The Story of Nitrogen: Its Industrial Chemical Revolution and Global Impacts

Nitrogen is an essential chemical component of life, playing vital functions in nucleic and amino acids (Cherkasov et al., 2015; Galloway & Cowling, 2002). Comprising 78% of air, nitrogen is abundant. However, the majority of organisms are unable to use this form because it is unreactive (Cherkasov et al., 2015; Erisman et al., 2008). Nitrogen gas is composed of two nitrogen atoms bonded together with a triple bond (Figure 1), rendering it highly stable and inert (Cherkasov et al., 2015). The conversion of nitrogen gas into a reactive form of nitrogen necessitates the breaking of the triple bond, a process that is inherently energy-intensive (Cherkasov et al., 2015). This process of transforming atmospheric nitrogen into a reactive form is called nitrogen fixation.

Figure 1: The triple bond of nitrogen gas (Gas Encyclopedia, 2024)

In nature, specially adapted microorganisms have developed biological processes to fixate nitrogen into biologically usable forms (Galloway & Cowling, 2002). Following the discovery of the importance of nitrogen for crop growth in the mid-19th century and the subsequent rapid industrialization and population growth in the early 20th century, which created unprecedented demands for food, a demand for reactive nitrogen was born (Galloway & Cowling, 2002; Whalen et al., 2022). This demand for reactive nitrogen prompted humans to first search out natural sources of reactive nitrogen and then develop an industrial process to fixate nitrogen into ammonia at a large scale (Galloway & Cowling, 2002). The Haber-Bosch process, the first industrial-scale nitrogen fixation process, remains the dominant method for creating ammonia today. The industrial fixation of atmospheric nitrogen has profoundly impacted human civilization, enabling the development of industrial agriculture and increased food production but also leading to environmental degradation (Erisman et al., 2008; Whalen et al., 2022).

Using nitrogen and its fixation as a lens, this article aims to examine the ways in which human demand for reactive nitrogen and chemistry have shaped modern society and the environment. First, this article will introduce the historical conditions which led to the development of the Haber-Bosch process before proceeding to present an analysis of its industrial chemical process. Subsequently, employing a systems perspective, this article will examine the contemporary implications of industrial nitrogen fixation, its impact on the earth systems, and future developments towards a more sustainable future (Whalen et al., 2022).

The Demand for Nitrogen in the 19th and 20th Centuries

With rapid population growth in the 19th century and the development of more intensive agricultural practices, natural sources of reactive nitrogen were sought out. Two primary sources of reactive nitrogen were guano, bird excrement from the islands of Peru, and saltpeter, inorganic nitrate deposits in Chile (Erisman et al., 2008). Guano was abundant on these islands, with deposits often exceeding 100 feet in thickness due to the arid climate of the Peruvian coast (Figure 2) (Clark & Foster, 2012). The Pacific Islands, covered in guano, were described as resembling a landscape covered in snow. Guano had long been recognized as a fertilizer, used by Indigenous peoples for many centuries. Soluble in water, guano was fast-acting, and as soil conditions worsened in Britain and the United States from intensive agriculture, guano provided a solution (Clark & Foster, 2012).

Figure 2: Workers excavating a "mountain" of guano (Smithsonian, 1860s).

In the mid-19th century, a global guano trade was established, with guano being mined off the coast of Peru by Chinese laborers and then shipped to Europe and North America (Clark & Foster, 2012). From 1866 to 1877, Peru exported between 310,000 and 575,000 tons of guano a year to the global market (Clark & Foster, 2012). In addition to guano off the coast of South America, nitrate deposits were discovered in the Tarapacá desert and surrounding regions. These nitrates could be used as fertilizer and in the production of explosives. Over the latter half of the 19th century, multiple scrambles for power between states ensued over regions containing reactive nitrogen (Clark & Foster, 2012).

