Pollutant Information: Nitrous Oxide 

About Nitrous Oxide

Category: Greenhouse gases

Nitrous oxide (N₂O) contributes to climate change due to its positive radiative forcing effect, and the gas has a relatively high impact, with a global warming potential (GWP) of 298 compared with a figure of 1 for carbon dioxide. The agriculture sector dominates emissions of N₂O: emissions from agricultural soils in 2021 account for 57% of total UK emissions, and other agricultural sources add another 13%. Other important sources in recent years include road transport, other fuel combustion sources and waste processes. Historically, industrial processes have been a significant source, due to emissions from the manufacture of chemicals – nitric acid and, in particular, adipic acid. In 1998 the sole UK manufacturer of adipic acid commissioned an abatement unit, leading to the significant reduction in the contribution to total emissions from that plant. That process subsequently closed in 2009. The contribution of road transport to total N₂O emissions is small, but there was an increase in N₂O emissions in the early 90s from this source. This was due to the introduction of catalytic converters, since N₂O was formed as an unwanted by-product in reducing NOX, in particular by the early generation of cars with catalytic converters. Total emission levels have fallen by 57% since 1990.

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