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When you go to the grocery store, you probably expect to find a luscious buffet of fresh produce. Big heads of lettuce, ripe tomatoes, giant pumpkins. Blueberries the size of grapes. Grapes the size of large grapes has anybody noticed that blueberries and grapes have gotten big, is that just me? But the gardeners out there know that the plants we eat don't get that big and plump and nutritious all on their own. There's a whole lot of science that goes into feeding the plants that feed us, and it's taken farmers and botanists thousands of years to figure out that secret growth sauce.
These days hardware stores have stacks of fancy designer fertilizers with custom nutrient mixes to feed whatever you want to grow. But in 19th century England, the cream of the crop fertilizer was bones. And eventually, they ran out. [INTRO] At the start of the 1800s, England was getting crowded. By the middle of the century, its population had doubled and showed no signs of slowing down. This explosive growth was possible in part thanks to the good ole Industrial Revolution and the many ways it improved food production. For centuries, farmers' productivity had been limited to the strength of their oxen or draft-horses,
how many family members they could muster during harvest, or how strongly the local river drove the watermill. But the steam engine changed all of that. Steam powered labor-intensive processes like threshing, milling, and field preparation. Combined with other new inventions like mass-produced iron plows and long-bladed scythes, farmers could suddenly do a lot more with the same number of hands. Fields were improving, too. Steam-powered pumps could turn soggy swamps into fresh farmland. And a new form of crop rotation came in vogue.
Instead of farmers leaving fields empty once every three years, according to tradition, they started planting cover crops like clover. They didn't know exactly what was happening to the fields during these recovery rotations, chemically speaking, but the results spoke for themselves: crop yields were better when the field was rotated. Plus the cover crops could serve as animal feed. Can we get by the way, just a cute illustration of a cow eating some clover?
These major agricultural advances meant farms grew bigger and could feed more people, while also needing fewer hands to work them. This revolution probably accelerated the migration of people from rural areas to the city. Former farmhands became factory workers, hastening the UK's shift toward mechanization and industry. Despite all those improvements, there was still only so much food to go around. To sustain the kingdom's intense pace of growth, they needed even more food. And that meant they could use a boost from fertilizer.
Now, there was a pretty easily accessible fertilizer that humans had known about for a long time: manure. There's evidence that farmers in Europe were using livestock manure to fertilize their fields as far back as 8,000 years ago. After all, it makes a lot of sense to return your leftovers back to the soil. That ancient, poopy tradition had carried England through its first round of population explosion. But it quickly became apparent that there simply wasn't enough animal manure in Britain to meet growing demands. Poop more! Poop! Poop More! Luckily, by now people had figured out that bones could also work as a fertilizer.
Farmers didn't fully understand why manure and bones worked, just that returning the remnants of life to the soil gave crops a boost. What they couldn't have known at the time was that poop and bones have one very important plant-growing nutrient in common: phosphorus. So now It's time to zoom over to our chemistry corner for a bit. Phosphorus is a chemical element, just like any of the others you can find on the periodic table. In the wild, it's mostly bound up in more complex compounds called phosphates.
A phosphate is one phosphorus atom bonded to four oxygen atoms. And they're, uh, kind of one of the most important elements for life itself. While elements like carbon, hydrogen, and oxygen may be more common in living things, but phosphorus is a key component of a few things that life could not exist without. Like DNA. The backbone of DNA is made of sugars and phosphates bonded together. Without it, your DNA would just be… alphabet soup. Same goes for RNA, the other genetic molecule. Phosphorus is also part of the molecule ATP, which is short for adenosine tri-phosphate. That's the molecule cells use to store energy.
It's kind of the double-A battery of life. It's actually what the mitochondria - the powerhouse of the cell - spit out. And, actually, the energy is contained in the phosphate bonds. Cellular machinery loads them up, then snaps a phosphate off every time it needs to release a bit of energy later on. So cells can use ATP to power all kinds of mechanisms. In plants, it's also made by chloroplasts, those photosynthesizing organelles. Then the ATP helps power the process that spins carbon dioxide and water into long chains of sugar and starch. In animals, ATP powers the ion transporters that keep your brain cells charged and make your muscles contract. So yeah, ATP is pretty important,
and all organic life including your organic life needs phosphorus to make it. And this brings us back to those phosphorus-rich poop and bones. Phosphorus is in poo kind of by accident. It's there because animals eat plants… or other animals that eat plants… and because our digestive systems aren't perfect, some of the phosphorus passes straight through. As for bones, phosphorus is there very much on purpose. It turns out that, in addition to DNA and ATP, phosphorus is also a key component of hydroxyapatite, he primary mineral for bones.
