Highland cattle relaxing in a field. Image courtesy of Dr Aimable Uwizeye.
Dr Aimable Uwizeye, who was featured in a recent Afrisnet Spotlight, led an international team of researchers during an impact assessment of the large amount of human-associated nitrogen that is released into the environment every year. In their latest paper, Nitrogen emissions along global livestock supply chains, published in the journal Nature Food, the group describes attempting to measure the amounts of human-associated nitrogen that is released into the environment and the impact it has.
The amount of human-associated nitrogen that is released into the environment has been growing steadily over the past several decades. Prior research has shown that nitrogen amounts have surpassed the “planetary boundary” where too much of an atmospheric constituent, in this case nitrogen, could jeopardize humanity’s ability to survive. Nitrogen is released in a few different ways as either nitrates (water pollution), ammonia (air pollution), or nitrous oxide (greenhouse gas). Nitrogen that makes its way into the surface water can produce algal blooms, a rapid increase or accumulation in the population of algae in freshwater or marine water systems.
Human-associated nitrogen emissions come from a variety of sources, including synthetic fertilizer, sewage, power plants, and other industrial sources. However, one of the largest contributors is the livestock supply chain. Staggering amounts of nitrogen-containing fertilizer are used to grow food that is then used to feed livestock, and massive amounts of nitrogen is later released from livestock manure processing systems.
After studying data from around the globe, the team calculated that the livestock supply chain emits 65 trillion grams of nitrogen into the environment every year, which exceeds the number calculated to represent the planetary boundary. They also found that the livestock supply chain makes up approximately one-third of all human-associated nitrogen released into the environment. Nitrogen emissions must be reduced if we are to prevent future disaster.
Fig. 1 | Global N flows and sources of N compound emissions allocated to the livestock sector. N emissions associated with manure used to produce food
crops and non-food products are aggregated. Losses of N2 to the atmosphere from manure management systems are estimated at 8.3 Tg N yr−1 and are not
shown here. All numbers are expressed in Tg N yr−1.