In nature, nitrous oxide comes from the nitrogen cycle. This greenhouse gas also comes from the burning of oil products and the use of synthetic fertilizers.
Plants, animals and microorganisms in soil contribute to the nitrogen cycle that emits nitrous oxide into the atmosphere. Most of these emissions are from bacteria breaking down nitrogen in soils and oceans.
Globally, about 40 percent of total nitrous oxide emissions come from human activities, such as agriculture, transportation, wastewater management and industrial activities. In agriculture, synthetic fertilizers added to the soil accounted for 75 percent of all U.S. nitrous oxide emissions in 2012. Nitrogen broken down from livestock manure and urine contributed to 4 percent of nitrous oxide emissions in 2012. In transportation, motor vehicles are the biggest source of nitrous oxide, tough the amount released depends on fuel type, vehicle technology, maintenance and operating practices. In industry, nitrous oxide is the byproduct of nitric acid production (used to make synthetic commercial fertilizer) and adipic acid production (used to make fibers like nylon and other synthetic products).
In 2012, nitrous oxide from human activities accounted for about 6 percent of all U.S. greenhouse gas emissions. Most nitrous oxide stays in the atmosphere an average of 120 years before it's destroyed by light and excited oxygen atoms or absorbed by certain types of bacteria. A pound of nitrous oxide has over 300 times the impact of a pound of carbon dioxide in warming the Earth's atmosphere.