Nitrogen oxides act as indirect greenhouse gases by producing ozone—a powerful greenhouse gas and air pollutant in the lower atmosphere. It has been assumed that fossil fuel combustion (e.g., from coal-fired power plants and vehicles) is the primary source of rising NOx levels, leading to regulatory action to mitigate these emissions. A new study shows that non-fossil fuel NOx emissions (biomass burning, microbial N cycling) are an equally important source, indicating non-fossil sources should also be equally considered in environmental policies aimed at mitigation of NOx pollution.
Song, W., XY Liu, CC Hu, GY Chen, XJ Liu, W.W. Walters, G. Michalski, and CQ Liu (2021). Important contributions of non-fossil fuel nitrogen oxides emissions. Nature Communications 12, 243.