Turning Marine Waste into Resources: Closed-Loop Recycling of Polyolefin Mussel Farming Nets

Marine plastic pollution represents a critical environmental challenge, with extensive accumulation of waste forming vast “garbage patches” across global oceans. Beyond visible debris, the synergistic effects of UV radiation and mechanical stress from wave action promote the fragmentation of plastic waste into macro-, micro- and nanoplastics. These particles pose a severe threat to marine ecosystems and human health through ingestion and bioaccumulation. The fishing industry significantly contributes to this issue through Abandoned, Lost or otherwise Discarded Fishing Gear (ALDFG) that continue to trap and kill marine life, causing the so-called “ghost fishing” phenomenon. A similar environmental burden is generated by mussel farming nets, which are traditionally manufactured from non-biodegradable polymers. During their operational life, these nets accumulate significant organic and inorganic fouling, making their recovery and conventional reuse economically and technically challenging. Current literature primarily explores two mitigation strategies: the adoption of biodegradable materials and the reuse of the nets after appropriate cleaning. However, from an industrial standpoint, mechanical recycling offers superior scalability and efficiency for producing high-quality secondary raw materials. This study proposes a closed-loop mechanical recycling route for mussel nets as a sustainable alternative. The first part of this work is devoted to identifying a cleaning process that achieves the highest level of cleanliness, thereby producing the highest-quality secondary raw material possible. Next, virgin nets (VN),cleaned mussel nets using the treatment identified as the most effective (CN) and densified nets (DN) and were comprehensively characterized through ATR-FTIR, DSC, TGA and rheology. Fibers obtained from reprocessed DN exhibited promising rheological and mechanical characteristics, confirming the feasibility of reintroducing this waste into its original application cycle.