The "unprecedented" changes means there's still a shortage of recycled pellets for Chinese factories, one that can't be filled by domestic recyclers, he said.

"We talk about 5 million tonnes of recycled pellets needed in China, I would say actually more than 5 million tonnes, because of the growth of infrastructure we have in China, the One Belt, One Road [government plan]," he said.

At its peak in recent years, he noted that China imported about 9 million tons (19.9 billion pounds) of scrap plastics.

Wong predicted the shortfall in China will be met, in the short-term, at least, with virgin materials.

"What they will do is it will be filled by the prime material," he said.

While the global recycling business model is shifting, Wong cautioned the new strategy of sending scrap to other countries and reprocessing it into pellets to be exported to China faces challenges too. Chinese customs officials, for example, are making very detailed inspections of recycled pellet shipments in ports.

A March report from CSPA said that 50 percent or more of shipments of recycled pellets were being subjected to random checks by customs officials, who want to make sure that that the imports are going directly to factories as feedstock.

Wong repeated that 50 percent figure in his speech and said government officials are concerned about unprocessed plastic scrap being mixed in with the pellets. The upshot, CSPA's report said, is that it can take up to a month for the pellet shipments to clear customs.

"Once they find that recycled pellets imported are not in line with their declaration, the container will be sent back," Wong said. He said companies need to standardize recycled resin pellet shipments to China, including color and size of pellets.

As well, there are concerns about long-term viability of some of the new recycling hot spots. Wong said some Chinese recyclers who have shifted operations to other countries are wary of a similar import ban happening there, if those governments follow China's lead and become concerned about the water, air and soil pollution from recycling operations.

"People move from China to these countries because of the relatively cheap conditions, but nobody can guarantee that these Southeast Asian countries will not enforce their own National Sword or certain plastic will be banned," Wong said.

He advocated some technology improvements, such as recycling companies using dry wash cleaning to reduce wastewater contamination. And he said there's demand in the industry to develop better machinery to process lower-end recycled materials.

Wong said the larger solution is for more recycling in the countries where the waste is generated.

Only about 14 percent of the 340 million metric tons of plastic used each year globally is recycled, and that, combined with concerns about ocean pollution and other environmental problems, will lead to more pressure to reduce single-use plastics and boost recycling, he said.