2. Non-CO₂ Emissions

Due to incomplete combustion of hydrocarbons in fuel, small proportions of carbon are released as carbon monoxide (CO), methane (CH₄), or non-methane volatile organic compounds (NMVOCs), all of which eventually oxidize to CO₂ in the atmosphere. In addition, combustion processes result in emissions of nitrous oxide (N₂O) and nitrogen oxides (NO_x).

Unlike CO₂, emission estimates of CH₄, N₂O, NO_x, CO, and NMVOCs require detailed process information. Accurate estimation of their emissions depends on knowledge of several interrelated factors, including combustion conditions, size and vintage of the combustion technology, maintenance, operational practices, emission controls, as well as fuel characteristics. The methods should be applied at a detailed activity/technology level so as to take, to the extent possible, these factors into account.