Haber-Bosch process - bread made of air

Haber-Bosch process - bread made of air

All living things need nitrogen compounds in order to grow and multiply. Almost four fifths of the air we breathe consists of gaseous nitrogen, but only a few living things can use this nitrogen from the air. These include the nodule bacteria. They live in the root system of legumes (eg lupins) and can convert around 50?150 kg of air nitrogen into nitrogen compounds per hectare. When we eat meat or vegetables, we absorb the nitrogen compounds from animals and plants. But how does nitrogen get into the plant if it is not a legume?

Ever since mankind has been farming, it has known how to use the animal's leftovers (dung) for fertilization. They contain nitrogen compounds that arable crops use. Now, in the middle of the nineteenth century, humans began to reproduce rapidly. The nitrogen in the fields was becoming scarce. A serious famine of global proportions was foreseen 1.

Quelle: eigene Darstellung

It would probably have occurred if the chemists Fritz Haber and Carl Bosch had not succeeded in converting the nitrogen in the air into ammonia from 1903 to 1913, and thus into nitrogen that can be used by plants. Experts also speak of the "fixation" of nitrogen. The way to the artificial fertilizer made of ammonia was clear. Almost 8 billion people live on our planet today 2. It is estimated that around six billion of them would starve to death if there were no nitrogen fertilizers 3.

Around 150 million tons of ammonia are produced annually around the world 4. If you were to load this amount of ammonia into tank wagons, the result would be a freight train that once reached around the world (approx. 42,000 km)! More than 80% of the ammonia produced is converted into nitrogen fertilizer. Most of it in urea.

So the challenge of feeding eight billion people has been solved thanks to the Haber-Bosch process? Unfortunately, as is so often the case, it is not that easy. The amount of nitrogen compounds in the cycle, which was still modest in 1860, has expanded enormously for three reasons 5. The nitrogen fixation by the Haber-Bosch process contributes about half of it. The other two causes are about half the cultivation of pulses (legumes) and the burning of fossil and renewable raw materials (the NO x problem) 6. This causes environmental problems; Nitrate in groundwater and the ozone killer laughing gas in the atmosphere are examples of this. Not a few are calling for the use of artificial fertilizers to be drastically reduced 7. Intelligent science and technology are needed to both feed eight billion people and protect the environment.

Another downside of the Haber-Bosch process must not be concealed here. 1914, at the beginning of World War I, was the production of explosives from ammonia in the isolated Germany a political issue of the first order. 8 The First World War would very likely not have been so devastating and would not have lasted as long had it not been for the production of ammonia, and thus explosives, on an industrial scale 9.

Literature:
[1] Haber-Bosch method in Wikipedia.
[2] http://www.worldometers.info/de/.
[3] J. Renn, B. Johnson, B. Steininger, Naturwiss. Rundschau 2017, 70, 507.
[4] US Department of the Interior, US Geological Survey: Mineral Commodity Summaries 2018.
[5] Federal Office for the Environment, FOEN (Switzerland): Nitrogen - from a blessing to an environmental problem.
[6] Federal Environment Agency: Nitrogen - Too much of a good thing (January 2011).
[7] R. Hahn: How does the world get full? Frankfurter Allgemeine Zeitung, December 29, 2016
[8] The " saltpeter promise " in Wikipedia
[9] H. Bontrup, N. Zdrowomyslaw: The German armaments industry. From the Empire to the Federal Republic, Heilbronn 1988, p. 85.

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last modified: 27.04.2021 11:09 H from