St. Paul Tests Single-Stream Recycling
The city of St. Paul, Minnesota and its non-profit organization, Eureka Recycling, studied the city's 15-year-old recycling program in 2001. A new single-stream recycling facility had opened in the area and the city wanted to find out if this was a recycling method that should be considered for its residents.
Tim Brownell, president of Eureka Recycling, said that they were able to receive a grant from the Minnesota Department of Environmental Assistance to conduct the study. The study looked at the total recovery of materials, the total costs involved and the convenience for its customers.
Mr. Brownell said, "Since many communities are struggling with ways to maintain or increase their recycling rates, single-stream recycling has taken on significant interest and has resulted in many unanswered questions. Many communities moved to this system without thorough analysis of its challenges and benefits in hopes of increasing residents' convenience and thereby increasing recycling rates.
"While we found that single-stream collecting is the most inexpensive form of collection for St. Paul, the increase in processing costs and decrease in revenues due to material loss made it the most expensive method when looking at the overall system," he explained. "There is no single answer to every community's values and needs to accomplish recycling goals, but we believe the study methods we developed can be used in other communities to assess their recycling systems."
Over 14 months, Eureka developed five different methods of collections. One was the current method, which included two-stream separation. Residents sorted paper materials in one bin and sorted all other recyclables into another bin. Those recyclables included glass, steel, and aluminum. St. Paul currently does not collect plastics.
There were two two-stream recyclable scenarios with different size bins, collected bi-weekly. Another two-stream scenario included a third bin for organics and was collected weekly. The other set-up was single-stream recycling in which all recyclables (not including organics) went into a large 60-gallon container collected bi-weekly. All of the residents received a large amount of educational materials on the recycling system. Each scenario included approximately 400 households and was monitored for four months.
Mr. Brownell said, "We went into this assuming that single-stream would be the easiest method for residents, and therefore, would bring in the most materials. What we found was that the sorting did not impact the amount of material being put out for collection. What had the most impact was the bin capacity and the amount of storage space a resident had available."
For St. Paul, the study found smaller 18-gallon bins were preferable because of storage space available. Senior citizens also liked the smaller bins, which were easier to carry to the curb.
Collection costs varied. Mr. Brownell said that source-separated collection was cost prohibitive for the city. Single-stream was the cheapest for collection because there was only one container to provide to residents and collect. Two-stream collection costs fell in the middle.
"Once you looked at the processing costs and the recovery of materials, it flips upside down. Source-separated items are the cheapest to process, with single-stream being the most expensive to process. Two-stream falls in the middle again," he explained. "Single-stream recycling required more processing equipment."
Mr. Brownell said the other factor considered was how much material was lost because of contamination or damage. The source-separated had the least amount of loss with one to five percent ending up at the landfill. With two-stream, the rate increased to 6 to 12 percent and with single-stream recycling, the loss was 15 to 27 percent.
"The total system cost for St. Paul showed that the single-stream was most expensive in the end because there were less recovered materials to send to the landfill, which costs money."
Through single stream recycling, paper contamination caused less recovered paper, though Mr. Brownell said this recycling rate also depended on the mill that was purchasing the paper. Some mills accepted the paper and some did not. It depended on the type of equipment the paper processor had at its mill, he said. Some of the loads of paper were contaminated with glass, which made the loads unacceptable. There were problems with different paper fibers being separated. One issue St. Paul had to deal with was chipboard and box board in the newspaper. These other fibers are prohibited in St. Paul's newspaper stream. If it is mixed in, the paper will not be purchased.
"We did have a higher percentage of fiber mix from the single-stream facility," added Mr. Brownell.
Results show that recovered paper revenues from single stream recycling were $274,612 compared with more than $370,000 for two-stream recycling. In the two-stream scenarios paper was separated from the other recyclables which creates less chance of contamination.
In St. Paul, glass had the largest loss of any recyclable in the single-stream scenario.
"For us, 100 percent of the glass was broken to the point where it could not be sorted by color. This left us with mixed glass that we do not have a market for. All of the glass had to be used as alternative daily cover at a landfill," Mr. Brownell said.
In a follow up survey of residents, Mr. Brownell said that the residents did not like the glass being used for landfill cover and preferred a recycling method that allowed recovered glass to be used to make new glass.
"In St. Paul it is clear that the residents value the environment over convenience and costs, according to the surveys and feedback from the study," he said.
The recycling rate increased during the study. The highest increase was in the two-stream set-up that used two 35-gallon carts collected bi-weekly with a 32.8 percent increase. The two-stream weekly pick-up of two 18-gallon bins showed an increase of 26.1 percent and the single-stream methods showed a 20.8 percent increase in the amount of recyclables placed at the curb. Source separated recycling showed the least increase in the recycling rate at 6.2 percent.
While the largest increase was with the 35-gallon carts, Mr. Brownell said feedback showed residents preferred the smaller 18-gallon bins.
Mr. Brownell said that the results in St. Paul are unique to St. Paul, but he feels the methods used in the study can be used in other communities to look at their current recycling program or to start a new recycling program.
"One thing communities need to look at is the fact that while single-stream is more convenient for the residents, it may not bring the amount of recovered materials that sorting will bring. Having a single-stream system in place will make it very difficult to get residents to sort recyclables in the future if a change is to be made," he added.