York Times Science Follies
It isn't the fuels that are efficient of inefficient
|An article in the Pueblo Chieftain,
written by William K. Stevens of The New York Times carries the
Energy trend less damaging to atmosphere
The efficiency for burning fuels is, by definition, the ratio of the useful energy obtained divided by the energy contained in the fuel. Fuels themselves are not efficient or inefficient; the efficiency has to do with the machinery. An open wood fire is very inefficient; a fireplace is somewhat better, a good woodstove is much better, and a high-efficiency wood furnace is better yet. We doubt that Stevens was responsible for the misleading headlines.
Stevens, who is evidently attending the "global climate" meeting in Bonn, Germany, is speaking of something entirely different: the amount of carbon dioxide produced in the burning of fuels. Efficiency does play a role, of course. A coal-burning furnace that usefully delivers 90% of the heat from the coal produces only half as much carbon dioxide as one that delivers only 45% of the heat.
But that's still not what Stevens is driving at. He says that we are using fuels that produce less carbon dioxide (per unit of heat delivered).
"For nearly a century and a half, fuels with high amounts of carbon have progressively been replaced by those with less.Whoa! Aside from unwanted minerals that degrade the quality, coal is all carbon.
Then the New York Times scholar continues:
"Now analysts say that natural gas, even lighter, may be entering its heyday, and that the day of hydrogen --- providing no carbon at all --- may be about to dawn." [underlining added]Petroleum has roughly two atoms of hydrogen for every atom of carbon. Natural gas contains four atoms of hydrogen for every one atom of carbon. A large fraction of the energy comes from combustion of the hydrogen. Therefore, per unit of heat delivered, less carbon dioxide is produced, as any student of high-school chemistry will understand. (Drive by a coal-fired power plant and you will see nothing coming out of the chimney. Drive by a natural-gas-fired power plant and you will see clouds --- real ones of water vapor.)
Hydrogen, it is true, contains no carbon whatsoever. Burning hydrogen produces only common old water vapor. However, Stevens' argument contains an all-too-common non-sequitur.
Hydrogen is not a source of energy; there are no sources of free hydrogen whatsoever on the earth. All hydrogen must be freed from chemical compounds (such as water) at a high price --- a lot of energy. More energy, in fact, than will ever be released from burning the hydrogen.
Where's that energy going to come from?