Seaweed Cultivation as a Climate Positive Solution
There is a growing interest in the role of seaweeds in absorbing carbon and exporting part of this to Blue Carbon sinks during cultivation as particulate or dissolved organic carbon - POC and DOC, respectively. However, the potential for carbon sequestration from seaweed farms remains largely unknown and unquantified. The PhD project will collect data simultaneously from cultivated Saccharina latissima on carbon uptake, growth and erosion, as well as losses of larger fragments, DOC production and fate in a combination of field and lab experiments. Applications for industry such as carbon credits and multi-market opportunities will also be assessed in practical terms.
The first field experiment was deployed in March 2021, at the farm of Seaweed Solutions AS (SES) in Frøya. The aim was to investigate a multi-crop approach where 2 or 3 crops/harvests could be attained for the price of one seeding, and the resulting seaweed biomass could then target both the high-value-low-volume markets such as food, feed, biochemicals, etc., as well as a potential future carbon market for the high-volume-low-value seaweed, already fouled with bryozoans. This would be the first case study for mid-Norway of this type of cultivation strategy. An incident at the farm following a storm resulted in the early termination of this experiment in May 2021, however, it has been re-planned and re-deployed for further investigations during 2022. This work is now ongoing at a new seaweed site installed by SINTEF Ocean in Skarvøya, Hitra.
Seedlings of S. latissima produced at SES, were successfully deployed in October 2021 and January 2022 and will serve multiple parallel investigations comparing the two deployment groups: 1) Erosion dynamics, which affect all carbon pathways from seaweed farms to sea floor; 2) a closer look at the particulate and dissolved organic carbon produced by the seaweeds in enclosed bags; 3) the level of lability and recalcitrance of the macroalgae-carbon, in other words, the level of digestibility of the carbon to microorganisms, which helps to define how likely that carbon is to resist degradation and become sequestered in sediments off the shelf or the deep sea (permanently locked out of the system); and 4) cropping as a cultivation strategy for enhancing opportunities for farmers in future carbon markets, in addition to using the biomass in high value markets.
During 2022-2023 the project will help educate three MSc students, who will collaborate in field and lab activities.
A survey has also been initiated to gauge the publics level of interest and knowledge about :seaweeds for climate:, in particular seaweed farmers, who are essential to drive any future seaweed-carbon market into practice. Large volumes would be needed for any significant carbon sequestration initiative, and so their interests, opinions and contributions are especially valuable. Preliminary results of the survey will be analysed in 2022, and invitations will be distributed to more respondents in Norway and perhaps more widely in Europe.
Later, an assessment will be made on the potential contributions and suitability of carbon dioxide removal (CDR) products and services, including for example, seaweed biochar and sinking of seaweed biomass, as potential climate positive solutions.