Turning Toxic Ammonia into Treasure: Algae Offer Solution for Fish Farms

In a breakthrough discovery, researchers have found a way to transform ammonia and nitrates, potential toxins in fish farms, into valuable resources. Using algae, scientists are developing a method to convert waste nutrients into fertilizer and fish feed ingredients.

Recirculating aquaculture systems (RAS) offer a sustainable model for fish farming. However, maintaining safe nitrogen levels for fish requires adding fresh water, consuming a valuable resource. The Wasteless project, a collaboration of Norwegian research institutes and industry partners, has focused on finding more circular approaches within RAS facilities.

“Our focus has been on utilizing the existing microbial community in tanks to naturally cleanse the water,” explains researcher Charlotte Volpe. “This process, called bioremediation, is at the heart of our work on minimizing water use.”

The key is utilizing nutrient-rich water within RAS systems. The team discovered that nitrogen and CO2 could be used to cultivate a film of algae with valuable properties. This algal biomass, rich in proteins and lipids, can be harvested for fertilizer or fish feed.

Lab-based simulations at the SINTEF SeaLab, validated by pilot experiments in a RAS facility, confirmed the viability of this approach. Now, the team is working to scale up their innovation, aiming to create a new RAS module. This module would turn the costly process of water cleansing into a revenue-generating opportunity.

“The next stage is to build a larger pilot capable of producing enough biomass for fish feeding experiments,” says Volpe.