Overview of USA Recycling Systems

Broad Overview:

Recycling in the U.S. operates in a flow of processes:

  • collection: the recyclables are collected
  • processing: different types of wood, plastic, and glass are separated at a sorting or processing center
  • reclamation: the separated products are sent to the milling, glass, or plastic reclaiming facility, where the recyclables are turned into usable raw material[1]

Collection:

Depending on location, a person could have one of three types of access to recycling collection: 1) no access, 2) overall waste is collected then sorted to find recyclables, 3) a separate bin is used by the recycling service to only collect recyclables.

For type 1, then his/her waste never makes it to a recycling facility; however for type 2, some communities use dirty material recovery facilities that sort through general waste to possibly find any recyclables. [1]

For type 3, the recyclables are sent to clean material recovery facilities that can only deal with recyclable materials. The recyclables are either presorted into plastic, metal, and glass before being collected or lumped together as a single-stream system that is organized later at the facility. [2]

Processing:

Presorted Recyclables:

If the recycling is presorted, the process simply involves removing contaminates by hand, separating the plastic with lasers, and baling the respective types.

Single Stream Recyclables:

If the recycling is sent in a single stream, the process is carried-out as follows:[3]

  • Tipping the Floor – The trucks pile the mixed recyclables and do a visual check to make sure there are no oversized pieces.
  • Drum feeder – Huge claws grab the material and drop the recyclables into a drum than evenly distributes the recyclables onto a conveyor belt.
  • Inspection – Workers visually inspect the stream and take out plastic bags and other things that may jam up the line.
  • Large Star Screen – This special conveyor is used to take out large pieces of cardboard while smaller materials can fall through the conveyor for continued processing. A picture can be seen below:

 Figure 1: Star Screen Conveyor [4]

  1. Second Sorters – Humans take out smaller contaminant like KCups.
  2. Medium Star Screen –  Similar to the large star screen; large pieces of paper stay above the line while plastic, glass, and metals fall through.
  3. Glass Sorter –  Glass is the heaviest material that would be recycled, so star screens are used to allow the glass to fall through and get sent to a different area.
  4. Magnetic Metal Sorter – A large magnet passes above the conveyor, and anything that would be attracted to a magnet is then pulled out of the stream and sent somewhere else.
  5. Eddy Current Separator – A magnetic field forces electrons to create their own magnetic field by induction, and the resulting interaction pushes material off the main conveyor to a secondary one. The process is shown below:                                                                                                                                                                                                         

Figure 2: Eddy Current Separator [5]

  • Infrared Laser – Plastic is the last material left in the main line, so lasers are used to detect the different types of plastics described below into their own areas. The consumer can know what type their plastic is based off the number in the middle of the recycling symbol, as shown below:                                                                                                                                                                                                                                                         

Figure 3: Different types of plastics [6]

  • Baler – The different materials are congregated into large bales of their respective materials to be sent to other processing facilities. (Different types of plastics, different grades of paper)

Reclamation:

Plastics:

Of the types of plastics mentioned above, most curbside programs only take PET, HDPE, and PVC. Meanwhile, PS, PP, and LDPE are too difficult to recycle in an economically feasible way due to their large volume of air or their thermoset-plastic material properties (which prevent them from being re-melted and re-used).[7]

The plastics that can be recycled are shredded, cleaned, and melted into pellets. Care is taken throughout the process to prevent cross-contamination across plastic types. The pellets are then combined with new plastic to ensure that the resulting product has consistent properties. Unfortunately, plastics can only be recycled 7-9 times before their structure is so denatured that they are no longer recyclable. [8]

Cardboard/Paper:

These recyclables are sent to a mill where each type of paper is shredded, mixed with substances (paper, water and various chemicals) to break down fibers, and pressed through a screen to filter out contaminates. The paper is then spun into a cylinder and cleaned before being sent through a machine that sprays it onto a conveyor so that the fibers can start to bond together. The new sheet is then dried.

Paper can be recycled around 5-7 times before all of the fibers become too short. [9]

Glass/Metal:

The processes for reclaiming metal and glass are similar. For each, the material is crushed, washed, melted, purified, and finally allowed to solidify into whatever material the user wants.

The biggest difference between the other recyclables and glass and metal is that glass and metal can be recycled over and over again. [10]

Citations:

[1] US EPA. (2020). The U.S. Recycling System | US EPA. [online] Available at: https://www.epa.gov/americarecycles/us-recycling-system [Accessed 18 Feb. 2020].

[2] Garden, H., HowStuffWorks, Science, Science, Conservation and Issues (2020). Is what we’re recycling actually getting recycled?. [online] HowStuffWorks. Available at: https://science.howstuffworks.com/environmental/conservation/issues/recycling-reality.htm [Accessed 18 Feb. 2020].

[3] Popular Science. (2020). How It Works: Inside The Machine That Separates Your Recyclables. [online] Available at: https://www.popsci.com/technology/article/2013-07/how-it-works-recycling-machines-separate-junk-type/ [Accessed 18 Feb. 2020].

[4] Group, B. (2020). Lubo Commingled STARSCREEN®. [online] Bollegraaf.com. Available at: https://www.bollegraaf.com/lubo-systems/lubo-commingled-starscreen-2 [Accessed 18 Feb. 2020].

[5] Dingsmagnets.com. (2020). Eddy Current Separators | Dings Magnetics. [online] Available at: http://www.dingsmagnets.com/Products/eddy-current-separators/ [Accessed 18 Feb. 2020].

[6] Eartheasy Guides & Articles. (2020). Plastics by the Numbers. [online] Available at: https://learn.eartheasy.com/articles/plastics-by-the-numbers/ [Accessed 18 Feb. 2020].

[7] Carrillo, L. (2020). Recyclable thermoset plastics | IST 110: Introduction to Information Sciences and Technology. [online] Sites.psu.edu. Available at: https://sites.psu.edu/ist110pursel/2015/10/20/recyclable-thermoset-plastics/ [Accessed 18 Feb. 2020].

[8] Carrillo, L. (2020). Recyclable thermoset plastics | IST 110: Introduction to Information Sciences and Technology. [online] Sites.psu.edu. Available at: https://sites.psu.edu/ist110pursel/2015/10/20/recyclable-thermoset-plastics/ [Accessed 18 Feb. 2020].

[9] OurAuckland. (2020). How many times can it be recycled?. [online] Available at: https://ourauckland.aucklandcouncil.govt.nz/articles/news/2016/08/how-many-times-can-it-be-recycled/ [Accessed 18 Feb. 2020].

[10] Anon, (2020). [online] Available at: https://www.brackenbox.com/2016/09/13/how-is-metal-recycled/ [Accessed 18 Feb. 2020].