Sometimes called the most important technological advance of this century, the Haber-Bosch process allows the economical mass synthesis of ammonia (NH3) from nitrogen and hydrogen. It was developed immediately prior to World War I by Fritz Haber and Carl Bosch, German chemists. Haber won the Nobel Prize for Chemistry in 1918 for his discoveries, while Bosch shared a Nobel Prize with Friedrich Bergius in 1931 for his work on high-pressure chemical reactions. At first a German national secret, the chemistry and techniques behind the effective synthesis of ammonia spread to the rest of the world in the 20s and 30s.

Ammonia is important because it is the primary ingredient in artificial fertilizers, without which modern-day agricultural yields would be impossible. Sometimes called the "Haber Ammonia process," the Haber-Bosch process was the first industrial chemical process to make use of extremely high pressures (200 to 400 atmospheres). In addition to high pressures, high temperatures (750 to 1200 degrees Fahrenheit or 400 to 650 degrees Celsius) are used. The efficiency of the reaction is a function of pressure and temperature - greater yields are produced at higher pressures and lower temperatures.

In the first decade of the 20th century, the artificial synthesis of nitrates was being researched because of fears that the world's supply of fixed nitrogen was declining rapidly relative to the demand. While nitrogen in its inactive, atmospheric gas form is very plentiful, agriculturally useful "fixed" nitrogen compounds were harder to come by at that time in history. Agricultural operations require liberal amounts of fixed nitrogen to produce good yields. At the turn of the century, all the world's developed countries were required to mass import nitrates from the largest available source - Chilean saltpeter (NaNO3). Many scientists started worrying about the declining supply of nitrogen compounds.

The Haber-Bosch process provided a solution to the shortage of fixed nitrogen. Using extremely high pressures and a catalyst composed mostly of iron, critical chemicals used in both the production of fertilizers and explosives, were made highly accessible to German industry, making it possible for them to continue fighting WWI effectively. As the Haber-Bosch process branched out in global use, it became the primary procedure responsible for the production of chemical fertilizers. Today, the Haber-Bosch process is used to produce more than 500 million tons (453 billion kilograms) of artificial fertilizer per year; roughly 1% of the world's energy is used for it, and it sustains about 40% of our planetary population.