Blue growth and bioextraction potentials of Danish Saccharina latissima aquaculture — A model of eco-industrial production systems mitigating marine eutrophication and climate change

The present study explores the prospect of S. latissima cultivation in Denmark and the economic and environmental implications of detailed system designs and management practices. An environmental Cost-Benefit Analysis (eCBA) of nine S. latissima cultivation systems tested in Danish waters throughout the past decade is conducted based on case-specific data. Overall, five systems are economically feasible with a Net Present Value of 68–446 k €/10-year at a scale of 1 ha and the current technology readiness level. A full carbon footprint accounting is conducted for the systems, covering both carbon capture by seaweed biomass and the embodied carbon footprints of system inputs, the latter of which is quantified by performing a Life Cycle Assessment. Four systems are identified as carbon-negative contributing to greenhouse gas (GHG) emission reductions of 174–1160 kg CO₂ₑq./ha/year. These four systems are also economically feasible, thereby representing potentially replicable models of eco-industrial production systems contributing to sustainable blue growth in Denmark. All systems contribute to local marine eutrophication mitigation via the bioextraction of 1.2–81.6 kg N/ha and phosphorous bioextraction of 0.2–5.3 kg P/ha. This work identifies electricity and manpower as primary hotspot system input for carbon footprint and financial cost. Significant reductions in electricity-related carbon footprints can be obtained by applying sharing economy principle for the hatchery and adopting a greener electricity mix. Direct seeding method has proven more advantageous from the lens of energy and carbon footprints compared with the conventional spore seeding method. This study also provides a deeper insight into the impacts of harvest time on the quantity and quality and more importantly, the valorization potentials of the cultivated S. latissima.