This is part of a series around A Smarter Gun, Motherboard's new documentary.
Warning: Do not try any of this at home.
Arming a militia used to be a lot more shitty. Poop and guns have a long history together—one we've all but forgotten thanks to a technology developed at the turn of the 20th century that allowed gunpowder to be made from air instead of poop. In modern times—with annual US gun production reaching 5.5 million firearms as of 2010, according to the Small Arms Survey—we're still trying make sense of laws and legislation written when revolution still meant gathering vast quantities of fecal matter.
There are actually some video guides on YouTube about this very procedure, meaning do-it-yourselfers can technically do it at home. Where I live in Wisconsin, bat guano is available on the cheap. I convinced a tour guide from Crystal Cave to let me take home a five-gallon bucket "for science!"
Since the beginning of life on earth and up until the 20th century, the only practical source of fixed nitrogen was bacteria living in the soil.
The process involves rinsing the guano over wire mesh with a roughly equal volume of water, before adding several handfuls of hardwood ash to the rinse. This slurry, after settling overnight, produces a yellowish, mostly clear liquid. Discarding any settled solids and allowing the liquid to evaporate for a week yields a layer of whitish-brown flakes. What's left in a jar, after adding roughly equal volumes of flakes and a high-proof spirit like vodka, then pouring off the excess alcohol and leaving all remaining solids to air dry on a plate for about an hour, should be a powder close-to-white in appearance: saltpeter, a vital component of gunpowder that makes up about three quarters of its mass.
Saltpeter is a purified form of fixed nitrogen. Since the beginning of life on Earth and up until only about 100 years ago, the only practical source of fixed nitrogen was bacteria living in the soil. Nitrogen in the air can pretty much be imagined as invisible fluff, its inert qualities stemming from the fact that every nitrogen molecule possesses a triple bond that's notoriously hard to break. Nitrogen fixation is, fundamentally, any process capable of breaking this bond.
Your body can't fix nitrogen. You breathe more than a ton of nitrogen every day, and not a single atom becomes part of your body. This may come as a surprise since nitrogen is an essential ingredient to your (and all) biology. It's impossible to make proteins and DNA without nitrogen atoms, and every one of those atoms must be "fixed" before any biology can use them. Ultimately, this means the amount of life that can exist on Earth is limited by the quantity of fixed nitrogen.
Since the only life capable of fixing nitrogen are special soil bacteria, many plants, including beans, peanuts, lentils, and clover farm these bacteria in their roots, allowing them to make lots of protein. We humans get at this fixed nitrogen by eating the protein of plants at the bottom of the food chain, or else critters like chickens and cows that are a bit further up. Any nitrogen not used in the construction of muscle (or other proteins) passes straight through our bodies, leaving in the form of feces or urine. This means the most concentrated forms of fixed nitrogen existing in nature are dead animals and poop.
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To recap: gunpowder needs saltpeter, which is a form of fixed nitrogen, and concentrated fixed nitrogen comes from poop. While the recipe for gunpowder originates in 9th century Chinese alchemy, perhaps the last man to really make practical knowledge of the poop-firearm link was Joseph LeConte in 1862. By this point in time, the Confederacy had been cut off by the Union blockade for nearly a year, meaning the South would soon have to produce all its gunpowder domestically. LeConte, a professor of chemistry and geology at South Carolina College, was tasked with telling the South how to fulfill this need.
After soil from bat caves, LeConte then suggested looking for saltpeter in cellars, stables, livestock pens, and manure heaps. Cellars were a prime source since cities were filthy places where animals constantly pooped and died in the street, and all the filth "oozes through and dries on the walls and floor of the cellars as a whitish crust, easily detectable as saltpeter by the taste," LeConte wrote. He recommended similar taste tests for the "soil beneath stables of several years' standing, particularly if lime or ashes have been used to hasten the decomposition of the manure."
LeConte expected these caves, cellars, and stables to last long enough for domestic production to kick in, being explicit in the fact that "sufficient and permanent supply… can only be done by means of niter-beds."
"The heap is watered every week with the richest kinds of liquid manure, such as urine, dung-water, water of privies, cess-pools [sic], drains, etc."
Niter beds are best viewed as a last resort, because they're absolute hell: shacks with pounded-clay floors, filled to a height of several feet with rotting manure and straw to make the contents porous. Per LeConte, "the heap is watered every week with the richest kinds of liquid manure, such as urine, dung-water, water of privies, cess-pools [sic], drains, etc." After a year of feeding and occasionally turning-over this malodorous monster, the concentration of fixed nitrogen would finally be high enough to process into gunpowder.
The Union didn't have to resort to these drastic measures since it could obtain saltpeter through trade. Shit was still the source of all gunpowder, but indirect methods were far cheaper and less labor (and smell) intensive. Prime international poop sources were the fossilized guano of the Chilean Atacama Desert, or the evaporated flood waters of the monsoon plains in Northern India. Inability to trade was but one of many reasons why the South lost the war. Perhaps during Reconstruction, the thought of anyone pooping their way through another revolution seemed so unlikely the Second Amendment remained largely unchanged.
All this business of gunpowder coming from feces petered out around 1910. German chemists Fritz Haber and Carl Bosch, applying the newfound knowledge of chemical equilibrium, figured out how to fix nitrogen directly from the air. The "Haber Bosch process," or just "Haber process," as it came to be called , allowed gunpowder to be mass-produced independently of soil bacteria. This new source of fixed nitrogen also allowed the creation of nearly all the weapons technologies we associate with 20th century warfare. The "nitro" in many explosives such as nitroglycerine, TNT (trinitrotoluene), and C4 (trinitroperhydrotriazine) are all forms of fixed nitrogen, as are many poisonous gases like cyanides—the most famous being Zyklon B—and a few varieties of mustard gas.
Today, the Haber process produces around 131 million tons of nitrogen fertilizer a year, and since we eat the plants fertilized directly or indirectly by this technology, nearly 80 percent of the nitrogen present in our bodies is fixed artificially. Not being limited by the fixation rate of soil bacteria, artificial nitrogen fixation has allowed the human population to quadruple in only a century.
It can be argued because of the Haber Process, violent revolution lost its viability as a check on power more than a hundred years ago.
This is by no means the first time a discovery driven by weapons research has been a boon to humanity, but it is by far one of the more striking examples of a combat technology trickling out to society at large. No other technological development leaves behind a legacy so shitty and tempting to forget in the evolution of the modern firearm. After all, the Second Amendment was written when revolution meant arming a militia with poop-powered muskets that could fire only three rounds a minute.
Watch Motherboard's new documentary, A Smarter Gun.