Solutions to Environment Threats - Nitrogen Cycle

Robert Howarth, professor of ecology and environment biology, Cornell university.

Human activity has greatly altered the flow of nitrogen across the globe. The single largest contributor is fertilizer use. But the burning of fossil fuels actually dominates the problem in some regions, such as northeastern US. The solution in that case is to conserve energy and use it more efficiently. Hybrid vehicles are another excellent fix; their nitrogen emissions are significantly less than the traditional vehicles because their engines turn off when the vehicle is stopped. (Emissions from the conventional vehicles actually rise when the engine is idling.) Nitrogen emissions from U.S. power plants could be greatly reduced, too, if plants that predate the Clean Air Act and its amendments were required to comply; these plants pollute far out of proportion to the amount of electricity they produce.

In agriculture, many farmers could less fertilizer, and the reductions in crop yields would be small or nonexistent. Runoff from corn fields is particularly avoidable because corn’s roots penetrate only the top few inches of soil and assimilate nutrients for only two months of the year. In addition, nitrogen losses can be reduced by 30 percent or more if farmers plant winter crops, such as rye or wheat, which can help the soil hold nitrogen. These corps also increase carbon sequestration in soils, mitigating climate change. Better yet to grow perennial plants such as grasses rather than corn; nitrogen losses are many times lower.

Nitrogen pollution from concentrated animals feeding operations (CAFOs) is a huge problem. As recently as the 1970s, most animals were fed local corps, and animals’ wastes were returned to the fields as fertilizer. Today most U.S. animals are fed crops growing hundreds of miles away, making it “uneconomical” to return the manure. The solution? Require CAFO owners to treat their wastes, just as municipalities must do with the human wastes. Further, if we ate less meat, less waste would be generated and less synthetic fertilizer would be needed to grow animal feed. Eating meat from animals that are range-fed on perennial grasses would be idea.

The explosives growth in the production in the production of ethanol as a biofuel is greatly aggravating nitrogen pollution. Several studies have suggested that if mandated U.S. ethanol targets are met, the amount of nitrogen flowing down the Mississippi River and fueling the Gulf of Mexico dead zone may increase by 30 to 40 percent. The best alternative would be to forgo the production of ethanol from corn. If the country wants to rely on biofuels, it should instead grow grasses and trees and burn these to co-generate heat and electricity; nitrogen pollution and greenhouse gas emission would be much lower.