Single-stream dip going swimmingly
By: Charlotte Pitt
February 13, 2006

In June 2005, the city and county of Denver took the plunge into the world of single-stream recycling. Since then the recycling program has experienced an 18 percent increase in tonnage collected and an increased excitement around recycling in the city.

Along with the move to single-stream, there is a phased-in effort to automate the collection of recyclables. Phase one was completed in October 2005 with the purchase of three automated collection trucks and the delivery of 12,000 new 65-gallon purple recycling carts.

(Yes, purple is an odd color, but it has been the Denver Recycles brand for more than 13 years. Plus, it is unique!)

The original plan was to phase in recycling carts over a period of five years, but the response from the public has been so positive that Mayor John Hickenlooper prioritized funding to speed up the cart implementation.

Plans are now to finish delivery of carts to the rest of the city no later than spring 2007, two and a half years ahead of schedule.

Automating the collection of recyclables and creating a user-friendly service were the primary drivers for the city's move to single-stream.

The Solid Waste Management staff wanted to reduce injuries on the crew, increase route efficiencies and increase customer satisfaction.

The decision to move to single-stream was not one that was made quickly. Staff thoroughly investigated and considered the implications of single-stream and automated collection. Concerns ranged from the ability to find automated trucks that could service tight alleys, to the possible decline in material quality, the decrease in revenue generation, the ability for the private sector to provide quality processing services (there was not a single-stream material recovery facility in Colorado) and the ultimate question of how does single-stream affect recycling overall.

The concern of decreased revenue was addressed with the knowledge that increased volume would allow the program to offset a lower dollar-per-ton value. The concerns about single-stream processing capabilities were put to rest when the city issued a request for proposals and received three very strong proposals. And the concerns about material quality are now beginning to ease as the city works with the processing contractor and partner, Waste Management Recycle America. Preliminary findings demonstrate an increasing satisfaction in the processing operations and the level of commitment provided by them.

The quality of the end product is also greatly affected by the quality of material delivered. Staff just completed the first material sort from a sampling of 1,200 homes using the new recycling carts.

The results of the sort showed that less than 1 percent contamination is being delivered, and when run through the single-stream sort line, less than 2 percent was lost as residue.

Although it is expected that contamination will increase as the rest of the program is automated, the city is committed to minimizing contamination through education and route audits.

Whatever your position is on single-stream recycling, we in Denver feel confident that we made the right decision in taking the Denver Recycles program single-stream. We recognize that we still have much to do and learn, but the positive response to the program, the route efficiencies gained, and the general increase in awareness and excitement are all steps in the right direction.

Pitt is recycling program manager for Denver's solid waste management division.