Executive Summary: Sustainable Jewellery

Summary of Project and Key Findings:
This project explored how agricultural and forestry wastes and by-products can be transformed into natural colourants for biodegradable plastic jewellery. Fruit and vegetable powders such as beetroot, pumpkin, spinach and blueberry, along with forestry by-products such as pine bark tannins, were used to colour PHA biopolymers, which were then processed via extrusion and injection moulding into prototype bangles and test pieces. The work was carried out with fashion brand Loopback Limited to support lower-impact, circular material options for jewellery.

A key finding is that whole, freeze-dried powders are more effective than extracted and purified pigments. Extracted pigments, even when encapsulated, were less stable and required more energy, chemicals and processing time. Whole powders produced strong, attractive colours in both PHBV and PHBH, with PHBH providing greater vibrancy due to its lower processing temperature. Seven new colourants were demonstrated, and the resulting jewellery samples were reviewed and approved by Loopback Limited.

Colour can be further tuned by adjusting pigment loading, adding whitening agents such as TiO₂, and changing processing conditions, although TiO₂ raises environmental concerns and alternatives such as calcium carbonate and kaolin should be explored. UV exposure tests showed that natural pigments fade over time, so future work will need to address long-term colourfastness and protective strategies. Overall, the results confirm strong commercial potential for jewellery made from biodegradable polymers coloured with upcycled food and forest waste.

TRL at start of project = TRL 4 Small scale prototype built in laboratory environment (‘ugly’ prototype)
TRL at end of project = TRL 4 Small scale prototype built in laboratory environment (‘ugly’ prototype)