Dinitrogenoxide (N2O)

The substance
Under normal environmental conditions dinitrogen oxide (more commonly known as nitrous oxide) is a colourless gas with a slight sweetish taste and odour. It is non flammable itself but will support combustion and is only slightly soluble in water. It has an anaesthetic and an analgesic property, offering pain relief when inhaled in sufficient amounts. In the 19th century it was termed 'laughing gas' after the amusing effects it had on people that inhaled it.

As a weak anaesthetic gas, nitrous oxide has been in use since the 19th century in medicine and dentistry. It is used in the dairy industry as a mixing and foaming agent as it is non-flammable, bacteriostatic (stops bacteria from growing) and leaves no taste or odour. In motor sport it is used to speed engines and it is even used in diving to avoid nitrogen narcosis and other effects experienced in deep dives.

Major emissions
Nitrous oxide is produced both naturally-from a wide variety of biological sources in soil and water-and anthropogenically by a variety of agricultural, energy-related, industrial and waste management activities. Nitrous oxide is also produced naturally in soils through microbial processes of nitrification and denitrification. The two major sources of man-made nitrous oxide emissions are in general agricultural soils and the manufacture of adipic acid (a feedstock for nylon manufacture) and nitric acids. Lower level emissions arise from combustion processes in the power generation sector and from road transport. Of the emissions from agricultural soils the most significant sources are fertiliser application and leaching. Emissions from road transport are increasing as a result of the increasing number of petrol driven cars fitted with 3 way catalytic converters, since the converters produce significantly larger emissions of nitrous oxide. The contribution of road transport is minor but important because it is steadily growing in contrast to the other sectors which are declining.

Impacts on human health and environment
The main impact of nitrous oxide on the global environment is as a greenhouse gas, leading to global warming. Nitrous oxide is for many countries the third most important greenhouse gas, after carbon dioxide and methane. Although the emissions of nitrous oxide to the environment are smaller its global warming potential is 310 times that of carbon dioxide. The concept of global warming potential has been developed to compare the ability of each greenhouse gas to trap heat in the atmosphere relative to another gas. Nitrous oxide is also an ozone depleting substance causing damage to the ozone layer when it reaches the upper atmosphere.

Emission to air reporting threshold: 10000 kg/year

Data source: European Pollutant Emission Register