You might have thought that bones are made of calcium, And if you did, you're right that is also correct, Hydroxyapatite does have calcium. But for every 5 calcium atoms in a molecule of hydroxyapatite, you also need 3 phosphorus atoms. Just like DNA, without phosphorus for your spine, you, too, would be alphabet soup. So to recap: phosphorus. Very important. But we didn't figure out just how important until 1840. By now, people knew plants were getting something from the soil. But they weren't sure what exactly. One idea was that humus, decaying material from plants and animals, transmitted some sort of vital essence that non-living matter lacked.
Despite being spelled very similarly to hummus, Humus and hummus are different things, so don't get them confused Because that would be messy It took a German chemist named Justus von Liebig to identify that the critical factor in humus was not some vital essence, but simple minerals like phosphorus and potassium. Importantly, it didn't matter whether these minerals came from living or non-living matter. He figured this out by analyzing the chemicals in plant matter.
Essentially, he burned plants like hay or fruit he had collected from various different places. Then he examined the ash to quantify which elements were burned off and those that were left behind. His key finding was that some elements always appeared in about the same amounts, no matter where the sample came from. Like a kilogram of hay from Norfolk should have as much carbon in it as a kilogram of hay from Devon, even if one field was chock full of humus and the other wasn't. Today we know that plants get carbon primarily from the air, not the soil, so that makes perfect sense. But von Liebig also noticed that even if the carbon content was the same,
some other elements, like magnesium, potassium, and calcium, did vary by location and soil quality. Von Liebig believed these elements explained why some crops grew huge and hearty while others were small and anemic. Eventually, he narrowed it down to the three most important soil elements for crop success: potassium, nitrogen, and - you guessed it - phosphorus. He proposed that when the soil had enough of these three minerals, plants thrived. But when any of these elements were missing, it didn't matter how much of the other two you had, the plants' growth was limited to the least available of the three.
This is now known as the Law of the Minimum. Other scientists had previously suggested this idea, but von Liebig brought it into the light. So when farmers added manure or bones to their field, or planted cover crops to let their fields recover, they were actually adding these three key nutrients back into the soil. With all that chemistry covered, let's return to 19th century England. Demand for food was soaring and the fields needed fertilizer. English farmers were eager to get their hands on bones by all means necessary.
I really mean that in the most dramatic sense. I mean - they didn't kill anybody I don't think Because they needed a lot of bones. By the 1820s, mills were churning out 10-20 bushels of crushed bone per acre of cropland. A bushel is about 35 liters by the way, roughly the same size as a big bag of potting soil. So that's like twenty potting soil bags per acre. But instead of potting soil it was, of course, bonemeal. Now, a lot of these bones were undoubtedly from… what I guess I have to describe as normal bone places, like slaughterhouses and fisheries.
And at the time, knife handles and buttons were often made of bone. So shavings from these factories were also bound for the bonemills, since everything was getting crushed to powder anyway. But pretty quickly, England was consuming more bones than they could domestically produce. So they looked abroad, and boatloads of bones started docking in England's harbors to fertilize the kingdom's phosphorus-hungry fields. And demand was so high that importers were often willing to overlook a shipment's provenance. Many of the bones that fed 19th century England were undoubtedly from less than savory sources.
The fields at the Battle of Waterloo, for example, are suspiciously bereft of bones despite the heavy casualties incurred during Napoleon's last stand in 1815. I'm just going to let you feel how you feel about that But looting a battlefield is nothing new. Valuables, metal, and teeth were probably the first resources to be scavenged from this infamous field. But if you visit Waterloo today, you won't find many bones at all. And some experts think those skeletons might have ended up as fertilizer for English crops.
