Chen Hao yawned and put the cup on the table. The water was still warm. He glanced at the robotic arm, then at the resin buckets and old pipes piled up in the corner.

“Your system is quite intelligent,” he said, “but our base is still missing one thing.”

Nana's optical glasses flickered slightly: "Please specify your requirements."

“It’s not a need,” he waved his hand. “It’s a waste. Sheep dung is almost piled up to the roof, and straw is scattered everywhere. It’s smelly and takes up a lot of space. Do you think these things can be turned into something useful?”

Nana paused for two seconds, then began searching the knowledge base. Her voice was flat: "Organic matter can ferment to produce biogas under anaerobic conditions. The main component is methane, which can be used for combustion and heating. The technology is simple and suitable for current conditions."

"I knew you could do it." Chen Hao slapped his thigh and stood up. "Let's build a biogas digester. We won't need to burn stored fuel for cooking anymore, and it'll save electricity."

“The plan is feasible,” she said. “I suggest using discarded resin barrels as fermentation containers, along with existing pipelines to vent the gas.”

“Let’s do it then.” He rolled up his sleeves. “Anyway, I don’t have to do the cleaning now, so I can use the time to do some side hustles.”

The two moved three unused resin buckets and assembled them into a sealing device in an open area on the east side of the base. Nana used a cutting module to trim the joints, while Chen Hao was responsible for applying a honey-mixed resin as a sealing layer. As he applied it, he muttered, "This time they really used food as glue."

“Honey has a high sugar content, which promotes the growth of microorganisms,” she said. “Short-term consumption is acceptable.”

After connecting the containers, they mixed sheep manure with crushed crop straw in the correct proportions, added water, and poured it in. Once the container was full, Nana closed the feed inlet and activated the pressure monitoring program.

"Gas production is expected to begin in 48 hours," she said. "We need to keep the ambient temperature stable."

"Okay." Chen Hao wiped his sweat. "Once it starts bubbling, I'll cook a nice meal to celebrate."

The next day at noon, Chen Hao squatted beside the fermentation vat, pressing his ear against the side of the vat to listen for any sounds. He heard a slight gurgling sound coming from inside.

“There’s potential.” He grinned. “This thing is really generating gas.”

Nana's scan data showed that the methane concentration had reached the ignition threshold. "We can proceed with the initial ignition test," she said. "Remote operation is recommended."

“I don’t have that kind of patience.” He waved his hand. “I’ll come here myself and experience the power of technology.”

He turned on the exhaust valve, took out a lighter, and brought it close to the vent. The flame had barely touched the gas when it shot up half a meter high with a whoosh.

"Wow!" Chen Hao leaned back, almost falling to the ground. "So fierce?"

“The initial gas contains impurities, making combustion unstable,” she said. “I suggest adjusting the ratio.”

"Make a note of this." He patted his pants. "At least it proves it can burn."

Over the next two days, they continuously fine-tuned the proportions of the ingredients. After adding a small amount of waste honey residue, the gas production rate increased significantly. On the morning of the third day, a stable blue flame finally ignited on the stove.

"It's a success?" Chen Hao stared at the flames, not daring to blink.

“Gas production efficiency has increased by 62 percent,” she said, “enough to support cooking two meals a day.”

“Wow,” he laughed. “I feel like a farm scientist now.”

“Identity tags do not affect actual functionality,” she said.

Just as he was about to turn off the valve, his elbow accidentally hit the exhaust pipe. The resin at the connection point had aged and broken, and a burst of gas shot out.

"It's leaking!" He immediately reached out to plug it.

The sparks hadn't died down yet, and the drifting gas was ignited, with flames climbing up the outer wall of the pipe.

By the time Chen Hao realized what was happening, the flames had already reached shoulder height. He grabbed a damp cloth from the side and covered the flames with it, trying to extinguish them. A wave of heat hit him, and his right arm stung.

"Don't force yourself," Nana said, her voice unchanged.

She raised the robotic arm, aimed it at the top of the fermentation tank, and started the preset program. The exhaust valve opened fully, and the remaining gas was ejected from the high-altitude release port, rapidly diluting in the air.

The fire was extinguished within seconds.

Chen Hao, panting, loosened the wet cloth; his arm was red and his skin was slightly swollen.

"Does it hurt?" she asked.

"It's alright," he said, pulling his hand back. "It's just a little hot."

"I recommend immediate cooling," she said. "To avoid skin damage."

"Wait a minute," he shook his head, "Let's fix this broken pipe first."

