Ammonia Use in Agriculture
Ammonia is a source of nitrogen for growing plants. Every fertilizer contains nitrogen either in the form of ammonia or compounds derived from ammonia. The widespread uses of ammonia in agriculture was brought about by the green revolution, which also involved development of high yielding crops and advances in pesticides. A field that produced 20 bushels of corn in 1940 produces over 100 bushels today. While high yield crops and pesticides have contributed to greater production, fertilizer has been the most influential factor in driving the green revolution.
Production of Ammonia
Nitrogen is absolutely necessary for plants to grow. Nature provides nitrogen-fixing bacteria that are harbored by the roots of plants to supply nitrogen compounds. It has long been known that nitrogen rich sources help plants grow, but only since the industrial revolution has nitrogen been produced in large quantities in the form of ammonia. The process by which ammonia is synthesized is referred to as the Haber-Bosc process. Producing ammonia is very energy intensive, as it is directly synthesized from the nitrogen in the air and hydrogen over an iron catalyst. This process is carried out at both very high temperatures and very high pressures.
Ammonia Production is Significant
The production of ammonia is massive in scale, consuming nearly 2% of global energy production. Of the ammonia produced, a full 83% is used directly in fertilizers. The production of ammonia is specifically suited to natural gas, accounting for 5% of worldwide natural gas consumption. Like transportation and energy, our food is entirely fossil fuel dependent.
What is in Fertilizer?
The three primary nutrients in fertilizer are nitrogen, phosphorous, and potassium. The sources of phosphorous and potassium tend to be rocks, and are obtained by mining. For example potassium can be obtained from potassium carbonate, a relatively abundant rock. There is no nitrogen rich ore that plants are capable of feeding on, so the nitrogen must be synthesized in the form of ammonia. Fertilizer also contains several secondary nutrients, and each farming application has a particular optimal fertilizer makeup. Because fertilizer is so dependent on ammonia production, and fertilizer is a large part of agricultural costs, the price of food and the price of natural gas do mimic each other to some degree.
The Future of Ammonia in Agriculture
Over the past 20 years, ammonia production has doubled. It is reasonable to assume that ammonia will be produced for agriculture from natural gas in very large amounts in the future. Is this a sustainable way to feed the world? Fortunately there are very large natural gas deposits in the world, although the global effects of burning that gas in large quantities are beginning to be felt. Ammonia can be generated from any form of energy, by producing hydrogen by hydrolysis, and using the standard Haber-Bosc process. Ammonia will remain a key ingredient in modern industrial farming, even through the transition to clean energy.
"Uses of Ammonia" R.M. Technologies: https://www.rmtech.net/uses_of_ammonia.htm
"Ammonia" From Uses in Agriculture and Beer Making to Prolonging the First World War" Connexions: https://cnx.org/content/m33048/latest/