The large amounts of fish oil used by the aquaculture industry has traditionally been sourced from small fish which inhabit the mid-depths of the open ocean known as the pelagic zone. However, the rapid growth of aquaculture has outpaced the renewable rate of these wild marine resources.
Consequently, researchers around the globe have been developing alternative feed ingredients to reduce dependence on fish oil, while still delivering similar nutritional and health benefits.
Identifying a suitable alternative for fish oil requires understanding the impact such a substitution would have on the environment.
Microalgae have been one area of focus, due to their high content of the omega-3 fatty acids DHA and EPA, which are not found in land-based plants. Schizochytrium sp. has received particular attention, because it is already produced commercially for use in nutritional supplements and aquaculture feeds.
But the potential environmental impacts of growing Schizochytrium sp. in the quantities needed to fully replace fish oil in aquaculture feeds has not been well established. Fortunately, researchers at the University of Santa Cruz have helped to bridge this knowledge gap with a study published in July 2022 in the journal Elementa: Science of the Anthropocene.
“Comparative life cycle assessment of heterotrophic microalgae Schizochytrium and fish oil in sustainable aquaculture feeds” (McKuin et al. 2022) takes a comprehensive look at the environmental impact of growing and processing Schizochytrium sp. for aquaculture purposes by examining 6 key environmental consequences:
- Global warming potential
- Water consumption
- Land use
- Nutrient runoff into the ocean
- Nutrient runoff into freshwater sources
- Consumption of plant- and animal-based resources
While previous studies have attempted to quantify the environmental impact of Schizochytrium sp. cultivation, the University of Santa Cruz study examines elements of production and processing not previously scrutinized–specifically, the growing of sugar beets and sugar cane, from which sugar is sourced to feed the microalgae, and the extraction of Schizochytrium oil using either solvent- or microwave-based processes.
The researchers concluded that a blend of microalgae and canola oil would yield the most nutritious aquaculture feed with the most reduced environmental impact.
In comparing the various options for refining Schizochytrium sp. for use in feed, the study found that simply using the microalgae in a solid state (whole cell), rather than extracting oil from it, was the best option for minimizing environmental consequences–while also possibly offering greater health benefits than Schizochytrium oil.
The most impressive advantage noted by the study was that production of the microalgae/canola oil blend used 1/29th of the plant- and animal-based resources necessary to produce fish oil.
However, the study uncovered a significant concern when it came to producing Schizochytrium sp.—specifically, growing and processing the sugar needed to feed it.
The necessity of sugar cultivation with current production methods, Schizochytrium sp. has a greater impact than fish oil on global warming potential (or GHG), land use, and nutrient runoff into ocean and freshwater sources.
The aquaculture industry is united in the effort to reduce GHG in all aspects of operations and recognizes that feed ingredients are the largest contributor to the overall carbon footprint. The GHG or carbon impact for oil produced from Schizochytrium sp. can be up to 9.09 kg of CO2/kg oil, whereas the carbon impact for canola is between 2.30 to 2.64 CO2/kg oil. Aquaterra Omega-3 canola oil has been independently verified at 2.57 kg of CO2/kg oil.
Aquaterra Advanced Omega-3 oil allows for producing an alternative aquaculture feed that addresses the environmental challenges of producing algal oils. Aquaterra provides DHA and EPA fatty acids in addition to the benefits of canola, eliminating the reliance and impact of sugars to produce microalgae.
We are grateful to the researchers at the University of Santa Cruz who collaborated on this study. By recognizing the advantages and disadvantages of alternative aquafeed inputs we can identify the most beneficial options for reducing aquaculture’s reliance on limited marine resources.