A suitable main polymer does not guarantee correct sorting. Assess the complete pack through the relevant mechanical and optical operations. RecyClass’s Sorting Evaluation Protocol can provide evidence where design features create uncertainty.
Why can packaging made from PET, PE or PP miss the correct stream despite having a suitable main material?
A sorting facility identifies the physical object rather than the manufacturer’s declaration. Dimensions, shape, decoration coverage, mechanical behaviour and optical response can direct packaging into another fraction or the reject stream. Sortability is therefore a key stage of recyclability assessment.
1. Recycling starts before the recycler
Before packaging reaches recycling, it must pass through collection and sorting. If it is not separated into the correct stream, even a well-designed material may not be recovered.
RecyClass therefore treats sorting as an integral part of recyclability assessment.
2. NIR is an important material identification technology
Near-infrared spectroscopy, or NIR, is widely used to recognise plastics on sorting lines.
The system analyses the material’s characteristic response and controls separation of the object. If the body’s signal is obscured or distorted, sorting performance may deteriorate.
3. A large label or sleeve can obscure the body material
If decoration covers a substantial part of the packaging, a detector may recognise the label or sleeve material instead of the main body.
The risk depends on format, materials, geometry and the particular stream. A single universal coverage threshold should therefore not be applied to all packaging.
4. Colour and pigments can hinder identification
Some colouring solutions can absorb radiation or alter the optical response in a way that makes material identification difficult.
Pigment selection should therefore follow the current guidelines for the relevant stream; innovative solutions may require testing.
5. Sorting involves more than NIR
An industrial sorting line may use size screening, ballistic separation, air separation, magnets, eddy currents and optical systems.
The RecyClass Sorting Evaluation Protocol includes a range of such stages to assess packaging behaviour under conditions representative of industrial sorting.
6. Dimensions and shape also matter
Very small items can be lost during screening, while unusual shapes can affect ballistic separation or movement along the conveyor.
Assess the packaging as a physical object, not just a list of materials in a specification.
7. Metal and multi-material elements can change the route
Metal, conductive layers or unusual components can affect behaviour in different separators.
They do not automatically imply a negative result. They do require assessment against the current guidelines and, where uncertainty remains, the relevant testing protocol.
8. RecyClass has a dedicated Sorting Evaluation Protocol
The protocol standardises testing of packaging behaviour during sorting. RecyClass develops it as a complement to material assessment.
An auditor can request an additional sortability test where the packaging has features identified by the methodology as potentially problematic.
9. Sorting performance affects overall recyclability
If a significant share of the packaging misses the intended stream, its material cannot reach the appropriate recycling process.
Improving sortability can therefore be as important as changing an adhesive, barrier layer or another technical component.
10. A common mistake: assuming the main material is enough
This assumption overlooks how sorting facilities work. A label, sleeve, decoration or geometry can completely change a package’s route after use.
Design for recycling must therefore address both compatibility with recycling and the likelihood of reaching the correct recycler.
11. How to reduce risk during design
- Use current Design for Recycling Guidelines.
- Limit decorations that obstruct recognition of the main material.
- Assess the effects of labels and sleeves.
- Consider dimensions and shape.
- Use the Online Tool during concept development.
- Commission a Sorting Evaluation where the design leaves uncertainty.
12. Sortability is a developing field
RecyClass updates its recommendations in response to industrial tests and new research campaigns. An assessment from several years ago should not be transferred uncritically to a new design version.
Record the protocol version, applicable guidelines and test date when documenting the assessment.
Frequently asked questions
Is NIR the only sorting technology?
No. Lines also use other mechanical and physical operations, and the RecyClass protocol covers a wider sequence of processes.
Does a large sleeve always disqualify a pack?
Not automatically. The effect depends on material, coverage, stream and assessment outcome. A test may be necessary in some cases.
Is black colour always a problem for NIR?
That is too broad a conclusion. The particular pigment and current guidelines for the stream matter.
Who can require a sortability test?
During certification, the auditor can identify the need for additional testing where packaging characteristics require it.