Before starting this lesson, you may want to view the What is STEM? video below.
Many communities transport collected recyclables to a materials recovery facility (MRF, commonly referred to as a “murf”). A MRF is a facility for sorting, separating, and processing trash and recyclables. A MRF may take commingled recyclables such as aluminum and steel cans, plastic jugs, glass bottles, and newspapers and separate them by hand or use mechanical processing. Some MRFs process discarded waste, and extract and separate recyclables from trash that will be landfilled or incinerated.
Here's an example: Homeowners place their trash and recyclables in bags or bins at the curb. The recyclable materials are either collected all together or separated, depending on the community. The collection truck then hauls the materials to the MRF for further processing. At some MRFs, materials go across a screen, separating lightitems like paper,and heavy materials, like glass. An eddy current pulls out aluminum cans. Magnetic separators gather up metals, like steel and tin. Water can separate items that float from those that sink, while fans blow light material like certain types of paper away from the other items in the waste stream. Other types of recycled paper areusually hand picked and separated by grade or type of paper. Additionally, plastic bags are often removed by hand. Both paper and plastic bags can clog the machinery, making human separation necessary. Workers constantly ensure that materials are appropriately sorted during the entire process.
The following photo essay, which you can share with students as part of this lesson, provides more information. (You can also access the PPT version of this essay under Teaching Guides so that you can customize it for your classroom needs.)
After sorting the recyclables according to the manufacturers' end use specifications, the materials are usually baled and loaded onto trucks for transport. These raw materials go to businesses that perform the next step in the recycling process, manufacturing new products.
The new products are then transported to stores for the final step in the recycling process -- purchase by the consumer.