Add biodegradable bags to the list of take-home carriers that retailers will not be able to distribute to customers at checkout when an Oahu-wide plastic bag bill takes effect next July 1.

Flanked by representatives from several environmental groups, Mayor Kirk Caldwell signed into law Bill 38 during a news conference at Ala Moana Regional Park on Thursday despite lingering questions about allowing compostable plastic bags.

Caldwell said that when he swims laps off Ala Moana, there’s nothing he hates more than feeling his arm getting entangled by a discarded plastic grocery bag.

“They end up going … into the water and they’re eaten by sea life, or they sink to the bottom, or they wrap around coral heads,” he said. “They’re bad for the environment.”

Bags meeting the definition of “compostable” will still be allowed, as will all nonplastic bags, including paper and cloth.