Question: While I suppose that most of the carbon in America's favorite fossil fuel is botanical in origin, it's easier to get a gut feel for urenew-ability by considering dinosaurs.

So to be more specific, if you estimate the number of carbon atoms in one full-grown adult tyrannosaur, what volume of 92 octane gasoline would that represent? And conversely, how many dinosaurs could you build out of the carbon in one gallon of gas?

Answer by Dr. David from GOOGLE ANSWERS
Subject: Re: Carbon content of fossil fuels and dinosaurs
Answered By: drdavid-ga on 25 Apr 2002 15:49 PDT

  The answer is that the carbon content of one tyrannosaur is equivalent to that in about 460 gallons of gasoline. (You can build 1/460th of a tyrannosaur using the carbon in 1 gallon of gasoline.)

  You are probably well aware that gasoline is derived from crude oil by separating it out in a refinery. Crude oil, in turn, is pumped from underground reservoirs which are generally believed to have taken millions of years to form. As such, oil is considered a "non-renewable" resource in that we are essentially pumping out in a few hundred years what took millions of years to form and concentrate. And, as you note, the current understanding of the formation process is that oil is derived primarily from non-animal sources--probably mostly plankton. The conversion process from a tyrannosaur of 70 million years ago to 92-octane gasoline now would be, shall we say, not impossible but rather indirect.

  You can find a brief discussion of fossil fuel origins in general in "Topic #14 Power from the Earth - Fossil Fuel," part of the Geology 100 notes for the Department of Geology at the University of Illinois at Urbana-Champaign:  http://ijolite.geology.uiuc.edu/02SprgClass/geo100/Lectures/100_T14_fuel.html

  We will, however, ignore any inefficiencies in the conversion process and imagine that we can convert all the carbon in a T. Rex into 92-octane gasoline. Searching a few websites for a consensus on the weight of an adult tyrannosaur, one finds a range of estimates between 5 and 8 tons (no point in worrying about whether these are US, English or metric tons). A reasonable consensus seems to be about 6 metric tons (6000 kg).
  A Google search on Tyrannosaurus = weight:
http://www.google.com/search?q=tyrannosaurus+weight
gives many sites with weight estimates. Of those 6000 kg, of course, most is probably water. I had a little trouble turning up an accurate estimate for how much is likely to be carbon.

  Looking up the carbon cycle in John Kimball's Biology text: http://www.ultranet.com/~jkimball/BiologyPages/C/CarbonCycle.html
one finds an estimate of 18% carbon for living matter in general. That's probably right for a dinosaur to within better than a factor of two. So, one Tyrannosaur contains about 1100 kg of carbon. Now, we need the carbon content of 92-octane gasoline. If we approximate the gasoline as pure iso-octane (C8H18) see, for example, "Fuel Chemistry" at http://www.altfuels.org/fuelchem.html  , then carbon represents 84% of the weight of gasoline.

  The density of gasoline is about .75 gm/cc. See, for example, the
"MSDS Hyperglossary" at http://www.ilpi.com/msds/ref/density.html  .
One US gallon contains 3785 cc
online unit conversion at http://www.onlineconversion.com/volume.htm  .
  Thus, one gallon of gasoline contains 3785 x .75 x .84 / 1000 = 2.38 kg carbon.

  Dividing this into the mass of carbon in our average tyrannosaur, we can convert one animal into about 460 US gallons of gasoline, assuming 100% conversion of the carbon.

  Some useful Google searches:
http://www.google.com/search?q=origin+fossil+fuel
http://www.google.com/search?q=tyrannosaurus+weight
http://www.google.com/search?q=carbon+cycle
http://www.google.com/search?q=specific+gravity+gasoline
http://www.google.com/search?q=unit+conversion 

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