By the beginning of the 20th century, reactive nitrogen deposits in South America began to be exhausted, while demand only increased (Clark & Foster, 2012). The demand for reactive nitrogen increased in conjunction with the necessity for greater food production, as well as the demand for nitrates to manufacture explosives and ammunition during the First World War. The British monopoly of Chilean nitrates and blockades cut Germany off from the South American sources of nitrate (Clark & Foster, 2012; Erisman et al., 2008). Germany, deprived of nitrogen supplies from South America, sought to establish a domestic source of reactive nitrogen.

A few years earlier, Fritz Haber, a chemist and a German patriot, devoted his attention to the fixation of nitrogen (Erisman et al., 2008). By 1909, Haber and his colleagues had developed a process to fixate atmospheric nitrogen into ammonia (NH3) in the laboratory (Kissel, 2014). Subsequently, BASF, a German chemical company, purchased Haber's patents and assigned Carl Bosch the responsibility of developing an industrial-scale production of ammonia (Dybkjaer, 1995). Scaling the production of ammonia to an industrial scale came with multiple challenges.

Ammonia production was to be conducted on a continuous basis, in contrast to the previous practice of synthesizing it in batches. This necessitated the creation of entirely new machinery that would also be capable of withstanding the elevated pressure and temperature conditions required for ammonia production (Kissel, 2014). In 1913, the inaugural ammonia plant was operational in Oppau, Germany, producing 30 tons a day (Figure 3). By 1916, the output had increased to 250 tons of ammonia daily (Dybkjaer, 1995).

Figure 3: The BASF ammonia plant in Oppau in 1913 (BASF, 1913).

Haber-Bosch Process

The production of ammonia from atmospheric nitrogen was a remarkable feat of chemistry and engineering. This achievement earned Haber the Nobel Prize in Chemistry in 1918, and Bosch was subsequently awarded the Nobel Prize in Chemistry in 1931 for his contributions to high-pressure chemistry (Haber, 1920; Bosch, 1932). Today, the Haber-Bosch process remains the dominant process to fixate nitrogen. The Haber-Bosch process turns relatively unreactive atmospheric nitrogen gas (N₂) and hydrogen gas (H₂) into ammonia (NH₃) (Erisman et al., 2008).

N₂ + 3H₂ + ⇌ 2NH₃ ΔH° = -92.28 kJ

This equation shows that one nitrogen gas molecule and three hydrogen gas molecules combine to form two ammonia molecules, but the reaction doesn't go to completion. Instead, it reaches a dynamic equilibrium, whereby both the forward and reverse reactions occur simultaneously. In order to maximize ammonia production, a combination of high pressure, moderate temperature, and catalysts is required to shift the equilibrium toward the formation of ammonia.

Pressure and Temperature

The application of high pressure is crucial in favoring ammonia production. In accordance with Le Chatelier's principle, an increase in pressure results in a shift towards the side with a lower number of gas molecules. In the case of the Haber-Bosch reaction, two molecules of ammonia are formed from four molecules of nitrogen and hydrogen, thereby reducing the overall number of gas molecules and favoring ammonia production under high pressure. The process typically operates at pressures around 200 atmospheres (Cherkasov et al., 2015). Furthermore, temperature also plays a vital role in this reaction. Since the formation of ammonia is exothermic (releases heat), lower temperatures would favor greater yields. However, at lower temperatures, the reaction rate is too slow to be practical because of the high activation energy needed to break the strong triple bond in nitrogen molecules. To overcome this, the reaction is carried out at moderately high temperatures of around 450–500°C (Cherkasov et al., 2015), striking a balance between sufficient ammonia yield and acceptable reaction rates.

Catalyst

A significant advancement in the Haber-Bosch process was the introduction of an iron catalyst, which markedly accelerated the reaction. The use of catalysts serves to reduce the activation energy required to break apart nitrogen molecules, thereby rendering the reaction feasible at industrial scales. However, the iron catalyst requires high temperatures to operate efficiently (Cherkasov et al., 2015). Although these high temperatures reduce the ammonia yield, they increase the reaction rate, making the process economically viable.

