Comprehensive Plastic Waste Characterisation to Enhance Landfill Diversion in New Zealand’s Construction Industry

The plastic profile of construction waste is varied and complex, particularly when compared to other waste streams such as timber, concrete, metals, and plasterboard. There are fewer incentives for recycling this low-density, low-value waste stream. Plastic waste generated by construction activities remains poorly characterised, obstructing efforts to optimise reduction, reuse, and recycling practices. To understand its types and sources, and better address plastic waste management, this study audited plastic waste produced across six new-build construction sites in Auckland, New Zealand. A total of 7.2 tonnes of plastic construction waste was collected on-site and audited. Plastics were separated, weighed, and categorised by function and construction stage. Polymer type was determined using Fourier transform infrared (FTIR) spectroscopy. In total, 62% of plastic waste was diverted from landfill through reuse or recycling. On average, 0.61 kg of plastic was generated per m2 of construction. Soft plastics were the most generated by mass (33%), followed by PVC and HDPE pipes (22%), shrink wrap (12%), and expanded polystyrene (5%). The majority of plastic waste was generated in the final stages of the projects. The authors recommend the separation of soft plastic, pipes, shrink wrap, and polystyrene on construction sites, particularly towards the finishing stages of construction.