The Different Types & Methods Of Recycling

In the guide below, we list and explain the different types and methods of recycling.

We discuss mechanical vs energy vs chemical recycling, primary vs secondary vs tertiary recycling, recycling by waste material type, and more.

 

Different Types Of Recycling

Some of the main types of recycling might be categorised in the following ways:

– Mechanical, energy and chemical recycling

– Primary, secondary and tertiary recycling

– By waste material type, and by recycling facilities that process different types of waste

– Plus, other types and categories of recycling

 

Mechanical vs Energy vs Chemical Recycling

There’s a difference between mechanical, energy and also chemical recycling.

A description of each might include:

 

– Mechanical Recycling

Mechanical recycling has been, and still is one of the most common forms of recycling for various waste materials

It’s the recycling of waste material without changing (or significantly changing) it’s chemical structure

If we use plastic as one example, the general mechanical recycling process involves collecting, sorting, washing, drying, melting and reforming plastic waste material

According to twi-global.com, it may also include shredding, grinding, and re-processing (instead of melting)

bluevisionbraskem.com also has a good infographic of the mechanical recycling steps, where pelletization takes place (which involves agglutination, extrusion and cooling), before plastic becomes raw material or new plastics.

 

– Energy Recycling

Energy recycling is the recovery of energy or heat from manufacturing or industrial processes that normally would have been wasted, or discharged elsewhere

Heat energy may be recovered and either returned to the production process to be re-used, converted to steam, or converted to electricity

Electricity can be generated when steam is used to turn turbines

According to wikipedia.org, equipment like ‘waste heat recovery boilers’ can be used to capture heat in the areas it’s released, and re-use it

 

– Chemical Recycling

Chemical recycling can also be referred to as either molecular recycling, feedstock recycling, or advanced recycling

Chemical recycling involves chemically or thermochemically breaking materials back down into their raw materials (i.e. the chemical structure of the material is changed to revert back to the molecular level)

Once broken down, these raw materials can be converted back into new materials

There’s various processes (and technologies) that can be used for chemical recycling, with depolymerisation and pyrolysis being two of them

Chemical recycling can be used where waste materials aren’t easily mechanically recycled, although it’s not used at the scale mechanical recycling is at the moment

One example of chemical recycling might be breaking down some textiles to the molecular level.

Another example is chemically recycling plastic. In the case of plastic, plastic polymers are broken back down into individual monomers

 

Using plastic as an example, cen.acs.org indicates there’s two processes that can be used:

‘Depolymerization can break down polyester and polystyrene into their raw materials for conversion back into new polymers.

And pyrolysis can turn mixed plastic waste into naphtha, which can be cracked into petrochemicals and plastics.’

 

What Is Advanced Recycling?

As mentioned above, advanced recycling is another phrase used to describe chemical recycling

It’s called advanced recycling because it’s a newer and different form of recycling than traditional forms of recycling like mechanical recycling

It has different capabilities than traditional mechanical recycling

 

Primary vs Secondary vs Tertiary Recycling

There’s a difference between primary, secondary and also tertiary recycling.

A description of each might include:

 

– Primary Recycling

Primary recycling is the mechanical recycling of waste materials into a product that serves the same or a similar use as the original use

To do this, the recycled material usually has to maintain a similar or the same quality too

Primary recycling is sometimes called ‘closed loop recycling’, because the product is kept in circulation (and away from landfills and waste disposal), and can be recycled without degradation in quality

An example of primary recycling might be recycling used plastic bottles into more of the same plastic bottles

 

– Secondary Recycling

Secondary recycling is the mechanical recycling of waste materials into a product that has a different use (which is usually a downgraded or less demanding use) to the original use

It might involve a degradation of the quality of the material too

Secondary recycling is sometimes called ‘open loop recycling’, because the product can’t be recycled indefinitely, and eventually leaves the utlisation loop (of being able to be used for the same product, or, being able to keep the same quality)

Repurposing, upcycling, and downcycling might be considered forms of secondary recycling

An example is repurposing or downcycling plastic products like plastic bottles into carpeting or plastic fibres

