How is Plastic Recycled? A Step by Step Guide to Recycling

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Have you ever wondered what happens to your plastic after you put it in the recycling bin? This article is here to provide the answers...

More and more businesses and people at home are recycling [1] but not a lot of people understand what happens to plastic recycling once it has been put in the recycling bin. There are a number of steps and organisations involved who ensure plastic recycling is transformed into new products.

 

HOW PLASTIC IS RECYCLED - THE BASICS

Plastic that is collected from your homes, businesses, and local recycling centres, is sent to a Material Recovery Facilities (MRF), which separates plastic and non-plastic, and/or a Plastic Recovery Facilities (PRF), which sorts plastic by type. These facilites use sorting equipment such as an optical sorter which can distinguish between between different types of plastics.  The plastic then goes to a reprocesses where it is washed,  shredded and sorted further. The plastic is then melted and extruded a into new recycled plastic pellets. These pellets are sold on for use in new products. This page will now explain each stage in more detail.

 

PAGE CONTENTS

Stages Of Recycling Plastic

Step By Step Detail

Which Companies and Organisations Collect and Recycle Plastic Waste?

Where Can You Deposit Your Plastic Items?

How To Identify What To Recycle

Types of Recycling

Plastics Recycling FAQ's

 

THE STAGES OF RECYCLING PLASTIC

There are a series of stages needed to recycle plastic which involve collecting, sorting, and reprocessing the plastic ready to be used in new products:

Collection &#; plastic  is deposited by the users into a recycling container

Sorting &#; facilities sort plastic from other materials and also into the different types of plastic

Reprocessing &#; plastic is washed, ground into flakes, heated and extruded into new pellets

 

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STEP BY STEP DETAIL

Collection

This is the first stage of the recycling process, it involves the collection of recycling from our homes, businesses, and schools [2]. For this stage it is important that everyone is correctly sorting their plastic ready for collection and recycling all the items they can. 

This recycling is collected by a local authority either directly or using a waste management contractor. 

It is taken to a Material Recovery Facilities (MRF), and/ or a Plastic Recovery Facility (PRF) ready to be sorted. The material may be bulked at a waste transfer station before being transported to these facilities.

Other collection opportunities include recycling centres, front of store or local recycling sites [3].

The collection of plastic is key for the recycling system to operate well. The more plastic suitable for recycling that is collected the more material available to be reprocessed and used back into new products. 

 

Sorting

The second stage is sorting plastic from other materials and this is done at a Material Recovery Facility (MRF). This material may then go onto a Plastic Recovery Facility (PRF) for further sorting into the different types of plastic.

The mixed recycling  will initially be removed from the collection vehicles and then mechanically placed onto conveyer belts.

Conveyer belts are used to maintain the constant flow of waste passing through the sorting facility. A series of techniques are used to separate the material ready for further processing.

Below are some of the sorting techniques. The techniques used in practice will vary by facility. 

 

Manual Picking

Manual picking involves sorting by hand. During manual picking large items, non-recyclables and obvious contamiantion is removed. The items removed are sent for further processing or go for diposal. 

 

Trommels

After non-recyclables have been removed the waste is feed into trommels.[5] Trommels are cylindrical drums with holes that allow finer materials to fall through as the trommel rotates.

 

OCC Screening

The OCC screen separates old corrugated cardboard (OCC) from mixed recyclables.  This is achieved by passing material over a rotating disc system.  The thick discs provide lateral agitation of materials. The cardboard travels across the top of the screen and the other material fall through the rotating dics.

 

Ballistic Separator

A ballistic separator is a mechanical device which consists of two oscillating paddles. These oscillating paddles work in a way that means it moves rigid waste items to one end and flexible items (Paper, card) to the other allowing glass and finer materials to fall through the mesh. The rigid items can be bottles, containers or cans while the flexibles may be paper, card, newspapers, and plastic wrapping. 

 

Magnet Separator

A magnet separator is used to remove any metal that are present. Waste travels on conveyer belts under a magnet where metals are separated and placed into a separate storage bin.

 

Eddy Currents &#; for non-ferrous metals

Eddy Currents separators are used to remove non-ferrous materials such as aluminium and copper from non-metallic material. Non-ferrous materials pass over the shell containing rotating magnets creating eddy currents. In turn this creates a magnetic field around the metals repelling them away from the magnet. This repulsion of the non-ferrous materials separates them from the non-metallic materials. Using an eddy current allows for easy and efficient separation of metals and non-metals.

