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Students will learn about the challenges waste management centers face and different methods they use to sort recycling. In small teams, students will brainstorm and design a system to sort a mixed-up recycling bin.
Age Levels: 8 – 14
Place design on a long table (or a few short tables placed together), add recyclables to the design and document how well each design sorts the recyclables into separate bins.
Inside a Recycling Facility
Every day at the Sims Municipal Recycling facility in Sunset Park, Brooklyn, roughly 800 tons of recyclables are sorted. (Video 4:43)
Source: Science Friday YouTube Channel
Check out these cool factory robots on robots.ieee.org
AI-driven Sorting Robots
MIT and CSAIL* developed “RoCycle” a robot that can automatically sort recyclables. http://news.mit.edu/2019/mit-robots-can-sort-recycling-0416
Source MIT News
You are an engineer working to design a system to sort a mixed-up recycling bin. The goal is to gain an understanding of the challenges waste management centers face and different methods they use to sort recycling.
Student Reflection (engineering notebook)
The lesson can be done in as little as 1 class period for older students. However, to help students from feeling rushed and to ensure student success (especially for younger students), split the lesson into two periods giving students more time to brainstorm, test ideas and finalize their design. Conduct the testing and debrief in the next class period.
Divide into teams
Review the challenge and criteria constraints
Brainstorm possible solutions (sketch while you brainstorm!)
Choose best solution and build a prototype
Test then redesign until solution is optimized
Reflect as a team and debrief as a class
What is Single-Stream Recycling?
Single-stream (or no-sort) recycling is a system in which recyclables, such as paper, metals, plastics, and glass, are mixed together rather than being sorted by citizens before collection. In a single-stream recycling system, people don’t need to separate their recyclables. Instead, all recyclables are collected in a single truck, and then are separated for reuse at a materials recovery facility (MRF). At a MRF, materials are separated using conveyor belts and multiple separation methods. Once the materials are separated, they are collected together and sold for reuse.
Single-stream recycling means there are fewer barriers to recycling for citizens. The hope is that since it takes less effort to recycle, more people will do it, and more materials will be collected. In Minneapolis, the switch to single-stream recycling lead to a 29 percent increase in recycled materials within a few years.
Single-stream recycling also makes the collection of recyclable materials cheaper, easier, and safer. Recyclables can be collected in one single-compartment truck, which costs much less than multiple-compartment trucks. Collecting recyclables in a single compartment also makes the job easier and safer for materials collectors.
Single-stream recycling comes with a number of disadvantages as well. Since recyclables need to be sorted before they can be sold, the cost to process them is higher. It costs about $3 more per ton to process recyclables in a single-stream system.
There’s also a higher chance that recyclables will become contaminated. Contamination can happen when materials that can’t be recycled get mixed in with those that can. This can slow down or stop sorting at MRFs. Broken glass and wet paper can also get mixed in with other recyclables. This can mean that the recycled materials are worth less when sold. It can even mean that some materials that would normally be recycled may end up in the landfill.
How It Works
MRFs use an elaborate mix of machinery to sort materials. Some of these machines are fairly basic and mechanical, while others use newer and more sophisticated. Materials are spread out on a conveyor belt, then moved through a series of machines, such as a cardboard screen, a fines screen (which sorts out materials less than 2 inches long), a newspaper screen, magnets, and optical sorters that can detect and remove different types of plastics, and various other sorters and balers. Technologies like infrared sorters can be used to identify different kinds of plastic, image processing systems can sort materials based on color, and electromagnetic sensing technology can be used to eject metal objects from the main conveyor belt. At some point in most systems, people are also needed to remove unwanted objects by hand.
How You Can Help
When a single-stream recycling system is running smoothly, it can mean saving more recyclables from the landfill and helping to keep recycling profitable. If you live in an area that uses single-stream recycling, you can help make this happen by closely following the recycling rules and guidelines put out by your local recycling center. Following these rules means recyclables will arrive at the MRF facility in the best possible state for sorting. Some simple rules to follow are making sure loose plastic bags and unrecyclable plastics stay out of the recycling bin, and making sure that your recyclables are rinsed and allowed to dry, since wet paper and cardboard can’t be recycled.
The Baltimore Harbor Trash Wheel Project, affectionately known as Mr. Trash Wheel, uses a turning wheel to scoop trash and debris out of the water and collect it into a dumpster barge. The current from the Jones Falls River, which flows into the harbor, powers the trash-scooping wheel. On days when the current isn’t strong enough to turn the wheel, solar panels provide backup power. Mr. Trash Wheel has collected more than 999 tons of trash since May 9, 2014. What parts of the Baltimore Harbor Trash Wheel’s design do you think are the most helpful and important? Why do you think it is so important to a city like Baltimore? Think about where you live. Are there areas of your community that could use an inventive cleaning machine? What sort of cleaning machine would you create to help your community? What benefits would it bring? What challenges would it face?
Note: Lesson plans in this series are aligned to one or more of the following sets of standards:
MS-LS2-5 Ecosystems: Interactions, Energy, and Dynamics
ETS1: Engineering Design
ETS2: Links Among Engineering, Technology, Science, and Society
The Nature of Technology
Technology and Society
Abilities for a Technological World
In a single-stream recycling system, a series of machines is used to sort mixed recyclables into their correct categories. In this activity, you will work in teams and as a class to design a system to sort mixed recyclables (plastics, glass, steel cans, and paper) into their four categories.
1) Working in teams of 3 or 4, brainstorm ways to separate each type of recyclable from the mixed bin. You should feel free to get up and examine the different materials available. Your team is allowed to help run the system, acting as part of the machinery (students can pull materials on a conveyor belt, bump and agitate materials, etc.), but you cannot directly handle the recyclables. The paper recyclables are also required to remain dry.
2) As a team, choose your best ideas for separating each type of recyclable. Then combine these ideas together to create a full system for sorting the entire bin.
3) Sketch out your design and present your team’s plans to the class.
4) The class will vote on the best ideas and create a new, final design.
5) A designated member of each team will work to build this system using the available materials.
6) The building team will test the system. Watch to see how the system works.
7) Discuss with the class what worked and what didn’t. Brainstorm ways to improve the system and decide what changes should be made.
8) The building team will make the changes and test the improved system.
9) Discuss with the class what worked and what didn’t. What changes helped improve the system? What changes didn’t? If you were going to build a third version, what other changes would you make?
1) What were the characteristics (magnetism, weight, etc.) of each type of recyclable that allowed it to be sorted? What other characteristics and methods of sorting do you think could be used?
2) How important do you think human eyes and hands would be to a single-stream sorting process? When and for what materials do you think people would be needed most?
3) Given the advantages and disadvantages of single-stream recycling, do you think it’s a worthwhile system? Why or why not?
4) What do you think could be done to improve recycling where you live?