By Jacob Ahrens-Balwit
The image above is of an early 19th century high-pressure reactor used for ammonia (NH3) synthesis. Carl Bosch developed the process of industrial-scale ammonia synthesis in 1908 as a way for humans to access the nitrogen in the air. Fritz Haber is credited with discovering the conditions for ammonia synthesis in 1904 and his work with Bosch allowed for the mass production of commercially available nitrogen fertilizer. This specific object, the huge steel clad, iron reactor, was used in one of the world’s first ammonia factories when it began operations in 1913. Inside the chamber of the reactor, air (almost 80% atmospheric nitrogen) was put under extreme pressure and forced to bond with hydrogen gas. The result was the formation of liquid ammonia, which contains the fixed nitrogen necessary for plant and animal muscle tissue growth. This high-pressure reactor is a symbol of the Anthropocene because the nitrogen it captured effectively freed human food production from the biological old regime. After 1914 humans were in control of the nitrogen cycle, they could make their own fertilizers and nitrogen-based weapons. Today it is estimated that more nitrogen is captured through this process than through natural processes. The invention of an efficient form of nitrogen production allowed the world’s population to explode from two billion people to the current number of seven billion people and the process is critical for feeding the projected ten-twelve billion people who will inhabit the earth by 2050.
To give some context, the rapid increase in world population leading up to the 20th century was cause for serious concern among farmers, policy makers and scientists of the time. Improvements in public health, access to clean water and efficiencies in agriculture allowed the global population to reach its first billion people early in the 19th century. Since the 1700’s European scholars and demographers realized that the skyrocketing human population put a dangerous pressure on agriculture to create enough food to avoid starvation. Agricultural demand for nitrogen had surpassed natural supply.
For humans to be the major environmental force on the planet they must exist in sufficient numbers to significantly alter natural systems. For this reason, human control of the nitrogen cycle is crucial to the Anthropocene. The limiting factor of human population is food production and the limiting factor in food production is nitrogen. Nitrogen is a component of both nucleic acids (DNA) and amino acids (protein) so every living thing must be built with nitrogen. Most organisms, with the exception of certain free-living soil and root dwelling bacteria, are incapable of capturing their own nitrogen. Therefore, they must look to their environment for a source of nitrogen. Paradoxically, 79% of the air we breathe is atmospheric nitrogen (N2) but alas the triple covalent bond of N2 is useless to plants, animals and humans until it is split to form ions. The process of making nitrogen available for biological growth is referred to as nitrogen fixation. Humans obtain their fixed nitrogen from the plants they eat, or the plants that the animals they consume, feed on. The natural environment provides a limited amount of fixed nitrogen, not nearly enough to feed billions of humans. Nitrogen, the invisible element of life, has two states. “One is ubiquitous, inert and suffocating. The other is scarce, explosive and life giving.” It was in this massive reactor in 1913 that humans were able to change the state of nitrogen from the former, unavailable state to the latter, available state. The repercussions have transformed the human food system, human populations and the natural environment.
Around the turn of the 20th century the effects of over-farming had taken a great toll on European countries. The soil of European fields had become depleted of essential nutrients, specifically nitrogen, as a result of unrelenting cultivation. No major source of nitrogen existed within Europe and farmers had been relying on manure, compost and rotating nitrogen fixing crops to return valuable nutrients to their soils. AD 1802-1884 has been called the “guano age,” a time characterized by a global trade in Peruvian bird excrement for use as fertilizer. Another nitrogen rich fertilizer was also coming out of South America around the same time; saltpeter (potassium nitrate) was mined in South American countries, including Chile, to be exported globally. The wide proliferations of these fertilizers lead to a sort of global addiction to fertilizers that continues today. By 1900 most industrial countries relied on mined Chilean nitrates, the most potent nitrogen fertilizer of the time. Chile provided two thirds of the world’s fertilizer nitrogen in 1900, and by 1913 Germany was using about one third of Chile’s total nitrogen production. The rate of consumption was so great that the natural nitrate deposits in South America were becoming quickly exhausted. By this time Germany, and most of the developed world, relied deeply on foreign nitrogen inputs for agriculture. The prospect of dwindling natural nitrogen supplies resulted in a global push for humanity to gain greater control of the nitrogen cycle.
