A Look Inside a Recycling Plant

7 October 20200

Recycling is a process where you take items made of a specific material, break it down, and reuse it in some way. The metal can that you rinsed you gets sorted and crushed with thousands of other cans to be processed, melted, and reused. Together, they get melted down and turned into new cans. Paper gets turned into new paper products. Plastic, glass, metal (aluminum and steel), and paper are all materials that can be recycled in many regions. Some districts also accept untreated, unpainted wood scraps, tree branches, and food scraps for composting. While it’s easy to recycle many items, you probably have never thought about what happens after the recyclables leave your driveway. The bin is emptied into a truck, but what happens next?

Single-Stream vs. Double-Stream Recycling Methods

Methods do vary depending on if your recycling company uses the single-stream method or double-stream. Single-stream means all recyclables go into one bin. At the plant, they go onto one conveyor belt and machines separate all of the recyclables into the appropriate category. If your local recycling company uses double-stream, you have a bin that has you separate paper/cardboard from other recyclables. At the plant, there are two conveyor belts. Paper and cardboard go on one and the rest goes on the other belt. Many districts in the U.S. use single-stream. If you have a no-sort recycling bin, your town/city uses a single-stream method. You place these bins out on the appropriate day of the week and a truck comes and hauls them away. You may drive them to a waste district on your own. Either way, what happens next is that trucks bring these items to a recycling plant for processing.

The First Step Involves Separating the Items

Items are separated by rotary screen separators. In a double-stream method, this step isn’t necessary. Air blows from below the rotary screens. That causes paper items to keep moving up the separators to a new conveyor belt. Heavier items like jars and cans fall through the screens to their conveyor belt. Workers monitor the paper products conveyor belt for lightweight plastic or metal items that accidentally make it to the wrong area. They’re removed and sent to the lower conveyor belt. Paper products are moved into bins for the next stage of recycling. On that lower conveyor belt, a cross belt magnet sits over the belt to draw steel recyclables from the belt. The steel is baled and sold to foundries that will melt it down and mix it with new steel to create new metal goods. Recycled steel may be used to make cans, steel beams, sheet metal, etc. Plastic, glass, and aluminum items continue traveling to a machine called an air classifier. This chamber blows air around to force lighter items up and out of the machine. Heavier glass items fall to another conveyor belt for processing. This leaves plastic and aluminum items on the conveyor belt. They all move into an eddy current separator, which is a drum that creates an induction field that will magnetize aluminum. As the aluminum items pass over a magnetic rotor, the force of the opposite poles pushes aluminum items away from it and off the conveyor belt.

How Paper Is Recycled

Paper is made from cellulose (wood) fibers and water. You first have to remove any inks or dyes. A paper mill usually takes over this process. Most recycling plants bale up paper products and ship them off to a paper mill. That’s done in a hot water bath, which breaks it down to the wet, mushy paper form known as pulp. Once it’s in a pulp form, it’s filtered to remove impurities like glue and ink. After the first filtration step, it goes into a de-inker that’s an aerated tank with surfactants and more water that removes the inks. Inks are lighter and float to the surface. The pulp is heavy and sinks to the bottom. It’s removed and used to create new paper products.

How Glass Is Recycled

Glass continues on its new conveyor belt into a drum where it is shattered into pieces of a certain size. While clear glass is made of silica, limestone, and soda ash, there is also colored glass that cannot be melted down with the clear glass. Colored glass needs additives like iron and sulfur and dyes that make it blue, green, brown, etc. Colored glass has to be processed in each color due to the dyes and additives. Workers or camera systems sort the smaller pieces of glass into these different colors. Once all of the glass pieces are separated, they’re smashed into much smaller pieces. This fine glass is known as glass cullet. It is melted at a low temperature in order to be poured or molded into new glass items.

How Aluminum Is Recycled

Aluminum is put into shredders that chop it into small pieces that are easy to melt. Once melted, it’s poured into molds. Those molds end up in manufacturing plants where they are turned into aluminum sheets and reused for different products. An aluminum sheet may be turned into beer or soda cans. It might be turned into products like decorative or DMV-issued license plates, aluminum foil, or pie plates.

How Plastic Is Recycled

This leaves plastic. Plastics come in several types depending on the resin used to create that item:

  • #1 (PET) – Polyethylene Terephthalate is used for food and drinks as it blocks oxygen from getting in and carbon dioxide from getting out. Its purpose is to keep food and drinks from going bad.
  • #2 (HDPE) – High-Density Polyethylene creates a stronger product due to the polymer chains. It’s often used to make shampoo bottles, skin cream bottles, and bottles for medications.
  • #3 (PVC) – Polyvinyl Chloride is commonly used to make pipes. It cannot be melted down and has to be ground into a powder, which makes it harder to recycle.
  • #4 (LDPE) – Low-Density Polyethylene is used in many things. It’s what trash bags, food storage bags, and dry cleaning bags are made with. It’s thinner but durable.
  • #5 (PP) – Polypropylene stands up to heat, so it’s commonly used as the outer covering of a diaper or for hot foods packaged for restaurant takeout.
  • #6 (PS) – Polystyrene is most commonly called styrofoam. It is not easy to recycle.
  • #7 (Other) – When you reach #7 plastic, you’re usually getting a plastic that contains several types of plastic. It’s very hard to recycle, so you may not get your waste district to take it. Because it’s hard to recycle, some manufacturers no longer use it. You may find that your water cooler jugs, reusable water bottles, and baby bottles are made from #7.

How can all of these different plastics get sorted? Some plants use workers to check each item and sort it by number. Newer plants have infrared sensors that use light to determine the type of plastic and sort them based on that information. Some plastics are not worth recycling and go into the trash instead. Styrofoam is one of them. While it could be melted down, it changes the structure, so it isn’t worth the cost. PVC has to be converted into a powder at specialty plants due to the toxins it releases if it is melted down. Other plastics are melted down and turned into new items like clothing, carpet fibers, water bottles, soda bottles, etc. The more that gets recycled responsibly, the better it is for the planet. You may be able to recycle more than you realize. While waste districts used to mail guides, more are skipping that step and expecting people to look for the latest update online. Discover an easier way. Visit Recycle Nation and enter your ZIP code and item you want to recycle. You’ll know exactly where to bring your items along with hours and contact information.

Source: https://recyclenation.com/2020/08/a-look-inside-a-recycling-plant-how-your-items-get-sorted-and-recycled/

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