How does fertilizer create carbon dioxide?

Answer 1

Nitrogen fertilizer production converts nitrogen from the atmosphere into urea, a form of nitrogen fertilizer. Nitrogen fertilizer is the main macronutrient used by plants, i.e, the main component of fertilizers (the others are potassium and phosphorus). The atmosphere is 78% nitrogen. Google the nobel prize-winning Haber-Bosch process. The two scientists identified a method of using enormous amounts of heat and pressure to convert atmospheric nitrogen into a form usable to plants. And there's the source of your answer: the required heat and pressure is usually generated by natural gas, which gives off CO2 when combusted. Without the increased plant growth that the Haber-Bosch process enabled, the planet would probably be unable to support more than a couple billion fewer people than it does now. But good luck nailing that number down--estimates are all over the place, and for good reason. For example, without nitrogen fertilizer and with the food scarcities that scenario would create, would we be converting as much grain into livestock? Would we be burning it as fuel in our cars? Would we have better agriculture technology or better management if prices were higher? You get the picture. There is a small dark side to this. When overapplied, nitrogen fertilizer emits nitrous oxide, a powerful greenhouse gas, and pollutes surface and groundwater. Google the U.S. Gulf "dead zone".