Environmental assessment of an upscaled production of macroalgae - A prospective Life Cycle Assessment of the Swedish production of Ulva fenestrata

Abstract

Aquaculture, including macroalgae production, is one of the most rapidly growing economies worldwide. Off-shore cultivation of macroalgae, also known as seaweed, is a biomass production recognized to have significant potential as a sustainable food source and is also considered a suitable option for up-scaled production. Despite the acknowledged environmental and profitable benefits and potential of macroalgae production in Europe, there are still many existing knowledge gaps and challenges regarding the topic and mapping the environmental impacts of new potential blue foods is necessary. Therefore, this study investigates the environmental impacts of coastal (off-shore) seaweed production by conducting a prospective life cycle assessment (pLCA) on an initiated Swedish cultivation of the green macroalgae, Ulva fenestrata. The study also includes an upscaled future scenario to point out the potential environmental impacts and give insight into how the upcoming Swedish aquaculture practitioners could decrease the environmental impact of their systems. Additionally, life cycle assessment (LCA) lacks clear possibilities for including local marine environmental impacts. By conducting an exploratory literature search of the current state of knowledge regarding local impacts of seaweed cultivation, the thesis strives to holistically review the environmental impacts of the studied seaweed cultivation. Additionally, to find tools and methods for evaluating local environmental impacts and increase the knowledge about how to assess the environmental impacts both within and outside the scope of LCA. The study was divided into three main parts: The base scenario (using pLCA), future upscaled scenario (using pLCA) and local environmental impacts (using exploratory literature search). The data for the pLCA was mainly gathered from interviews, a study visit and contact with researchers and personnel at Nordic Seafarm, KTH and RISE. The pLCA was performed with Excel in combination with the LCA software SimaPro v.9.3.0.3 and information mostly from the databases EcoInvent v.3.8, Agribalyse 3.0.1 and Agrifootprint 5.0. For the future upscaled scenario information was based on the result of the base scenario, academic papers, and grey literature. Information for the exploratory research was collected from academic papers using databases Google Scholar and Scopus. The pLCA results show that dominant factors contributing to environmental impacts proved to be mainly the processes of spore preparation and cultivation, where the components: carrying line, screw anchors, anchor buoys and longlines were dominant. Additionally, diesel and gasoline had high impacts in most impact categories. The sensitivity analysis showed significant changes when investigating e.g., different seeding line options, weight of screw anchors and amount of biomass yield. Factors that contributed to a higher impact were the use of plastics and fossil fuels and the lifetime, volume and duration of the components used in the system. The future upscaled scenario yielded decreases in environmental impacts compared to the base scenario in most impact categories. From the exploratory literature search, several local impacts of upscaled aquaculture and seaweed farming, both positive and negative, that could affect local marine ecosystems were identified—for instance, carbon and nutrient uptake, shading, animal entanglement and seabed damage. Several ways of including local impacts into environmental evaluation exist, including specifically developed characterization factors, ecological risk assessments and specific methodological recommendations. However, further research is needed to find suitable ways to holistically include a broad spectrum of possible local impacts of upscaled seaweed cultivation.