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Episode:
49
The Invention That Feeds (and Threatens) the World: The Story of Fertiliser
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Today we’re talking about something ingrained into modern civilisation that has huge impacts on climate change and human rights, but is something you may never really think about.
Synthetic fertiliser.
Yep, it’s responsible for feeding billions of people but it is also driving climate change, it's poisoning waterways, and it plays a major role in global conflicts. It’s impacts are huge, so I’m going to be giving you a quick run down on everything you need to know, and this will probably also include a little bit of a history lesson.
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Transcript
I'm your host, Brianne West—an environmentalist and entrepreneur trying to get you as excited about our planet as I am. I'm all about creating a scientific approach to making the world a better place without the judgement, and making it fun.
And of course, we’ll be chatting about some of the most amazing creatures we share our planet with.
So, if you’re looking to navigate through everything green—or not so green—you’ve come to the right place.
Kia ora, and welcome back.
Today, we're talking about something that might be a little left field, but it has shaped modern civilisation more than almost any other scientific discovery: synthetic fertiliser.
Yeah, fertiliser.
It's responsible for feeding billions of people, but it's also driving climate change, poisoning waterways, and playing a major role in global conflicts.
I know—weird.
If you’re listening to this, about half of the nitrogen in your body came from a fertiliser factory. And that’s not an exaggeration.
The process that makes synthetic fertiliser is called the Haber-Bosch process, and it literally sustains half the global population. Without it, modern agriculture as we know it would not exist.
But of course, as with most things we create, it has come with some pretty serious unintended consequences.
So, this is a story—I’ve never done a story pod before—but this is the story of scientific breakthroughs, war, and unintended consequences.
We have always struggled to produce enough food. Before synthetic fertiliser, soil depletion was a growing crisis—it was the big one.
The search for fertiliser drove colonisation, global trade wars, and led to horrific labour conditions. But in the early 20th century, two German chemists figured out a way to—well—save the world.
Let’s travel back in time to 1898. The world was heading towards a food crisis. The global population sat at around 1.6 billion, and much of that depended on crops grown in soil rapidly depleted of essential nutrients.
And I mean, this isn’t news. Farmers had always known that soil needed to be replenished to stay productive, but traditional methods—crop rotation, composting, manure—weren’t keeping up. Every single harvest, every single year, pulled nitrogen, phosphorus, and potassium out of the ground, and we didn’t really have a way to replace those at scale.
So, of course, yields were declining.
British chemist Sir William Crookes was one of the first to raise the alarm. He warned at a big conference that food production in Europe and its colonies would collapse very soon if new sources of fertiliser weren’t found.
His argument? Well, it was largely framed around Britain’s control over food security and power—making it clear that if the empire wanted to maintain its dominance, it needed to secure nitrogen-rich resources.
Yeah. That’s kind of a theme.
His predictions weren’t unfounded, though. In some parts of the world, crop failures were already leading to famine.
Governments started to panic. We were on our way to a full-blown crisis.
At that time, the best natural source of nitrogen was poo.
Bird and bat poo, called guano, is an incredibly rich fertiliser. It’s packed with nitrogen, phosphorus, and potassium—exactly what was needed.
Indigenous cultures in South America had used it for centuries, but by the mid-1800s, the global demand for fertiliser had turned guano into one of the world’s most valuable commodities.
Peru had some of the largest guano deposits in the world—built up over thousands of years on dry coastal islands where seabird colonies thrived.
By the 1840s, the guano trade had become such a big industry that the United States passed the Guano Islands Act, which allowed American citizens to claim any unoccupied island in the name of the U.S. if it contained guano.
And I’m sure they really stuck to the rule that it was unoccupied.
That sounds familiar, doesn’t it?
The industry was brutal. Both European and American economies relied heavily on it. Thousands of indentured Chinese labourers were forced to work in horrific conditions, mining the guano. They often suffered from horrendous respiratory diseases caused by inhaling the dust.
The ecological impact was just as bad. Entire bird populations were wiped out because humans stripped their islands bare.
And despite all of that destruction? It still wasn’t enough.
Demand continued to outpace supply.
And soil degradation? It still continued.
(And if you’re wondering if soil degradation has stopped today... nope. It still continues—just in a different way. I might do another episode on that.)
As those smelly piles of poo dwindled, attention turned to another natural source: saltpetre, also known as sodium nitrate.
Saltpetre was found in huge deposits in Chile’s Atacama Desert. By the late 19th century, Chile had become the world’s leading supplier of nitrogen fertiliser, exporting millions of tonnes of saltpetre to Europe and North America.
