System dynamics modeling of membrane technology deployment in Australia

Introduction National Packaging Targets have mandated 70% plastic packaging recovery by 2025, yet recovery rates have stagnated at 24%–27%, despite voluntary commitments and $690 million in investment (2018–2024). Membrane technology offers the potential to process contaminated flexible plastics, but deployment economics remain uncertain. Methods This study developed a system dynamics model with eight interconnected feedback loops that govern Australia’s plastic packaging circular economy (2015–2040). The model distinguishes rigid (bottles, containers) from flexible (films, pouches) plastics, incorporates empirical cost structures ($800/tonne mechanical vs. $19,500/tonne membrane), and integrates policy levers (EPR, CDS, and elimination mandates). Historical validation against Australian Plastics Flows and Fates data (2015–2024) achieved <8% error. Five scenarios were simulated to 2040. Results Model validation reproduced voluntary approach failures and the REDcycle collapse. Scenario analysis reveals that attempting 70% recovery through universal processing (Scenario 3) costs $1.18 billion annually while achieving only 57% due to exponential cost escalation above 60%. An 80/15/5 strategy (Scenario 4) that eliminates 80% of unnecessary flexible formats achieves 68% recovery at $510 million annually—2.3 times cheaper with 11 percentage points higher recovery. Marginal costs remain under $25 million per percentage point with elimination versus over $50 million without. Discussion The flexible–rigid plastic divide is fundamental, not transitional. Rigid plastics exhibit profitable recycling activating growth loops, while flexible plastics face catastrophic losses, triggering constraint loops. Elimination costs $130 per tonne and saves $12.4 billion annually in avoided processing—a 150:1 cost–benefit ratio. EPR frameworks that enable elimination are essential; voluntary approaches have systematically failed.