Modelling material flows and cost-benefit of sorting PLA packaging waste in material recovery facilities under different market penetration scenarios

• PLA packaging sortability and economic viability are analyzed using a coupled material flow and cost-benefit model. • PLA does not disturb downstream PET recycling at current market levels. • PLA sorting can be technically and financially viable when it reaches 2.4% of input at material recovery facilities. • Improved sorting efficiency lowers the required amount of PLA for profitable sorting. • Profitable PLA sorting depends on market demands for sorted PLA and gate fees for landfills/incinerators. Currently, bio-based and compostable plastic packaging is generally not sorted at material recovery facilities (MRFs) due to its limited market penetration. Instead, such bioplastics are criticised for contaminating other target streams, such as PET bottles at MRFs, yet there is limited evidence to support these claims. This work aims to fill this knowledge gap with a focus on polylactic acid (PLA) packaging waste, by applying a mathematical model to predict the material flow of PLA within MRFs and evaluates the economic viability of bioplastic sorting under different market penetration grades. Our model shows that under current market penetration, the predicted presence of PLA in the PET bottle stream is 7.8 ppm, which is below the suggested threshold concentration without degrading PET recycling (1000 ppm). This still holds true even under high market penetration conditions (200 ppm), assuming that the sorting sequence is adapted to accommodate variations in input waste composition at MRF. The sorting cost of PLA decreases from 906 EUR/t at current market penetration to 170 EUR/t when 1% of post-consumer PLA packaging material is reached at MRF input streams, with an expected break-even point at 2.4%. Moreover, the required PLA volume decreases with increasing near-infrared spectroscopy NIR sorting efficiency alongside the expansion of PLA packaging applications. Furthermore, labour cost, market demand for recovered PLA, and landfill/incineration gate fees are key parameters that substantially affect the cost model result. Overall, the findings from this work suggest that PLA present at MRFs pose no significant issue in current sorting practices, whereas investing in PLA sorting only makes economic sense under strong market growth scenarios of PLA, to achieve circular bioeconomy goals and recycled content targets.