Though dry-cell batteries are labeled as environmentally friendly products, some feel differently, including Mao Da, an expert in solid-waste management from the NGO China Zero Waste Alliance.

"If a battery is dumped along with household waste and incinerated, the metals it contains could pollute the air or concentrate in ashes produced by the combustion process. And if it ends up in a landfill, the metals may leach into water and soil," he said.

On top of environmental concerns, experts said it also reduces resource waste to recycle spent batteries.

For every 10 billion dry-cell batteries produced, 156,000 tons of zinc, 226,000 tons of manganese oxide, and 2,080 tons of copper are consumed, Cao Guoqing said. If the metals contained in waste batteries are recycled, large amounts of resources can be saved, he said.

As the world's largest producer of dry-cell batteries, China produced 31.8 billion units in 2017, according to statistics from the China Industrial Association of Power Sources. The volume of dry-cell batteries made annually accounted for more than 85 percent of all batteries.

In 2016, the Ministry of Environmental Protection (now the Ministry of Ecology and Environment) issued a guideline on the prevention and control of pollution from used batteries.

The guiding document encourages "classified collection of spent primary batteries in places with proper conditions for recycling". The primary batteries category includes dry-cell batteries, lithium batteries and accumulators.

The guideline was hailed by environmentalists as a positive signal for raising recycling rates of used batteries.

"The guideline is expected to end confusion about whether we should collect used batteries or dump them," China Zero Waste Alliance said in a statement.