Managing Carbon and Nitrogen Sustainably
In the course of his work at the Center for Energy and Environmental Studies at Princeton University Robert Socolow has worked on many chemical elements: helium, radon, uranium, plutonium, lead, nitrogen, and carbon. Unfortunately, the only element which we have succeeded in putting where we want it is lead -- which we got out of our blood once we got it out of our gasoline. In addressing his talk on "Managing Carbon and Nitrogen Sustainably" to the centennial meeting of the American Physical Society in Atlanta on 25 March 1999, Socolow observed that the carbon concentration in our atmosphere has increased 50% since the Industrial Revolution due to burning fossil fuels. Nitrogen in nitrous oxide grew similarly during the same time because of increased use of fertilizer.
Energy and food are the two problems preoccupying us in the 21st century, he pointed out, adding that since 1985 energy use appears to have recoupled to the gross national product as we have lost our focus on energy efficiency. He proposed a process of carbon dioxide sequestration as a method of managing carbon sustainably. He noted that Exxon is proposing to pump the 70% carbon dioxide mixed with natural gas back into the field near Singapore from which it will be extracted and that such a carbon dioxide extraction system is already working at Sleipner West in Norway. Socolow also includes management of the carbon from the natural gas in his plan, proposing to react it with steam to produce molecular hydrogen fuel and more carbon dioxide, which would also be sequestered.
Developing a plan to manage nitrogen seemed more elusive, however. Before the Industrial Revolution nature "fixed" nitrogen at the rate of 130 Teragrams per year, but industrialization has more than doubled this, leading to 80 Teragrams per year from fertilized crops, 50 Teragrams per year from legume crops, and 30 Teragrams per year from fossil fuel combustion. As Irma Jarcho has already pointed out in her Winter 1998 "Observations" column, excessive "fixed" nitrogen is of great concern to the environment. Excess runoff from fertilizer degrades ecosystems, nitrous oxide is a greenhouse gas which also depletes stratospheric ozone, and nitric oxide and nitrogen dioxide are smog precursors. The only advantage is that nitrogen fertilizer reduces carbon dioxide through crop growth.
"Should we be manipulating the Earth?" Socolow asked. "If so, who decides? Given the mess we have made should we not clean it up?"
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