Life cycle assessment (LCA) on waste management options for derelict fishing gear

Purpose: Derelict fishing gear (DFG) is one of the most abundant and harmful types of marine litter that gets increasingly retrieved from the ocean. However, for this novel waste stream recycling and recovery pathways are not yet commonly established. To identify the most suitable waste management system, this study assesses the potential environmental impacts of DFG waste treatment options in Europe. Methods: This study applies an attributional life cycle assessment (LCA) to four DFG waste treatment scenarios, namely a mechanical recycling, syngas production, energy recovery and landfill disposal. The scope spans from the retrieval and transport processes to pre- and end-treatment steps until the outputs are sent to landfill or assumed to substitute products or energy. Primary data was collected from retrieval and waste treatment trials in Europe. Contribution, sensitivity and uncertainty analyses were conducted using the LCA software SimaPro and ReCiPe as the impact methodology. Results and discussion: The results show that the mechanical recycling and energy recovery achieve the lowest potential environmental impacts. The syngas production and landfill disposal scenario are not environmentally competitive because they require too much electricity, or their avoided production credits were too small to offset their emissions. Unlike the pre-treatment and transport processes, the retrieval and end-treatment processes have a significant impact on the overall results. The transport distances, energy mix and market and technological assumptions are least sensitive, while changes to the waste composition significantly affect the results. Especially a reduced lead content benefits the human toxicity impact potential of the landfill disposal scenario. The uncertainty analysis showed that the results are very robust in nine of twelve impact categories. Conclusions: This is the first LCA study that compares waste treatment options for marine litter. The results indicate that a disposal of DFG is hazardous and should be replaced with mechanical recycling or energy recovery. While this may be technologically possible and environmentally beneficial, economic and social factors should also be considered before a final decision is made. To further reduce environmental impacts, marine litter prevention should play a more important role. Graphical abstract: [Figure not available: see fulltext.].