The single stream process involves multiple sorting steps utilizing state of the art sorting technology. This video highlights the sorting steps in our Des Moines facility.
- Entry - Material is dumped onto the “tipping floor” where it is loaded into the hopper.
- Presort - Bulky items are removed (trash is taken to a compactor and plastic and metal are sorted into containers).
- Rolling discs - Cardboard is removed from the stream while other items drop to the next conveyor.
- Screens - sort fibers (paper) and containers (bottles, etc.) into separate components
- Screens and air drums - separate fibers into types (newspaper, cardboard)
- Magnets - pull steel (cans) from the stream
- Optical Sorters - identify plastic bottles and use air to separate them
- Manual Sorting - HDPE (colored and natural plastic containers) are usually removed by hand sorting, but can also be optically sorted.
- Eddy current magnets - use reverse polarity to separate aluminum cans
- Residue recovery - Manual removes any material that has bypassed the sorting process including plastic bottles & aluminum.
- Mixed Paper recovery - Manual sorting removes any fiber material to be sorted and sold as “mixed paper” (multiple grades).
- Residue - Any remaining material falls off the end of the conveyor into a roll off container that is taken to the landfill where the material is disposed of.
- Baling – Material is compressed in a chamber to create bales and secured with an automatic wire tier. Bales can weight from 1,200 to 2,100 pounds and allow for easy handling and shipping.
I know that single stream is convenient, but does the use of sorting equipment create a negative environmental impact?
- The convenience of single stream greatly increases participation rates, resulting in more recycling tons. This increase creates a larger positive environmental impact while also providing local green jobs.
- Here is an interesting quote from Popular Mechanics on the merits of single stream recycling: “Such state-of-the-art facilities now feature magnets to attract steel, eddy currents to deflect aluminum, infrared spectrometers to identify different types of plastics, and a host of other sorting technologies. These plants are expensive, so they only make sense if 100 to 200 tons of recyclables are being processed daily, and they still require some human sorters to oversee the process. But the collection costs of picking up a single bin, rather than multiple ones, are much lower--and because it's easy for homeowners, the recycling rates are higher--so the overall economics of mechanized sorting pays off. “