Once the cleanup of Block D was put on the agenda, disposing of the bodies became an even bigger problem than killing the walkers.
At first, the Defense Force simply dragged the dead walkers into open areas, piled them up, soaked them in fuel, and burned them in the open.
But problems quickly followed.
The thick columns of black smoke could be seen from several kilometers away, and toxic gases from incomplete combustion drifted downwind toward Blocks A, B, and C, leaving a wave of workers coughing.
Even worse, the smell of charred flesh drew more walkers from outside the industrial park. They seemed to treat the burn site as some kind of "food signal."
Still nauseous from the stench earlier, Calista stood atop a building at the edge of Block D, staring at the mountain of corpses belching black smoke in the distance.
"We can't keep burning them like this," she said after finding Leah and Rickson.
Rickson coughed twice. "Calista, if we don't burn them, what are we supposed to do?
"We've already cleared close to two thousand walker corpses from Block D, and there are still more buried under the rubble.
"If we leave them there, we'll risk an epidemic. That'll be even worse than dealing with the walkers."
"Then we'll use a method that doesn't produce black smoke or stink up the whole area." Calista turned and pointed toward a cluster of buildings in Block D. "That's the cement plant over there, right?"
Rickson narrowed his eyes. "Yeah. Looks like it has two rotary kilns."
"Rotary kilns," Calista repeated. "What's their maximum operating temperature again?"
"Uh, normal cement production runs at around 1,450 degrees. If we're only using them for incineration..." Rickson did a quick calculation in his head. "Dropping it to 1,200 degrees should still be enough to completely carbonize organic matter. And because the kiln operates under negative pressure, all the flue gas is routed through the exhaust treatment system, assuming we have enough power to run it."
Leah immediately understood what Calista was thinking. "Use the bodies as fuel, drive a generator, then supply power to the chemical plant?"
"Not fuel. Supplementary energy," Calista corrected. "The calorific value of the bodies isn't stable enough to rely on directly, but if we recover the waste heat, we can reduce our dependence on diesel generators. More importantly..."
She raised a hand above her eyes and looked toward the cement plant's towering smokestack.
"High-temperature incineration, exhaust treatment, energy recovery. All three together.
"It solves the sanitation problem, gets rid of the smell and reduces the risk of disease, and it might even give us some practical benefit. That has to be better than burning them in the open."
Leah and Rickson's expressions shifted from skepticism to thoughtfulness, then gradually to excitement.
"Let's ask the engineers."
The Base's engineering team soon came back with a preliminary estimate.
The rotary kiln's drive system needed electricity to start, but once the kiln was turning, its own rotational momentum would carry most of the load, leaving only a small amount of auxiliary power necessary.
The steam produced by the waste heat boiler could then drive a steam turbine.
But how many bodies would it take to keep the system running?
"Run the numbers," Calista told the engineers.
For the next two hours, the command center's whiteboard filled with formulas and rough sketches.
One rotary kiln at the cement plant could process roughly eight tons of material per hour.
Assuming an average walker weighed sixty kilograms, though dehydration and partial decomposition would reduce that somewhat, and factoring in the necessary combustion aids and stabilizing materials, they estimated that the kiln could process about a hundred bodies per hour.
"If it runs continuously for twenty-four hours, that's 2,400 bodies a day." The engineer's hand trembled slightly as he wrote the number on the whiteboard. "That's... more than the entire population of our Base."
"We don't need to run it continuously," Calista said calmly. "We're estimating around two thousand walkers total in Block D.
"If we process four hundred a day, we'll finish within a week.
"After that, the rotary kiln can switch to other combustible waste. Wooden furniture from the ruins, old clothes, discarded plastics.
"Anything that burns and doesn't produce highly toxic exhaust can become a source of energy."
She paused and looked at Leah.
"But first, we need to get those two machines running."
The engineering team quickly handed Calista a densely written materials list.
"Anything we have in storage, allocate it. Anything we don't have, mark by priority. I'll find a way to get it."
"The biggest problem is the exhaust treatment system." One of the engineers pointed at the cement plant's process diagram. "Electrostatic precipitators, baghouse filters, the desulfurization tower. All of them need electricity and compressed air.
"If the treatment system can't run properly, then the only difference between burning bodies in the kiln and burning them outside is that the toxic smoke comes out of a proper smokestack."
Calista stared at the complicated process diagram in silence for a moment.
