How algae and seaweed are dealt with today: A bad smell and eutrophication!
Eutrophication results in the production of large amounts of filamentous algae and seaweed along the Swedish coasts. In total, this involves up to 80,000 tonnes (wet weight) along the coast of Skåne alone. The algae and seaweed are torn off the seabed by the waves and washed up on the beaches or clumped in the marinas. There, a process of decay begins, which results in a very unpleasant odour. To make the beaches more appealing to bathers, they are cleared away during the summer months and the collected masses of algae and seaweed are piled up in the sand dunes or at a nearby location. After the bathing season has drawn to a close, the collected material, and thereby the nutrients that cause the eutrophication, is returned to the water.
Why make biochar out of algae and seaweed?
Algae and seaweed contain relatively large amounts of phosphorus. By converting the algae and seaweed to biochar, the phosphorus that has previously leaked into the sea from the agricultural land can be returned. The cycle is closed and the need to add newly extracted phosphorus, of which there is currently a limited supply, is reduced.