Jill Slovin

With more than 6,500 plastics drop-off sites and curbside collection programs in the United States today, organizations such as the American Plastics Council (APC), Washington, D.C., are beginning to analyze the effectiveness of collection methods.

As part of APC's Model Cities Demonstration Program, the organization set out to find the most cost-effective, state-of-the-art collection system for plastics, said Ron Perkins, APC's director of recycling operations.

Two Seattle suburbs, Mercer Island and Point Cities, were selected to host a pilot study, partially because of their recycling programs' high participation rates. Organizers of the study focused on the operational and economic impacts of collecting plastic bottles on two types of commingled curbside collection routes.

Mercer Island and Point Cities already used 90-gallon carts to collect commingled materials including aluminum cans, newspaper, mixed paper and cardboard. The carts included a 17-gallon insert for glass recyclables.

The study varied collection methods in the areas to measure the different costs and participation rates. For example, Mercer Island residents placed plastic bottles and glass into the insert. Residents of Point Cities, however, put their plastic bottles into the 90-gallon cart for commingled materials.

"Because of the large number of narrow streets and cul-de-sacs, both areas have inherent collection inefficiencies," said Perkins. "Maneuvers such as backing up, turning around and other time-consuming actions are performed frequently on recycling and garbage collection routes. The study determined that these activities consumed 6 percent of the typical collection day."

Each area used side-loading compaction vehicles with an 18-cubic-yard capacity compartment and three non-compacting compartments for glass. While both trucks were equipped with right-hand, stand-up drive, only the Mercer Island truck featured an on-board plastics compactor.

In Mercer Island, where the plastic bottles were collected separately, approximately 20 minutes of the entire collection route were required for collecting plastic bottles. As expected, the majority of plastic bottles set out were polyethylene terephthalate (PET) and high-density polyethylene (HDPE). Together, the resins comprised 95.8 percent of the bottles collected in Mercer Island and 88.5 percent in Point Cities.

To calculate the cost per ton for plastics collection, Perkins said he had to identify how much time, labor, fuel, maintenance and truck space each material used. The resulting fully allocated cost for plastic bottles was approximately $682 per ton in Mercer Island and $910 per ton in Point Cities (see chart). However, according to the American Plastics Council, the cost per ton figures are misleading and inappropriate to use for evaluating recyclable materials. The cost per ton was much lower when calculated on the basis of incremental costs, or considering only the new additional expenses for collecting plastics. For example, the net incremental costs for adding plastics to existing programs in Mercer Island and Point Cities was $69 and $22 per ton, respectively.

Since the recyclables in Point Cities were commingled, subsequent separation increased the costs. Also, Mercer Island's lower collection costs can be attributed to the dedicated compactor, according to APC. The uncompacted plastic bottles from Point Cities took up more space on the truck, which boosted labor and capital costs. In comparison, the cost of Mercer Island's plastics compactor has been offset by lower collection expenses than Point Cities.

By thoroughly evaluating current operations, collection managers and trade organizations can help mold the future of plastics collection programs.