Over the 20 years since its full operation, the Qinghai-Xizang Railway has carried 104 million passengers and 824 million tons of cargo. Yet few have noticed: where does the passenger-generated waste go? How are the waste and sewage from sealed carriages disposed of? Can waiting rooms be heated both warmly and cleanly?

At the very beginning of its operation, the Qinghai-Xizang Railway set an ironclad rule: no drop of sewage or speck of waste shall be discharged onto the plateau while trains are running. This is not just a technical standard, but a promise.

Over the past 20 years, teams of workers have stuck to their posts day after day in places invisible to passengers, keeping the "Sky Road" always spotless even amid surging passenger flows.

The "weight" of cleaning

At 15:00 on June 28, under the blazing sun, a train that had just arrived from Golmud slowly pulled into the Lhasa Rolling Stock Servicing Center.

After the train came to a stop, workers placed warning flags at the locomotive. During the 14-hour journey from Golmud to Lhasa, all waste generated by passengers must be carried back to the depot -- there are no waste disposal points at high-altitude stations along the route.

"Every day we have to clear waste from 10 trains entering Xizang. A single round-trip of one train produces about 1 ton of solid waste, twice the amount from 20 years ago," said Zhao Wei, foreman of the Lhasa Branch of the Qinghai-Xizang Railway Service Co., Ltd., as he and his coworkers carried the garbage bags sorted by train attendants to the waste collection truck under the scorching sun.

This seemingly simple job often brings "unexpected troubles" -- garbage bags get punctured by hard objects. Whenever this happens, Zhao Wei quickly takes out a spare garbage bag to replace the damaged one, then cleans the carriage floor before moving the waste onto the collection truck.

The whole process of waste removal for one train, from unloading the garbage to transporting it to the transfer station for compression, and finally sending it to the Lhasa Municipal Domestic Waste Incineration Plant, takes about 2 hours in total.

Yulgyel and Tashi Dorji are veteran team members who work together with perfect coordination. What they fear most is not the dirt, but the tight schedule -- when the previous train is still being cleared, the next one is about to pull into the depot, and any delay will cause a backlog of operations.

After delivering the last bag of waste, Yulgyel drove to the waste transfer station for compression. When talking about the types of waste, he said, "in the early days of operation, the waste was mainly scraps of paper, plastic bags, and leftover food. Now, fruit peels, meal boxes, disposable slippers, and bed sheets and covers make up the majority. These changes show that people's living standards are getting better and better."

After chatting, they arrived at the transfer station. Yulgyel jumped out of the truck, patted the bulging garbage bags and said,"even though all the waste is packed well, handling it is a meticulous task." He explained that in summer, with poor ventilation in the sealed carriages, the pungent smell of fermented waste can penetrate even two layers of masks. In winter, the waste full of moisture freezes rock-hard, so it has to be broken with shovels before being fed into the feeding port.

"Someone has to do this work. Seeing the trains running cleanly on the plateau is where our value lies," said Zhao Wei, who has stuck to this daily routine for more than 5 years.

"Depths" of the pipes

Along the Qinghai-Xizang Railway, only three stations -- Xining, Golmud, and Lhasa -- have the capacity to receive wastewater and human waste generated during the journey.

Compared with waste collection, sewage disposal is an even lesser-known process.

Every train entering and leaving Xizang is equipped with a fully sealed waste collection system that gathers and seals all sewage, which is then handed over to the ground for disposal at designated stations. The people who unload this waste are a dedicated group of workers, and He Jianming, foreman of the Golmud servicing team, is one of them.

The train stops at Golmud for only 25 minutes, during which water refilling, sewage suction, and waste disposal must all be completed.

Before the train came to a full stop, He Jianming had already led his team members to wait beside the tracks. The 12 workers took their positions at different carriages. They pulled open the sewage suction port covers on the side of the train body, lifted the wrist-thick hoses, aligned them with the valves, and tightened them. The moment the machine started running, a gurgling suction sound came from the pipes.

