Aurelia still had a vivid memory.
It was around the time she had just evolved into a Queen Dryad when Teo taught her something important.
[Listen carefully. There’s something called the Malthusian Trap.]
The Malthusian Trap.
An economic hypothesis proposed by the modern economist Thomas Malthus.
According to this hypothesis, humanity can never escape famine.
Food production increases arithmetically, but population grows exponentially.
The rate of population growth will always surpass the rate of food production.
[My lord, I understand that humans breed like animals in heat to increase their population. But why doesn’t food increase along with them?]
[Because the land available for farming is limited.]
This was partly because the amount of arable land itself was finite.
[More importantly, there isn’t enough nitrogen in the soil.]
[What’s nitrogen?]
[Ah, nitrogen is an element with the symbol—]
[………]
[Anyway, most fertilizers are just a way to supply nitrogen to the soil. There aren’t many crops that can grow without it.]
Nitrogen is an essential component of proteins.
Naturally, it plays a crucial role in plant growth.
However, the nitrogen levels in the soil could never keep up with humanity’s demand for food production.
Even if people used manure to supplement it, that was merely recycling the nitrogen humans had already consumed.
This was one of the key points Teo considered in the Malthusian Trap.
[My lord? Didn’t you say that over 80% of the air is nitrogen? How can it be lacking?]
[Good question. That brings us to the properties of atmospheric nitrogen… It’s tightly bound by something called a triple bond.]
Atmospheric nitrogen exists in a triple-bonded form.
Chemically speaking, that makes it extremely stable.
Breaking this bond and converting it into a form that plants can use as fertilizer is incredibly difficult.
[You know lightning, right?]
[Yes, the one Lucia showed me recently…]
[You need that kind of power to break the bond and supply nitrogen to the soil—as nitrate ions.]
[……You’re telling me it takes the kind of force that could kill me instantly if I got struck!?]
[Yep. That’s why I’ve been asking Lucia for lightning more often lately.]
Without lightning strikes, there was no way to convert atmospheric nitrogen into usable fertilizer.
This was one of the fundamental reasons famine was so widespread across the continent.
[Then why haven’t humans starved to death already?]
[Because they’re too busy killing each other. Their population naturally regulates itself, so the issue hasn’t become too obvious yet.]
[As expected of lower lifeforms.]
[Right? I think they’re pretty primitive too.]
Of course, there were other factors in the Malthusian Trap.
But it was undeniable that the ultimate barrier to food production was the lack of nitrogen in the soil.
[Then won’t your future nation be in danger too, my lord…? Other races seem to consume much more food than humans do.]
Aurelia was concerned.
She worried about the future of the Millennia Federation, the nation her lord was planning to build.
And then, Teo said—
[——That’s when Fritz Haber appeared.]
“More precisely, it was a device created by a man named Haber.”
That marked the end of the long flashback.
Aurelia’s gaze returned to the knights before her, a genuine smile spreading across her lips.
— Whisper, whisper.
“…Making fertilizer out of thin air? What even is fertilizer?”
“You know, the stuff commoners throw waste on their fields.”
“So that thing is… a machine that makes crap?”
“And they’re proud of that? As expected of barbaric monsters…”
But the knights didn’t quite understand.
Born with noble blood, they had never concerned themselves with farming. None of them grasped the importance of fertilizer.
Even their commander, Seras, was no different.
“How is this related to food… Hmm? You there. What’s the matter?”
“Huh!? N-No, my apologies!! A mere servant like me shouldn’t be so presumptuous.”
“It’s fine. Speak. What shocked you so much?”
Fortunately, there was someone who did understand its significance—
the servants accompanying the knights.
Among them were those who had once been tenant farmers.
A young boy hesitated for a moment, then stepped forward.
“You see, without fertilizer, farming is impossible.”
“How can there be a shortage of fertilizer? Isn’t all commoners do just eat, sleep, and relieve themselves?”
“That’s not how it works. Even if we gather all the manure from livestock, it’s still not enough. In our domain, we even had a tax on urine because of that.”
“…You’re telling me they tax piss now?”
“That’s how badly we need fertilizer.”
And so, Seras realized something—
It wasn’t that fertilizer was unimportant. It was simply something he had never needed to understand.
Aurelia, relieved that she didn’t have to explain it herself, smiled.
“That boy is right. Farming is impossible without fertilizer. Without it, there would be no bread on your tables.”
“Understood. I apologize for my ignorance.”
“Good. Now then, that’s why Haber thought about how to increase the supply of fertilizer.”
With that, the conversation returned to the chemist, Fritz Haber.
“His title is ‘The Scientist Who Made Bread from Air.’ A legendary figure who banished famine from the land.”
“Bread from air…?”
“Yes. Through a process called ‘nitrogen fixation.’”
Fritz Haber—
A chemist born in an era where the Malthusian Trap was believed to be an unshakable truth.
He was the one who finally invented the nitrogen fixation process.