 

Optic Sorting Machine

This is an important machine for separating different types of plastic.

An optical sorting machine helps to identify plastics at a high and efficient rate using near infrared (NIR) measurements. The NIR sensors are sensitive instruments that measure the absorbencies of samples at specific wavelengths. [15] In this instance identifying types of plastics through their absorption of light. Waste is then separated through upward or downward ejection methods.

Initially, material is fed onto a fast conveyor that causes the material to be spread onto a single layer. A vibratory feeder can be used to feed the material onto the belt because it helps spread the material to the full width of the conveyor. It is scanned by the NIR sensor from around 12 inches away. Different plastics such as PVC have different known NIR spectral images. This allows the scanner to identify that objects' plastic type. Jets of air are used to separate the different plastic types in different directions.

 

Sink-float Separator

Another important method used to separate plastic materials is a wet process known as a Sink-float separator. A tank is filled with water and plastic recycling, the high-density plastic sinks, and low-density plastic floats. The separated plastics will be recovered for more processing.

 

Reprocessing

Once the material has been sorted it will be transferred to a plastic reprocessor for the next stage.  

 

Further Sorting For Quality Control

Some reprocessors will have the equivalent of mini PRFs at the beginning of their processes to undertake further sorting depending on how the material arrives with them. Most facilities will do further sorting even if they purchase already sorted material to ensure any remaining contamination is removed. The sorting may include optical sorting machines and sink float separators to separate plastic by thickness, colour, size, and plastic type. Furthermore, plastic may be rerun through magnets to remove any metals that may have not been completely removed previously [5].

 

Washing &#; Contaminants Are Cleaned Off The Plastic recycling

Washing helps remove adhesives, residual waste left in containers, food waste and labels. It is important that these are removed and the material is as clean as possible as it can affect the quality of the recyclate. 

This stage is where the actions of people at home can make a big difference [3]. By simply rinsing the plastic quickly to get off some of the food or other materials before they become dry and stick more severely helps ensure that the whole recycling system operates more effectively.

During the washing process the plastic may go through a range of washing methods depending on the contamination and processors. Firstly, friction washer which are the most common form of washer due to their low operation cost and effectiveness. Friction washers use heat, kinetic energy, and pressure to wash plastic of contaminants. Rotary washers use a caustic solution that is heated to removes oils and food stuff, depending on the degree of contaminations rotary washers can be used as a pre washer.

 

Shredding / Grinding &#; Plastic Products Are Ground Into Smaller Pieces

A critical stage in recycling plastic is shredding or grinding plastic into smaller flakes.

The washed and sorted plastic is sent through shredding machines where it is ground into smaller pieces of plastic.

The plastic is shredded in different manners depending on the classification and methods of the shredder. An example of a method is Hammer Mills: these are used to pulverize plastics in a rotary drum using swivelling hammers to do so. Other examples being Shear Shredders: using rotary cutters and guillotines to cut plastics to industry size requirements. [16]

Further sorting may take place to ensure a pure stream of material is produced.

 

Extrusion &#; Plastic is Melted and Extruded into New Pellets

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This is the final stage of plastic recycling.

Extrusion is the process of melting down the plastic and forcing this through an extruder. The plastic is cut as it comes out of the extruder to form pellets.

Pellets are sold onto manufacturers.

 

Recycling your plastic bottle or plastic furniture involves several organisations working together. There are varying roles and positions involved in the whole recycling system from the public to manufacturers and designers.

For the recycling system to work efficiently it requires all the independent organisations of the recycling system to work in unison. The public, businesses and industries initially sort and put out their recycling to be collected. From here local authorities and independent waste collectors, collect the recycling and transport it to transfer stations.  The transfer station acts as a central location for the recycling to be collected before it is moved on to a recycling facility, in this instance a MRF or a PRF. Recycling is deposited and loaded onto conveyer belts by recycling facilities workers.  The recycling undergoes various sorting processes before it is sent to reprocessors. Reprocessors wash, shred and extrude the plastic  and process it into pellets. Here manufacturers purchase the recyclate and incorporate it into their products. Designers, brands and retailers  also play a role in the recycling system by designing products so they can be recycled easily and effectively and can incorporate recycled plastic. All these various roles play a part in the recycling system for it to work.

