Recycling is uneconomical, in part because small impurities in materials to be recycled can make such materials useless.

“There are some states and some markets where mixed paper is at a negative value,” said Brent Bell, vice president of recycling at Waste Management, which handles 10 million tons of recycling per year.

In the Pacific Northwest, Republic has diverted more than 2,000 tons of paper to landfills since the Chinese ban [on imported paper] came into effect, Mr. Keller said. The company has been unable to move that material to a market “at any price or cost,” he said.

Theresa Byrne, who lives in Salem, Ore., said the city took too long to inform residents that most plastics and egg and milk cartons were now considered garbage. “I was angry,” she said. “I believe in recycling.”