To further increase yields, gas leaving the converter chamber with the catalysts is cooled, condensing the ammonia out of the gas mixture. The unreacted hydrogen and nitrogen are then reheated and returned to the synthesis converter (Figure 4) (Hignett, 1985). This recycling helps to overcome the low conversion rate in a single pass through the reactor.

Figure 4: Haber-Bosch ammonia synthesis Industrial process (Ikpe, A.E. et al., 2024).

Hydrogen Production

While nitrogen is readily available in the atmosphere, the hydrogen needed for ammonia synthesis must be produced. The most common method for hydrogen production in the Haber-Bosch process is steam methane reforming, where natural gas (methane, CH₄) reacts with water vapor at high temperatures to produce hydrogen gas and carbon monoxide (CO) (Dybkjaer, 1995).

CH₄ + H₂O ⇌ CO + 3H₂

The carbon monoxide produced in this reaction is then further reacted with water in a water-gas shift reaction to produce additional hydrogen:

CO + H₂O ⇌ CO₂ + H₂

After removing residual carbon dioxide (CO₂) and other impurities, the hydrogen is then fed into the Haber-Bosch process. However, this method of hydrogen production relies heavily on natural gas, making it a significant source of carbon emissions (Cherkasov et al., 2015).

Impacts of Anthropogenic Nitrogen Fixation

The synthetic production of ammonia since 1913 has had a profound impact on global developments. Domestic ammonia production was vital in Germany’s war effort, both in producing fertilizers and explosives (Erisman et al., 2008). The advancements made during the synthesis of ammonia from atmospheric nitrogen also allowed the development of chemical warfare, including chlorine gas and, later during the Holocaust, for the development of Zyklon B (Hager, 2008). The Haber-Bosch process of nitrogen fixation remains the dominant method for the synthesis of ammonia. It is estimated that nitrogen fertilizers are responsible for feeding approximately half of the world's population (Erisman et al., 2008). In this sense, Haber can be regarded as the father to millions for the creation of a process that ‘turns air into bread’ while also being recognized as the father of chemical warfare (Hager, 2008).

Currently, the intentional and industrial fixation of nitrogen is around 190 million metric tons a year (Richardson et al., 2023). The advent of synthetic fertilizers has led to a notable increase in food production. However, the extensive production and utilization of nitrogen have resulted in significant alterations to the biogeochemical flows of nitrogen. Only approximately 14% of the nitrogen applied to crops ultimately ends up in food consumed, with a significant portion of the nitrogen utilized in agriculture being lost to the environment (Galloway & Cowling, 2002). The excess nitrogen from agriculture enters waterways, which contributes to eutrophication and algal blooms, decreasing oxygen levels. These conditions create “dead zones” where organisms struggle to survive, leading to significant declines in biodiversity (Erisman et al., 2008). One notable example of a dead zone is the area where agricultural runoff from the Mississippi River basin enters the Gulf of Mexico, as shown in Figure 5 (Dodds, 2006). 

Figure 5: The dead zone, shown by the teal areas, around the Mississippi Delta (NASA, 2002).

Additionally, the utilization of anthropogenically fixed nitrogen results in the emission of ammonia and nitrogen oxides (NOx). Nitrogen oxides are potent air pollutants that increase tropospheric ozone and decrease stratospheric ozone, contributing to the formation of smog, acid rain, and particulate matter, all of which negatively impact air quality and human health (Erisman et al., 2008; Fowler et al., 2013). Moreover, approximately 1% of the world's total energy is used to fix nitrogen (Cherkasov et al., 2015). This energy predominantly comes from fossil fuels, the combustion of which releases carbon dioxide, increasing the amount of greenhouse gases in the atmosphere, contributing to climate change. Further, the hydrogen used in the Haber-Bosch process is primarily derived from natural gas, a non-renewable resource (Cherkasov et al., 2015). Natural gas emits greenhouse gases during its extraction and carbon dioxide during the production of hydrogen (Cherkasov et al., 2015). Current levels of nitrogen use are unsustainable because anthropogenic nitrogen fixation has exceeded the planetary boundary (Figure 6) (Richardson et al., 2023; Rockström et al., 2009). The planetary boundary for nitrogen is set at 82 million metric tons of anthropogenically fixed nitrogen (Richardson et al., 2023). Exceeding this level means that humanity is not operating safely within the Earth's limits, and crossing the threshold can cause abrupt environmental change on a planetary scale (Rockström et al., 2009).