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Kerbside Collection

Kerbside collection is a service provided to communities where household recycling is collected on weekly or bi-weekly schedule. Recycling is collected by the local authorities or by a waste management  contractors working on their behalf. Material is presented by householders in individual or communal bins. Kerbside collection is the most common form of plastic packaging recycling collection. As this is a convenient form of collection for householders it yields high recycling rates.  

 

Recycling Centres

Local authorities provide recycling centres for disposing of larger items of waste or material not collected via the kerbside. Recycling centres will normally accept electrical items and may have a separate area to collect non-packaging plastic such as old garden furniture, toys etc. There are normally also facilities to recycled plastic packaging. Recycling centre are in a centralised accessible location for the public.

 

Deposit Return Schemes (DRS)

DRSs work by adding a small deposit charge to, mainly, drinks prices.  The consumer will receive the deposit back for recycling the item. This deposit is usually redeemed for cash. In some countries, this can yield high recovery rates as the incentivised return promotes recycling. England is consulting on providing a DRS and Scotland already plans to initiative a DRS. 

 

Recycling Sites

Smaller recycling sites are provided in communal areas such as supermarket or councils car parks. They will accept plastic packaging along with other types of plastic items. They may for example also provide facilities to recycle small electrical items.

 

Take back schemes

A variety of take back schemes exist, normally for larger items. When new products are purchased in some cases the company will arrange for the recycling of the old product. An example is electrical items where retailers are obligated to provide a take back scheme for old items.

 

Front of store

Larger supermarkets may offer recycling facilities for plastic film and bags within their stores alongside some other niche products.

 

HOW TO IDENTIFY WHAT TO RECYCLE

On-pack recycling labels are an easy way to identify items recyclability.

Packaging labels are usually found on the back of products and inform whether the product can be recycled or not.

On packaging recycling labels may also provide recycling instructions such as &#;remove cap before recycling &#; or &#;remove sleeve&#;.

Local authority websites will also provide information on recycling for individual areas. Some local authorities will send householders information directly on recycling services.

There is also a recycling locater which is available here. Plastic Recycling Locator - What can you Recycle? (bpf.co.uk)

 

Mechanical Recycling

Mechanical recycling is by far the most prevalent recycling of plastic . It is the traditional method that has been in use for decades, responsible for the vast majority of plastic recycling around the world. Mechanical recycling uses grinding, washing, sorting and reprocessing to repurpose plastic material. The plastic recyclate can then be converted into other products substituting for the use of virgin plastics. [19] This article deals primarily with how plastic is collected, sorted and reprocessed via the traditional mechanical recycling route.

Chemical Recycling

Chemical recycling is the process of recycling plastics through the chemical change of the polymer structure forming a raw material that can be used to manufacture new products [18]. Chemical recycling can deal with plastics that may not be suitable for mechanical recycling. Read a lot more about chemical recycling here.

 

PLASTICS RECYCLING FAQ'S

1. Why should i rinse my plastic waste?

Rinsing where possible before disposing of your waste will make the process of recycling easier at MRFs. It will also help prevent odour from recycling containers.

Washing is important as any contamination could ultimately affect the quality of plastic recyclate produced at the end stage.

Plastic heavily contaminated with food waste may not be picked up by the near infrared sensors (NIR), ultimately leading to its disposal. This is a loss of material which could have been recycled. Therefore, rinsing plastic waste or recyclable materials before disposal is beneficial[5]. It should be noted that generally quick rinsing is preferred to extensive washing as it helps to save water.

 

2. How can I help recycle more plastic?

You can recycle more plastic by:

• Making sure your recycling is placed in the right container when at home, work or on-the-go
• Checking you are recycling everything accepted by your local authority
• Purchasing products that can be recycled or are made from recycled content .
• Identifying product specific recycling schemes in your local area and recycling through these schemes

 

3. Places I can recycle my plastic other than my household collection?

Other places you can recycle are recycling centres, communal recycling bins and recycling sites.

 

4. How do I set up a recycling scheme from my office?

Recycling programmes can be set up by firstly conducting an audit to identify the waste streams and volume of waste generated at your office. Implementing a waste team within the business whose roles will be to improve recycling within the workplace. Clear communication between cleaners/janitors is essential in setting up a recycling scheme. Implementing recycling bins with clear graphic and information to reduce contamination.  Communicate effectively with staff on the importance of recycling and make it clear how to use the recycling scheme in place. Furthermore, regular audits to identify improvements or if improvements need to be made. [20]

 

REFERENCES

[1] &#;We are a nation of recyclers&#; - https://www.letsrecycle.com/news/latest-news/a-nation-of-recyclers/

[2] Municipal Solid Waste - https://archive.epa.gov/epawaste/nonhaz/municipal/web/html/#:~:text=Municipal%20Solid%20Waste%20(MSW)%E2%80%94,schools%2C%20hospitals%2C%20and%20businesses.

