Nitrous oxide (N₂O) comes from both natural and human-related sources. Natural sources:
- Microorganisms in soils under natural vegetation produce about 60% of natural nitrous oxide emissions by breaking down nitrogen compounds
- Oceans contribute about 35% of natural emissions through microbial activity in anaerobic conditions around sinking particles
- Atmospheric chemical reactions and wetlands also emit smaller amounts naturally
Human-caused sources:
- Agriculture is the largest human source, accounting for roughly 70-78% of global nitrous oxide emissions. This mainly comes from nitrogen-based fertilizers, livestock manure, and soil cultivation, which stimulate microbes to produce more N₂O
- Industrial processes, especially the production of nitric acid and adipic acid (used in fertilizers and nylon), release significant amounts of nitrous oxide as byproducts
- Fossil fuel combustion and biomass burning also emit nitrous oxide, though at lower levels compared to agriculture
- Treatment of solid wastes and human sewage contributes smaller but notable amounts of nitrous oxide emissions
In summary, nitrous oxide originates from microbial processes in natural ecosystems and is significantly increased by human activities, primarily intensive agriculture and certain industrial processes
