Misleading sustainability statistics
November 15, 2019
To the Editor,
I recently was shown the latest issue of the Installment, which is published by the campus Sustainability Office. The following was provided as resulting from the energy challenge between dorms. They were able to save 6,452,949.1 pounds of CO2e resulting in reductions up to 27.1 percent. I am intrigued by the precision of the amount of CO2 saved (eight significant figures!) when the percentage decrease is only reported to a precision of three significant figures.
More troubling is that, according to the Installment, this is claimed to be the amount of CO2 emitted by a car driving 33,107 miles. Doing some quick math, at 33 Miles Per Gallon, it takes 1000 gallons of gas to drive 33,000 miles. Gas has a density of 6.3 pounds per gallon, translating to 6300 pounds of gasoline for the trip. Using octane (C8H18) as a proxy for gasoline, this is equal to about 5300 pounds of carbon (6300 x 96/118) and therefore 19400 pounds of CO2 (5300 x44/12) for the drive. The two amounts differ by a factor of above 320! Did we stop the reported 6.45 million pounds or the 19,400 pounds of CO2 emitted by driving 33,000 miles from entering the atmosphere? We can do better than overly precise and wildly inaccurate.
Professor of Chemistry
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