A few years later, in the 1840s, von Liebig made his big discovery that phosphorus was the crucial mineral plants needed. And bones had plenty. it's what plants crave He proposed creating artificial fertilizers, because he now knew that it was chemistry that made plants grow, not a mysterious vital essence. A chemistry problem meant you could search for a chemistry solution. His idea was to treat the bones with acid to break the bones' chemical bonds, making their phosphorus even more accessible to plants.
It was a great idea, and superphosphate factories started to pop up across the country. But even this wasn't enough! The country was still starving for bones, supposedly going so far as to scour European catacombs and Egyptian tombs. For human and cat mummies alike. Allegedly. In 1862, von Liebig himself complained: "England is robbing all other countries of the condition of their fertility. Already. she has turned up the battlefields of Leipzig, of Waterloo and of the Crimea; already from the catacombs of Sicily she has carried away the skeletons of many successive generations… Like a vampire, she hangs around the neck of Europe-
nay, of the entire world - and sucks the heart blood from nations." This guy had feelings about this and probably for good reason In the interest of fairness, we should note that while we've been picking on England a lot this episode, by this point many, many other countries, like the USA, had also developed their own appetites for phosphorus. an appetite for hydroxyapatite you might say, I mean I would But we are going to pick on bone-hungry England a bit longer. Because by the middle of the 18th century, they had nearly exhausted every source of bones possible. Luckily for them, they were about to learn about a poo from halfway around the world.
A poo that was way better and fancier than their domestic supply. But before we get to that, I'll make like England, that is, no bones about it, and tell you that we've got a real quick. Thanks to privacy dot com for supporting this scishow video Privacy dot com exists to prevent your data from Being leaked in data breaches, prevent fraud, and control your online spending They do that by creating a secure layer of temporary card numbers Between your real card and the merchant So even if the merchant gets compromised, there's nothing to steal Your actual bank account or credit card information is shielded from merchants And therefore from potential merchant data breaches
One of our motion designers actually could really use privacy dot com Someone tried to buy a couple luxury bags and luxury cars in Spain Using her credit card Sounds like those people were having a great time But she shouldn't have to pay for it And that's what privacy is here to ensure With privacy's mobile app, she could get real time alerts and quickly generate new card numbers with the browser extension Our motion designer and you can sign up for a free plan with no transaction fees For domestic purchases in exchange for more peace of mind Privacy doesnt sell customer data, ever They're here to protect you in a world where data breaches happen everyday So next time you're making mind bending animations for a complexly video
You can do it without being interrupted by fraud Go to privacy.com/SciShow That's p-r-i-v-a-c-y.com /scishow, or the link in the description To get your five dollar sign up bonus today That five dollars can be used on your first purchase Around the turn of the 19th century, the German explorer Alexander von Humboldt travelled to the Pacific Coast of South America and learned local Peruvians were using guano, or bird poop, harvested from some nearby islands as fertilizer. The islands were home to giant colonies of seabirds. And their guano, it turned out, was especially phosphorus-rich, since these birds ate naturally phosphorus-rich fish. And because the birds were eating whole fish, not just their bones,
the guano also came loaded with the other two minerals in von Liebig's fertility trinity: potassium and nitrogen. The dry and desert-y climate meant there was rarely any rain to wash the poop off the island, so these guano deposits grew bigger and more nutrient rich all the time, consolidating the ocean's best nutrients into, essentially, island-sized desiccated turds. The local people had, of course, long recognized the value of seabird guano. In fact, it was so valuable to them that, according to some accounts, during the Incan Empire, the penalty for anyone caught endangering the seabirds was death.
And I guess the inca empire had a lot of death penalty in it, but still Even after the Inca empire fell, folks in that region continued to apply guano to their crops. Which is exactly how von Humboldt got the brilliant idea that it could also maybe be used to fertilize European crops. Von Humboldt brought a guano sample back to Europe and a handful of small-scale agricultural tests had great results. You might think that this would have been an immediate sensation, but people actually ignored him for a while. Like, for multiple decades. But as England got desperate and started running out of bones in the 1840s,
they finally started paying some attention to this alternative fertilizer. And by "paying attention" we mean turning guano harvesting into a full-scale industrial behemoth. It was the industrial revolution, after all. One thing led to another, and pretty soon, in addition to Egyptian mummies and other bones of questionable origin, boatloads of petrified poo were also clogging England's ports. It was 2.7 million kilograms of poo in 1841, 18 million kilograms of poo in 1842, and at least 215 million kilograms of poo annually by 1846.
