With more and more people learning about the importance of sustainability, recycling has become a routine part of life across America. In fact, the practice has grown so common that people rarely stop to think about the processes (for example, single-stream and dual- or multistream) involved in recycling common household items.
Single-stream recycling is essentially a process that allows various materials—from paper to glass to metal—to be collected in the same receptacle and recycled all at once. After collection, sophisticated equipment sorts and processes the items. Nearly 65 percent of communities in the US use this process, and this figure has grown substantially in the past decade.
Other popular recycling processes include dual-stream recycling and multistream recycling, which are sometimes called source-separated recycling. These forms of recycling require people to separate paper from glass, plastic, and metal prior to collection. In addition, multistream recycling boasts lower contamination levels, lower processing costs, as well as higher quality recyclable materials.
Cities across the country are eager to adopt single-stream recycling technology because of its cost effectiveness and the ease of participation for citizens. In particular, residents like that single-stream recycling takes the tedious aspect of sorting waste out the equation, while experts in single-stream recycling field estimate that the process can reduce recycling costs up to 25 percent.
The Single-Stream Recycling Process
Once people put waste into a single-stream receptacle, workers collect it and cart it off to a sorting and processing facility. There, high-speed optical sorters identify the materials and separate them using a variety of methods, including magnetic belts designed to automatically sort metals. Other materials like paper, plastics, and glass are also sorted separately.
The first stop at the processing facility is what is referred to as the “tipping floor,” a central location where workers dump all collected waste. After they remove large items, workers scoop up the remaining waste and placed it into a drum feeder that puts the items on a conveyor belt. Next, facility workers remove any waste that can cause a blockage on the belt or that will not fit in the sorting machine. The conveyor then moves the material through large screens in order to sort out cardboard and heavier paper, while the remaining waste falls through the screen.
The waste proceeds through a secondary sorting process in which workers further extract waste before it goes to a medium-sized screen designed to sort smaller paper fragments and separate glass, plastic, and aluminum. Glass is then sent to a separate sorter and crushed before being sent to glass recyclers. Once metal is separated, the remaining plastic is then illuminated by a laser beam that senses varying types of plastic and sorts them appropriately. Any remaining items go to a landfill.
Much of what people collect is can be easily recycled, and the volume at single-stream facilities is high thanks to wider municipal recycling participation rates. According to the Governmental Advisory Associates firm, the US now boasts about 240 single-stream processing facilities.
Limitations of Single-Stream Recycling
Though placing all trash into one container is easier for residents and cost effective for municipalities, there are some problems associated with single-stream recycling. Namely, mingling non-recyclable or hard-to-recycle items in the same receptacle basically creates more work for those responsible for sorting, and some of these items may still end up in landfills.
One of the most difficult challenges presented by single-stream recycling is how it handles glass, which is fragile and susceptible to breakage during the collection and sorting processes. Because glass fragments are so common, processing facilities are rarely able to recycle them, and they end up being crushed and scattered about. Further, when broken glass is inadvertently mixed with other recyclable materials, it makes those materials more difficult to use and sometimes results in the materials being completely unusable.
One of the key selling points of single-stream recycling is volume, and proponents believe that no matter the processing challenges, increased volume helps the environment. However, critics state volume shouldn’t be the only consideration and believe that there are other, more effective ways to increase recycling volume. These suggestions include placing limitations on how much people can throw away, imposing costs for non-recyclables, and encouraging sorting in lieu of being charged for single-stream methods.
Another issue raised by critics is the overall cost effectiveness of single-stream recycling. Though municipalities save money on collection costs, the processing facilities often see an increase in costs due to the processing of difficult-to-recycle items. Additionally, anything that cannot be recycled ends up in landfills, which can result in environmental costs in addition to the financial ones.
Whether single-stream or multistream, recycling remains a critical part of saving our environment. People should make a concerted effort to purchase recyclable items and educate themselves on proper recycling techniques to make the process more effective.