But that vision is still several years off, Howarth points out. Meanwhile, the SCOPE report suggests that even grassoline may not be the best use of biomass: "The world would be better off using the cellulose directly for combustion," Howarth says. "If you try to use biomass in a stationary way, it's much more efficient." Direct combustion of switchgrass for heat and electricity can provide 2.6-fold more energy than converting the same source to ethanol—and 9-fold more energy than producing ethanol from corn. The proof is out there: 35 percent of homes and commercial buildings in Sweden are heated by combustion of biomass, mostly willows grown on nearby plantations.
Biofuels are a hot topic right now, but the litany of issues surrounding fertilizers and nitrogen pollution are far more complex. Foremost among the challenges is the need to use more fertilizer to combat hunger in many parts of the world, points out ecologist Alan Townsend of the University of Colorado at Boulder. Townsend, like Howarth, has spent much of the past 15 years analyzing the human perturbations to the global nitrogen cycle. More fertilizer is badly needed to help feed burgeoning populations in much of the developing world, and yet mistakes of the West are being repeated elsewhere. A study published in February suggests that China could cut its fertilizer use by a third without reducing crop yield. Pursuit of meat-intensive diets, which requires massive production of fertilized crops to feed animals, is another problem Townsend and Howarth point out.
Despite their dire warnings, neither scientist is a pessimist. Haber's discovery has been a miracle for a century, Howarth says. We just need to be smarter about how we apply it.