On the Issues of NOx as Greenhouse Gases: An Ongoing Discussion…

Abstract

Nitrogen oxides (NOx = NO + NO2) emitted from a stationary combustion chamber (including waste to energy plants) or engines cause numerous undesirable environmental effects. These include negative influences on human and animal health, detrimental effects on plants and vegetation, acid rain, and smog. These negative influences are commonly accepted by the scientific community. However, the impact of NOx on the greenhouse effect (GHE) is not generally accepted by the scientific community. In this paper, the issue of the impact of NOx on the GHE is discussed, and it was analyzed and explained that NOx are an indirect greenhouse gas (GHG). However, the impact of NOx on the GHE is a complex process affected by different parameters (cooling and warming nature is possible). It has been estimated that NOx emitted from stationary, ground-placed sources (such as boilers and furnaces) have little impact on the GHE compared to CO2 and other direct GHGs. The contribution of NOx in the GHE compared to the emission of all GHGs is less than 3%. NOx sources from waste incineration and co-incineration plants were especially considered and analyzed. The co-incineration in smaller plants (capacity range of 1 ÷ 5 MW) gives more benefits to the environment due to a decrease in the NOx emission standards when the share of the waste increases.