Nordic Seaweed Conference

Keynote speaker
Muki Shpigel
Professor of Marine Sciences, University of Haifa

The Use of Ulva in Integrated Multi-trophic Aquaculture (IMTA), an Ecological Approach For
A Sustainable Aquaculture

The scarcity of freshwater, overfishing and declining ocean biodiversity, marine eutrophication by anthropogenic activities, and the increasing demand for seafood have all required attention from a more comprehensive, global perspective. Moving from conventional aquaculture toward an ecological approach to developing and managing a sustainable aquaculture that cares for environmental and sociological aspects can bring relief to at least some of these problematic issues. Nutrient removal using Integrated Multi-Trophic Aquaculture systems (IMTA) is a promising ecological approach for sustainable aquaculture. The rationale behind the IMTA systems is to convert the excretions of the organisms cultured upstream into valuable food for the organisms cultured downstream. In marine IMTA systems, algae and halophyte plants have a high capacity for nutrient uptake per unit of culture area and can be an essential additional valuable product. In addition to nutrient removal by the green seaweed Ulva lactuca, the IMTA system proved to be a reliable source of sustainable biomass for human consumption, animal feed and high-value by-products for the food additive industries.
IMTA systems in offshore cage cultures and land-based facilities will improve the food conversion rate (FCR) and diversify the mariculture products, ultimately increasing profit for the farmer. In addition, they will often create additional jobs and, no less importantly, will reduce environmental pollution.

Keynote speaker
Marianne Thomsen
Professor, KU Food, Copenhagen University

Emission capture and utilization – the role of seaweed in regenerative circular bioeconomies

In climate-neutral societies, emissions of greenhouse gases from our production systems are compensated by a corresponding uptake of CO2 from the atmosphere.
Offshore seaweed cultivation systems have shown opportunities of seaweed as a nature-based solution for nutrient and carbon emission capture and utilization for the production of food, feed and ecosystem services. As such, the net carbon footprints obtained from balancing carbon emissions with carbon capture for technological mature Saccharina latissima cultivation system produced offshore are ranging from –739 to 3131 kg CO2e/ton dw of algae biomass. This illustrates the opportunity for algae cultivation systems to deliver water quality restoration and climate change mitigation services. Similar, net emission capture have been obtained from gentle harvest of green tide Ulva in Danish fjords.
While offshore seaweed production systems represents open loop circular nutrient management instrument, a new innovation project co-funded by the InnovationFund Denmark aims to further develop a closed loop emission capture in land-based ITMA systems by utilizing residual nutrients and CO2 from shrimp and fish farming to grow high-value seaweed for the food and healthcare industries.
Using a whole system carbon footprint accounting including direct and indirect emissions, avoided emissions through environmental mitigation, functional products and the substitution of fossil-based products, challenges and opportunities in role of seaweed in accelerating the transition to a sustainable food system are discussed.