Post-industrial and post-consumer waste may be made of the same material, yet still require very different recycling processes. The reason lies in their origin and in everything that has happened to them before they reach the plant.
A scrap cut directly from a factory is usually in a more controlled condition than a container that has already been used, collected and sorted. This affects the uniformity of the material, the level of contaminants and the preparation required before it can be recycled.
At Silmisa, we design and manufacture machinery for recycling plastic and other materials. In this article, we explain the differences between post-industrial and post-consumer waste, and how these differences affect their processing
Post-industrial waste
These are the waste materials produced during a manufacturing process before the product is put to use. This may include offcuts, surplus material, rejected parts, scrap, burrs or other waste that is not part of the main production run.
One of its advantages is that its origin is usually clearly identified. The factory knows what material it is using, which production line it comes from and, if it is sorted correctly, it can maintain fairly consistent characteristics from one batch to the next.
Post-industrial recycling can be more straightforward when the waste arrives clean, sorted and with a known composition. Even so, it is advisable to check each waste stream. Industrial waste may also contain paints, adhesives, metals, other plastics or mixtures that require the material to be pre-treated before it can be reduced or reused.
Post-consumer waste
They come from products that have already served their purpose. Containers, parts, packaging, tyres or appliance components may fall into this category when they are no longer in use and are channelled into a collection and treatment chain. There is usually greater variation within this stream. The material may come from different sources, become mixed during collection, and carry labels, product residues, soil, metals or other components.
For example, post-consumer plastic may contain a variety of polymers, colours, sizes and levels of contamination. Before recycling it, it is important to know what it contains and to separate out anything that should not be mixed together. The more heterogeneous the input, the more work is required to produce a stable fraction.
Differences between post-industrial and post-consumer waste
The first difference lies in their origin. Post-industrial waste comes from the manufacturing stage. Post-consumer waste, on the other hand, has already been used and reaches the recycling stage after a longer chain of events.
From that point onwards, other factors come into play that directly affect the processing. Industrial waste generally offers greater control over composition and consistency, particularly if the factory sorts its waste properly from the outset. Post-consumer waste may contain more mixtures and show greater variation from one batch to the next.
Pollution also varies. Post-consumer waste may contain traces of use, dirt or substances added to the product. In contrast, many industrial residues are cleaner, although this always depends on the process from which they originate.
Therefore, whilst the origin provides guidance, it is the actual condition of the waste that determines the process. A well-sorted post-consumer material may require less preparation than industrial waste consisting of various components that are difficult to separate.
How does the recycling process vary depending on the source of the waste?
Before choosing the machinery, it is important to understand the characteristics of the material arriving at the plant. Its origin helps to anticipate certain requirements, but the decision also depends on its composition, the degree to which it is mixed, the level of contamination, and the end result we are aiming for.
In post-industrial recycling, a clean, separated stream may require only a few stages before it can be reused. If it contains various materials or residues from the manufacturing process itself, additional preparation stages will be needed. In post-consumer recycling, greater attention usually needs to be paid to sorting and cleaning, as the input material can vary considerably.
Each stage has a specific function, and not all waste has to go through all of them.
Sorting and preparation of the material
The first step is to separate materials that should not remain together and remove any items that might affect the rest of the line. Effective sorting helps to ensure a more uniform feed, reduces unnecessary mixing and prepares the waste so that the subsequent equipment can operate more reliably.
Size reduction
Industrial shredders prepare large parts for the subsequent stages and help to separate components that arrive joined together. The output size must be adapted to the subsequent process. Shredding too much increases energy consumption and wear and tear, whilst leaving parts too large can make sorting or handling difficult.
Washing and removal of contaminants
When the material contains soil, adhesives, product residues or other dirt, a plastic washing plant can remove a large proportion of these contaminants before the process continues. This stage is particularly important in certain post-consumer waste streams, although clean and properly sorted waste may not require it.
What factors influence the choice of recycling machinery?
Two types of post-industrial waste made from the same material may require different equipment. A change in their form, composition, level of contamination or required output is enough to necessitate a change in the way they are treated.
Before specifying a machine or a complete production line, there are several points to consider:
- Origin and composition: knowing which process the waste comes from and what materials it contains helps to determine which stages will be required.
- Consistency: a stable input allows us to work with more consistent parameters and reduces unnecessary changes during production.
- Contamination: soil, adhesives, organic matter, liquids or metals may require preliminary cleaning or separation stages.
- Input parameters: size, hardness, thickness and shape determine the feed rate and the type of reduction required for the material.
- Required output: the number of kilograms per hour that the plant must process affects the capacity and configuration of all the equipment.
- Desired outcome: the end-use determines the size, cleanliness and degree of separation required for the recovered fraction.
The machinery is selected on the basis of the entire process. Focusing solely on the type of waste can lead to the addition of unnecessary equipment or, conversely, to omitting a stage that is essential for producing a usable material.
From waste to a material ready to be reintroduced into the production process
Proper recycling involves processing waste to produce a material that can be reused under known conditions. To achieve this, it may be necessary to sort, shred, wash, remove contaminants or combine several of these stages.
The better we understand the origin and condition of the waste, the easier it is to decide what treatment it requires. This avoids over-processing the material and helps to maintain a more consistent output.
At Silmisa, we design and manufacture industrial recycling machinery tailored to the input material, the plant’s production requirements and the desired end result. We analyse each process to determine the necessary equipment and prepare the waste so that it can continue its journey within a new production chain.