The red warning light flashed once.

Chen Hao's hand froze in mid-air; he was about to reach out and touch the outer casing of the laser device when his movement stopped. He blinked, thinking he was seeing things.

“It flashed again.” Susan pointed to the fuel monitor and said in a low voice, “This time it wasn’t just a flash, it stayed on.”

Nana immediately went to the control panel and brought up the data interface. A red curve on the screen was slowly but steadily declining, with the remaining number of jobs marked next to it: 3.

“The fuel consumption is abnormal,” she said. “Based on transport records and initial pressure values, the current usable cycle should be more than six. The actual rate of fuel consumption exceeds the theoretical value by 23.7 percent.”

Carl squatted down next to the fuel tank, shining a flashlight around the connection point to inspect it. "No cracks in the outer wall, and the sealing ring isn't deformed. The connector is tightened to the bone; it doesn't look like there's a leak."

"So it evaporated on its own?" Chen Hao plopped down on the folding chair next to him, looking up at the ceiling. "This thing isn't a kettle, it can't produce smoke, can it?"

“Minor vibration damage may occur during long-distance transportation,” Nana said. “Microscopic cracks in the internal sealing layer can lead to slow evaporation. Such leaks are difficult to detect with the naked eye or through routine inspections.”

The room fell silent.

The energy he had used to dig the tunnel deflated like a punctured balloon. Chen Hao looked down at his hands; the machine that had been pounding away just moments before was now too dangerous to even turn on.

“Three times,” he said. “Three times and we have to finish the remaining seventy meters? And we have to leave two more times to deal with sudden hard rock? You’re dreaming.”

"It's unusable?" Susan asked.

"It works." Chen Hao raised his hand, "but we have to be careful. Every time we turn it on now, it's like opening a blind box; we don't know if we'll be able to light it next time."

Carl stood up and put his tools back into his bag. "I suggest immediately suspending non-essential operations. Put the equipment into standby mode, disconnect the main power supply, and reduce standby power consumption."

"Okay." Chen Hao nodded. "Turn it off."

Nana pressed the power button, and the screen went dark. The entire shed suddenly became eerily quiet.

The four people stood still, none of them moving.

After a few seconds, Chen Hao looked up at Susan: "You just said... in which valley did you see something that could be burned?"

“On the south side of the dry riverbed,” Susan said, regaining her senses. “There’s a large patch of withered shrubs. I lit one when I passed by before. It burned for quite a while, and there wasn’t much ash. Unlike ordinary weeds, which go out as soon as they’re lit.”

“How long?” Carl asked.

“I didn’t time it, but one branch burned for about ten minutes. And there are still quite a few living plants in that area, with thick stems and smooth skin, like they have a waxy layer.”

“It doesn’t sound like ordinary firewood.” Chen Hao sat up straight. “What we lack right now isn’t a heat source, but energy density. If we could find a plant that we could dry and compress to make fuel rods, it might last us a while.”

“It’s theoretically feasible,” Nana said. “After carbonization and compression, the calorific value per unit volume of biomass fuel can be increased by three to five times. If the raw material itself contains oil or wax, the effect will be even better.”

"Then let's not talk about it anymore." Chen Hao stood up, cracked his knuckles, and said, "Let's go, let's collect samples."

The three prepared their equipment. Carl carried an empty sack, and Susan brought scissors and protective gloves. Chen Hao casually picked up an old shovel, saying that they could dig up any old roots buried in the ground.

It was just getting light outside, and the wind was a bit chilly.

They followed the route they had taken on their last exploration southward, passing through an abandoned parking lot and then climbing over a half-collapsed concrete wall. The landscape in the distance had indeed changed; the previously waterlogged depressions were now completely dry, cracked like wrinkles on the earth.

“It’s just ahead.” Susan pointed to a grayish-green area. “See those short trees? They’ve lost all their leaves, but the trunks are still standing.”

Upon closer inspection, these plants were more robust than expected. The main stem was about the height of a person, hollow, and covered with a thin layer of white wax that felt smooth to the touch. Chen Hao broke off a section and snapped it off forcefully, revealing a loose fibrous structure inside.

“This thing is light,” he said. “It’ll probably catch fire quickly, but it’s not necessarily durable.”

“It needs to be tested.” Susan took out her knife and cut off a small piece. “Take it back for a preliminary combustion experiment.”

They collected a dozen or so branches and put them in a sack. Carl casually dug up a sample tree, uprooted, saying he wanted to check if there was any oil-bearing tissue underground.

Back at the base, the samples were first spread out on the tin roof to dry. Under the sunlight, the wax layer reflected a slight sheen.

