Minneapolis recyclers: Think twice before tossing that takeout container in the blue bin.

The city wants to keep certain plastics out of curbside recycling bins, because they will probably end up in the landfill or incinerator. It recently sent mailers asking residents to avoid recycling black or No. 6 plastic items, responding in part to a crisis in the recycling industry.

China no longer wants America’s recyclables, which has flooded U.S. markets with recycled goods and sent prices plummeting. Sorting centers are under pressure to produce loads of strictly recyclable materials so they can stay in business.

“We’re seeing a lot of communities and cities … changing their educational strategies, going from ‘Recycling More,’ to ‘Recycling Better,’ ” said Lynn Hoffman, co-president of Eureka Recycling, which sorts Minneapolis’ recyclables.

Eureka has long maintained that there are no local markets to buy No. 6 plastic, which is found in plastic-foam and Solo-style drinking cups. And the sophisticated optical sorting machines that detect which type of plastic is whizzing by on a conveyor belt cannot decipher the composition of black items, Hoffman said.

“Those plastics have never been valuable. They’ve always been hard to capture,” Hoffman said.

Eureka also handles recycling for St. Paul, which already advises residents to keep black and No. 6 plastic out of their recycling bins. Typically No. 1, 2 and 5 plastics are the most recyclable.

Minneapolis handles recycling for residential buildings up to four units. Larger buildings and commercial properties contract with their own haulers, who could take the material to a number of facilities.

Dave Herberholz, Minneapolis’ director of solid waste and recycling, said black and No. 6 plastics make up a small part of the waste and recycling stream. But the city wants to be more transparent about what is actually being recycled, he said.

“Our desire is not to collect anything we’re not going to recycle,” Herberholz said.

Other items that recyclers do not want include plastic bags and electrical cords — which clog the sorting machines — as well as batteries and sharp objects. Hoffman said really problematic materials have been the focus of education campaigns in the past.

“What’s changed now … is public awareness that recycling isn’t a great solution for a lot of plastics,” Hoffman said.