And it wasn’t just valuable for agriculture. This is where it starts to get a little more interesting—it was also a key ingredient in explosives.
This made it not only a very important resource—it also made it a strategic one.
So, conflicts started to break out over control of these Chilean saltpetre fields. The industry created enormous wealth for Chile, but the conditions for workers were still exploitative. Indigenous labourers were forced into what was effectively slavery.
Yeah, I know. I’m not surprised either.
But despite the scale of that massive mining operation, it became clear that it still wasn’t enough. The demand for fertiliser kept rising, and even those deposits weren’t limitless.
And, of course, scientists were aware that there was another potential solution.
Because, if any of you out there are chemists, you’ll know that our air is about 78% nitrogen.
So, why don’t we just somehow figure out how to get it out of the air and onto the land?
Well, that’s a little more complicated.
In its gas form, nitrogen is almost entirely useless for plants.
Some bacteria and legumes have evolved to capture nitrogen and convert it into a usable form for plants. But humans hadn’t yet found a way to do that.
And that was the solution—one of the biggest unsolved scientific problems at the time.
Obviously, chemists knew that atmospheric nitrogen was abundant, but its molecular structure made it very stable and difficult to break apart.
For plants to use it, nitrogen has to be converted into ammonia or nitrates—which is something nature does relatively well through certain bacteria.
And this problem attracted the attention of German chemist Fritz Haber.
He was a brilliant but—let’s say—controversial scientist. He was relentlessly ambitious, desperate to please, and that willingness kind of showed that he had no real ethical boundaries.
At that point, he was theorising that if nitrogen and hydrogen could be forced to react together under the right conditions, they would form ammonia.
Because, of course, ammonia is NH₃—one atom of nitrogen, three of hydrogen.
And that compound could then be used to create a fertiliser.
It took him a long time, and I’m not going to talk you through the process because, to be honest, it’s a whole lot of chemistry and a whole lot of maths.
But by 1909, he actually succeeded.
Using high temperatures, massively high pressures, and an iron catalyst, he managed to synthesise ammonia from the nitrogen in the air.
I cannot overstate how groundbreaking that was.
He had proved that it was absolutely possible to create unlimited amounts of nitrogen fertiliser artificially—thus solving one of the largest problems we were facing.
But there was a problem.
Because his method only worked at small scale.
The conditions required were so freaking extreme—so hot and under so much pressure—that there wasn’t any equipment or even materials that could handle it.
The process needed scaling.
And that’s where Carl Bosch came in.
I can tell you now, as someone who has scaled a lab process a couple of times, it’s way harder than you think.
Carl Bosch was a chemical engineer working for the German company BASF, and his task was to take Haber’s discovery and make it commercially viable.
And this was, without question, one of the greatest engineering challenges of the 20th century.
The pressures required were so intense that they literally destroyed every piece of machinery he used for years.
So they had to invent entirely new materials, design high-pressure reactors from scratch, and solve complex issues—finding new catalysts and figuring out heat management.
And sure, it’s not as extreme as the scientists working on cracking fusion right now, but back then? It was almost insurmountable.
And it’s kind of sad that nobody’s really heard of him.
Because he was not a Nazi.
And there’s a reason I bring that up—which we’ll come to shortly.
He was a good guy.
He died alone and very, very depressed because of what happened.
But he effectively built an entirely new industry from the ground up.
After years of constant failure and stress, and what sounded like a life I wouldn’t wish on anyone, they built the first large-scale ammonia production plant in Opau, Germany, in 1913.
And that was officially the birth of the Haber-Bosch process.
With that plant, they could produce nitrogen fertiliser on an industrial scale—unlocking massive agricultural potential and making farming as we know it today possible.
Global food production skyrocketed in the following decades. The human population surged.
It’s kind of obvious—the rest is history.
The Haber-Bosch process is one of the most important industrial achievements in history.
And the vast majority of you have never heard of it.
As I mentioned, this did have an unintended consequence.
Because ammonia isn’t just useful for fertiliser—it’s also a key ingredient in explosives.
And when World War I broke out just a year later, in 1914, the first thing the British did was cut off Germany’s supply of natural nitrates—which, of course, they were using to produce explosives and synthetic fuel.
That’s 100% what I would have done too—a strategic move.
Unfortunately, Germany had the Haber-Bosch process, which meant they—and only they—had the ability to produce their own explosives.
And historians reckon that without synthetic ammonia, the war would have lasted six months to a year.