[3] Plastic Recycling - https://www.bpf.co.uk/sustainability/plastics_recycling.aspx#s2

[4] The Complete Plastic recycling process - https://www.rts.com/blog/the-complete-plastics-recycling-process-rts/

[5] MRF &#; how does it work- https://www.veolia.co.uk/hampshire/materials-recovery/process

[6] What is the waste sorting process - https://www.slrecyclingltd.co.uk/what-is-the-waste-sorting-process/

[7] From transfer station to MRF - https://www.mswmanagement.com/collection/article//from-transfer-station-to-mrf

[8] Materials Recovery Facility - https://www.britannica.com/technology/materials-recovery-facility

[9] PRNs Explained - https://www.recycle-pak.co.uk/PRNs_Explained.htm

[10] Extended producer responsibility- https://www.oecd.org/env/tools-evaluation/extendedproducerresponsibility.htm 

[11] Kerbside Collection- https://www.buschsystems.com/resource-center/knowledgeBase/glossary/what-is-curbside-collection

[12] Recycling Centres - https://science.howstuffworks.com/environmental/green-science/recycling5.htm#:~:text=Drop%2Doff%20centers,like%20paint%20or%20propane%20gas.

[13] Recycle More - https://www.recycle-more.co.uk/recycling/plastic/plastic-recycling-process

[14] Letsrecycle - https://www.letsrecycle.com/news/latest-news/oprl-launches-binary-labeling-system/

[15] Optical sorting - http://www.eaglevizion.com/optical_sorting 

[16] What is a plastic shredder- https://www.buschsystems.com/resource-center/knowledgeBase/glossary/what-is-a-plastic-shredder#:~:text=In%20the%20process%2C%20large%20plastic,granulated%20and%20sent%20to%20manufacturers.

[17] Extrusion - https://www.ptonline.com/knowledgecenter/profile-extrusion/profile-extrusion-fundamentals/history-and-fundamentals-of-extrusion#:~:text=In%20the%20plastics%20extrusion%20process,the%20barrel%20of%20an%20extruder.&text=This%20allows%20the%20plastic%20resin,cause%20degradation%20in%20the%20polymer.

[18] Chemical Recycling - https://www.plasticsrecyclers.eu/chemical-recycling

[19] Mechanical Recycling technology - https://docs.european-bioplastics.org/publications/bp/EUBP_BP_Mechanical_recycling.pdf

[20] Recycling programmes- https://archive.epa.gov/wastes/conserve/tools/rogo/web/html/index-3.html 

[21] plastic washing machinery - https://plasticwashing.co.uk/#plasticwashhome

In waste plastics recycling process, waste plastics crushing is one of the most important processes, the volume of waste plastic is reduced, which is convenient for subsequent processing. The equipment mainly includes the cutting machine and the crushing machine, whose basic principle is to destroy the material's integrity depend on the shear strength and the impact strength.

Different shredder equipment have their own advantages. Relatively speaking, waste plastic crushing machine is suitable for shredding soft small, broken materials, such as PE film, beverage bottles, EPS shredding machine is suitable for crushing large lump material, rolled into a tube, extruder head materials, such as bundles of woven bags etc..

The commonly used crushing equipment has different kinds of compression type, impact type, shear type, knock type and grind type. The choice of crushing equipment mainly depends on the type, shape and the degree of the grinding material. Different materials should be used in different crushing equipment. Hard PVC, polystyrene, organic glass, phenol formaldehyde resin, urea formaldehyde resin, polyester resin, etc. are brittle plastic. They are fragile brittle, once compressed, are very easy to broke into small pieces, this type of plastic is suitable for crushing.

And for the ductile plastic, such as polyethylene, polypropylene, poly acid amine, ABS plastic, etc., are suitable for shear type polystyrene crushing equipment, because they are easy to be effected by outside compression, bending impact and other forces.

In addition, for elastic materials, soft materials, it is best to use low-temperature crushing. In addition, we should determine the extent of crushing equipment according to the need to crush the waste. If crushing the large pieces into small pieces, we should use compression, impact or cutting equipment; if putting small pieces into fine powder, we should use abrasive grinding equipment.

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