Where plastic packaging is required to be black in colour, WRAP encourages retailers, brand owners and packaging manufacturers to use detectable black colourants to enable the environmental benefits of recycling black plastics to be fully realised.
The majority of black plastic packaging is coloured using carbon black pigments which do not enable the pack to be sorted by the optical sorting systems being used widely in plastics recycling. As a result, black plastic packaging commonly ends up as residue and is disposed of in landfill or recycled into lower value materials where polymer sorting is not required.
WRAP has worked in partnership with key players in the retail supply chain to improve the recyclability of black plastics and prevent these materials from going to landfill.
This work was carried out in three phases and based on the results of this work, it is recommended that detectable black colourants be used as a viable option to carbon black pigments in the manufacture of black packaging such as amorphous polyethylene terephthalate (APET), crystallised polyethylene terephthalate (CPET), polyethylene (PE) and polypropylene (PP) packaging.
By selecting a detectable black colourant that enables the polymer to be detected by optical sorting systems the packaging supply chain can enable black plastic packaging to be recycled into a high quality, high value material which can substitute for virgin plastic in the manufacture of new items, and benefit the environment as well as the financial viability of mixed plastics recycling.
A range of potential solutions was investigated including the use of alternative sorting technologies and alternative coloration systems. Novel NIR (near-infrared) detectable black colourants were developed and shown to look satisfactory in APET, CPET and PP food trays, and enable the packs to be sorted by polymer using NIR sorting systems used commercially in plastics recycling. It is anticipated that the incremental costs of using detectable black colourants will reduce over time as demand and volume increases.
WRAP investigated the masking strength (covering power) of the novel detectable black colourants in more detail. The ability to mask mixed colours is helpful to plastics processors as it allows them to re-use production waste and off-cuts of all colours. A key finding from this phase of work was that UK converters generally do not mix coloured skeletal waste and therefore inferior masking strength is not a limiting factor for most converters in the UK.
The objectives of this work were to ensure that UK plastics sorters are able to sort detectable black plastic (particularly PET) into the correct polymer and colour streams and to identify end markets for coloured jazz rPET containing detectable black APET and CPET. Our research reveals:
- plastic recyclers can sort packaging with the detectable black pigments by polymer type and colour without adversely affecting the value of other streams (such as clear PET or CPET);
- end markets are available for coloured PP (polypropylene) and PET; and
- there is potential for closed-loop recycling of black CPET for the very first time.
Under current conditions, black CPET trays are not detected by optical sorters, and end up being missed and sent to landfill and/or energy from waste. Previous WRAP work demonstrated that CPET trays manufactured with an alternative black dye pigment could be identified and recovered by equipment, thereby potentially diverting this material from the waste stream.
This trial aimed to take this test on a wider scale, working with Marks & Spencer, Sainsbury’s and other leading industry organisations to manufacture, distribute and recover detectable black CPET trays through household recycling collections. Once recovered at the material recovery facility (MRF), the trays would be flaked and assessed for their suitability for remanufacturing into food grade black CPET trays.
The project demonstrated that it is possible to incorporate detectable black pigments into ready meals products, recover the trays, sort and recycle these back into food grade trays. The availability and recovery of enough detectable black CPET material is paramount for the closed loop process to work. This requires investment and support to prove its operational and economic viability in full scale commercial conditions.