He Jianming recalls that in the early days, suction relied entirely on mobile tank trucks, which often caused bottlenecks during peak travel seasons, leaving everyone so anxious that they stamped their feet on the platform.

In 2018, Golmud Station put into use the ground sewage suction devices along the tracks. The sewage is directly transported through pipelines to the septic tank, and each sewage suction port only takes 1 minute to complete the operation, greatly improving efficiency.

Unlike the platform operations in Golmud, the operations inside the Lhasa depot are not constrained by the 25-minute departure deadline, but the procedures of sewage suction, water replenishment, cleaning, and maintenance are closely linked, with equally tight schedules and process arrangements.

While Zhao Wei's team was clearing the waste, Wei Xiaoming, foreman of the field servicing team, and his colleagues came between the tracks to start the sewage suction operation. Sewage suction is carried out on the right side of the train, and water replenishment on the left, with both operations proceeding simultaneously.

Over the past 15 years, Wei Xiaoming has developed the skill of identifying the progress by the sound: as soon as the sound of the water flow in the pipe changes slightly, he knows that the sewage is almost fully sucked out.

Along the more vast "Sky Road", the sewage from station areas has been connected to urban pipe networks, and solid waste is regularly inspected. The sewage treatment station of the Golmud Building and Life Section adopts the "MCR membrane treatment + ultrafiltration" process (a highly efficient membrane separation technology), which significantly improves sewage disposal effects, with the treated water quality meeting the standards for domestic drinking water source quality.

Over the past 20 years, the number of trains running on the "Sky Road" has been increasing. In invisible places for passengers, such as platforms and tracks, the "Wei Xiaomings" of the railway unload, transport, and purify the sewage from train after train, leaving behind a clean environment.

The "transformation" of energy

The Qinghai-Xizang Railway's commitment to the plateau ecosystem is reflected not only in the "zero discharge" of waste and sewage, but also in the green transformation of its energy structure.

With technological upgrades, most coal-fired facilities along the Qinghai-Xizang Railway have been transformed to use clean energy, reducing coal consumption by 86% and significantly cutting carbon emissions.

In winter, Golmud Station is freezing cold outside, but the waiting room remains warm and cozy.

The warmth comes from a quiet boiler room in the corner of the station area. Xu Junshuai, foreman of the station boiler workshop of the Golmud Building and Life Section, started his career in 1992. Over more than 30 years, he has worked with both coal and natural gas boilers.

Flipping through old photos, his memories came flooding back.

At that time, the station heating relied entirely on two 4-ton coal-fired boilers. Coal was shoveled into the furnace by hand, and ash residues were carted out one by one. The first thing everyone did after work was to wash their faces and clothes, and the water was still black even after being changed three times.

Xu Junshuai said that in 2005, Golmud Station completed the transformation from coal to natural gas, and in 2020, it was upgraded to a fully automatic natural gas boiler. The operation changed from fully manual work to one-touch start on a touch screen, and the working environment became much cleaner.

The fire in the furnace burns in a different way now, but the fire in the hearts of the workers has never gone out -- to keep the waiting room warm at all times.

The transformation of Lhasa Station came even earlier.

In 2006, Lhasa Station tried to use roof solar collector pipes for floor heating, but due to the variable plateau weather, diesel boilers were still needed for supplementary heating on cloudy days. In 2018, Lhasa Station replaced diesel with cleaner natural gas, and later applied ground-source heat pumps and air-source heat pumps to staff heating and hot water supply.

In Delingha, known as the "City of Solar Thermal Energy", the station was designed with reserved space for photovoltaic power generation installation from the very beginning. After it was put into use in 2024, it can meet about 28% of the station's electricity demand in winter, and 35% in summer when sunlight is strong.

According to the 2025 Xizang Autonomous Region Ecological Environment Status Bulletin, the proportion of days with good air quality in the region reached 99.8%. Xizang remains one of the regions with the best ecological environment quality in the world.

Behind this achievement, their efforts have played a part.

Reporter: Lu Wenjing

Translator: Luo Rongting, Zhi Xinghua

Review: Phurbu Tsering, Drakpa Wangchen