Chapter 8: The environmental impact of HDPE mechanical recycling: Case studies from the Norwegian aquaculture industry

Life cycle assessment (LCA) enables the quantification of how use, reuse, and recycling methods affect the environmental footprint of gear types from the aquaculture industry. Several Norwegian actors have recently proposed new solutions for the end-of-life treatment of used aquaculture equipment, including chemical recycling of nets and mechanical recycling of ropes and pipes from floating aquaculture farms. Concurrently, the fishing industry faces similar challenges concerning discarded or abandoned fishing equipment, and methodologies employed in aquaculture can also be applied to the fishing industry. In this chapter, LCA is used to quantify the global warming potential (GWP) for aquaculture cases. The cases have been selected by screening front-runners in the field of producing and recycling equipment. The cases are (1) a comparison of incineration vs. mechanical recycling of HDPE originating from aquaculture components, and (2) a cradle-to-gate production of an aquaculture floating collar made from recycled high-density polyethylene (HDPE). Results obtained from these case studies, which aim to understand plastic waste management today and potential improvements in the future at both company and systemic levels, are presented in the chapter. In case (1), utilising a recycling facility located 100 km from the collection point results in 119 kg CO₂-eq being emitted by treating 1 tonne of aquaculture HDPE plastic, primarily due to the building (68%) and the mechanical recycling line (32%). Incineration produces 2,433 kg CO₂-eq., primarily from the incineration itself (96%). In case (2) we find that using recycled plastics for a floating collar significantly reduces the carbon footprint, with a 1% increase in recycled plastic content in the component lowers emissions by approximately 0.3 tonnes CO₂-eq. Virgin HDPE would result in 41 tonnes of CO₂-equivalent (CO₂-eq.), while 100% recycled HDPE would reduce this to 11 tonnes. The described results aim to guide manufacturers and users of plastic products, as well as policymakers, in developing a methodology to assess pathways for establishing sustainable circular plastic value chains that reduce waste from the fisheries and aquaculture industry.