Brookhaven officials' efforts to increase recycling in the town have proved more successful than expected, a Stony Brook University professor said Thursday.

The town's switch to single-stream recycling produced a larger than anticipated 25 percent increase in the amount of paper, plastics and metal collected last year, according to a report prepared by David Tonjes, an assistant professor of technology and society. The town program encourages residents to put paper and plastic, metal and glass containers together in recycling cans, rather than in separate bins.

"The 25 percent increase is larger than a lot of people thought and is the effect of single-stream recycling," Tonjes said in an interview. He said he had forecast a 5 to 10 percent increase, and a town consultant predicted a 10 to 15 percent improvement.

"I was very pleasantly surprised. I was all set to be skeptical about this," Tonjes said.

His report backed up a study released this year by Brookhaven officials. "This report only confirms what we knew all along," Supervisor Edward P. Romaine said. "I think that people want to do their bit to protect the environment."

Tonjes' study looked at trash collection in Stony Brook, Ronkonkoma and Shirley last year, when the town began single-stream recycling, compared to the same hamlets in 2012, when recyclables were separated. He said town officials paid the university $80,000 last year for expenses, including stipends for two student researchers.

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Homeowners became better at recycling -- placing more paper and containers into recycling bins than they had previously, Tonjes said. As a result, the town cut recyclables sent to an incinerator from more than 50,000 tons in 2012 to about 40,000 tons last year.

More than a half-dozen Long Island municipalities, including Huntington and Smithtown, have contracted to join Brookhaven's single-stream recycling program. "We think probably what happened in Brookhaven is going to be seen in other towns as well," Tonjes said.

He said his study, while mostly positive, also found residents showed a greater tendency to place non-recyclables -- such as soiled paper, yard waste and wood -- into recycling containers. And paper and plastic still don't get recycled enough, he said.

"Expecting residents to be totally efficient in separating recyclables is just not feasible," Tonjes said. "It's hard to get everyone to comply. . . . There's always room for improvement."

Romaine said the town recently hired a part-time recycling educator to speak to community groups.