Nutrients recovery from seaweed biomass with pulsed electric fields and screw press: A pathway for sustainable large scale offshore seaweed farming, sinking and harvesting

Seaweed farming has gained recognition for its environmental benefits, including carbon sequestration and nutrient absorption, positioning it as a potential solution for climate change mitigation and adaptation. However, large-scale harvesting can result in nutrient depletion in marine ecosystems. This study explores the use of pulsed electric fields (PEF) combined with a screw press as a method to recover essential nutrients such as nitrogen and phosphorus from Ulva sp. biomass before it is harvested or sunk for carbon sequestration. We employed a laboratory continuous PEF system to process the biomass, achieving 50.03 ± 2.96 % compression in PEF treated biomass, with respect to control, and particle size reduction 8.61 ± 1.98 mm 2 in PEF treated biomass vs 128.19 ± 24.75 mm 2 in control. The PEF and screw press treatment increased the biomass sinking speed as tested in the lab water tank. In addition, our findings show that PEF treatment facilitates the release of nitrogen and phosphorus, which are crucial for maintaining marine ecosystem health. The recovered nutrients supported the growth of marine bacteria ( Alteromonas sp.), which was the highest in extracts from PEF treated biomass. This approach addresses the challenge of nutrient depletion in offshore seaweed farming and offers a sustainable solution for nutrient recovery, enhancing the overall feasibility and environmental impact of offshore seaweed farming for materials extraction or offshore carbon sinking. • Pulsed electric field (PEF) enables significant nutrient recovery from Ulva biomass. • PEF combined with a screw press enhances volume compression and particle reduction. • Nutrient recovery from seaweed biomass supports marine bacteria growth. • PEF treatment enhances nitrogen and phosphorus release, improving ecosystem health. • Modified sinking velocity of Ulva biomass could faciliate offshore carbon sequestration.