Researchers say the average American produces forty-two kilograms of nitrogen pollution a year. Some of that comes from fossil fuels like oil and coal. But more than seventy percent involves food.

University of Virginia researcher Allison Leach says Americans eat almost twice as much protein as the government recommends. She says eating only the recommended levels could reduce nitrogen footprints by almost half.

Professor Galloway says animal protein plays a big part. He points to the example of cattle that are given feed grown with nitrogen fertilizer.

JIM GALLOWAY: "For large animals like beef, a very large fraction of the nitrogen that enters the cow’s mouth is excreted out the back end."

Last year, a study supported by American beef producers found that their industry's environmental impact has decreased over the past thirty years. Jude Capper at Washington State University reported that by producing more beef from fewer animals, the industry cut its carbon footprint by eighteen percent.

The nitrogen calculator is currently designed for people in the United States, Germany and the Netherlands. Another online calculator will be designed for India.

And that's the VOA Special English Agriculture Report, written by Jerilyn Watson and Steve Baragona. For a link to the nitrogen footprint calculator, go to voaspecialenglish.com. I'm Jim Tedder.