"The flood of synthetic nitrogen has fertilized not just the farm fields but the forests and oceans, too, to the benefit of some species (corn and algae being two of the biggest beneficiaries) and to the detriment of countless others. The ultimate fate of the nitrates spread in Iowa or Indiana is to flow down the Mississippi into the Gulf of Mexico, where their deadly fertility poisons the marine ecosystem. The nitrogen tide stimulates the wild growth of algae, and the algae smother the fish, creating a "hypoxic," or dead, zone as big as New Jersey—and still growing. By fertilizing the world, we alter the planet's composition of species and shrink its biodiversity." Michael Pollan.
It takes a half gallon of oil to grow a bushel of corn. Why would ethanol be a positve choice for your family car? Ask Fritz Haber:
Fritz Haber? No, I'd never heard of him either, even though he was awarded the Nobel Prize in 1918 for "improving the standards of agriculture and the well-being of mankind." But the reason for his obscurity has less to do with the importance of his work than an ugly twist of his biography, which recalls the dubious links between modern warfare and industrial agriculture: during World War I, Haber threw himself into the German war effort, and his chemistry kept alive Germany's hopes for victory, by allowing it to make bombs from synthetic nitrate. Later, Haber put his genius for chemistry to work developing poison gases—ammonia, then chlorine. (He subsequently developed Zyklon B, the gas used in Hitler's concentration camps.) His wife, a chemist sickened by her husband's contribution to the war effort, used his army pistol to kill herself; Haber died, broken and in flight from Nazi Germany, in a Basel hotel room in 1934.
His story has been all but written out of the 20th century. But it embodies the paradoxes of science, the double edge to our manipulations of nature, the good and evil that can flow not only from the same man but from the same knowledge. Even Haber's agricultural benefaction has proved to be a decidedly mixed blessing.
When humankind acquired the power to fix nitrogen, the basis of soil fertility shifted from a total reliance on the energy of the sun to a new reliance on fossil fuel. That's because the Haber-Bosch process works by combining nitrogen and hydrogen gases under immense heat and pressure in the presence of a catalyst. The heat and pressure are supplied by prodigious amounts of electricity, and the hydrogen is supplied by oil, coal or, most commonly today, natural gas. True, these fossil fuels were created by the sun, billions of years ago, but they are not renewable in the same way that the fertility created by a legume nourished by sunlight is. (That nitrogen is fixed by a bacterium living on the roots of the legume, which trades a tiny drip of sugar for the nitrogen the plant needs.)
Liberated from the old biological constraints, the farm could now be managed on industrial principles, as a factory transforming inputs of raw material—chemical fertilizer—into outputs of corn. And corn adapted brilliantly to the new industrial regime, consuming prodigious quantities of fossil fuel energy and turning out ever more prodigious quantities of food energy. Growing corn, which from a biological perspective had always been a process of capturing sunlight to turn it into food, has in no small measure become a process of converting fossil fuels into food. More than half of all the synthetic nitrogen made today is applied to corn. From this article by Michael Pollan.