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Ok, who's ready for some science?
Today I'm going to teach you about the Nitrogen and Phosphate cycles, the late history of agriculture, and the "Peak Phosphate" problem that may destroy civilization in 200-300 years, assuming climate change doesn't do us in first.
Today I'm going to teach you about the Nitrogen and Phosphate cycles, the late history of agriculture, and the "Peak Phosphate" problem that may destroy civilization in 200-300 years, assuming climate change doesn't do us in first.
All living organisms are made out of cells. Cells are made out of molecules, and molecules are made out of atoms. The most common atoms in most organisms are Hydrogen, Oxygen, and Carbon, but there are less common atoms that are required for specific molecules essential to life.
One essential atom is phosphorous, specifically in the form of phosphate [PO₄]³⁻. Phosphate is an essential building block of DNA, RNA, ATP, and the phospholipid bilayer that makes up cell membranes.
Another essential atom is nitrogen, which humans mostly get from digesting plant and animal proteins. Nitrogen is a critical component of almost all proteins, as well as DNA and RNA base pairs.
Humans absorb nitrogen and phosphate by eating food. We can eat meat, or vegetables, but the nitrogen and phosphate in meat mostly come from plants eaten by the animal we're eating. The vast majority of nitrogen and phosphate we imbibe ultimately comes from plants.
Plants get nitrogen and phosphorous through their roots, which absorb these elements from soil, either in the form of naturally available phosphates, nitrates, and nitrites; or from artificial fertilizer; or from symbiotic bacteria that convert inorganic nitrogen into nitrate.
Let's talk about nitrogen first. The earth's atmosphere is 78% nitrogen, but that nitrogen is not bioavailable, meaning plants and animals can't absorb it. This is because atmosphere nitrogen is N₂, two nitrogen atoms held tightly together by a strong triple bond.
If a plant wants to absorb nitrogen from the air, it must do so with the help of nitrogen fixing bacteria, symbiotic organisms that live in a plant's root system and use enzymatic reactions to convert N₂ into nitrate [NO₃₋]
If a plant does not have the help of nitrogen fixing bacteria, it must absorb mineral nitrates that are already present in the soil. One of the main ways that soil is depleted is through plants absorbing all available nitrates in the soil, requiring the nitrate to be replenished.
Nitrate can be replenished in soil through a couple processes: either fortification via planting crops that have strong colonies of nitrogen fixing bacteria, such as peas and clover; or by direct application of nitrate fertilizer.
Where does nitrate fertilizer come from? We'll talk about modern production in a sec, but for most of human history nitrate fertilizer was only available through composting waste products: plant matter, meat scraps, bones, feces, and urea (piss).
As a human population grows, planting and eating crops, raising and butchering animals, generating waste products and recycling them back into the soil, they can often, with careful management, slowly increase the amount of bioavailable nitrogen enough to grow enough food for all
However, with the start of the industrial revolution, human populations started to grow faster than agricultural output could be increased. The yield on existing fields could not be increased sufficiently, so new land had to be brought under till.
Land is a finite resource, and control over land in general became a huge social and political issue. The anxiety over the tightening food supply was expressed via Malthusianism, a pseudoscientific ideology that justified much of the evils of the industrial era.
In a drive to increase crop yields on existing land, external sources of fertilizer were sought out. Medieval and early modern battlefield graves were dug up, the bones ground into powder, and used to fertilize fields. Bat guano was mined from caves and used as fertilizer.
While the scientific basis of Malthusianism was wrong, and the social implications of it horrendous, by the end of the 19th century there was a genuine risk that Europe would not be able to grow enough food to feed itself, through unavailability of nitrogen (and also phosphate)
(Important to note this crisis had social and economic roots as much as biological ones. Europe had extremely poor land use driven by church hoarding of real property, the inefficiency of private land ownership, and poor agricultural methods.)
There was also another drain on nitrogen resources: war. The transition to gunpowder warfare, and later to explosives based warfare, required massive amounts of nitrates. Black powder is charcoal, sulfur, and potassium nitrate. The K-nitrate was harvested as scum that formed
on the tops of open pits of human piss and feces, as well as a few small mines in Italy and Spain. Later smokeless powder required fuming nitric acid, a highly refined chemical product made from mined or biological nitrates.
Explosives such as nitroglycerine, TNT, PETN, cordite, and others also required hundreds of pounds of nitrogen per artillery shell. The need to manufacture explosives and gunpowder during WWI contributed to shortages of fertilizer that worsened contemporary famines.
Enter Fritz Haber, an evil man responsible for billions of living human beings today. Haber was a chemist working for the German Empire during WWI. His main passion was developing chemical weapons, but he also set his mind to solving the issue of wartime explosives production.
Balancing the need for nitrogen for explosives vs fertilizer was a major problem for the German Empire. Fritz developed a process called the "Haber Process", which used vast quantities of electricity to rip atmospheric N₂ molecules apart and turn them into nitrates.
Although the Haber process did not create enough nitrates in time to substantially impact the course of the great war, the technology would prove instrumental to the entire course of the 20th century.
Although intended for making nitrogen for explosives, the Haber process works just as well for producing fertilizer (tbh they're basically the same thing. Ask Seamus, or one of the survivors of the Texas City disaster).
Nitrate fertilizer produced by the Haber process feeds approx 4 billion human beings today, and has made the biochemical limits of the natural nitrogen cycle irrelevant to human civilization. The main downside of the Haber process is it is a medium contributor to CO₂ emissions.
