Green carts that can be filled with fruit scraps, pizza boxes, chicken bones, cotton balls and other compostable waste began hitting the curb in Minneapolis on Monday morning.

The city began rolling out the first phase of its new organics pickup service with a small news conference in a northeast Minneapolis alley, where a homeowner carried out a banana peel on a glass serving tray and dumped it into her new organics cart. Hers was the first of about 7,000 households that will receive their carts over the next month in neighborhoods that were tapped to be among the first to try the service.

A second phase of the program is set to begin in the rest of the city in March. So far, more than 31,000 households have signed up to participate in curbside pickup.

City officials said haulers will be checking to ensure that residents are putting the right items in compost bins. They'll leave tags on bins where they spot problems. Organics should be placed in the bin inside either a compostable plastic bag or a paper bag, to help ensure the contents don't get stuck to the bin or freeze during the winter months.

Kellie Kish, the city's recycling coordinator, said many residents know they can dump their scraps from dinner in a compost bin. But when it comes to trash from the bathroom or the laundry room, the sorting process can be more daunting. Dryer lint, for example, is compostable, as are cotton swabs, tissue and nail clippings.

"People get the food," she said. "That's the easy part. But when we get to the paper products, that's the hard thing."

Coffee cups can also be a point of confusion. Lined cups marked as compostable are safe, as are wax-lined cups. Paper cups from Starbucks or Caribou Coffee, however, shouldn't go in the compost bin.

Participants in the organics pickup program will receive a "welcome packet" from the city about a week before their cart is dropped off. It includes a guide to setting up an organics recycling system at home and coupons to help purchase small compost containers for the house. Residents can also request stickers — much like the ones on large compost containers at public events — that show which items should go in each bin.

Officials say they hope more people will sign up for the service as the bins roll out. All eligible homeowners are already paying for compost pickup. The annual cost for waste pickup went up this year by $48.