Nana took out a spare metal clamp, secured the broken part, and then sealed the gap with thickened resin. After confirming there was no leakage, the system resumed operation.

“The emergency protocol has been updated,” she said. “The next time the gas concentration exceeds the standard, high-altitude emissions will be automatically activated.”

"That's good." He flexed his wrists. "Don't make me a human fire extinguisher anymore."

“You were closest at the time,” she said, “so your response was the most efficient.”

"You really dare to tell the truth."

As the sun began to set, the first round of fermentation ended. They opened the discharge port, and the dark brown residue slowly flowed out.

"Can this stuff be used as fertilizer?" Chen Hao pinched off a small amount and smelled it.

"The nitrogen, phosphorus, and potassium content meets the standards," she said. "It is rich in organic matter and suitable for soil improvement."

“Then I’ll give it a try.” He found a shovel and mixed the residue into the experimental plot at the edge of the vegetable garden.

Three days later, the vegetables in that field grew taller than those elsewhere, and their leaves were glossy.

"It really works." He squatted down to look at it. "So even trash can be turned into treasure."

“The essence of ecological cycles is the redistribution of resources,” she said. “Your idea aligns with the logic of sustainability.”

"That sounds like a compliment." He stood up, dusted himself off, and said, "Actually, I just wanted to do less work and eat more."

"Motivation does not affect the outcome."

That evening, Chen Hao sat by the newly built stove and cooked a pot of noodles using a biogas stove. The water boiled quickly, and the flames quietly licked the bottom of the pot.

“I used to think that living was just about making do.” He stirred the noodles. “Now I realize that being able to turn garbage into food is a skill in itself.”

Nana stood in front of the control panel recording data. "The biogas system has entered a stable period," she said. "It can produce 3.2 cubic meters of gas and 1.5 kilograms of residue per day, which has been included in tomorrow's scheduling plan."

“I’ll go tomorrow too,” he said. “My hand still hurts a little, but I can’t let you do all the work alone.”

"You just need to supervise."

“Supervision is also a form of labor.” He picked up a piece of noodles with his chopsticks and blew on it. “Besides, I’m usually eating when I’m supervising.”

The fire in the stove continued to burn, its blue flames reflecting on his face. In the distance, tiny bubbles rose slowly and steadily to the surface of the fermentation tank.

After finishing his noodles, he handed the bowl to the robotic arm for cleaning. As he stood up, he casually touched the burn on his right arm; it didn't hurt much anymore.

"What else do you think we can do next?" he asked.

"Based on the current resource distribution," she said, "it is recommended to develop rainwater harvesting systems."

"More work," he sighed. "Can't you give me some projects that I can do while lying down?"

"for example?"

"For example, let the sheep shear their own wool and line up themselves for milking." He leaned back in his chair. "Ideally, they should even pile up their manure neatly so that it's easy for us to collect."

“The level of automation is limited by the capacity of the equipment,” she said. “Currently, it cannot support the modification of animal behavior.”

"Sigh." He closed his eyes. "I thought technological progress was meant to make people lazier."

"Technological progress is aimed at improving survival efficiency."

"It's just something I use to be lazy."

She didn't respond; the robotic arm placed the washed dishes into the cabinet. The only sound in the room was the faint crackling of the stove.

Chen Hao opened his eyes: "Hey, what if one day I'm too lazy to move? Would you put me in some kind of automatic conveyor belt so I can eat, sleep, and poop on time every day?"

Nana turned her optical glasses toward him: "We already have basic capabilities for monitoring vital signs."

"No way!" He sat up straight. "Then we'd be like laboratory animals."

“Your request includes full-process management,” she said. “The system can plan delivery routes based on work and rest schedules.”

“I was just kidding.” He waved his hand. “If you really do that, I’d rather go out and scavenge for a living.”

“The decision-making power is yours,” she said. “But I must point out that relying on the system does not mean losing autonomy.”

“I know.” He yawned. “I just think… things are fine as they are. We have food to eat, we have sleep to do, and we can even make a fire out of sheep dung.”

He stood up and stretched his limbs. "Let's go," he said, "let's see if that pool is still bubbling."

The two walked towards the east side of the base. The fermentation tank stood silently, tiny bubbles rising continuously from its surface. The biogas valve vibrated slightly, and a flame flickered on the stove.

Chen Hao reached out and touched the flame, feeling the warmth spread to his palm.

"We'll need to add more feed tomorrow," he said. "The sheepfold needs to be cleaned."