Single stream recycling: Could be coming to a theatre near you

Jim Close
Public Works Director
City of Harrisburg, Pennsylvania
Member, APWA Solid Waste Management Committee

Collection is the most expensive part of a solid waste management system. This statement is especially true for residential curbside and commercial recycling programs. In this day of tight municipal budgets and lower profit margins in the private sector, the incentive for collection efficiencies is great, as they provide the biggest bang for the cost-savings buck.

The origin of recycling was to separate from the waste stream all materials that could be reused or remanufactured. This concept led to the theory that the better the materials were separated at the source, the better they could be marketed; hence, a more successful recycling program. Unfortunately, the better the materials were separated at the source, the higher the collection and handling costs became. In many cases, the cost to collect and process a ton of recyclables was greater than the cost per ton to collect and dispose of trash in the same community.

In the past few years several manufacturers, specializing in material handling equipment, have introduced improved technologies for the automated separation of co-mingled recyclables. Although this equipment is expensive at the front end, it has given recycling managers the option to consider eliminating source separation in favor of collecting all residential and commercial recyclables—including cans, glass, plastic, paper, and cardboard—in one collection vehicle. Using one truck often involves the compaction-type vehicles, which increases the number of stops and amount of recyclables that can be collected. Compacting mixed recyclables can lead to semi- or fully-automated collection in large tipper carts. Such automated collection of refuse has proven to greatly increase productivity while reducing workers’ injuries and should work as well for recycling. In a large enough scale the savings in collection and handling efficiencies will reasonably amortize the initial equipment investment at the separation center.

This concept of mixing recyclables should not be confused with collecting municipal waste and recyclables together. That process involved what was commonly referred to as a “dirty MRF,” or a Material Recovery Facility that had to first separate the waste from the recyclables. Many earlier mixed facilities had problems with recyclables being lost into the waste stream on the tipping floor plus a lower quality of recyclables because of the contamination from garbage, which caused marketing problems.

Most modern MRFs receive the recyclables directly from the point of origin through collection vehicles and onto either a single or dual sort system (fiber/containers). MRFs can be classified as “low technology” or “high technology,” depending upon the sophistication of the sorting equipment and the complexity of their flow-through design. The common goal is to have like material separated for their respective markets. The impetus for single stream MRFs is the steady volume of materials marketed. Quantity becomes the driving force.

What is not recovered and marketed is considered waste and taken to a regular trash disposal facility. This residue can be dirt, rocks, shredded paper, broken glass, or other material that either fell through the screens or was somehow rejected in the sorting process. The percentage of residue is a performance measurement for any MRF or recycling program. A higher percentage can indicate the need for a better education program for the people placing the recyclables out for collection or not a thorough enough sorting process at the MRF. Many recycling advocates fear the quantity-driven single stream process will create greater amounts of residue.

Another performance measurement is marketability of the recovered materials. This measurement is not only an economic factor for the sustainability of recycling but also closes the traditional loop, that has become the universal logo for recycling. The consistent volume of materials produced at the larger single stream facilities can help stabilize the volatile feedstock market with reliable long-term supply contracts. On the other hand, many mills and end-users have quality concerns with the high through-put of these new facilities.

Plastics can be problematic for a MRF, particularly plastic bags that can become entangled in sorting equipment or shredded into unrecoverable flakes that cling to paper stock causing quality problems. Mixing paper grades is another concern for high-volume systems. The real quality culprit for MRFs is glass, which normally makes up less than 10 percent of the recycling stream. The highest market value for glass is when it is color sorted—clear, amber, green. Once sorted it can be crushed into cullet. Unsorted or mixed cullet has a lower market value, if any, and often ends up in the residue, costing the MRF a disposal fee.

Further compounding the sometimes marginal economics of glass recycling is that broken glass becomes embedded into plastic and paper. These tiny pieces of glass called shards require extra expense for the mills to remove and are the leading cause for rejection of recycled feedstock. Broken glass is also extremely abrasive on the sorting equipment and, therefore, maintenance costs increase.

Many analysts fear that the use of compaction-type collection vehicles and the new, automated, high-volume sorting equipment will result in more glass breakage and contamination problems. Some MRFs are refusing to accept glass, which is causing concerns in the recycling community.

The bottom line on any recycling program is usually expressed in terms of revenue and avoided costs. Revenue for separated recycled materials fluctuates with the marketplace and has not always been self-sustaining. Paying a disposal fee at a landfill or waste-to-energy facility can be reduced by separating recyclables out of the waste stream. The avoided disposal costs have not always balanced the extra expense of collecting recyclables, causing some budget shortfalls.

Is single stream the panacea for recycling’s bottom line? In theory, one collection bin should be easier and lead to greater participation, thus creating more materials for market and a higher diversion rate from disposal costs. Using one collection truck, particularly the compaction type, reduces manpower, increases payload, eliminates half-filled compartments on segregated vehicles, allows more flexibility for adding recycle materials, and decreases truck traffic. The potential seems great.

The volumes required to justify the investments in the new high-technology single stream systems could lead to large regional facilities possibly creating transportation problems for some outlying areas. Small community curbside and rural drop-off programs could face increased costs. Collection schedules could change to every other week or monthly with larger containers, possibly causing confusion and disinterest. The challenges also seem great.

Every recycling manager and other decision makers need to understand the potential impact of single stream recycling on their community, and the opportunities it may present.

Jim Close is a current member and past chair of APWA’s Solid Waste Management Committee. He can be reached at (717) 236-4802 or at