Comments

Mr. Tilman claims that the best agricultural non-food energy yields come from prairie grasses. However, what energy is he talking about? Is it the total energy content of the prairie grass? If so, how would it benefit us, would it replace coal in an electric power plant? Would the harvested prairie grass be fermented to ethanol or butanol using some yet to be invented process? How much energy would be required to grow and to process prairie grass to useful fuel or useful energy? Would there be a net increase in energy in the process? How many harvests of prairie grass could be tolerated before the soil is depleted of minerals and nutrients? How many acres of marginal arable land would be required for prairie grass production in order to replace just 5% of our transportation energy needs with the energy derived from prairie grass? Mr. Tilman proposes and answers none of these questions. There is no substance to Mr. Tilman’s article, just fluff. In many ways Mr. Tilman is like Barack Obama, a lot of meaningless words and no substance, just promises. Unfortunately, in the last few years, articles such as this have significantly decreased the stature of this once-great popular science magazine. I concluded long ago that Popular Science has an agenda that is not compatible with good science and economics. Jose Sanchez