Throughout it all, he has remained a persistent voice for the environment in the city of more than 30 million people and, as some of them have learned, he refuses to give up.

On mainland China, cities have banned littering and some hit offenders with fines as high as 200 yuan. However, the rules are rarely obeyed and feebly enforced, and while there are plenty of dustbins in public places, litter is still a nuisance.

Zhong said his mission started in 2015 after he met a woman in her 70s in Sanya, the southern coastal city on the South China Sea island of Hainan. He was struck by how dedicated she and her husband were when they went litter picking each day.

“They are retired professors from a prestigious university in Beijing,” Zhong said. “I chatted a lot with her and I asked her, ‘What’s the point of collecting rubbish every day? You clean up the beach today, but tomorrow new rubbish appears’.”

The way to solve the problem was to teach people to not litter, she told him, but she said she “dared not” try to do that. Zhong said that encounter gave him his purpose and he would dare to change attitudes.

Shanghai recycling scheme slips up on 9,000 tonnes of waste

Back home, Zhong watched and learned – concluding that customers of restaurants and fast food businesses tended to be the people who dropped rubbish most.

“Perhaps it’s because when people dine in restaurants, they throw their rubbish wherever they like. Going outside, they keep on doing it,” he said.

“People in shopping malls are generally more civilised.”

While on patrol, Zhong makes himself easy to see in an orange T-shirt that bears his clean-up message. His tools include a metal pincer for picking up tissue paper, plastic bags, drinks bottles, nappies and other everyday detritus and putting it into bins.

He also carries a voice recorder that sends out an appeal to restaurant customers: “To protect our environment and not to affect our kids’ healthy growing up, dear friends, please don’t throw rubbish.”

Can China sort its household waste recycling problem by 2020?

Zhong said that at first he felt afraid and self-conscious when he stood in front of a crowd of diners with his green gospel. But time and practise taught him he had almost nothing to fear, he said.

One of the bigger challenges is getting through to the many people who do not listen to him and refuse to dispose of their rubbish the right way.

“It’s normal that our society has various kinds of people and I need to face this reality,” Zhong said. “I was prepared in my mind that I would be called ‘nut’ since this is such an arduous but fruitless cause.”

He tackles the problem with his usual persistence, so argument and persuasion is all part of the job. When Zhong insists the rule breakers take their rubbish and bin it, some ignore him and others walk away – but he is ready with an answer.

“I tell them, ‘If you don’t pick it up, I guarantee that you will lose face today. I will let passers-by see and hear what a humiliating thing you have done. Everybody will then condemn you and you will be embarrassed’,” he said.

When people tell him what they do is none of his business, Zhong replies that what he is doing is in the public interest.

Sometimes there is a heavier price. Zhong said he once watched several men in their 20s throw rubbish onto the road from their car. He set off after them in his SUV. He waylaid them and asked them to clean up after themselves – the men refused, swore at him and beat him up. Their day ended in a police station.

Zhong said he hoped his work would bring “positive energy” to the employees of his vehicle components and packaging materials companies, but his mission was not about business prestige.

However, last year, he was named as one of the top 10 public welfare figures of Chongqing by the municipal government, while his family was honoured as a Chinese good family by the semi-governmental All-China Women's Federation, a women’s rights organisation established in 1949.

Street cleaner who found US$22,000 in rubbish refuses to accept a reward

There were trials for Zhong closer to home – his wife, Yang Zuhui, did not support his mission at first and threatened to divorce him.

“It’s OK that you picked up trash on the street and you were just another cleaner there,” she told him in an interview with Hunan Television in 2017. “But what worried me was that you tried to persuade others – physical violence [against him] was inevitable.”

She also said: “My husband is not very tall and, on many occasions, he was at a disadvantage and got beaten up. I am worried about his personal safety.”

But two years ago, their 10-year-old daughter helped change Yang’s attitude towards her husband’s mission after a school outing.

After lunch that day, Zhong gave the adults and children who had left rubbish behind one of his lectures.

His daughter, who was embarrassed by Zhong’s speech, came to appreciate him when classmates told her: “Your father is awesome. He is like a hero who protects the Earth.”

Yang was won over because she knew her husband was a determined man and once he decided on a course of action would not change his mind.

Their son – who is in his 20s and has returned to Chongqing after studying in France – always stands by his father, Zhong said.

“My son told me that environmental voluntary work normal abroad and it is respected,” he said.

Going out to collect rubbish has become part of Zhong’s life, he said.

“In the evening, if I stay at home, my wife and daughter will ask me ‘Why don’t you go to pick up rubbish?’”

He said it was important to go litter picking every day because the more he did it the more people he could influence.

“By breaking the littering habit, Chinese people can stand tall when they travel abroad,” Zhong said.