"Start it in stages," she finally said. "Step one, repair the kiln itself and the most basic drive system. Incinerate using the simplest setup possible.
"Feed the bodies in from the tail end. Discharge the ash from the head. For now, route the flue gas through the emergency bypass and vent it directly."
"But that's still pollution..."
"Step two," Calista cut in, "use the first electricity generated from incineration to repair the electrostatic precipitator.
"Step three, repair the desulfurization tower.
"Step four, connect the waste heat boiler to the steam turbine and make the system self-sustaining."
She looked at the engineer.
"How long?"
The veteran engineer wiped sweat from his forehead. "If everything goes smoothly... three days for step one, five for step two, a week for step three. As for step four... I can't say. The boiler and steam turbine are precision equipment. They may already be too corroded to use."
"Then focus on the first three steps," Calista decided. "At the very least, we make corpse disposal sanitary.
"If step four works, that's a bonus. If it doesn't, it won't affect the main objective."
The plan was settled.
How much diesel. How many labor hours. How many bodies. How much ash. How much risk reduced.
That was what a major project looked like in the apocalypse. Not perfection, just something that worked.
Early the next morning, the work on the cement plant began.
The rotary kiln was even larger than they had imagined.
A steel cylinder more than four meters in diameter rested horizontally on a concrete foundation, its thirteen-meter-long body coated in a thick layer of dust.
Shining a flashlight through the inspection port at the kiln head revealed large sections of the refractory brick lining had flaked away, while an unidentified black residue had accumulated along the bottom.
It looked difficult.
But in the apocalypse, anything that could be fixed through brute force, patchwork, and enough hands wasn't truly impossible.
Three days later, after burning through three hundred liters of diesel, twenty kilograms of lubricating oil, and countless hours of hammering, cutting, and welding by the engineering team, the rotary kiln finally moved.
The feed opening at the kiln tail opened.
The first walker corpse was pushed inside by a mechanical arm.
It slid into the high-temperature zone and was instantly swallowed by flames reaching 1,200 degrees.
No black smoke.
The rotary kiln's combustion system had been adjusted to ensure complete combustion.
The exhaust gas was vented directly into the upper atmosphere through the emergency bypass. It was still untreated, but at least it was far cleaner than open-air burning.
Calista stood in the control room, watching through the observation window as gray-white ash came out from the kiln head.
It fell into a water-cooled screw conveyor, where it was quenched and reduced to harmless powder before dropping into a collection bin for disposal in a designated landfill.
Calista still felt the ash had to be buried deep.
Anything connected to the virus had no business remaining on the surface.
"First one," she said quietly. "Combustion temperature, 1,150 degrees. Close enough."
The veteran engineer stared at the instrument panel. "The exhaust temperature is a little high, which means the heat recovery efficiency is poor, but it burns."
"If it burns, that's enough," Calista said. "Start feeding them in batches. Notify the transport team. Bring over every body from the open-air burn site."
And so, a strange transport line appeared in Block D.
The Defense Force loaded dead walkers onto flatbed trailers, which modified trucks hauled toward the cement plant.
Workers received the bodies at the feed opening and used mechanical arms to push them into the kiln.
Ash came out the other side, was collected, then transported to a specially designated burial area.
They processed eighty bodies on the first day.
By the second day, everyone had become familiar with the procedure, and they processed one hundred and twenty.
...
When the rotary kiln had been running for a full week, Rickson burst into the command center, visibly excited.
"Calista, the waste heat boiler... it's producing steam!"
Calista ran with him toward the cement plant.
Beside the massive waste heat boiler near the kiln head, the needle on the pressure gauge was slowly climbing.
0.1 MPa.
0.2.
0.3...
"The temperature still isn't high enough, and we're not getting much steam, but there is steam!" The veteran engineer overseeing the system was practically waving his arms with excitement. "Let's try it. Start the exhaust treatment system!"
Five more days passed.
When the first batch of "clean flue gas," treated by the electrostatic precipitator and desulfurization tower, finally came out of the smokestack, the entire cement plant erupted in cheers.
That evening, the lights in the cement plant's control room came on.
The electricity came from steam.
And the heat that produced that steam came from incinerating more than a hundred walkers.
...
In the apocalypse, we aren't creating a new world.
We're simply taking the monsters that devour people and, little by little, turning them into light in the ruins.
That's all.
And that's enough.