UVa scientist ties nitrogen to global climate change

By Brian McNeill

Published: May 16, 2008

One of the key causes of global climate change remains something of an unsung eco-villain, one University of Virginia researcher believes.

In a study to be published in today’s issue of the journal Science, UVa environmental scientist James N. Galloway argues that reactive nitrogen is accumulating in the planet’s soil, water and air at an alarming rate.

“Excessive reactive nitrogen is causing a negative environmental impact, which can be detrimental to humans and to ecosystems,” Galloway said.

The volume of reactive nitrogen being pumped into the environment has accelerated in recent years. During 1995, roughly 156 million metric tons of nitrogen were emitted worldwide. By 2005, that figure had jumped to 187 million.

“We have a nitrogen issue,” he said.

In its inert form, nitrogen is essentially harmless. It makes up around 78 percent of the planet’s atmosphere.

Yet the widespread use of nitrogen-based fertilizers and the burning of fossil fuels have created large amounts of reactive nitrogen compounds, such as ammonia. These compounds are contributing to global warming, atmospheric ozone depletion, smog, haze, soil acidity, acid rain, fish kills, insect kills and respiratory ailments, Galloway said.

Good and bad for farming

On one hand, nitrogen is inarguably a good thing, Galloway said, because it allows farmers to grow crops on a large scale. On the other hand, around 85 percent of the nitrogen used in farming is wasted. Only 10 percent to 15 percent of the reactive nitrogen used in food production ever enters a human’s mouth. The excess nitrogen is lost to the environment and emitted into the atmosphere.

“We found that we’re making more reactive nitrogen than ever before,” said Alan Townsend, co-author of the study and a professor at the University of Colorado. “A lot of that is driven by our increasing agriculture demands.”

One culprit is China’s growing taste for meat, which echoes America’s long-standing love affair with beef and pork. Raising cows and pigs produces substantially more reactive nitrogen than does raising crops such as soybeans or vegetables.

“Just by cutting back on your steak and pork chop consumption, you’re reducing your nitrogen footprint,” Galloway said.

Galloway is the founding director of the International Nitrogen Initiative, which seeks to optimize the use of nitrogen in food production while minimizing the negative effects on human health and the environment. After five years, he stepped down from the position Thursday.

Award-winning research

Last month, Galloway was a co-winner of the Tyler Prize for Environmental Achieve-ment, which is essentially the equivalent of the Nobel Prize in the fields of environmental science, energy and health. His development of the “nitrogen cascade” — a model that demonstrates how nitrogen cycles through and affects the environment — was noted as a key reason he was selected.

Galloway is using his share of the $200,000 prize to develop an online tool that will allow people to calculate their nitrogen footprint.

Similar calculators exist on the Internet for people to see the size of their carbon footprint.

Individually, people can reduce their nitrogen footprint by driving less, eating locally produced food and by eating dairy, chicken and fish instead of pork and beef.

“When it comes to food, the three key words to remember are local, organic and less meat,” he said.

Personal changes will not be enough, Galloway said, to protect the environment. Systemic changes will also be needed.

New technology will be needed for food production so excessive reactive nitrogen is not produced. Coal-fired power plants will need to be fitted with scrubbing technology. Sewage treatment facilities need to ensure that a minimal amount of nitrogen is discharged.

Harrison Rue, executive director of the Thomas Jefferson Planning District Commission and a member of Gov. Timothy M. Kaine’s advisory panel on climate change, said he is eager to see Galloway’s recommendations. “We’re looking forward to seeing his study,” he said.

Rue added that he suspects many of the strategies that aim to curtail carbon dioxide emissions will also cut down on reactive nitrogen. He praised UVa and other Virginia universities for tackling research that could help prevent the dire predictions associated with climate change.

Virginia’s water affected

The new study is notable because it shows that nitrogen is not just polluting the Chesapeake Bay, but is also affecting the environment as a whole, said Josh Tulkin, deputy director of the nonprofit Chesapeake Climate Action Network.

“It’s rather disconcerting,” he said. “It should be a wake-up call that even more human activity is contributing to climate change.”

Virginia’s Department of Environmental Quality is working to curtail discharges from sewage treatment plants across the state and to protect air quality, spokesman Bill Hayden said. The “next frontier” for the DEQ, he said, will be to address agricultural use of nitrogen.

“Nitrogen is a chemical that affects, in one way or another, the air, the land and the water of Virginia,” he said.