Ask China: A day with an 'air sniffer'

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Garbage is easily forgotten for most people. Into the trash can, and never thought of again. But under the radar, an army of specialists is taking care of your waste – and its environmental consequences.

Beijing Environment and Health Station /CGTN Photo‍

So where does it go after you throw it away? And how is the impact on air quality of all that rubbish controlled?

Zhang Chao (L) and CGTN Digital Editor Shan Yuan (R) /CGTN Photo

To find out the answers, CGTN Digital interviewed Zhang Chao, an odor analyst from the Beijing Environment and Health Monitoring Station. He’s been “inhaling” rubbish smells for 12 years, including at a waste-to-energy plant powering homes in Beijing. Join us as we explore Zhang’s “sniffing” life!

Where does the garbage go?

Beijing Gaoantun Waste-to-Energy Plant /CGTN Photo

Beijing had 21.7 million permanent residents by 2015, according to the National Bureau of Statistics. That’s almost equal to the entire population of Australia. Beijingers generated around 7.9 million tons of household waste the same year, the most in China, according to the Ministry of Environmental Protection.

So what to do with all this trash? In 2009, local authorities issued a new guideline on how to improve waste treatment with a focus on incineration.

Odor analyst Zhang’s “outdoor office” was Beijing Gaoantun Waste-to-Energy Plant on the day CGTN Digital went to meet him. The facility began operations in 2009, and now treats about 70 percent of the waste from Chaoyang District’s two million residents.

Beijing Gaoantun Waste-to-Energy Plant /CGTN Photo

Zhang must monitor the environmental impact of the plant’s operations. He detects the concentration of odor pollutants at the incinerators to ensure emissions comply with national standards and the impact on the environment is minimal.

His first task is to conduct a general check on the five-story-high dump pit, which has a maximum capacity of 20,000 tons of garbage.

Gao, the incinerator operation director, said an average of 400 garbage trucks a day arrive at the plant, which processes about 600,000 tons of garbage a year.

The operator uses a mechanical claw to move piles of garbage (7-8 tons each time) from the pit to the incinerator, which runs 24/7 and generates about 280 million kwh of electricity annually.

The role of an odor analyst

Zhang is preparing for testing. /CGTN Photo

Zhang must test the treated smoke coming out of the incinerator as well as the air within the Gaoantun plant, to check whether the pollutant emissions meet national standards. The results will help determine whether environmental authorities need to take further measures, such as fining the plant.

Staircases to the sampling platform /CGTN Photo

To test the incinerator’s emissions he uses an analyzer, as the smoke is too hot for humans to smell.

With sweat streaming downing his face, Zhang then heads to collect an air sample.

Shan and Zhang are on the sampling platform. /CGTN Photo

Very slowly, Zhang squats down and takes out a vacuum bottle from the equipment case. He pulls out the stopper and air is sucked in at a steady rate.

The air inside the bottles should be first exhausted until the pressure is close to negative 100,000 Pa, according to the national standard for determination of odor – known as the Triangle odor bag method, a process used in China since 1993.

“Its odor concentration should be 30," the veteran confidently stated, basing his informal judgement on 12 years’ experience.

Zhang is collecting air inside the plant to a vacuum container. /CGTN Photo

CGTN Photo

Making an official determination requires six odor analysts, one judging person and two assistants.

Zhang, together with Shan is at the lab for sniff gas. /CGTN Photo

Back at the lab in the station, the six analysts are handed three bags each. Two of the bags contain ordinary air and one is filled with a diluted sample from the plant. After smelling each bag, the analysts mark down which is odorous and which is not. When a judgement is incorrect, the analyst will be eliminated from the process.

The dilution and elimination process is repeated until five out of six analysts give the wrong answer. Then the data gathered is used to calculate a threshold value through exacting formulas, which determines the odor concentration.

Zhang is sniffing the content in a tube. /CGTN Photo

If the concentration exceeds 20, the national standard for odorous pollutant emissions, Zhang will submit it to environmental authorities, who will in turn use it as the legal basis for action against polluting plants.

CGTN Photo

The process is methodical, but very labor intensive. Can machines not replace the human odor analysts? Zhang explained that the concentration in each sample is typically very low, so impossible for most machines to sense. Also, there are numerous compounds in the air that only humans can immediately detect.

“Human noses are smarter," he summarized.

Why do the job?

CGTN Photo

Zhang, one of the 12,800 qualified odor analysts in China, must pass a rigorous national exam on theories and sense of smell every three years. But he is cool about the job and its risks, despite worries from friends and relatives.

From Zhang Chao's photo album

"It's for the city we live in. We are taking part in the city management. When I think of this, I won't feel the job is dirty, tiring or hard.” Zhang said.

But it does need commitment, Zhang added, as odor analysts must accept certain limits in order to maintain a strong sense of smell ahead of detection: no smoking, no perfume or makeup, no pungent food.

CGTN Photo

"I felt more at ease after joining the Communist Party of China" in 2011, Zhang said, recalling the old days when he taught rookies and voluntarily took on the most difficult tasks.

"I might have been a role model," he added.

Zhang also urged more citizens to be community leaders.

“Whether our garbage is effectively separated, sorted and delivered is significant for the disposal of waste as well as for the entire urban environment, which can be improved through small actions.”

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