Single stream versus dual stream recycling collection is a persistent issue. Which approach to recycling collection promotes the most cost effective method to recover, process, and market usable materials and reduces the amount of material going to landfills or incinerators? A review of the recent literature (See Appendix A Annotated Bibliography) mostly indicates a preference for a dual stream system, as more often than not dual stream recycling is seen as more beneficial for the MRF and makes the overall process of recycling more worthwhile for cities and counties.
A highly functional and cost effective recycling system comprises a series of choices, not just collection stream type. The system must include cost effective processing that meet industry market requirements. However, single stream has hampered the ability to collect high quality recyclables. “In effect,” states Neil Seldman, ILSR, “the waste industry and cities that followed their recommendations and pressure to move to single stream had on blinders to the actual realities of recycling by focusing solely on the collection efficiency of single stream. These collection, processing and marketing structures were built on a foundation of sand as eventually revealed by the import bans on dirty recycling bales.”
Single stream recycling may reduce the costs of collection, but if the materials are contaminated the cost and quality of processing is poor, then materials cannot be sold. Collection efficiency should not be the only criteria for adopting a system. China’s National Sword policy, implemented at the end of 2017, highlighted the need for clean recycled materials and caught US processors off guard, even though U.S. processors were warned by the 2013 Green Fence policy. Imports were effectively banned to protect the Chinese environment and to eliminate the cost of cleaning up bales of materials with as much as 30% contamination. Without clean materials, domestic and overseas markets rapidly eroded. The cost of handling single stream materials has increased in order to compensate processors for these losses. Contamination rates were found to be about ten percent higher than their dual stream counterparts. Compromised materials either fetch lower market prices, or cannot be sold and must be sent to landfills or incinerators. Revenues for contaminated materials can be up to seventy percent lower for certain high volume recyclables, such as mixed plastic. Additionally, operating costs for single stream facilities are about eight percent higher than those of dual stream facilities. Furthermore, capital costs for single stream facilities are on average thirty five percent higher than those of dual stream facilities.
Given lower market revenue and increased cost of processing, the economics of single stream recycling recycling has changed dramatically. Recycling processors either shut down or renegotiate their contracts, charging prohibitive prices for recycling. In 2019 Washington, DC started paying $120 per ton to process its recyclable material. Recycling glass, which is 20% by weight of the recycling stream, costs an additional $25 per ton surcharge. These fees include shipping materials to a centralized processing facility 40 miles out of town. The cost of recycling is more than twice that of landfill or incineration disposal; threatening the sustainability of recycling.
Dual stream can offer lower processing fees, reduced contamination, better quality materials, better market access and higher prices and closer ties between processor and end markets. Furthermore, dual stream can offer greater flexibility in deciding compaction levels, co-collection, timing and frequency of collection, properly scaled processing equipment, proper configuration of equipment, and establishing stable, long term relationships with end markets.
Cities may achieve greater success in cost effective recycling by matching collection, processing and markets with than by being enticed by the collection efficiency of single stream collection. Louise ‘Louie’ Mann, has proposed a transparency ordinance for Fayetteville, AR that would require all processors to make public the destination of all materials. Cities should explore multiple variables that go into a cost effective recycling system rather than being seduced, or cajoled, into a rigid single stream system that requires long hauls for processing and distances themselves from end markets.
In terms of equipment usage, commercial generator companies that require strict source separation of recyclables by customers allow for the use of non-hydraulic trucks; regular fleet trucks that have dead head loads provide an ample hauling fleet that can take materials directly to end markets or dual stream processors. This combination of revenue and shared savings lowers the cost of recycling for businesses.
In summary, the central arguments in favor of single stream is the increased total recycling rate the system brings. Dual stream proponents note that their system usually has a higher net recycling rate and fetches higher prices for end market products. In order for recycling to be sustainable there needs to be economic incentive. Overall, the data shows that dual stream systems are more likely to foster conditions where that can happen, but single stream can work in certain places where the MRF has high quality sorting equipment, there is a culture of recycling, and strong end markets for lower grade materials. However, it is important to remember that the purpose of recycling is not simply more material in the bin, but more material diverted from the landfill, more material being made into another high quality product, more value kept in the local and regional economy, and a decrease in materials sent to the landfill. At this time, it appears that dual stream is the best way to meet those goals, but select single stream systems can work.
Research on the effect of various processes within recycling, such as the use of compactors, the size of collection containers, timing and frequency of pickup collection, in-school educational and public awareness programs, incentives through unit pricing (Pay As You Throw) are needed to understand how changes can encourage citizens to recycle at a greater, cleaner rate and for end markets to receive cleaner materials. Additionally valuable would be comparative studies on recycling programs which share common characteristics such as population density, overall population, and access to nearby recycling facilities.
For more information, see Appendix A, Dual Stream Annotated Bibliography.