This study explores the design of a sustainable closed-loop supply chain for Polylactic Acid (PLA), a bioplastic derived from organic raw materials with high starch content. The aim is to provide a viable alternative to hydrocarbon-based polymers and contribute to reducing plastic pollution. The supply chain encompasses the fermentation process to produce lactic acid and its subsequent polymerization into PLA, along with the reception and processing of returned PLA for composting. A multi-objective optimization approach addresses three key objectives: operational costs, environmental impact, and collaboration with local suppliers. A comparison is made between the multi-objective approach and a single-objective approach. While previous research has explored technical aspects of PLA production and composting, no studies have focused on the design of a multi-objective closed-loop supply chain for PLA. This research fills that gap and provides insights into the potential of sustainable supply chains for bio-plastics, offering a step forward in the transition towards more environmentally friendly production systems.