Food industry wastewater treatment water promotes seaweed cultivation


Process water from the food industry is an excellent fertilizer for terrestrial seaweed cultivation. Not only does seaweed grow faster; it also multiplies in its protein content. In this way, process water can be transformed from a cost to a resource for the food industry.

Could macroalgae like sea lettuce be a competitive source of protein in the food of the future as soybeans are today? The protein content of seaweed is naturally lower than that of soybeans, but with the use of fertilizers, the difference decreases.

A scientific article published by researchers at the University of Gothenburg and Chalmers University of Technology shows that process water in food production can be used as an excellent fertilizer for seaweed cultivation. The algae grew more than 60% faster and the protein content quadrupled with the addition of process water.

“The protein content of soybeans is about 40 percent. By using process water, we have increased the protein content of the seaweed to over 30 percent,” says Kristoffer Stedt, PhD student at the Department of Marine Sciences at the University of Gothenburg.

We already know that algae grow better near marine fish farms due to the diffusion of nutrients in the fish poop through the water. Process water from the food industry is often enriched in nitrogen and phosphorus in a similar manner.

different food producers

The researchers tested four different types of seaweed and added process water from several different food producers – from the herring industry, salmon farming, shellfish processors and oat milk manufacturers. A quantity of nitrogen-controlled process water is added to seaweed cultivation. After eight days, the researchers analyzed the results.

“We added oat milk to make it fully vegan. All the different types of process water have proven to work well as a fertilizer for seaweed,” Stedt said.

Food production requires large amounts of water, and treating process water is currently a cost to producers. But this water can be turned into a valuable resource.

“We think, for example, you can do land-based cultivation of seaweed, such as sea lettuce, near a herring factory. Seaweed farming removes most of the nutrients from the process water. This brings us closer to a sustainable approach, and these companies in turn You can stand your ground,” Stedt said.

Seaweed has no odor

Researchers are concerned that seaweed could be contaminated with process water. Not everyone likes herring-flavored sea lettuce. But the test team did not notice any effect of the process water on the taste of the seaweed.

In the future, Kristoffer Stedt and his colleagues will focus on scaling up experiments on seaweed cultivation. They will use process water from the herring industry, which has shown very promising results, and focus on the stone lettuce (sea lettuce) species.

“As a first step in a controlled environment, we need to do a larger test. But we believe this could be an alternative source of protein in food in the future. If we use farmed seaweed as feed for land-farmed salmon, and use Process water fertilizes seaweed farming, and it could also be a fully recirculating system,” Stedt said.

Huge demand for new protein sources

With an estimated 10 billion people living on Earth by 2050, there is a high demand for sustainably produced food protein. From 2000 to 2018, seaweed production tripled to 32 million tons. Nearly 99% of products are produced in the Far East.

In the CirkAlg research project, researchers from the University of Gothenburg and Chalmers University of Technology are collaborating on processes that could generate new sources of Swedish marine protein in a resource-efficient manner through seaweed cultivation and processing.

“In addition to boosting the protein content of seaweed with process water, we are also investigating several ways to extract protein from algae for use in other foods, just as protein is extracted from soybeans today. However, this presents a challenge because The proteins in seaweed are more tightly bound than those in soy,” said Ingrid Undeland, professor of food science in Chalmers’ Department of Biological and Bioengineering. She is also the Coordinator of CirkAlg.

refer to: Stedt K, Trigo JP, Steinhagen S et al. Cultivation of seaweed in water for food production: assessment of growth and crude protein content. Algae resources. 2022;63:102647. doi: 10.1016/j.algal.2022.102647

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