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Cooking the Books
[Doomberg] "The path of sound credence is through the thick forest of skepticism." — George Jean NathanImagine, if you will, a green chalkboard. In the upper left corner is written CH4, the chemical formula for natural gas, and in the bottom right is everybody’s favorite molecule, CO2. In between these extremes—sloping downward and to the right—are the words oil, coal, and wood, in that order. What our chalkboard illustrates is a gross approximation of the extent to which the carbon atoms embodied in those materials are already burned (i.e., oxidized), and by extension how much residual energy can be extracted from these feedstocks by burning them further. In essence, it serves as a proxy for energy density. Since CH4 has no oxygen atoms and every carbon is surrounded by four hydrogens, it is not burned at all and is rich in potential energy. Oil has fewer hydrogens per carbon atom and barely any oxygen, so it is only slightly more burned than CH4. Coal contains less hydrogen still and a fair bit of oxygen, so it is measurably more burned than oil. Wood is replete with oxygen-rich celluloses and other complex natural polymers, putting it below coal on our chalkboard. Finally, CO2 is saturated with oxygen, and so the carbon in it is fully burned. It is a thermodynamic sink. It follows from this rudimentary chemistry lesson that burning wood emits more CO2 per unit of energy produced than burning coal, that coal is worse than oil, and that oil is worse than natural gas. The same can be said about other undesirable byproducts of combustion, as wood and coal in particular contain all manner of contaminants that do not burn very well. As an instructive contrast, natural gas burns so cleanly and efficiently that we use it for cooking indoors with nary a thought given to ventilation, but starting a campfire in the middle of your living room would be, well, kind of nuts. The clouds of smoke that blanketed much of North America last year as a result of forest fires in Canada are testimony to these obvious empirical truths. Posted by: Besoeker 2024-05-04 |
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