Nitrogen, the other greenhouse gas

This often-overlooked global warmer is worse than CO2, and the amount of it in our waterways is increasing.

By Jessica A. KnoblauchThu, Jan 14 2010 at 5:22 PM EST

Photo: Associated Press

Nitrogen has become a staple for farmers to grow bigger crops, but too much nitrogen is wreaking havoc on the environment, which researchers say is awash in man-made nitrogen, according to a recent article in the Christian Science Monitor.

Though farmers use nitrogen to boost crop yields, much of the fertilizer is wasted, eventually making its way into nearby waterways, causing dead zones where algae blooms choke off marine life.

The most well-known dead zone is at the mouth of the Mississippi River in the Gulf of Mexico, where scores of fish and shrimp have been eliminated across an 8,000-square-mile area. More than 400 dead zones with a total area of 245,000 square kilometers were identified worldwide last year, according to the Monitor.

U.S. farmers waste as much as 40 percent of the nitrogen that they apply to their crops. In China, the rate is even worse, where about twice as much nitrogen fertilizer is used as in the U.S. to yield about the same amount of crops. In fact, as much as three-fourths of all nitrogen used to grow rice in China may be wasted, said Vaclav Smil, a nitrogen expert at the University of Manitoba in Winnipeg.

“Nitrogen plays a tremendously important role in feeding the world’s peoples, so that’s a very positive benefit for humanity,” said James Galloway, a professor of environmental science at the University of Virginia, Charlottesville, and a leading nitrogen researcher. “The problem is how to maximize nitrogen’s benefits while diminishing its negatives — especially waste.”

But farmers aren’t the only culprits of nitrogen overload. Vehicle exhaust, power plant exhaust, and large-animal feeding operations are all sources of nitrogen emissions, according to the report. These increased nitrogen loads from power plants and other sources are causing smog, acid rain and global warming.

Unlike carbon dioxide, nitrogen doesn’t stick in the atmosphere for long periods of time. Instead, it precipitates out within a few days as ammonia-laden rain — a mixture of hydrogen and nitrogen that fertilizes plants as it falls to the ground. Researchers have found major growth in ammonium in air quality data across 15 U.S. national parks, including Rocky Mountain, Yellowstone, Mount Rainier and Canyonlands parks, according to a previous Associated Press report. In addition, invasive grasses in the Mojave and Sonoran deserts are taking over native plants and fueling wildfires — all because of an increase in nitrogen.

“The more nitrogen that we use in agriculture or that comes from various combustion processes — cars or power plants — the more ends up in the world’s ecosystem,” says Lester Brown, president of the Earth Policy Institute in Washington. “By altering concentrations of this key nutrient in the system, we are altering that ecosystem in many, many ways.”

Luckily, there are people working to reduce nitrogen in the environment. EPA’s recently proposed clean air standards could cut 90 percent of nitrogen emissions that come from stationary sources like power plants. In addition, some farmers are working hard to decrease their nitrogen use by increasing efficiency.

“Getting nitrogen right is critical for getting climate change right, food security right, and a lot of issues associated with poverty that have to do with nutrition depletion,” said Bill Herz, vice president of scientific programs for the Fertilizer Institute, a Washington trade organization that represent North American fertilizer manufacturers.