As you might know, I enjoy big numbers. So it's just natural that I was attracted by this news release from the University of Utah, "Bad Mileage: 98 tons of plants per gallon."
A staggering 98 tons of prehistoric, buried plant material is required to produce each gallon of gasoline we burn in our cars, SUVs, trucks and other vehicles, according to a study conducted at the University of Utah.
For a reasonably efficient car, riding 25 miles per gallon, this translates to 4 tons of prehistoric plants per mile, or more than two tons per kilometer.
"Can you imagine loading 40 acres worth of wheat -- stalks, roots and all -- into the tank of your car or SUV every 20 miles?" asks ecologist Jeff Dukes, whose study will be published in the November issue of the journal Climatic Change.
So how did Jeffrey S. Dukes calculate this?
Dukes calculated how much of the carbon in the original vegetation was lost during each stage of the multiple-step processes that create oil, gas and coal.
He looked at the proportion of fossil fuel reserves derived from different ancient environments. Then he examined the efficiency at which prehistoric plants were converted by heat, pressure and time into peat or other carbon-rich sediments.
Next, Dukes analyzed the efficiency with which carbon-rich sediments were converted to coal, oil and natural gas. Then he studied the efficiency of extracting such deposits.
Now, here is the interesting part. The generation of fossil fuels was an extremely inefficient process.
The calculations showed that roughly one-eleventh of the carbon in the plants deposited in peat bogs ends up as coal, and that only one-10,750th of the carbon in plants deposited on ancient seafloors, deltas and lakebeds ends up as oil and natural gas.
Dukes then used these "recovery factors" to estimate how much ancient plant matter was needed to produce a given amount of fossil fuel.
Please read the news release for the detailed calculations.
Dukes also found other interesting gems.
Dukes also calculated that the amount of fossil fuel burned in a single year – 1997 was used in the study -- totals 97 million billion pounds of carbon, which is equivalent to more than 400 times "all the plant matter that grows in the world in a year," including vast amounts of microscopic plant life in the oceans.
"Every day, people are using the fossil fuel equivalent of all the plant matter that grows on land and in the oceans over the course of a whole year," he adds.
His research paper, "Burning Buried Sunshine: Human Consumption of Ancient Solar Energy," is still not finalized, but you can read it online in its pre-publication form, as a 14-page long, 164 KB PDF file.
A last word: even if these numbers are too large, this still makes you think about how inefficient our cars are.
Sources: University of Utah, via EurekAlert!, October 26, 2003; Climate Change Journal, from Kluwer Academic Publishers
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