If I review the term Haber Process and accompany it with descriptive words such as industry, ammonia, nitrogen, fertilizer, and energy consumption, it is almost inevitable that most people will picture factories working non-stop, emitting columns of smoke into the air through their long chimneys, and ultimately polluting the environment. And there is certainly some – or a lot – of truth to that. But paradoxically, it also has positive effects, fundamental in fact, and I don’t just mean the economy or the jobs it generates.

To be exact, this process is called the Haber-Bosch process because its creators were Fritz Haber and Carl Bosch, two German chemists who collaborated hand in hand in 1910 to develop a system for producing ammonia through a reaction of atmospheric dinitrogen and dihydrogen induced by a metallic catalyst at high temperature and pressure.

The invention was of great importance due to the difficulty until then in producing ammonia on an industrial scale, as the existing systems until then, such as the Birkeland-Eyde or Frank-Caro processes, were not efficient.

Fritz Haber and Carl Bosch/Image: ZdBdLaLaLa on Wikimedia Commons

And why was so much ammonia needed? Nowadays we would say that it is the basic component of fertilizers. However, in those early decades of the 20th century, the goal was the production of explosives and ammunition.

In that sense, Germany had a special interest due to the arms race in which it was immersed in the face of the increasingly inevitable war that was looming and which, when it finally broke out, meant a limitation of raw materials for the German armament industry, as the Allies blocked their imports of saltpeter from Chile (the companies were British).

In reality, the growing demand for ammonia and nitrates was not only German but worldwide since the previous century. As we mentioned before, there is an important source of nitrogen, our own air, in which that element constitutes 87%, but it is so stable that it is complicated to make it react with other chemicals; that is why achieving its conversion was a challenge for science. Fritz Haber built a high-pressure instrument with which he managed to produce ammonia from the air drop by drop, and in 1909 he presented it officially.

Chilean saltpetre workers in 1876/Image: public domain on Wikimedia Commons

The German company BASF acquired the invention to apply it on an industrial scale, with Carl Bosch in charge of adapting it the following year, and ammonia production starting in 1913. Success became evident when they began to obtain around twenty tons per day, which allowed for the desired amount of ammunition production. Thus, Germany was able to face the First World War without depending on anyone, while sales of Chilean saltpeter, by the way, were reduced by two-thirds and its price collapsed.

After the war, possible prejudices were set aside and academic justice prevailed: the work of Haber and Bosch was recognized as part of their merits, which were later expanded with research on other topics, resulting in them being awarded the Nobel Prize in Chemistry in 1918 and 1931, respectively.

It should be noted that Haber, a proud patriot, had participated in the development of dichloro gas used in the Second Battle of Ypres and the Eastern Front; however, he refused to work for the Nazis because, although Christian, he was of Jewish descent (ironically, they used his gases for the Final Solution). Bosch also refused to have dealings with them.

German gas attack on the Eastern Front. Dichloro formed an ominous but easily detectable green cloud, hence it was replaced by phosgene and iperite./Image: Bundesarchiv. Bild, on Wikimedia Commons

Times have changed and nowadays the main use of the Haber Process is the production of ammonia for fertilizers. To achieve this, nitrogen and hydrogen (the latter obtained from methane from natural gas in a nickel catalyst that separates carbon and hydrogen atoms) are combined at a temperature of around 400-500°C and between 150 and 300 atmospheres of pressure.

The original catalyst, osmium, was later replaced by uranium, which is more abundant, but now a magnetite-based catalyst (iron powder subjected to oxidation) is used to reduce costs.

Until Haber devised his system, industrial fertilizers were produced using the Cyanamide Process, invented in 1898 by Adolph Frank and Nikodem Caro (hence it is also called the Frank-Caro Process).

Haber-Bosch Process Diagram/Image: Sven on Wikimedia Commons

It consisted of an exothermic reaction (i.e., energy-producing) of calcium carbide with nitrogen, carried out in large steel cylinders heated to a temperature of one thousand degrees, which resulted in two things: on the one hand, carbon; on the other hand, nitrolim (a solid mixture of calcium cyanamide, white, odorless crystals that formed the basis of fertilizers).

The problem was that this method required the consumption of enormous amounts of electricity and a huge workforce, which relegated the diffusion of the Haber Process to a secondary position. It is still used, but it is the other method that truly dominates the industrial sector, with a production of around 450 million tons per year.

This, on the other hand, requires the use of between 3% and 5% of the world’s natural gas, which represents approximately 1% to 2% of the planet’s energy supply.

Intense eutrophication in the northern part of the Caspian Sea/Image: public domain on Wikimedia Commons

The data may seem entirely negative, especially if other derivatives are added, such as the fact that only 17% of the manufactured ammonia is consumed, with the rest remaining in the soil, air or water; something that, according to some studies, has altered the natural nitrogen cycle. Thus, over half of the ammonia and nitrates end up spreading through the soil and, through runoff, into rivers and seas, affecting their biological habitats by providing an excess of nutrients. This causes algae and bacteria to proliferate, consuming the oxygen that other species need. This is what is known as eutrophication.

In fact, something similar occurs in the atmosphere, altering its balance, as the excess nitrogen enriches the ozone in the troposphere and reduces it in the stratosphere. Looking at the glass half full, the higher percentage of nitrogen in the air favors the capture of CO2 in large forest masses. Furthermore, a second, much more positive reading can be added to all of these drawbacks, related to the growth and food of the world population: the use of these fertilizers has quadrupled the productivity of farmland in the last century, allowing them to occupy less than 15% of the total surface area of the Earth.

It has also led to a demographic explosion that has increased the number of inhabitants from 1.6 billion in 1900 to the impressive 7 billion today. But thanks to fertilizers, agriculture and livestock have reached such important levels that they sustain a third of the human beings on the planet, because otherwise the land would not be productive enough.

This article was first published on our Spanish Edition on January 22, 2019. Puedes leer la versión en español en El proceso químico inventado para fabricar explosivos que hoy sustenta a un tercio de la población mundial


HABER & BOSCH. Most influential persons of the 20th century (according to Nature, July 29 1999) (Jürgen Schimdhugen)/Enriching the Earth. Fritz Haber, Carl Bosch and the transformation of world food production (Vaclav Smil)/Armas químicas. La ciencia en manos del mal (René Pita)/Fritz Haber. Chemist, Nobel Laureate, German, Jew (Dietrich Stoltzenberg)/Detonator of the population explosion (Vaclav Smil en Nature)/Wikipedia

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