Chapter 58

"Let's start with the rubber. We'll continue searching for it while we look for saltpeter."

"Rubber, huh? That's a good choice. It has many uses, from window frames to wheels."

"Yeah. That's why I want to find it. The other thing is that I want to build a purification system."

"Treating wastewater, huh? Indeed, that's urgent. In that case, I'll also work on developing a motor."

"Got it. That would be a big help. Mmmph."

Huh, what's going on?

Suddenly, Sequoia covered my mouth from the front.

It seems that when I leaned over the desk, Penguin was also squished.

"Joshua, you and Sojiro discussing secrets isn't very friendly, you know."

"Ah, sorry. I was getting ahead of myself. I'll explain the system simply."

If only there was a blackboard, but there's no such convenient thing here. I'll have to explain it verbally, but since Sequoia is here, a brief explanation should be enough.

No, wait. Since we're at it.

"Alru."

"Yes!"

"Since we're at it, let's have Alru join us too."

"But I—"

"No, it's fine. We need to explain the installation and management of the purification tank to someone who doesn't have the knowledge. It's more convenient that way."

"Okay!"

I smile at Alru, who nods and moves her cat ears.

"Imagine a small pond. There are fish in the pond, and aquatic plants are growing."

I look at Alru and Sequoia in turn, waiting for them to nod before continuing.

"The fish eat the aquatic plants and excrete waste. This waste dissolves in the water and decomposes. Then, the waste becomes nutrients, and the aquatic plants grow."

"Hmm. So it's the cycle of nature."

"Exactly. But the decomposition of the waste isn't just happening naturally; tiny organisms that we can't see are eating it."

"Oh, so there's such a mechanism."

"Now, let's apply this to wastewater. Wastewater is similar to the fish's waste, so it can be food for the tiny organisms. It decomposes and returns to the soil."

"Hmm, hmm. So, these tiny organisms breathe like fish?"

"Exactly! Think of wastewater as a large amount of food. To feed a large number of tiny organisms, you need a lot of air for them to breathe."

"I understand. So, this leads to the motor, right?"

As expected, Sequoia is quick to catch on.

Wastewater (organic matter) is decomposed by microorganisms. To supplement the oxygen consumed by the microorganisms, aeration is used—like the bubbling pump in an aquarium to supply a large amount of oxygen.

This accelerates the decomposition of wastewater by microorganisms.

After the decomposition is complete, the aeration is stopped, and the sludge sinks to the ground. This sludge is rich in decomposable microorganisms.

When the next batch of wastewater is treated, the sludge is aerated again to further enhance decomposition.

Excess sludge can be recycled as fertilizer for fields, which is efficient because it contains a large amount of nitrates, making it a good fertilizer.

"Alru, what do you think?"

"Hmm. The tiny organisms munch and munch, and the water becomes clean?"

"Exactly. And the device for the tiny organisms to breathe will be developed by Penguin."

"Okay!"

It seems that both Sequoia and Alru have understood the concept, which is great.

They understood the mechanism, but the biggest issue is whether Penguin can create the aeration device.

"That's a good explanation. You cut out the unnecessary details while making the mechanism understandable."

"Hey, you were listening?"

"Sequoia was repeating your words in his head. By the way, there's electricity here. The key is to mix the wastewater in the purification tank."

"Water wheels or steam could also work. Can you let me know when you have a plan?"

"Of course. There's a lot to research, and it's quite enjoyable."

"Is it?"

"Indeed. Especially the unique techniques of this world. Like mana—"

Ah, I'm getting carried away again.

It seems Penguin can manage it, so I'll leave it to him and focus on finding materials.

◇◇◇

Sequoia was indecisive until the end, but he eventually decided to investigate the mineral samples collected with Penguin.

So, I set out with Alru on horseback to the southern part of Nellac.

As Baltro had described, the southern region is a desolate land with exposed reddish-brown earth as far as the eye can see.

There are a few low shrubs and weeds, but the vegetation is clearly sparse.

The eastern part of the city is covered by a lush forest, but the landscape here is quite different.

The high mountain range to the north of the Rubicon River might be influencing the climate.

However, it's risky to assume the vegetation works the same way as on Earth.

The border between the principality and Cumberland is not clearly defined, but it's considered the frontier of Cumberland after traveling a few dozen kilometers from the border village.

The vegetation changes dramatically over these few dozen kilometers, from a fertile, lush landscape to the desolate land I'm in now.

The reason is unknown. Well, the boundary between desert and non-desert areas is often vague.

It's better to accept it as it is.

"There's nothing. Is there?"

Alru, who is holding onto my waist from behind, comments.

As we ride, I look at the reddish-brown earth, but there's no sign of people or animals.

"I don't think there's absolutely no life. It's probably just a coincidence. We don't always encounter wild boars when we head to the Rubicon River, either."

"Yes. I can sense... something."

"Really? Is it far?"

"Yes, far away."

"Hmm. It might be interesting to have Baltro and the others explore this area."

Hmm.

The vegetation is indeed sparse. Given that there are guavas here, cacti might also grow naturally.

"Master Joshua, is saltpeter here?"

"I don't know. I came here because saltpeter is more likely to exist in dry areas..."

"Does it mean it's not wet?"

"Yeah. But even if we dig the ground randomly, it's unlikely to go well."

In the end, it's best to dig up samples and take them back for investigation.

Is there any way to pinpoint a location?

Guh-guh-guh-guh!

A creepy sound came from the sky!

I jumped and looked up to see a bird with a long beak flying by.

"Maybe it's a vulture or something like that."

"Can we eat it?"

"Are they going to attack us!?"

"No, Alru and I can eat it. Master Joshua, do you like bird meat?"

"Ah, no, not now..."

She said something scary so casually, and it startled me.

Hmm. Birds. Birds.

"I have an idea. I remember there's a cliff to the west that looks like the earth has split."

"Huh?"

Maybe there's saltpeter there.