Now, you might also be saying to yourself, hey, 215 million kilograms of poop per year is a lot of poop. That's maybe too much poop. And you'd be right. Because if you think being a dockworker at this time would have been very unpleasant Yeah, it was being a guano miner was much, much worse. While local people had been taking small amounts of guano from the islands, the scale of the British operation was immense. And mining conditions were harsh and dangerous. Many locals refused to throw themselves into that extractive machine, so the mine owners turned to coercion, kidnapping, enslavement, and convicts to meet their labor demands. And when there weren't enough of them to force into the mines,
they coerced Chinese laborers, who were often just seeking a better life overseas. Many of these laborers did not survive their employment, whether by industrial accident, failed escape attempts, illness from breathing in powdered feces all day, or just plain exhaustion from the inhumane conditions. Also, turns out extracting that much guano every year was really unsustainable. I'm no expert, but I think you'd need a LOT of seabirds to replenish 600 million pounds of poo each year. The guano mines were basically out of guano by 1890. But there was one more form of phosphorus that remained to be tapped. Because by the mid-1800s,
paleontologists had uncovered even older poo. In the 1820s, the criminally under-appreciated, OG fossil hunter Mary Anning, found these weird lumpy fossils in the guts of the ancient sea reptiles she was digging up. She recognized them as poop. More specifically, they were coprolites, fossilized poo from animals like ancient mammals, sea creatures, or even dinosaurs. They're fairly common in some fossil-rich coastal areas, like where Anning was working. They were actually pretty easy to find scattered on those beaches.
Scientists wondered if these ancient poos were also phosphorus rich. And von Liebig himself was on scene, once again, for another discovery of poo as a source of phosphorus. While coprolites themselves didn't really take off as the next great phosphorus source, this discovery did seem to focus scientists' attention on the idea that geology could hold answers to the phosphorus problem. Scientists had already found that some types of sedimentary rock were rich in phosphorus. These rocks, now known as phosphorites, can be formed in several different ways. On land, for instance, they can form around ancient bonebeds.
At sea, phosphorus is deposited by rivers, then processed by plankton as it sediments. As other organic marine matter breaks down, especially in low oxygen environments, it also adds to the phosphorus pile These sedimentary rock deposits can be millions of years old, making them fossil resources. Not fossil fuels, but still, a type of agricultural "fuel" made from fossils. Running low on bones and poo, farmers were ready to give rock a try. Small deposits were discovered across England and then, predictably, depleted by the 1890s. And what did they do next?
Did they think, hey, maybe we're burning through all this stuff at kind of an alarming pace? Maybe we should think about the future and what could happen when it's all gone? No, they did not do that, they just looked for new places to mine. After all, there were a lot of hungry mouths to feed, and without food, they would die. Soon prospectors started unearthing phosphorus rock deposits all across the globe. Around 1899, some Brits recognized phosphorus rock on a tiny spit of land in the Pacific, situated between Hawai'i and Papua New Guinea.
The Brits named their "discovery" Ocean Island, but it's known as Banaba to the local people, and is today part of the country of Kiribati. Banaba was blanketed in phosphorus rock, and the tiny island suffered for their coincidental fertility. It was stripmined and plundered for the United Kingdom, Australia, and New Zealand, as well as Japan during World War II. Massive tracts of the ground were simply ripped away, leaving a strange, jagged landscape behind. The locals, meanwhile, were pushed into unfair contracts that paid virtually nothing for the rights to ravage their land.
They were forced to relocate, and, in some cases, just straight-up killed. The amount of violence enacted in Banaba was staggering. And by the late 1970s, the island was utterly depleted. A few hundred people have moved back since then, but the legacy of phosphorus mining, such as depleted and polluted water supplies, still scar this island. As of 2021, most Banabans live in Fiji. That story isn't unique to Ocean Island, either. This extraction was repeated on other islands across the Pacific, like Nauru, as well. Island after island was sacrificed on the altar of agriculture, but still, the world was starving for phosphorus.
