Natural gas - Important fuel source and fertilizer component consisting primarily of methane, and is found in fossil fuels and coal beds, among other places. Considered to be the cleanest of the fossil fuels, but requires extensive processing in order to remove elements other than methane.

Natural gas combined cycle (NGCC) - Systems that generate electricity using gas turbines, and then capture waste heat to generate steam and additional electricity using a steam turbine.

Natural gas desulfurization - Broad process consisting of several applications (e.g. amine treatment or membrane adsorption) that removes sulfur from natural gas thereby purifying said gas and removing pollutants. Recovered sulfur can be used in various chemical industry applications.

Natural gas vehicles - Vehicles with motors that run primarily, if not exclusively, on natural gas.

Net zero buildings (NZB) - Buildings that draw no net energy from the grid on an annual basis. Achieved through a combination of energy efficiency and on-site generation.

Neutralization - Process in which the hazardous components of waste are eliminated, thereby rendering them benign (e.g., a corrosive acid is neutralized with a basic substance so that it is no longer corrosive, etc.).

New energy vehicles - Vehicles that are not driven by gasoline or diesel internal combustion engines, but by other power sources (storage batteries, fuel cell, solar power etc.).

Nitrogen oxide (NO_x) - Generic designation for a number of mono-nitrogen oxides, NO_x is produced and released during combustion and is a chief component of smog.

Non-GHG air pollutants - Mainly sulfur oxides, nitrogen oxides, volatile organic compounds and other pollutants whose primary detrimental effects on health and environment do not stem from their global warming potential.