The Haber Process: The Invention That Fed the World

The Haber process, developed by the German chemist Fritz Haber and industrialized by Carl Bosch in the early years of the twentieth century, is the method by which ammonia is synthesized from atmospheric nitrogen and hydrogen. The development of the Haber process, also known as the Haber-Bosch process, was one of the most important inventions of the Second Industrial Revolution, and it has been credited with enabling the production of enough nitrogen fertilizer to feed a substantial fraction of the world’s population.

The Problem of Fixed Nitrogen

To understand the importance of the Haber process, it helps to understand the problem it solved. Nitrogen is one of the essential elements for plant growth, and it is a key component of proteins, nucleic acids, and other biological molecules. Although the Earth’s atmosphere is about 78 percent nitrogen, atmospheric nitrogen is in the form of N₂, a very stable molecule that does not react easily with other substances. For plants to use nitrogen, it must be “fixed,” or converted into a more reactive form, such as ammonia (NH₃), nitrate (NO₃⁻), or ammonium (NH₄⁺).

Before the development of the Haber process, the main source of fixed nitrogen was natural deposits of guano (bird droppings) and saltpeter (potassium nitrate), along with the small amount of nitrogen fixed by lightning and by certain bacteria. The supply of natural nitrogen was limited, and the demand for it was growing rapidly as the world’s population increased and as agriculture became more intensive.

The problem of fixed nitrogen became particularly acute in the late nineteenth and early twentieth centuries, as the demand for fertilizers and explosives (which also require fixed nitrogen) outstripped the supply. The price of natural nitrogen rose sharply, and there was widespread concern about a “nitrogen famine” that would limit the growth of agriculture and the production of armaments.

Fritz Haber and the Synthesis of Ammonia

Fritz Haber (1868-1934) was a German chemist who had been working on the problem of nitrogen fixation for several years. In 1908, he achieved a breakthrough when he succeeded in synthesizing ammonia from nitrogen and hydrogen at high pressure and temperature, using an iron catalyst. The yield was small, only about 6 percent, but it demonstrated that the synthesis was possible.

Haber’s discovery was of enormous strategic importance, and it attracted the attention of the German chemical company BASF, which had been working on the same problem. BASF assigned one of its leading chemists, Carl Bosch, to develop Haber’s process into a commercial reality. Bosch, working with a team of engineers and chemists, developed a large-scale process for the synthesis of ammonia, using high-pressure reactors, improved catalysts, and continuous-flow methods.

The first commercial Haber-Bosch plant came on stream at Oppau, Germany, in 1913, with a production capacity of about 30 tons of ammonia per day. The plant used the Haber process to produce ammonia, which was then converted into ammonium sulfate, a nitrogen fertilizer. The article on the aniline dyes describes the broader context of the German chemical industry.

The Haber Process and the First World War

The Haber process had a major impact on the First World War, which broke out in 1914. Before the war, the main source of nitrates for the production of explosives was the natural deposits of saltpeter in Chile, and the British navy controlled the sea lanes through which the saltpeter was shipped to Germany. With the outbreak of war, the German supply of nitrates from Chile was cut off, and the German war effort was threatened with a shortage of explosives.

The Haber process saved the German war effort. The Oppau plant, and other plants built during the war, produced large quantities of ammonia, which was then converted into nitric acid and used in the production of explosives. Without the Haber process, Germany would have run out of explosives within a year, and the war would have ended much sooner. The article on Henry Ford and the assembly line describes another important American contribution to the industrial age.

The Haber process was also important for the production of fertilizers, which became increasingly important during the war as the German agricultural system was disrupted by the Allied blockade. The production of synthetic fertilizers helped to maintain German food production during the war, although the blockade still caused widespread hunger.

The Haber Process After the War

After the war, the Haber process was rapidly adopted around the world, and the production of synthetic ammonia grew rapidly. The British and American chemical companies, which had been dependent on the German chemical industry, developed their own versions of the Haber process, and the technology was applied in countries throughout the world.

The development of the Haber process had a major impact on global agriculture. The availability of cheap nitrogen fertilizers made possible a dramatic increase in agricultural productivity, and the Haber process has been credited with enabling the production of enough food to feed a substantial fraction of the world’s population. Some estimates suggest that the nitrogen fixed by the Haber process now supports about half of the world’s food production.

The Haber Process and the Environment

The Haber process has had important environmental effects. The production of synthetic nitrogen fertilizers has contributed to the buildup of nitrates in the environment, with effects on water quality, soil health, and the nitrogen cycle. The article on the causes of the Industrial Revolution describes the relationship between industry and the environment in more detail.

The Haber process has also been controversial because of its association with the production of explosives and with the German war effort. Fritz Haber himself was a controversial figure, and he has been called the “father of chemical warfare” for his work on the use of chlorine gas during the First World War. Despite this, the Haber process is generally considered to be one of the most important inventions of the twentieth century, and it has been recognized as such by the award of the Nobel Prize in Chemistry to Fritz Haber in 1918.

The Legacy of the Haber Process

The Haber process is one of the defining inventions of the Second Industrial Revolution. It established the chemical industry as a major force in the modern economy, and it laid the foundation for the development of the modern fertilizer, agricultural, and food industries. The process has also had important political effects, since the ability to produce synthetic nitrogen has been a major strategic asset in both world wars and in many smaller conflicts.

The Haber process is also important as an example of the kind of large-scale industrial research that became characteristic of the modern chemical industry. The development of the process required the combined efforts of academic chemists like Haber, industrial chemists like Bosch, and a large team of engineers, technicians, and support staff. The model of industrial research that Haber and Bosch exemplified has been imitated by chemical and pharmaceutical companies around the world.

The Continuing Question

The unresolved historical question about the Haber process is how to weigh its benefits (feeding the world) against its costs (chemical warfare, nitrogen pollution, the strategic weaponization of fertilizer). The traditional answer, going back to the 1918 Nobel Prize and given its modern form in Vaclav Smil’s Enriching the Earth (2001), is that the Haber process was a net good: by enabling the production of synthetic nitrogen fertilizer, it has allowed the world to feed a population that would otherwise have hit a Malthusian ceiling sometime in the 20th century, and the nitrogen fixed by the Haber and Bosch plants now supports about 40 percent of the world’s food production. The revisionist answer, developed in the work of environmental historians and in the recent literature on nitrogen pollution, is more cautious: the Haber process has been a major contributor to the nitrogen cascade that has produced algal blooms in the Gulf of Mexico and the Baltic Sea, to the loss of soil microbial diversity, and to the greenhouse gas emissions of the modern agricultural system. The interesting current question, raised in the work of environmental historian John McNeill and developed in the recent literature on the planetary boundaries framework, is whether the Haber process has been a net benefit on the scale of the 20th-century world population, or whether it has simply substituted one form of constraint (Malthusian hunger) for another (planetary-boundary nitrogen). The honest answer, given the data, is probably: the Haber process fed the 20th century, but its 21st-century successors will need to do it without the environmental costs of the original.

Selected Sources

Vaclav Smil, Enriching the Earth: Fritz Haber, Carl Bosch, and the Transformation of World Food Production (2001).
John E. Lesch, “The German Chemical Industry in the Twentieth Century,” in World Industrial Transformation, ed. David C. Mowery (1999).
Anthony S. Travis, The Rainbow Makers (1993).
Robert H. Wiebe, The Search for Order, 1877-1920 (1967).