omission — which is quite frequent — makes an entire point meaningless to anyone who really cares about it. Confusion ensues when experts, rather than being accurate, use the term “carbon emissions” (a nod to Barbie no doubt…”carbon dioxide sounds too, like, well, y’know, scientific, right?”).