How did a tabletop ammonia machine feed billions and fuel a war?

A table-top machine could feed billions because it pulled fertilizer out of the air. Nitrogen makes up about 78 percent of air, but it is exceptionally stable and does not readily react with other chemicals. The Haber-Bosch process converts it to ammonia by reaction with hydrogen, using finely divided iron as a catalyst. Fritz Haber and Robert Le Rossignol demonstrated it in the summer of 1909, producing ammonia from air drop by drop at about 125 mL per hour.

Then the chemical company BASF bought the process and had Carl Bosch scale it up, and industrial production began at BASF's Oppau plant in 1913. It is estimated that one-third of annual global food production uses ammonia from the Haber-Bosch process, which supports nearly half of the world's population.

The same chemistry served war. In World War I the Allies had the big nitrate deposits of Chile and a highly effective blockade, so Germany made its own: synthetic ammonia was used to make the nitric acid behind explosives. Some accounts go as far as calling it virtually certain that Germany would have been defeated within months without the process, which is a judgment about what might have happened, not something anyone can measure. Haber also is considered the father of chemical warfare for developing and weaponizing chlorine and other poison gases. He won the 1918 Nobel Prize in Chemistry for the ammonia synthesis.

The process still has a cost. Ammonia production accounts for 1 to 2 percent of global energy consumption and 3 percent of global carbon emissions.