Also known as the Haber-Bosch Process a method to synthesize ammonia from atmospheric nitrogen.
“With this method, hydrogen and nitrogen can be made to react and form ammonia.”
The key requirements:
High temperature, high pressure.
Nitrogen, separated after liquefying air.
Hydrogen, produced through the water-gas reaction.
The two gases, combined over an iron catalyst, go through a series of steps to yield ammonia.
This was the explanation Aurelia kept to herself.
‘This is our core technology. No way I’m sharing it. Fufu.’
After all, Millennia’s greatest weapon was food.
There was no reason to leak technology that would put them at a disadvantage.
Not that it would be easy for others to replicate.
Even for them, it had taken three of her most brilliant vassals working together just to recreate it.
This is a product that those who learned chemistry from Teo and industry from Aurelia, the one in charge of agriculture, struggled to create for nearly three months…
But anyway, I can’t tell you about it.
That was the conclusion reached by Teo and Aurelia.
“Ammonia…? Hydrogen? What are those?”
“It would still be difficult for humans like you to understand.”
“I never imagined I’d hear such words after being born a noble.”
“It can’t be helped. After all, this is knowledge bestowed upon us by none other than the last dragon, Teonar. Even we struggled to learn it.”
“……”
“If Arkenia were to become an ally of our Millenia, perhaps our lord himself might be willing to teach you.”
Leaving behind a remark about the relationship between the two nations, she turned on her heels and walked away.
That was the end of the mechanical explanation, which they wouldn’t have understood anyway.
“Well then, shall we go now?”
“Go? Go where?”
“Just hearing about it won’t be enough for you to grasp the reality of it. I’ll show you directly.”
“……? Fine.”
“Show me? Show me what?”
Seras and the knights also boarded the carriage, looking as if they were still processing what they had just heard.
The concept of nitrogen fixation and all that was utterly incomprehensible with medieval knowledge.
But they didn’t even need to understand the principles.
“Th-this is…?”
“Is all of this wheat? Everything in this massive warehouse?!”
“Unbelievable! This is insane!!!”
The granary Aurelia led them to—
It was packed full of wheat.
A sight even noble families would struggle to see in their own storehouses.
Especially after enduring a long war and a series of poor harvests.
“The size of these wheat grains… they’re four times bigger than the ones in Uncle Hans’ field…”
“That’s thanks to my selective breeding, little one.”
“Wha—Whaaat!?”
“Despite how I look, I am a Queen Dryad. Cultivating flowers and sprouting plants is my specialty.”
“Aurelia. What do you mean by selective breeding?”
“It means I rapidly cultivate crops on a small scale, continuously crossbreeding the best-quality wheat. But I suppose that would be difficult for you to understand as well.”
She sighed.
If they were already this shocked, what would they do next?
“And more importantly, this is merely the warehouse for storing the food we need immediately.”
“…What? Are you saying there’s even more food elsewhere?”
“Of course. Look outside.”
The knights’ gazes all turned in unison.
Outside the granary stood several tall, cylindrical structures.
So tall they had to crane their necks just to see the tops.
“I was wondering about those since earlier… What are they…?”
“Silos. You can think of them as massive containers for storing surplus crops.”
“…………You’re saying all of those are filled with wheat? They’re practically as big as a magic tower!!!?”
“It’s not just wheat—there’s barley and various other grains in there too. That’s our Millenia’s food supply for an entire year. As for the surplus, we’re turning it into distilled liquor to prevent it from going to waste.”
“This is impossible…”
A gasp of shock escaped Seras’ lips.
She knew from her lord, Leopoldus, that their kingdom was suffering from famine.
Yet here was an enormous structure filled to the brim with crops?
And they were even producing alcohol—the very thing that had been banned in Arkenia due to its massive grain consumption?
Regardless of her noble status, as an Arkenian, she couldn’t help but feel overwhelmed.
Now she was starting to understand why Aurelia had spoken with such confidence earlier.
“Just what kind of sorcery is this nitrogen fixation that it allows for something like this…?”
“It’s a miracle invention from another dimension—one that increased the human population fivefold in just a century.”
“Fivefold? Which kingdom managed such a feat?”
“Not a kingdom—the entire human race. From 1.6 billion to 8 billion people.”
“E-e-eight billion…?”
Even for someone like her, the sheer scale of it was too much to process.
But as a medieval person, such a reaction was inevitable.
After all, Arkenia’s population barely reached a million.
‘Didn’t my lord say that if we revealed this much, they’d undoubtedly see us as a threat and attempt an invasion?’
“I assume you’ve seen enough of the warehouse? Then let’s move on to the next location.”
Before the stunned Seras, Aurelia snapped her fingers.
For some reason, Seras’ instincts screamed a warning.
“……What are you planning to show us now? Where are we going?”
“Hehe. You see, nitrogen fixation isn’t just about making fertilizer.”
Aurelia’s eyes narrowed very, very thinly.
“-This time, I’ll show you the mine.”