Figure 6: The status of control variables for nitrogen and the other planetary boundaries (Richardson et al., 2023).

Nevertheless, it is possible to feed the world's population without exceeding planetary boundaries; however, this will require a transformation in agricultural practices and our relationship with nitrogen fixation (Gerten et al., 2020). Gerten et al. (2020) emphasize that key prerequisites for sustainable food production include spatially redistributing cropland, improving water-nutrient management, reducing food waste, and encouraging dietary changes to reduce the overall nitrogen footprint (Gerten et al., 2020, p. 200).

Despite the negative impacts caused by large-scale nitrogen fixation, there are emerging solutions that offer hope for a more sustainable future. One promising avenue is the development of "green nitrogen" technologies, which seek to reduce the environmental footprint of nitrogen production. These include innovations such as plasma synthesis, which uses electrical discharges to fix nitrogen, and the development of novel catalysts that can improve the efficiency of the Haber-Bosch process, potentially reducing its reliance on fossil fuels (Cherkasov et al., 2015). Additionally, there is growing interest in utilizing biological nitrogen fixation more effectively by harnessing the abilities of nitrogen-fixing bacteria in agriculture, potentially reducing the need for synthetic fertilizers.

Ammonia is being explored as a potential energy carrier in the context of a low-carbon future. Ammonia can be used as a fuel, particularly in industries that are difficult to decarbonize, such as shipping. Additionally, ammonia can also be used as a storage medium for hydrogen, a key player in future renewable energy systems (Whalen et al., 2022) Ammonia can also be employed as a thermal energy store, helping balance future economies' energy demands (Ammonia: Zero-Carbon Fertiliser, Fuel and Energy Store, 2020). These developments suggest that nitrogen, long associated with environmental degradation, may also play a role in transitioning to a more sustainable, low-carbon world.

Conclusion

A juxtaposition exists within nitrogen. Nitrogen is ubiquitous in the atmosphere, yet it is not directly accessible as a constituent of life in its gaseous form. Through the industrial fixation of nitrogen, humans created the ability to feed billions while simultaneously using the same substance to create weapons of destruction. Further, nitrogen fixation has changed the Earth's biogeochemistry, impacting biodiversity, air quality, and climate change. At the same time, ammonia has the potential to be a tool for decarbonization and a sustainable transformation. Nitrogen has undoubtedly shaped the environment, society, and how humans interact with the world in which they live. The dual nature of nitrogen fixation reflects its vital role in sustaining life and its potential for harm when used unsustainably.

Bibliographical References

Bosch, C. (1932). The development of the chemical high pressure method during the establishment of the new ammonia industry, The Nobel Prize in Chemistry 1931. The Nobel Prize. https://www.nobelprize.org/prizes/chemistry/1931/bosch/lecture/

Cherkasov, N., Ibhadon, A. O., & Fitzpatrick, P. (2015). A review of the existing and alternative methods for greener nitrogen fixation. Chemical Engineering and Processing: Process Intensification, 90, 24–33. https://doi.org/10.1016/j.cep.2015.02.004

Clark, B., & Foster, J. B. (2012). Guano: The global metabolic rift and the fertilizer trade. In Ecology and Power. Routledge.

