Nitrous Oxide (N20) is an oxide of nitrogen that is often used in surgery and dentistry for its analgesic and anaesthetic effects. Nitrous oxide also gives rise to nitric oxide (NO) on reaction with oxygen atoms, which, in turn, reacts with ozone, making nitrous oxide a major, naturally occurring regulator of stratospheric ozone. Nitrous oxide is also a major greenhouse gas as it is very effective at absorbing long-wave radiation.

Anthropomorphic (man-made) nitrous oxide emissions are mostly caused by agricultural by-products, as nitrous oxide can be released through the application of nitrate fertilisers. N2O is also produced by the burning of fossil fuels in internal combustion engines but, as we will see below, this is not considered a major input of nitrous oxide into the atmosphere.

Nitrous oxide represents approximately 9% of the anthropomorphic greenhouse gas emissions released annually, and it is therefore important to understand the variety of sources and sectors that it can come from:

Nitrous oxide by sector

Source: Smithson et al, 2008, Fundamentals of the Physical Environment, Routledge.