Regional management options for floating marine litter in coastal waters from a life cycle assessment perspective

Abstract Purpose Despite the increasing number of publications focusing on the management of marine plastic debris, most research is carried out using an upstream perspective, focused on sources and pathways of marine litter accumulation, as well as actions to prevent plastics from entering the environment. The aim of this paper is therefore to investigate a combination of waste management technologies for marine litter in order to inform decision-making on environmental impact hotspots at regional level. Method A study of the North Sea German Bight identified existing technologies suitable for the collection and treatment of floating marine debris including, recycling of plastics, mechanical biological treatment (MBT), and landfilling. Processing data for reported marine litter compositions in the region are used to inform the modelling of a waste management strategic plan (WMSP) aimed at valorising various fractions. Hence, collected floating marine litter is separated into derelict fishing gear (DFG) and mixed marine litter (MML) which are sent respectively to a recycling plant for plastic granulates production and to an MBT plant for recovery of metals and electricity generation. Environmental impacts of the WMSP are evaluated using the Life Cycle Assessment methodology and compared with incineration considered as the prevalent waste scenario. Results and discussion As partly expected, the LCA results reveal higher environmental performance in all impact categories for the incineration scenario. In particular, the WMSP contributes to Global Warming Potential (GWP) more than 10 orders of magnitude less than the incineration scenario. However, the breakdown of results related to the WMSP indicates the highest contribution to environmental impacts attributed to electricity and heat generation from refused-derived fuel and emissions at the combined heat and power plant, as well as electricity and diesel consumption. Lowest contributions are attributed to the recycling plant. The sensitivity analysis revealed low contributions to GWP if plastic debris such as DFG is diverted to recycling while toxicity-related categories are improved by efficient metal and energy recovery at the MBT plant. Conclusion Findings of this study show that no single treatment method is enough rather a combination of different treatment pathways should be designed considering the composition and properties of accumulated marine litter in a specific area. However, recovering plastic litter and diverting useful materials from waste-to-energy to recycling improve the environmental performance. Reviews suggest inclusion of valorisation treatment options in future WMSPs of marine litter such as plastic-to-fuel technologies.