Anyone looking for ways to reduce their environmental impact has probably heard that they should eat less meat, especially beef. Even on a large scale, cows are an inefficient way to feed people – It takes nearly four tons of water to save one ton of beefand many agricultural practices produce greenhouse gases and pollutants.
Researchers at the University of Pittsburgh were the first to detect one of these pollutants, nitrogen, along the U.S. beef supply chain at the county level. They found that there are large spatial differences between where beef is eaten and where the effects of nitrogen are felt.
Previous studies examined the production-related impacts, Vikas KhannaProfessor of civil and environmental engineering at the Swanson School of Engineering. “They’ve asked, ‘What does it take to produce a certain amount of beef?’ And they tend to cite average environmental impacts,” such as how much water, greenhouse gases or other pollutants are produced throughout the process.
In a paper published in the journal Environmental Science and Technology, Khanna and graduate student Anaís Ostroski map the environmental impacts of nitrogen county by county, painting the clearest picture yet of which areas are affected by the environmental impacts of livestock farming. Khanna and Ostroski are joined by Oleg Prokopyev, a former professor of industrial engineering at Pitt who is now at the University of Zurich.
“It is important to measure nitrogen losses and understand where they occur due to the cascading environmental impacts,” said Ostroski, the study’s lead author. “A single molecule of reactive nitrogen can have multiple negative impacts until it is converted back to stable atmospheric nitrogen. Food supply chains have become increasingly complex. We found that, on average, beef consumption in a given county is associated with nitrogen losses in more than 200 counties.”
Our atmosphere is 70% nitrogen, but atmospheric nitrogen has strong bonds and does not react with other substances. However, the nitrogen used in fertilizers is reactive. When it builds up, it can form ground-level ozone, which can cause respiratory problems. When nitrogen fertilizers are washed by rain from farmland into waterways, it can lead to uncontrolled algae growth, which deprives the water of oxygen and suffocates fish and other marine life.
In 2017, beef consumption released about 1,330 gigagrams of nitrogen into the environment, enough to fertilize about 9.5 million acres, or 20% of all the corn grown in the United States.
Its effects are not felt evenly across the country.
The new study shows that people living on the East Coast and in much of California, Nevada and Arizona are more than 600 miles away from the nitrogen released into the environment by making their burgers.
Pollution occurs in several ways along the supply chain. Cows are fed feed grown using nitrogen fertilizers, much of which is washed away by rainwater and contaminates neighboring lands and water supplies.
Cattle are raised in processing plants where nitrogen is released into wastewater. Khanna sees an opportunity to minimize nitrogen pollution by implementing a circular economy model that recovers valuable nutrients such as nitrogen and phosphorus from wastewater.
“Recovering nutrients from animal wastewater would be a win-win solution,” he said. Nitrogen would be kept out of the ecosystem and farmers could reuse the nitrogen as fertilizer while also reusing the treated water for irrigation.
While it is important to look at technological solutions to reduce the environmental impact of livestock farming, Khanna cautions against technological over-exuberance: “We should not just look at the trees and miss the forest. It is important to look at potential solutions from a holistic perspective to ensure we are not solving one problem at the expense of others.”
— Brandie Jefferson, photography by Alabama Extension via Wikimedia Commons