In the early 1880s, deposits were discovered in central Florida, a region quickly dubbed "Bone Valley". The U.S. Army Corps were considering building a canal there when they discovered it was actually chock-full of fossils. Scientists think that during the Neogene Period, as sea levels fluctuated, this area might have flip-flopped between a shallow, productive sea and being land. The valley was studded with the fossilized remnants of ancient horses, whales, mastodons, other elephant relatives, even megalodons. name a bone, and Bone Valley's probably got a copy of that bone, pretty much
Alongside those fossils were rich veins of phosphorus rock, the remains of algae and all the other biological matter that sedimented on the floor of that ancient shallow sea. After the discovery of these phosphorus rock deposits, one Valley saw a mining rush as frantic as California's gold rush, or Texas' oil rush. This completely reshaped central Florida's landscape as the ground was torn into open-pit mines. Florida's bone rush came with its own complicated history of environmental devastation and poor working conditions. As for what came next in phosphorus, well, we're kind of caught up to the present. To this day, our agricultural system
is still entirely dependent on mining an incomprehensible amount of phosphorus rock. As of 2024, Bone Valley still produces more than 60% of the US's phosphate. Phosphorus rock mining is also big business in countries like China, Russia, Brazil, Peru, and Egypt, among others. It's particularly big in the Western Sahara, which is disputed territory mostly controlled by Morocco. That area is estimated to hold 70% of the world's phosphorus rock deposits. In the 1960s, the area was controlled by Spain, and Spanish geologists started mining the massive phosphorus deposits there.
Ever since, the mine has been churning out phosphorus rock. It's a gigantic operation, but also super remote. So to get the rock out of the desert, they built the world's longest conveyor belt, stretching about 100 kilometers from the mine to the ocean. Unfortunately, this has put the mine at odds with the local people. Morocco controls the land, but the UN doesn't formally recognize it as part of Morocco. In response, Morocco has built a 2,700 kilometer-long militarized wall to keep locals away. It's perhaps no surprise that our relationship with phosphorus continues to be shrouded in conflict and violence. Some experts have sounded the alarm bell that phosphorus is, in fact, a finite resource.
Deposits that took millions of years to form are being scraped out of the ground thousands of times faster than they could ever be replenished. Experts disagree on exactly how long we have before the amount of mineable phosphorus rock starts to decline. Some organizations, like the Global Phosphorus Research Initiative, have estimated that within 30 to 40 years, readily available supplies will be unable to meet global demand. Other estimates have stretched out that number and suggest it might be a few centuries before we crest the peak on phosphorus extraction. But either way, our supply of phosphorus rock is finite.
Also, having a world-critical resource in the hands of just a few countries… that hasn't always worked out great in the past. Fortunately there's still time to escape this corner we've painted ourselves into. And a crucial step is just to be smarter about our current fertilization methods. Because despite how important phosphorus is and has been for more than a hundred years, we're pretty wasteful with how we use it. A lot of the fertilizer we spread on fields doesn't actually go into the plants- it gets washed away and ends up as runoff.
Maybe only a fifth ends up actually going to the plants. And that runoff is part of what's fueling giant algal blooms that can choke waterways and shut down swimming holes. We could cut down on some of this waste with more targeted timing and location of artificial fertilizer application. Or we could go old school and revisit the millennia-old manure tradition. Letting livestock graze (and poop) on cropland on specific schedules could increase soil fertility while mitigating food safety concerns. And it'd reduce the amount of phosphorus rock we need to dig up.
Reducing food waste could further help us stretch what we already have. And there are even groups looking at solutions like gene and breeding technology to help crops use phosphorus more efficiently. There's also ongoing research aiming to recycle lost phosphorus, like by collecting it from wastewater treatment plants using fancy filtering systems. And maybe someday we'll even find an entirely new source of phosphorus. Like a new effort led by Swedish scientists who are using microbes to recover phosphorus from sea floor sediment. So what's the next great source of phosphorus?
We don't know yet. But we've used science to get ourselves out of a pinch before. And in the same way we're gradually shifting from fossil fuels to renewable energies, it's possible this fossil resource may also soon be replaced by better, more sustainable solutions. And ideally ones that don't involve stealing a bunch of bones. This epic survey of the history and science of phosphorus fertilizer was inspired by The Devil's Element by Dan Egan. If you found this story as fascinating as we did, be sure to check out the book for an even deeper look at phosphorus.
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