 

– Tertiary Recycling

Compared to both primary recycling and secondary recycling which each use mechanical recycling, tertiary recycling uses chemical recycling

Tertiary recycling involves completely breaking a product down molecules or raw material (sometimes referred to as feedstock) using a chemical process, and then using those raw materials (or feedstock) for a completely new product

Tertiary recycling can be referred to as ‘feedstock recycling’ for this reason

An example according to sciencedirect.com is ‘Waste plastic is used as the feedstock in a process that generates chemicals and fuels. An example of tertiary recycling is the glycolysis of PET into diols and dimethyl terephthalate that can then be used to make virgin PET’

 

Other Types Of Recycling

Some of the other ways to categorise recycling might include:

– Municipal vs Industrial Recycling

Municipal recycling is the recycling of municipal waste

Industrial recycling can involve the recycling of materials from manufacturing, construction and demolition, and so on

 

– Internal vs External Recycling

According to wastemanagement.conferenceseries.com: ‘Internal recycling is the reuse in a manufacturing process of materials that are a waste product of that process and external recycling is the reclaiming of materials from a product that has been worn out or rendered obsolete’

 

Recycling By Waste Material Type, & Recycling Facility Type

Recycling can also be categorised by the waste material type being recycled, or by the type of recycling facility.

 

Recycling By Waste Material Type

Some of the main ways to categorise recycling by individual waste materials might include:

1. Paper & Cardboard Recycling

2. Metal Recycling (especially Steel or Aluminum Recycling) – some metals are some of the most recycled materials in the world or in specific countries

3. Glass Recycling

4. Plastic Recycling

5. Timber Recycling

6. Fabric & Textile Recycling

 

Recycling Facilities

Recycling facilities can be classified by the main type or types of waste materials they recycle

For example, there may be dedicated household waste recycling facilities, or dedicated glass recycling facilities (that focus mainly on recycling these types of waste)

 

Different Methods Of Recycling

The methods of recycling can differ depending on the type of recycling used e.g. mechanical, energy and chemical recycling.

The technology and equipment used at a recycling facility can also impact the methods and processes used at a recycling facility.

Somewhere like San Francisco for example may have more advanced recycling facilities than other places in the US, whilst glass recycling facilities may differ in different countries as well.

 

Potential Pros & Cons Of Recycling

In this guide, we outline some of the potential pros and cons of recycling

 

 

Sources

1. https://bluevisionbraskem.com/en/intelligence/mechanical-energy-or-chemical-the-different-types-of-recycling-work/

2. https://www.csiro.au/en/news/news-releases/2021/advanced-recycling-turning-plastic-waste-into-resources

3. https://www.plasticmakers.org/advanced-recycling/

4. https://cdn.sanity.io/files/dyloixlh/production/3ac0d52182044ebdf10b28cebf5c81ff1eae6de8.pdf

5. https://www.packagingnews.com.au/sustainability/study-supports-aus-first-advanced-recycling-plant

6. https://www.sciencedirect.com/topics/engineering/plastic-recycling

7. https://en.wikipedia.org/wiki/Plastic_recycling#Mechanical_recycling

8. https://sustainablepackaging.org/mechanical-recycling-options/

9. https://www.twi-global.com/technical-knowledge/faqs/what-is-mechanical-recycling

10. https://en.wikipedia.org/wiki/Energy_recycling

11. https://cen.acs.org/environment/recycling/Plastic-problem-chemical-recycling-solution/97/i39

12. https://wastemanagement.conferenceseries.com/events-list/external-recycling-internal-recycling#:~:text=Internal%20recycling%20is%20the%20reuse,worn%20out%20or%20rendered%20obsolete.

13. https://www.plasticsforchange.org/blog/types-of-recycling

14. https://en.wikipedia.org/wiki/Recycling

15. https://www.jefferson-recycling.com/2017/03/different-types-recycling-facilities/

16. https://www.aboutmechanics.com/what-are-the-different-types-of-recycling-plants.htm

17. https://www.zerowastescotland.org.uk/content/waste-and-recycling-facility-types

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