Biodegradable bags pose wet trash challenge

Throwing plastic bags — even if they are biodegradable — into garbage bins for wet trash is not allowed, Shanghai's greenery authority has notified the public.

Food waste and other wet matter inside plastic bags must be emptied into wet trash bins, and the bags themselves then placed in dry trash bins, according to the Shanghai Greenery and Public Sanitation Bureau.

Even biodegradable plastic bags are banned from wet trash bins.

The biodegradable process is complex, involving water and temperature. It can takes one to two months when the pH index of the bags are within a certain range.

In the natural environment it takes longer, and harmful substances will still be produced.

People can be fined up to 200 yuan (US$29) if they fail to sort their trash properly and continue to do so, under Shanghai's new garbage management regulations.

"Separating the two is the most difficult part in garbage sorting at present," said Fan Minhan, secretary of the Youth League Committee of the Xinhong Subdistrict in Minhang District.

"Many residents are not willing to remove wet trash from bags for fear of getting their hands dirty as they make their way to work," he said.

Residents also believe the loose wet trash in the bins will produce foul odors and attract insects.

Angela Zhang, who lives on the first floor at the Meigui Guangchang residential complex in Hongkou District, said it was more hygienic to dump wet trash in bags.

"There will be more mosquitoes, flies and stronger smell if wet trash is removed from bags," she said.

"In addition, wet trash often contains leftovers, such as water and soup that will drip when you empty the bags, which is dirty."

But treatment factories said processing will be adversely affected if plastics are mixed with wet garbage.

"Plastic bags and dishware often jam equipment and affect the quality of fertilizers produced from wet waste," said Yang Yuanhui, head of the Minhang Center of Kitchen Waste Reutilization.

The Liming Organic Matter Solid Waste Treatment Plant in the Pudong New Area turns wet trash into methane for power generation.

"Plastics will stay above other substances inside the anaerobic containers and form an airtight membrane, blocking methane and water," said Hua Yinfeng, head of the factory. 

The plant recently had to shut down for a month for repairs.

Some complexes have prepared hand-washing facilities for residents and also tools to make it easier to open bags with wet waste.

"The tools might spur residents' willingness to sort garbage," said Zhang Minjie, Party secretary of the Jinhao neighborhood committee in Jing'an District.