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’
– Open vs Closed Loop Recycling
We mentioned these terms in the guide above.
However, we’ve also put together a separate guide on open vs closed loop recycling.
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
Water recycling is another form of recycling in addition to those above
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