"What's next?" Chen Hao asked Nana.

"After drying, crush it and press it into shape," she said. "I have simple mold drawings here, and I can weld a manual briquetting machine using scrap metal sheets."

“Then you draw the design, and I’ll do the welding.” Carl rolled up his sleeves. “Let’s take advantage of the good daylight.”

Susan then began her first round of burning tests. She used tongs to hold a fresh twig and lit it in the stove. The flames quickly leaped up, turning yellowish-white, and crackled slightly.

"The initial firepower was intense." She noted the time, "but it noticeably weakened after five minutes, and after ten minutes only embers remained."

“The calorific value is not stable enough.” Nana looked at the thermometer reading. “The peak value only reaches 58 percent of that when the original fuel is burning.”

"It's far from good enough." Chen Hao shook his head. "The laser has to be at full power the moment it starts up. If it fails halfway through, the lens might explode."

“So we can’t use it directly.” Susan poured out the ashes. “It has to be processed. It needs to be dried, carbonized, and pressed into high-density blocks before it can possibly meet the equipment requirements.”

At 3 p.m., Carl had finished welding the briquetting machine. It was an iron cylinder with a handle, closed at the bottom and open at the top to hold crushed plant fibers. By pressing down with a lever, cylindrical fuel rods could be extruded.

The first batch of samples has been produced.

It was dark brown in color and had a rough surface, but it was much denser than the original material. Susan took one and lit it in the stove.

This time the flames were more concentrated and lasted for fifteen minutes, with no significant decay in the middle.

"The temperature has risen." She glanced at the gauges. "It has reached a peak of 72 percent of the raw materials."

"Seventy percent?" Chen Hao leaned closer. "That's not far from enough."

“It’s still not enough.” Nana pulled up the equipment’s startup threshold curve. “The instantaneous power required for the laser generator to ignite is no less than 8,000 joules per second. Currently, the peak fuel release rate is 6,200 joules, so there is still a gap.”

“Almost.” Karl stroked his chin. “If only we could have increased the calorie content a little more…”

“Perhaps we could change the process,” Susan suddenly said. “I was thinking that if we first bake it at a low temperature to allow the water and volatiles inside the plant to slowly drain out, then carbonize it at a high temperature for a short time, and finally press it, it might increase the energy density.”

"Sounds like making cookies," Chen Hao grinned. "First, ferment, then bake, and finally press into molds."

“The principle is similar.” Nana nodded. “I can provide segmented temperature control parameters. For example, pre-drying at 60 degrees for four hours, carbonizing at 180 degrees for thirty minutes, and then pressing into shape.”

“Let’s try it.” Susan picked up her pen to take notes. “We’ll start optimizing the process first thing tomorrow morning.”

At that moment, Chen Hao remembered something, turned around and walked towards the storage area. He opened the detection valve of the last original fuel tank, glanced at the reading, and his expression changed.

"broken."

Others gathered around.

“The pressure has dropped again,” he said. “Last night when the checkup was at 47%, now it’s only 40%. It dropped seven percentage points in three hours.”

“The sealing problem may be more serious than we anticipated.” Carl frowned. “If this continues, the original one will be useless before we can develop a replacement.”

“Then we need to speed it up even more.” Susan grabbed a freshly made fuel rod. “We’ll run the new process through tonight.”

Nana opened the database, accessed the biomass processing module, and began setting the procedures. Carl went to check the securing of all the storage tanks and added a layer of sealing tape.

Chen Hao sat by the iron barrel outside the laboratory, holding the brown fuel rod in his hand and examining it over and over.

“If this thing actually works,” he suddenly said, “could we start a new energy company? We could call it ‘Firevine Power,’ and it’d cure all kinds of gas shortages.”

Susan glanced at him: "Let's fix the hole in front of us first."

“That’s true.” He smiled. “But I think it’ll be soon. Look at this stick, it’s all black, but it catches fire with a flick of a flame, isn’t that reliable?”

Nana looked up from the terminal: "The first round of optimization plan has been generated. It is recommended to use a double-layer earthen kiln for gradient heating to avoid uneven carbonization caused by local overheating."

"Whatever you say." Susan stood up. "The materials are ready, let's begin now."

Carl walked back and patted Chen Hao on the shoulder: "I'm going to move some firewood, do you want to lend a hand?"

Chen Hao didn't move. He stared at the fuel rod in his hand for two seconds, then held it up to his eyes and held it up to the light.

The waxy surface gleamed with a slightly yellowish light in the setting sun.

He squinted.

“Wait a minute,” he said. “Isn’t this thing… a little strange?”