Recycling of Metallized Plastic as a Case Study for a Continuous Sustainability Improvement Process

Emerging technological processes should be designed and operated according to the highest technological performance and sustainability standards. For this reason, assessments should be included during the design stage to track technological, environmental, economic, and social sustainability impacts. This study presents the concept of a Continuous Sustainability Improvement Process (CSIP) with the case study of project ReComp (Development of an Economically and Ecologically Sensible Recycling Method for Metal/Plastic Composites). In this project, metallized plastic production waste from the automotive industry was recycled to produce high-purity copper (Cu), chromium (Cr), and plastic, i.e., Polycarbonate/Acrylonitrile Butadiene Styrene (PC/ABS). Through CSIP, two stages of ReComp were developed, ReComp I and ReComp II. ReComp I was found to provide a significant environmental improvement compared to the primary production for Cu, Cr, and PC/ABS (>90% improvement for all environmental indicators). However, it was calculated as making 17,000 EUR/annum loss, with a unit processing cost of 103 EUR/kg of waste input and therefore was deemed as not economically sustainable. From this outcome, ReComp II was developed with the purpose of improving the economic outcome by increasing the process's throughput without the need for significant additional costs. Therefore, the mechanical treatment at the first process step was modified in such a way that the metallized plastics were separated into two fractions, metal flakes and plastic particles. Using these fractions in two parallel process streams, the cycle time was reduced from 15 to 5 days, and throughput of the process-limiting step (electrochemical treatment) increased. Although still not profitable, ReComp II was shown to reduce the process cost per kg of waste input by 93% compared to ReComp I, whilst maintaining the same revenue per kg of waste input. Additionally, ReComp II was shown to provide an improved environmental outcome compared to ReComp I. Therefore, this study proves an important result that a more ecologically sustainable solution can correlate with a more economically sustainable process, due to lower waste formation as well as less material and energy use.