Single-stream recycling is a system in which all recyclables, including newspaper, cardboard, plastic, aluminum, junk mail, etc., are placed in a single bin or cart for recycling. These recyclables are collected by a single truck and taken to a Materials Recovery Facility (MRF) to be sorted into various commodity streams for sale to markets, where it is processed into feedstock which can be used in the manufacture of new products.
Video: See a MRF in action
Under the single stream system, residents combine paper and containers in a single bin or bag. The bins or bags are collected and placed in a truck. When the bins or bags arrive at the MRF, the recyclables are sorted. The impetus for adopting single-stream was twofold: a belief that the added convenience of not needing to sort would entice more residents to participate in their curbside programs, and the desire to save money by reduced collection costs. While collections costs are lower with a single stream system, processing costs are much higher.
Single stream recycling was introduced in the late 1990s as a lower-cost alternative to "dual stream" collection: the predominant method of curbside recycling at the time ("source-separation," where each material type is kept in a separate bag or bin, and trucks have three or more compartments, was the predominant method of collection in the late 1980's, but had all but been abandoned in the U.S. by the mid 1990's). Under the dual stream system, residents usually combine all their food and beverage containers (aluminum and steel cans, glass jars and bottles, and some or all plastic bottles) in one bin, and they put their newspapers and/or mixed paper (such as junk mail, cereal boxes, and home office paper) in another bin, or in a brown paper grocery bag. The two material streams are picked up and placed in separate compartments on the recycling truck, and taken to a processing center (a materials recovery facility, or MRF). The fiber is sent to market with little or no processing, and the containers go through a variety of automated sorting equipment and hand-picking before being baled or containerized and sent to market. There are also hybrid co-mingled systems where plastic and metal, and sometimes paper, is combined, but glass is kept separate.
There is significant evidence that the resulting scrap material quality (and hence the revenue) is lower under single-stream collection than it is under a dual stream system or under systems like container deposits, where materials are kept separate. There is a particular concern that glass shards and PET bottles can contaminate paper loads and wreak havoc in a paper mill, and that glass, plastic and aluminum containers cross-contaminate each other.
Figure 3 from CRI's study, Understanding economic and environmental impacts of single-stream collection systems.
While collection costs are lower in single-stream systems, processing costs and the costs associated with disposing of contaminated materials are higher. Overall, single-stream costs about $3 more per ton than dual-stream.
In a Resource Recycling article, Daniel Lantz concludes that the proposed benefits of single-stream systems over dual-stream do not outweigh their costs:
In summary, with increased processing costs and lost revenues in total far exceeding collection savings in most instances (and zero under alternating-week collection), overall single-stream recycling does not show the cost advantage that was originally anticipated. As well, the expected increases in capture rate are also not apparent. Overall, dual-stream recycling still appears to be more advantageous.1
California Roundtable, May 23, 2005 www.conservatree.org/learn/SolidWaste/roundtable.shtml
Eureka Recycling www.eurekarecycling.org/inf_studies.cfm
1. Source: Lantz, D. "Mixed Residuals". Resource Recycling, December 2008. (Source of data findings, Metro Waste Paper Recovery, 2008)
2. Source: J.Poyry and Skumatz Economic Research Associates. Paper Recycling: Quality is Key to Long-Term Success. p.32. March 2004
3. In Oregon, almost all residential recycling and much commercial recycling is collected as commingled material. Oregon programs pick up glass containers separate from other materials or do not include glass in the on-route collection program, choosing to collect glass through recycling depots or some other method. This is unlike single-stream collection programs in much of the rest of the nation that collect all materials, including glass, mixed in together.
Costs of Contamination Report – 2012 [pdf, 325kb]Resource Association in the UK - Resource Association survey of reprocessor members’ assessment of the impact of poor and inconsistent quality recyclate on manufacturing costs – December 2012
Procurement outcomes for waste collection systems in the UK market [pdf, 851kb]Controversy over the relative merits of different recycling collection systems has raged for around two decades and is now a focus for the DEFRA consultation on whether co-mingling is an acceptable substitute for separate collection of recyclates. 4R Environmental April 2012
A Common Theme [pdf, 399kb] The importance of preserving material quality and avoiding cross-contamination has become a common theme in many recent technical reports on recycling. Unfortunately, there is widespread confusion about what losses in materials mean. CRI Susan Collins March 2012
Concerns With Single Stream Recycling Collection - 2011 [pdf, 336kb]Clean Water Action, MA - While communities report higher recycling rates from the new collection system, in fact not all of this “single stream” material actually gets recycled—that is, turned into new products. – August 2011
Composition of Commingled Recyclables Before and After Processing [pdf, 211kb] The commingled recycling systems in Oregon provide a solid example of the contamination that can occur in any recycling collection system. [see note 3] Oregon Department of Environmental Quality. March 2011
Kerbside Collections Options: Wales [pdf, 1MB]This report finds that curbside sort is clearly the both the best environmental and economic option for dry recyclables. Eunomia/WRAP. January 2011
Beyond the Curb - Tracking the Commingled Residential Recyclables from Southwest WA [pdf, 6.57MB] An analysis of what works and what doesn't in single-stream/commingled collection systems in southern Washington. Washington State Department of Ecology, June 2010
Understanding economic and environmental impacts of single-stream collection systems [pdf, 1.4MB] This report highlights the economic and environmental impacts of switching to a single-stream system. Clarissa Morawski, for the Container Recycling Institute, December 2009
Kerbside recycling: indicative costs and performance Systematic appraisal of the UK's principal collection systems in the UK, looking at both their cost and effectiveness. WRAP, June 2008
A Comparative Analysis of Recycling Collection Methods Eureka Recycling, May 2002
Single Stream: [pdf] An Investigation Into the Interaction between Single Stream Recycling Collection Systems and Recycled Paper Manufacturing. Conservatree, March 2003
Paper Recycling: [pdf] Quality is Key to Long-term Success American Forest & Paper Association, March 2004
Newsprint on the Orient Express [pdf] Clarissa Morawski, Solid Waste Mag, April/May 2011
Single Stream Uncovered [pdf] Clarissa Morawski, Resource Recycling, February 2010
Zero Waste and Separate Collection Zero Waste Europe, 10/2010
Single Stream Waste Age, 11/2003
California City Studying Single-Stream Program Recycling Today, 11/18/2004