In a landmark ruling in 2007, the central government banned the production of super-thin plastics nationwide and ordered retailers to charge customers a fee if they wanted a regular plastic bag.
The move followed a similar rule implemented by authorities in Lhasa two years earlier, which made Tibet's capital a front-runner in controlling single-use items. The ban was extended to the entire region in 2010.
The bans have worked well in supermarkets and other large operations, where additional charges for plastic bags have prompted many shoppers to opt for reusable items, such as cloth bags.
However, in rural areas where farmers' markets are abundant and law enforcement is less stringent, the feedback has been barely satisfactory, according to local officials and environmental activists.
Cai Jinping, co-founder of the Lhasa Ban-White Association and owner of a factory that makes reusable bags and other environmentally friendly products, said vegetables are extremely cheap so it proved impractical to ask farmers to pay extra for a bag while shopping for a few potatoes.
"Charging for bags would drive rural customers away and vendors would lack incentives to abide by the rules," he said.
The demand for cheap, super-thin plastics, coupled with lax law enforcement in rural areas, has emboldened factories to produce the bags and also prompted shop owners to offer them for free.
According to an estimate by the association, Lhasa's 16 farmers' markets use 216,000 bags every day, which amounts to 272 metric tons of plastic a year.