Your article states, “There are about 4.14 kilograms of carbon in a gallon of gasoline, says Dukes.” If he actually said that, this would seem to qualify this gasoline as an “alternative fuel,” since a gallon of ordinary gasoline is only about 2.5 kilograms in mass. Perhaps Dukes meant 4.14 pounds of carbon per gallon. Should we be concerned about the whole chain of calculations he used to arrive at a wheat-field equivalent for a gallon of gas?

Bob Masta
Ann Arbor, Mich.

Better stated, there are 4.14 kilograms of carbon in the oil used to manufacture 1 gallon of gasoline. Only about 55 percent of that carbon is in the gas. The remainder ends up in other petroleum products. Researcher Jeffrey S. Dukes’ calculations, as described in the story, are correct .–S. Perkins