Meet a technologist: Susan Holdt, exploring the secrets of seaweed

Home Technologist Online Meet a technologist Meet a technologist: Susan Holdt, exploring the secrets of seaweed

Danish biotechnologist Susan Løvstad Holdt is a self-confessed ‘seaweed nerd’. The brownish stuff that many beach-lovers would call a smelly mess, she calls a treasure. A promising source for new types of healthy food and carbon neutral biomass, this large type of algae might soon be farmed in many more of the world’s oceans.

Susan Holdt: exploring the secrets of seaweed

In Susan’s office at Technical University of Denmark (DTU) on the outskirts of Copenhagen, a small bowl filled with tiny flakes of dried seaweed sits on her desk. Evoking the taste of sushi, the slightly salty snack is packed full of nutritious and health-promoting ingredients. “Generally, seaweed contains 10 to 100 times more vitamins and minerals than land-grown fruit and vegetables,” Susan says. “It’s also very high in protein, which is another reason why seaweed is so interesting as a food source for people, or as feed for animals.”

From her very first encounter with biology as a subject in high school, Susan was ‘sold’. “Straight away, I knew that’s what I wanted to do,” she says. “I also soon realised it had to be field biology – getting out in nature. And it had to be closely connected to industry.”

Susan’s penchant for applied rather than basic research led her to pursue an industrial research degree through the independent Danish technological service institute DHI, the University of Copenhagen and the University of Southern Denmark. Her project involved – you guessed it – seaweed. And again, she was sold. “When you really delve into something, it just becomes more and more fascinating!” she says.

Currently an Assistant Professor at the National Food Institute, DTU, Susan is exploring various promising aspects of seaweed and seaweed farming.

Establishing seaweed farming in Danish oceans

Today, China is the world’s largest producer of edible seaweed, or macroalgae. In China and many other Asian countries including Korea, Japan, Indonesia and the Philippines, seaweed is an important part of traditional cuisine and health products – not just sushi. These nations increasingly export edible seaweed to Western countries.

In theory, nothing should prevent other coastal countries from farming seaweed on a commercial scale. As Susan has discovered through her research over the past few years, Danish oceans harbour many types of wild seaweed that could potentially be grown in special ‘ocean factories’ like those in the Far East. But seaweed is a sensitive creature that requires the right conditions, temperature, nutrients and salt content to be able to grow.

Seaweed harvesting in Denmark.

Susan Holdt (R) and Rasmus Bjerregaard, founder of Seaweed Seed Supply (L), harvesting a type of seaweed called sugar kelp (Saccharina latissima) in Horsens Fjord, Denmark. Photo: Julie F. Tjoncke.

Enlisting the help of local fishermen, she has tested a number of ocean spots, planting tiny sprouts of seaweed into the open sea. She has seen her ‘baby’ seaweed – nursed in the laboratory for months before being left clinging to long lines a couple of metres beneath the ocean surface – getting swept away and ruined by sheets of ice. She has battled tough winters, currents, marine traffic and other challenging conditions. And finally, she is getting somewhere.

Teaming up with a Danish offshore aquaculture business, she is pleased to see the commercial establishment of organic seaweed farming as part of the factory’s produce, alongside mussels and fish. But setting up seaweed farming in this part of the world is to enter uncharted waters, so to speak.

“We know it’s possible to produce seaweed continually throughout the year. But do we get the same amount of biomass when we harvest at different times? Do we get the same ingredients, for instance proteins? As it turns out, we don’t. There are large variations,” Susan explains. “We are currently working out which seasons are best for seeding and harvesting seaweed to get different types of end products.”

Exploring high-value markets

There is strong interest in locally grown seaweed among Danish food manufactures, restaurants and consumers. Seaweed is gaining popularity as an ingredient and flavour enhancer in various products, such as salads, pasta, ice cream, toothpaste, and beer, to name a few.

Two types of seaweed: dulse and sea lettuce

It may look like regular lettuce, but it’s seaweed. Top: dulse (Palmaria palmata). Bottom: sea lettuce (Ulva lactuca). Photo: Thorkild Amdi Christensen.

There may even be a market for Danish-grown seaweed in other countries, including those that produce plenty of their own, according to Susan. She recently travelled to China to explore the possibility of exporting Danish seaweed to the world’s most populous nation.

“The Chinese have a lot of mouths to feed, so they don’t produce enough seaweed for their own market,” she says. In particular, European-produced seaweed might have a competitive edge in high-value segments of the Chinese market, using for instance food safety or organic certification as selling points.

Some of Denmark’s several hundred seaweed types also have particular flavours and nutrient contents that would appeal to the Chinese market, as Susan discovered during her trip. One such feature is iodine.

“Many seaweed types have a very high iodine content, which can cause health problems – just as too little iodine can also be harmful. But some Danish seaweeds contain as little as one tenth of the amount in some Chinese types,” Susan explains.

“If you use small amounts of seaweed as a herb or vegetable ingredient, it’s not an issue. But if you use a fair amount in your daily cooking, as many people do in Asia, the iodine content matters.”

In addition to minerals, proteins and vitamins, some types of seaweed contain health-promoting compounds that can help prevent human diseases such as heart disease, obesity, diabetes and cancer. The hunt is on to discover even more bioactive compounds and find out how they work. But it’s still way too early to market seaweed products based on such properties, according to Susan. “Much more research is needed,” she says.

She has spent a lot of time adjusting the methods and instruments used to analyse all the interesting compounds in seaweed. “It’s essentially a new type of biomass, so we can’t just use our standard methods. Some of the sugar molecules in seaweed, for instance, are completely different to ‘regular’ sugars,” Susan explains.

Seaweed farming using floating lines.

A common way of cultivating seaweed: the seaweed grows on hanging ropes or ‘droppers’ attached to a floating long-line. Photo: Julie F. Tjoncke.

Seaweed: an environmentally friendly biomass

The potential applications and benefits of farmed seaweed are many. “You could argue that seaweed farming is one of the ‘cleanest’ types of farming, because it doesn’t need any added fertilisers or nutrients. In fact, the seaweed soaks up nutrients from the water, working as a biofilter,” Susan says.

This means if you farm seaweed alongside fish, you have an effective way of removing the waste products and access nutrients, such as nitrogen, which accumulate in the water as a result of the fish farming.

“Seaweed also soaks up carbon dioxide, so its biomass is carbon neutral,” Susan says. In addition to being used in interesting food or health products, this environmentally friendly biomass could become an important source for animal fodder. Or biofuel, potentially after extraction of high-value products.

Alongside seaweed, Susan also studies the much smaller type of photosynthetic algae – microalgae. She is looking at the sustainability of microalgae production as a resource for food, high value products and biofuel.

Apart from leading two international research projects, supervising a PhD student and liaising with industry contacts at home and abroad, Susan is running a Danish ’seaweed network’. Founded by Susan in 2008, the network has grown to include some 250 enthusiasts working within research, industry, national authorities and development of seaweed production. She is also co-organising the 22nd International Seaweed Symposium to be hosted by Denmark in 2016.

At home, Susan loves to spice up her cooking with fresh or dried seaweed – and thanks to her work she always has plenty of it at hand. You could say she lives and breathes her job. “I think what I do is incredibly exciting,” she beams.

– By Lillian Sando



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