After the war, the chemical industry built on that discovery continued to grow.
BASF got together with a couple of other chemical companies to form a behemoth called IG Farben.
One of those companies? Bayer—yes, the one that still exists today.
And one of the first things IG Farben did was align themselves with Nazi Germany.
They created products like synthetic fuel, synthetic rubber, explosives, and some of the chemical compounds used in concentration camps.
They also used forced labour from those concentration camps and were very much part of the Holocaust.
After the war, IG Farben was dissolved, but its key components—including BASF and Bayer—continued operating.
And BASF is actually one of the largest chemical companies in the world today—producing everything from plastics to agricultural chemicals, still using the Haber-Bosch process, and very much still a factor in your life.
The history of some companies is absolutely fascinating—and quite often, really quite dark.
So, we’ve established that this process was important.
Synthetic fertilisers transformed global agriculture.
Today, we use about 230 million tonnes annually.
That’s what makes it possible to sustain over half of the world’s 8 billion people.
It’s things like wheat, maize, and rice—staples that billions rely on.
But the environmental and social costs of this dependence are mounting.
One of the biggest consequences of synthetic fertiliser is nutrient runoff.
You’ve probably heard of it.
When fertilisers are applied to fields, a significant portion isn’t actually absorbed by crops.
Too much is applied, and it washes away, ending up in rivers, lakes, and oceans.
This leads to something called eutrophication—where excess nutrients fuel massive algal blooms.
These blooms use up all the oxygen in the water, the algae dies, it sinks, and it creates dead zones where other marine life cannot survive.
The Gulf of Mexico—let me repeat—the Gulf of Mexico—is home to one of the world’s largest dead zones, about 15,000 square kilometres in recent years.
And it’s primarily caused by fertiliser runoff from industrial farms in the U.S. Midwest, where nitrogen-heavy fertilisers are used to grow maize and soy.
Obviously, the problem isn’t limited to North America.
Dead zones have been recorded in the Baltic Sea, the South China Sea, and, of course, right here in Aotearoa.
That’s not all.
Groundwater contamination is a big concern.
In a lot of agricultural regions, nitrate levels in drinking water massively exceed safe limits.
And nitrogen is hard to remove from water. Your typical filter won’t do it.
High nitrate consumption has been linked to health issues like blue baby syndrome, which affects infants' ability to transport oxygen in their blood, and it is very strongly linked to increased risks of bowel cancer.
In Aotearoa, nitrate pollution from intensive dairy farming is a huge issue.
Some studies estimate that up to 800,000 New Zealanders may be exposed to drinking water with nitrate levels above those associated with cancer risk.
And because I’m not on town supply, I know that the water from my well is high in nitrates—which isn’t overly surprising, since I live close-ish to a farming area.
If you’re interested in finding out about your water supply, I’ll put a map in the show notes showing areas of Aotearoa with nitrogen levels broken down.
But that’s not all—because there’s also a climate cost.
These fertilisers are a major contributor to climate change.
When applied to soil, they release nitrous oxide—a greenhouse gas 300 times more potent than carbon dioxide in terms of global warming potential.
Fertiliser-related nitrous oxide emissions account for roughly 6% of total global greenhouse gas emissions—which is more than the entire aviation industry.
And let’s not forget—the Haber-Bosch process itself is hugely energy-intensive.
It actually uses about 1–2% of the world’s total energy supply, which primarily comes from fossil fuels.
Isn’t it amazing how so many things are linked that you’ve just never heard about?
Ultimately, as always, this is a super grey subject.
Synthetic fertilisers have played a critical role in modern agriculture.
They have enabled us to keep food production in pace with population growth.
But they have also caused massive environmental harm—accelerating climate change, polluting waterways, and degrading our soil.
And whilst there are other options, none of them are perfect—but they are getting better.
If we want a truly sustainable agricultural system, we need a mix of solutions:
Farmers are not the ones at fault here.
They carry so much blame for environmental destruction, but at the end of the day, the pressure on them is immense.
Without a scalable alternative, banning synthetic fertilisers would be disastrous.
What we need is a pragmatic approach.
And I don’t think an outright ban is even remotely pragmatic.
I hope you found that interesting.
If you know someone who enjoys science, feel free to share it with them.
Next time, I’m going to talk about International Women’s Day—why we still need it, and yes, there is an International Men’s Day.
So, men out there—if that’s all you’re putting in the comments when people talk about International Women’s Day, feel free to go and organise something for yourselves.
See you next week! Mā te wā.
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