Oregonians are good at recycling.
But do they recycle more – or less – depending on how often their trash and recycling is picked up on their curb?
Early analysis of a $300,000 Metro study yielded some surprising results.
The seven-month study looked at the content of trash and recycling loads, sampled from garbage and recycling trucks on residential routes around the Portland region. Crews took out a 250- to 300-pound sample of trash or mixed recycling and examined the sample's contents.
Overall, 14 percent of the material in residential garbage could have been placed in curbside recycling, the study said.
On the other side of that, 9 percent of peoples' recycling loads were un-recyclable garbage that should have been sent to the landfill or wasn't recyclable at the curb. Those are often referred to as contaminants.
"There are still some recyclables in garbage, said Marta McGuire, a planner in Metro's Resource Conservation and Recycling division. "The study also found unacceptable items in the recycling cart. The question on the table is, can we do better? Do we want to do more?"
The answer isn't necessarily yes. One of the questions raised by the study is what's an acceptable level of "misfiring" – essentially, assuming that perfection is impossible, what amount of recycling in garbage cans, and trash in recycling bins, is acceptable?
In looking through trash, the study found little difference among cities with weekly or every-other-week curbside recycling pickup. Beaverton, which has weekly recycling pickup, had the lowest proportion recyclables in the garbage, with 12 percent of trash contents being deemed recyclable.
About 15 percent of trash pickup samples from Tigard, Clackamas County, Lake Oswego and Sherwood was material that should have been in recycling. Clackamas County and Lake Oswego both have weekly curbside recycling; Sherwood has every-other-week recycling pickup.
"There was no statistical difference between every-other-week and weekly recycling collection programs," McGuire said.
On the other end of the study, research teams looked at how much material in recycling bins should have been put in the trash. One key question in that portion of the study was whether Portland's every-other-week trash pickup prompted Portland residents to put more trash in their recycling.
The answer was surprising – Portland had the lowest rate of contaminants in recycling in the study.
But one of those contaminants stood out. The study found that dirty diapers made up 0.3 percent of Portland's recycling.
That compares to 0.1 percent of recycling loads elsewhere in the Portland region. While that means only 3 pounds of every 1,000 pounds of recycling in Portland consists of diapers, that 3 pounds matters once the recycling gets sorted.
At transfer stations, employees and machines sort through recyclable material, making sure plastics, paper, aluminum and other recyclables go to the right recycling center.
"It's a very small amount," said Bruce Walker, solid waste program manager at the Portland Bureau of Planning and Sustainability, said of the diapers in recycling. "But clearly, they shouldn't be in there."
Another challenge at recycling centers are plastic bags, which get caught on and jam machinery. Workers have to stop machines and clear the bags off when they get stuck on equipment. Where metal cans can get picked up by magnets, and screens can sort out cardboard boxes, plastic bags are hard to get off the line.
"There isn't a plastic magnet, unfortunately, and those things get in the machinery and gum up the works," Walker said. "They stick to the belts and the screens that are used to separate some of the materials. They really are a major headache for recycling sorting facilities to deal with."
In Portland, which has banned most plastic grocery bags, researchers found six such bags in every 280-pound load.
In the other area cities and suburbs, researchers found 17 bags per load.
"We're the only one in this region who has (a bag ban)," Walker said. "To me it has a positive impact – why do we need all these bags in the first place?"
Note: An earlier version of this story incorrectly identified Tigard's recycling pickup schedule. Tigard has weekly recycling pickup. This post has been corrected.