The issue is a plastic coating used on the cups.

The new effort — which includes 86 locations in the city — builds upon an earlier and smaller scale pilot project that involved just seven locations over an eight-week period last fall.

Now Starbucks and Global Green USA are working with Action Carting Environmental Services Inc. to gather even more of the polyethylene-coated cups to see whether then can be mixed with other recovered fiber and recycled on a larger scale.

“Finding a sustainable solution is a top priority for Starbucks,” said Jim Hanna, Starbucks director of environmental impact, in an e-mail interview.

“During this pilot, our cups are being transformed into facial and bath tissue, paper towels and napkins, and other consumer paper products that contain post-consumer recycled fiber,” he said.

Test results from last year, when the cups were mixed with other recovered paper and recycled in a university laboratory setting, were promising.

“With the quick run we took I would be very confident to say post-consumer cups, we’re not going to see anything negative in the OCC [old corrugated container] stream,” said Joel Kendrick, director of recycling, paper and coating pilot plants at Western Michigan University, during a presentation posted on You Tube.

Annie White is director for the Coalition for Resource Recovery, a part of Global Green USA that’s serving as a third-party technical consultant on the project.

Increasing the size of the pilot project will allow for the collection of many more cups that will be tested in a variety of ways for their recyclability and end uses.

“It helps us build critical mass, get more data,” White said. “We need to have a certain volume of material to really be able to understand how it performs in the mill.”

Cups are being collected over a nine-week period that began Sept. 13. “We hope this test will allow us to better estimate the amount of material that can be collected from customers in store. Based on earlier results, we hope to collect several bales of cups for recycling,” Hanna said.

The amount of material collected last year was small, White said, but allowed researchers to determine that recycled paper including the cups performed well during testing.

Expanding the pilot program also helps determine whether individual stores can provide a clean enough waste stream to allow cups to be taken directly to paper mills for reuse rather than being sorted at a materials recovery facility.

“I think the key is to really find ways to figure out existing collection streams and minimize sorting,” White said.

A key to the project is use of a leak proof and recyclable paper bin liner developed by Duro Bag Manufacturing Co. to collect used cups at Starbucks locations, CoRR said. This could allow bags to be baled with OCC.

CoRR also is interested to see what information from the pilot program can be used for the bigger picture of recycling all food service packaging.

“We’re interested in working with all sorts of restaurants and all sorts of packaging beyond cups as well to really see and prove this model of collecting this material,” she said.

“The results of this large-scale pilot have the potential to institutionalize recycling across the foodservice industry and influence the redesign of all fiber-based food packaging for recyclability,” according to CoRR.

Contamination and coatings are two major hurdles that have to be overcome for food service packaging recycling.

“Starbucks has really taken a leadership role and is really forging ahead, which is wonderful because it’s helping us to understand more broadly the opportunity for this concept,” White said.

The coffee company also sees the potential to impact recycling beyond its own operations. “If the pilot is successful, it could make Starbucks paper cups recyclable more broadly and influence recycling practices across the foodservice industry,” Hanna said.

“Our overarching recycling goal is that 100% of our cups will be reusable or recyclable by 2015. By ‘recyclable,’ we mean in form and in practice — in our stores, in public spaces and at our customers’ homes. The ‘in practice’ point is an important distinction for Starbucks. We won’t call our cups recyclable until the local infrastructure is in place to make it happen,” Hanna said.