Dodds, W. K. (2006). Nutrients and the “dead zone”: The link between nutrient ratios and dissolved oxygen in the northern Gulf of Mexico. Frontiers in Ecology and the Environment, 4(4), 211–217. https://doi.org/10.1890/1540-9295(2006)004[0211:NATDZT]2.0.CO;2

Dybkjaer, I. (1995). Ammonia Production Processes. In A. Nielsen (Ed.), Ammonia: Catalysis and Manufacture (pp. 199–327). Springer. https://doi.org/10.1007/978-3-642-79197-0_6

Erisman, J. W., Sutton, M. A., Galloway, J., Klimont, Z., & Winiwarter, W. (2008). How a century of ammonia synthesis changed the world. Nature Geoscience, 1(10), 636–639. https://doi.org/10.1038/ngeo325

Fowler, D., Coyle, M., Skiba, U., Sutton, M. A., Cape, J. N., Reis, S., Sheppard, L. J., Jenkins, A., Grizzetti, B., Galloway, J. N., Vitousek, P., Leach, A., Bouwman, A. F., Butterbach-Bahl, K., Dentener, F., Stevenson, D., Amann, M., & Voss, M. (2013). The global nitrogen cycle in the twenty-first century. Philosophical Transactions of the Royal Society B: Biological Sciences, 368(1621), 20130164. https://doi.org/10.1098/rstb.2013.0164

Galloway, J. N., & Cowling, E. B. (2002). Reactive Nitrogen and The World: 200 Years of Change. AMBIO: A Journal of the Human Environment, 31(2), 64–71. https://doi.org/10.1579/0044-7447-31.2.64

Haber, F. (1920). The Synthesis of Ammonia from Its Elements, Nobel Prize in Chemistry 1918. The Nobel Prize. https://www.nobelprize.org/prizes/chemistry/1918/haber/lecture/

Hager, T. (2008). The Alchemy of Air: A Jewish Genius, a Doomed Tycoon, and the Scientific Discovery That Fed the World but Fueled the Rise of Hitler. Crown.

Hignett, T. P. (1985). Production of Ammonia. In T. P. Hignett (Ed.), Fertilizer Manual (pp. 49–72). Springer Netherlands. https://doi.org/10.1007/978-94-017-1538-6_6

Kissel, D. E. (2014). The Historical Development and Significance of the Haber Bosch Process. Better Crops with Plant Food, 98(2).

Richardson, K., Steffen, W., Lucht, W., Bendtsen, J., Cornell, S. E., Donges, J. F., Drüke, M., Fetzer, I., Bala, G., Von Bloh, W., Feulner, G., Fiedler, S., Gerten, D., Gleeson, T., Hofmann, M., Huiskamp, W., Kummu, M., Mohan, C., Nogués-Bravo, D., … Rockström, J. (2023). Earth beyond six of nine planetary boundaries. Science Advances, 9(37), eadh2458. https://doi.org/10.1126/sciadv.adh2458

Rockström, J., Steffen, W., Noone, K., Persson, Å., Chapin, F. S. I., Lambin, E., Lenton, T. M., Scheffer, M., Folke, C., Schellnhuber, H. J., Nykvist, B., de Wit, C. A., Hughes, T., van der Leeuw, S., Rodhe, H., Sörlin, S., Snyder, P. K., Costanza, R., Svedin, U., … Foley, J. (2009). Planetary Boundaries: Exploring the Safe Operating Space for Humanity. Ecology and Society, 14(2), art32. https://doi.org/10.5751/ES-03180-140232

Whalen, J. M., Matlin, S. A., Holme, T. A., Stewart, J. J., & Mahaffy, P. G. (2022). A Systems Approach to Chemistry Is Required to Achieve Sustainable Transformation of Matter: The Case of Ammonia and Reactive Nitrogen. ACS Sustainable Chemistry & Engineering, 10(39), 12933–12947. https://doi.org/10.1021/acssuschemeng.2c03159

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