Maria Marte, a supervisor in the recycling center at the Central Landfill in Johnston, collects needles on the conveyor belt that sorts cans and bottles.

The Providence Journal / Frieda Squires

JOHNSTON — A massive earth-moving machine scoops up bucket-loads of bottles and cans trucked to the Materials Recycling Facility at the state’s Central Landfill and drops them onto a conveyor belt. Every time the machine moves back and forth, it runs over bottles and they explode. All you hear is a roaring diesel and what sounds like continual gunfire.

In the back of the building, thousands of tons of paper flow by on another conveyor belt. Leaning over the passing paper, a worker wearing goggles and gloves and a safety belt reaches down with a hook and pulls away plastic bags. As fast as he pulls one away, he reaches for another.

Upstairs, dozens of workers stand over a conveyor belt, flicking off every plastic bottle they see. Aluminum cans fly off the belt for resale. But a lot of other material — wrappers, tubs, plastic bags — flow right by into waste containers. And every few minutes, someone pulls an alarm to stop the conveyor — because orange and white hypodermic needles are among the recyclables.

One worker with heavy gloves and tongs removes the needles one at a time, while everyone else waits.

Rhode Islanders recycle a lot of waste each year. And because of a new state law and renewed efforts by cities and towns, they probably will recycle much more in coming years.

But a lot of what Rhode Islanders throw in recycling bins is not recycled at the landfill, or can taint or damage the value of what is recycled.

In the year beginning October 2007, Rhode Islanders recycled nearly 100,000 tons of bottles, cans and paper. But 12,683 tons of that total were non-recyclables that were sorted out and buried at the landfill. People in the business call them “residues.”

In the following year, Rhode Islanders sent about 1,700 tons less in recyclables to the landfill, but the proportion that had to be discarded as “residue” soared to 15,139 tons.

It’s not clear why the “residues” are increasing, says Sarah Kite, director of recycling services at the landfill.

Some communities stepped up their recycling recently, so homeowners may be uncertain of the rules, Kite said. Resource Recovery could do more education, too.

When Providence got tough with homeowners recently by refusing to pick up garbage unless recycling bins were put out next to them — Kite said you could immediately see the consequences at the recycling center — nearly 60 more tons a day were being delivered. Overall, recycling this fall was up nearly 10 percent compared with last fall.

Most of the trouble occurs in the blue recycling bins. The most common offenders are plastic bags and yogurt and butter tubs.

Those items are not recycled by the state.

Also not wanted in the bins are bottle caps, plates, glass windows, Styrofoam containers or food containers of any kind, coat hangers, buckets of all types (cat litter, paint buckets, 5-gallon containers, recycling bins), laundry baskets, cable and wire, pipes (both plastic and metal), flower pots, chains, needles and propane tanks.

Kite said the recycling workers have also come across such unusual items as engine blocks, bikes, ammunition, knives and dead animals.

Kite said she sees improved recycling efforts around the state.

“All the cities and towns are looking for ways to save money,” says Kite. “I tell them, how many tax dollars do we have a direct influence on? The more we waste, the more we pay.”

And soon, a new state law will require even more effort. The law requires every city and town to recycle 35 percent of its wastes by 2012 and to recycle more types of plastics.

Middletown already does better than that, Kite said. Charlestown, North Kingstown and Barrington are close. But some other communities remain below 20 percent.

To handle increased recycling, Resource Recovery is considering spending $10 million to $20 million for a new and improved recycling center, or it may simply upgrade its existing building. It also is considering investing in a new, single-stream system that would assign each homeowner one large container to handle all their recyclables.

It sounds counter-intuitive, But Kite says experience elsewhere shows people recycle more when they have just one, large container, and automated equipment at the recycling facility would make it cheaper to sort everything.

Resource Recovery will discuss options with cities and towns in the coming months, she said.

For details on what you should and shouldn’t recycle, go to: http://www.rirrc.org, click on Questions, then click on How Do I Dispose. A panel discussion on recycling is scheduled for 5:30 to 8 p.m. Thursday, Dec. 3, at the Apeiron Institute for Sustainable Living at 17 Gordon Ave., in Providence.

plord@projo.com