Recycling of plastic-coated cartons in hydropulping using pretreatments

Plastic-coated cartons and multilayer packaging pose significant challenges in recycling due to prolonged pulping times, high energy consumption, and fiber loss. Efficient fiber-plastic separation enables both fiber reuse and plastic recycling, contributing to sustainability goals. This study evaluates the combined effects of hydraulic pressure and perforation as pretreatments to enhance pulping efficiency, reduce energy consumption, and optimize separation. Hydraulic pressure at 0.2 bar achieved 75 % swelling in 10 min and reduced pulping time by 33-67 % across high- and low-consistency pulpers. Perforation enabled swelling of entire cartons without shredding, improving swelling by 30-60 % and reducing pulping time by 25-50 % depending on the pulper type. Together, these pretreatments could cut energy consumption by up to 50 %, translating to annual savings of approximately 1 GWh for factories processing 100 kt of pulp. These findings demonstrate the scalability and economic potential of pretreatments for more sustainable carton recycling.