Synthetic fertilizer use is a source of greenhouse gas emissions for several reasons.
First, the chemical production of synthetic fertilizers is an energy intensive process as a result of which emissions of CO2 are relatively high.
In addition, N2O is emitted during the chemical reduction of atmospheric N2O to ammonium in industrial fertilizer
production.
Finally, when the fertilizer is applied to the field, part of it is converted to N2O by denitrificating bacteria in soils and sediments.