Non-methane volatile organic compounds (NMVOCs) are a set of organic compounds that are typically photochemically reactive in the atmosphere—marked by the exclusion of methane. NMVOCs include a large variety of chemically different compounds, such as benzene, ethanol, formaldehyde, cyclohexane, 1,1,1-trichloroethane and acetone. Essentially, NMVOCs are identical to volatile organic compounds (VOCs), but with methane excluded. Methane is excluded in air-pollution contexts because it is not toxic. It is however a very potent greenhouse gas, with low reactivity and thus a long lifetime in the atmosphere. The aggregation of these compounds and their collective properties are easier to study than the individual components.
Many NMVOCs carry importance due to their influence on atmospheric ozone. Ground level ozone is not directly emitted, but is instead formed by the reaction of sunlight with various other emitted compounds, including NMHCs (a type of NMVOC), methane, carbon monoxide, and nitrogen oxides.
Biogenic emission
In some non-urban areas, biogenic emissions of NMVOCs meet or exceed anthropogenic emissions of NMVOCs. These atmospherically important NMVOCs include compounds such as terpenoids, hexenals, alkenes, aldehydes, organic acids, alcohols, ketones, and alkanes). These NMVOCs which are emitted by vegetation can be divided by source as having originated from one of seven processes:
The chemical composition of emissions from biomass burning varies across different stages of burning, but total NMVOCs emitted from burning is estimated to be 4.5 grams of Carbon per kilogram.
Anthropogenic emissions
In the European Database for Global Atmospheric Research (EDGAR), anthropogenic sources of NMVOCs are divided into the following categories: The reported emissions are provided by sector as follows:
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|+ NMVOC Emissions by Sector