The German dependency on foreign inputs of nitrogen drove German scientists to attempt artificial fixation of nitrogen. In 1904, the German chemist Fritz Haber discovered the conditions for ammonia synthesis from hydrogen gas and atmospheric nitrogen. Since ammonia contains fixed nitrogen, if it could be produced from the unlimited reservoir of the atmosphere Germany would be nitrogen independent.
Fritz Haber partnered with Carl Bosch of the German chemical manufacturing giant BASF in 1908 and together they refined the process of ammonia production for use on the industrial scale. The high-pressure reactor was the culmination of Haber and Bosch’s work together. The development of the Haber-Bosch process, which converted atmospheric nitrogen in the air and hydrogen gas to ammonia for use as a commercially available synthetic fertilizer, transformed the global food supply. The subsequent global food production was critical to sustaining the increasing human population. This revolutionary development was termed “bread from the air.” The ability to fix atmospheric nitrogen is heralded as one of the greatest scientific discoveries of all times. However, replacement of traditional nitrogen sources for crops by synthetic fertilizer nitrogen proceeded slowly until the early 1960s. In the US synthetic ammonia plants were not widely used until after WWII munitions plants were converted to ammonium nitrate fertilizer plants.
Today more nitrogen is fixed artificially than naturally. Ammonia produced via the Haber-Bosch process weighs in at an overwhelming 275 billion pounds per year and its derivative products, ammonium nitrate and urea, are among the highest volume chemicals commercially produced. Chemical fertilizers contribute about half of the nitrogen input into global agriculture, while biological nitrogen fixation occurring in legumes like soybeans, peanuts and clover contributes the other half. That means that if you are a human in a developed country, on average, half of the nitrogen atoms in your body once passed through a high-pressure reactor similar to the one Haber and Bosch developed in 1913.
Perhaps no other invention in the history of humanity has had a more dramatic influence on the planet than the Haber-Bosch process. The effects of human control of the nitrogen cycle on the Anthropocene are both direct and indirect. Nitrogen fertilizer plants directly impact the environment by releasing vast amounts of greenhouse gasses. The Donaldsville Nitrogen Complex in New Orleans, North America’s largest producer of nitrogen fertilizer burns a million dollars worth of natural gas every day for its operations. The Haber-Bosch process consumes up to 5% of the world’s annual natural gas production to make hydrogen and generate sufficient heat to preform the reaction, and the process consumes about 2% of the world’s annual energy production.
Additionally, biologically available nitrogen retained in the soil can intensify climate change, lead to lake acidification, biodiversity loss, and weaken forest ecosystems. Of the 80 million tons of nitrogen fertilizer spread on soil annually, only 17 million tons are absorbed into food. The remainder causes environmental concerns such as hypoxia (low oxygen zones in water.) When nitrogen is over abundant primary production of algae surges and the growth and subsequent decay associated with the primary production boom deplete the water of oxygen. Nitrogen fertilizers are generally seen as responsible for the dead zone in the Gulf of Mexico.
The indirect effects of synthetic nitrogen fertilizers on the environment may be even greater. By allowing the world population to swell to unprecedented levels, synthetic nitrogen fertilizers allowed for the human demands on the planet to grow in turn. Such a positive feedback loop is characteristic of the Anthropocene. The Haber-Bosch process continues to allow humanity to feed itself and avoid famine. While starvation does still exist, it is rare, and is almost always caused by wars and political events, which disrupt agriculture and trade in agricultural products, or make food relief efforts too dangerous. Two hundred years ago, world population was a mere one billion, for better or worse synthetic nitrogen fertilizers have allowed humanity to increase sevenfold since that time. The problematic issues associated with synthetic fertilizer use are vast, and we are not going to stop using them any time soon. We must therefore accept our responsibility as stewards of the nitrogen cycle and learn how to responsibly use this technology to balance human metabolic needs maintain the natural environment.
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