Biddeford residents are being asked to make sure they place only recyclable items in curbside bins after being assessed a $4,370 fee for having a 19.4 percent recycling contamination rate. John Patriquin/Portland Press Herald Photo

BIDDEFORD — Not sure whether a specific item can be recycled? Until you know for certain, city officials say do not place it in your curbside recycling bin.

That is the request from Biddeford Public Works, after an audit of the city’s curbside recycling earlier this month turned up a contamination rate of 19.4 percent — and a bill to the city. In all, there were 137 tons of contaminated recycling — and at $31.90 per ton,  that works out to a $4,370 fee, said Communications Coordinator Danica Lamontagne.

Residents can help reduce the contamination rate by placing only clean, dry recyclables in their blue bins. Accepted items include plastic bottles, jugs, tubs, and lids; cardboard; aluminum and steel cans; glass bottles and jars; and paper bags, office paper, envelopes, and catalogs, she said.

That means no Christmas lights, no lamp posts, no shoes, and no kitchen knife blocks — all items that turned up in recycling at the audit — and no liquids, no food and no trash bags that will not fit in the regular trash bin.

“Some of the items we see frequently that are contamination are electronic items, larger plastic bags that get caught up in the containers, and sometimes bags of trash due to people not having enough room in their trash can and putting the bag in their recycling bin instead,” said Matthew Ayers, operations manager at Casella Waste Systems in a news release. “A lot of this comes back to the city in terms of a fee for contamination services and can actually void out a lot of the good recycling that you and your family are putting in your recycling bin.”

Recycling bins have closed lids and are picked up and emptied by automated trucks. That means an item that should not be inside may not be readily apparent, said Assistant Public Works Director Dylan Jewett by phone on Friday. He said random checks are conducted to try and ensure items in the bins are part of the curbside recycling program.

During the audit week, Lamontagne said, Casella and Biddeford Public Works staff sorted through curbside recycling collected from select streets representing a mix of single-family homes and multi-unit buildings from each day’s recycling pickup route. She said trash items that were found in the bins were separated from the recyclables, then weighed to determine the percentage of contamination.

Jewett, who participated in the audit, said the city has information flyers available at the Public Works Department at 371 Hill St. on what can and cannot be recycled; and those with computer access can check out: Biddefordrecycles.org for information.

The city has put word out on social media about curbside recycling and does random spot checks.

“If in doubt throw it out,” Jewett said, call Public Works at 282-1579, or take the item to the recycling center at the 371 Hill St. and ask.

Jewett said those in Public Works are happy to answer residents’ questions about recycling.

“We want it to be successful,” he said.