Wang Zhenghai calls himself a special "collector."
In the past eight years he has accumulated about three tons of used batteries.
That's right. The 74-year-old retired worker hops on his bicycle every morning and crisscrosses the city picking up used batteries scattered around the streets and in neighborhoods.
Wang may have more energy than the pink Energizer bunny in North American TV adverts and says at first the idea was just for fun. He never knew the hobby would stay with him for such a long time.
"One day I was watching TV with my grandson and I learned from a program that batteries could be very harmful to the environment," he says.
"According to the program, the benzene and mercury can pollute at least one ton of water."
The news was a shock to the old man, who has only attended primary school and can not read newspapers.
"I have always been thinking of offering something back to society after I retired from the factory," he says. "I can not read or write like others. However picking up batteries seems to be the right job for me."
Ever since, Wang has went about his journey around the city. Every day he leaves home at seven in the morning and returns at four in the afternoon.
"You can not imagine how many used batteries there are hiding in the city," he says. "At first I would collect at least ten kilograms per day."
According to Wang, neighborhood greenbelts are the "best place" to find discarded batteries.
Many people have the habit of throwing used batteries away.
"I always search the greenbelts closely until I am sure that there are no more batteries," he says.
Wang has also developed some unique ways to deal with the batteries. He usually uses a stick to pick out batteries buried deep in the soil.
He says initially many people didn't understand what he was doing. He was always asked to stop digging and leave neighborhoods.
"They thought that I was picking up the batteries to make money, or because I was a fool," Wang says. "But I have proved them wrong."
He puts the batteries in sacks and delivers them to the neighborhood's recycling station. In the past eight years, hundreds of sacks of batteries - enough to fill a large room - have been handed over.
Xianxia Community of Changning District, where Wang lives, has given him a special "Volunteer Environment Protector" card, which is now tied to his bicycle.
"With the card on my bike, it's easy to explain to neighborhood security guards what I am doing," he says. "Some of them didn't allow me to go into neighborhoods before. Now they collected used batteries themselves and give them to me when I arrive."
After checking all the neighborhoods near his home, Wang started to explore other parts of the city.
He says proudly that his footprints have already covered most downtown areas. The farthest neighborhood he cleaned up was a two hour bicycle ride from his home.
"I don't feel tired," he says. "I'm happy about what I have done. As far as I am concerned, I have brought residents a cleaner environment."
Wang says his family have been very supportive.
"Believe it or not, my heart disease has been under control since I started picking up batteries. I walk nearly 30 kilometers a day," he says with a smile.
His grandson, a middle school student, also joins the cleanup campaign from time to time during summer and winter vacations.
Apart from picking up used batteries, the senior has placed a wooden box near the mailbox in his building. He encourages people to throw advertising prints into it.
"I think it's better to collect the papers which would otherwise be thrown away," he says. "It is a different way to protect the environment."
He sells the recyclable paper and uses the money to buy bulbs and brooms for public use.
According to Wang, he is gathering less and less batteries nowadays. He says more and more new apartments and buildings are equipped with bins to recycle used batteries.
"It is a good sign and shows people the harm of used batteries," he says. "My biggest wish is that one day I will not be able to find one single used battery anywhere in the city."