40 participants went to the Aarhus International Sailing Center to hear the lecture 'Can seaweed save the world?', which the Folkeuniversitetet organized in March with Annette Bruhn, senior researcher in marine ecology at the Department of Ecoscience and representative of marine resources at the Center for Circular Bioeconomy at Aarhus University (CBIO). The lecture was about the many advantages of growing seaweed along the Nordic coasts, but also about keeping the message about the bliss of seaweed in a place where it is nuanced and supported by facts.

Food, climate, environment and biodiversity are crisis-hit areas that require immediate improvement. Seaweed can help alleviate the crises if seaweed production - in a sustainable way - is scaled up for feed and food. But not to the extent that the media can give the impression of.

Threatened kelp forests

There are 400 species of seaweed in Denmark, which are categorized according to the pigments they contain: green algae, red algae, and brown algae. Annette Bruhn had brought eleven of the seaweed species to the lecture after she had harvested them in the Aarhus Bay just below the sailing centre.

Seaweeds are algae - and not plants - but like plants on land, they live by photosynthesis and can bind CO₂ as well as remove nutrients, which are found in far too large quantities and which burden the marine environment. With the right living conditions, such as larger rock reefs that seaweed can attach to, kelp forests can be formed, which are important habitats and niches for fish and other animals in the sea. Therefore, rock reefs in the right places can increase biodiversity both within the plant and animal life in the marine environment.  

"We must take care of our kelp forests. Seaweed forests are endangered and they are important for biodiversity, but we fished large rock reefs for use in construction until it was banned in 2009. Something must be done now to protect our seagrass forests,” said Annette Bruhn.

A food and feed ressource

With a globally increasing population and pressure on land for cultivation, there will be a shortage of food in the future. Seaweed is a food resource that does not take up land and does not use fresh water, and if the production is scaled up in a sustainable way, it has great potential to reduce a future food crisis and at the same time contribute positively to the marine environment.

"Seaweed cultivation can become quite big, and we have gradually started production of three species, such as sugar kelp, dulse, and Ulvaceae on lines in Denmark. But the production must take biodiversity and sustainability into account," said Annette Bruhn and continued:

"Global seaweed aquaculture amounts annually to 36 million tons, most of which is grown in Asia in the sea. Seaweed cultivation in Europe and the western world is not as developed and accounts for less than 1 pct. of total global production. You can grow seaweed in the sea - on lines and nets. In the sea, you only have limited control over nutrition, water flow and fouling. If you grow seaweed on land - in tanks and in tubs - nutrition, water flow and fouling can be controlled. But it requires more energy and is therefore more expensive”.

The technology is in place if seaweed production is to be scaled up close to the coast, but the location of the facilities must be assessed in relation to optimal growth of the seaweed and the facilities must not come into conflict with other users of the sea if the production is to be an economically and environmentally sustainable solution. Another option could be to place plants for seaweed production offshore, but that kind of technology requires development.

There is a lack of standards for how facilities must be managed, and agreements for who the buyers must be if the production of seaweed is to be scaled up. Producers of cattle feed can be some of the takers, because feed mixing trials with certain species of seaweed show promising results, where the cattle's methane production can be reduced.

"The red algae Asparagopsis taxiformis can reduce cows' methane production by up to 98 pct. But the challenges are partly to be able to produce enough red algae at all, partly that this red algae cannot thrive in Danish waters, and the species is not native to Denmark, why it can’t be cultivated here. Therefore, one solution is to produce this species in a land-based cultivation system,” said Annette Bruhn.

Demand can increase seaweed production

The participants listened engaged while they had their hands in the different types of seaweed, and the Danish-produced seaweed chips, as well as biscuits with seaweed pesto, which were eaten.

Seaweed is not part of the Danish food culture, as it is in Asia. But we consume it without many of us being aware of it, as seaweed is used as a technical ingredient. Among them, it gives cocoa milk and pudding a creamy consistency and acts as a thickener in ice cream and wine gum.

But seaweed can also be eaten fresh or dried in soups or salads.

“Harvest the oarweed here from the growing point. If you were to eat this, I would blanch it. The blanching turns it green and reduces the iodine content. You can use it in salads and in soups, and you can freeze or dry it," said Annette Bruhn, while holding up an oarweed.

"What will it take for us to eat more seaweed?," asked one of the participants.

"Demand can advance production. As consumers, we can help make the market grow. In addition, those who work with food can integrate seaweed into their production as well as make pure seaweed products. If we can get the seaweed in meal boxes and in supermarkets, then it can be of some help," replied Annette Bruhn, who concluded with an appeal: "Denmark has such long stretches of coast with tasty seaweed. So harvest and eat seaweed, because there is no seaweed that is poisonous - harvest seaweed where you would also swim - and only take small amounts. Take good care of our kelp forests.”

Contact

Senior researcher Annette Bruhn

Department of Ecoscience

anbr@ecos.au.dk