Writing in the Journal of Applied Phycology, the team hails the microalgae as a sustainable and valuable source of EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) as well as high-quality proteins.
“Microalgae biomass cultivation that includes the burden of CO2 production still has similar or lower environmental impacts than aquaculture fish,” the team says.
“Microalgae cultivation is sustainable in a “colder” temperate climate like that in Germany, and microalgae are definitely able to compete with fish as an alternative nutrient resource.
“Regarding the recommended daily intake of EPA and DHA, microalgae represent—from an environmental point of view—an advisable source of nutrients.”
Susann Schade, one of the team members from the Institute of Agricultural and Nutritional Sciences at Martin Luther University Halle-Wittenberg (MLU), adds that up to now, photobioreactors had usually only been compared to pond cultivation often scoring worse due to their higher environmental impacts.
"However, little research has been done on the precise extent of the environmental impacts of algae produced for human consumption, especially under climatic conditions such as those found in Germany," adds Schade.
Global EPA & DHA demand
The study gains extra impetus after scientists have expressed concern over fish catch and aquaculture’s ability to meet global demand of EPA and DHA.
It has been calculated that based on a daily individual intake of 500 milligrams (mg) EPA+DHA, the annual global gap between EPA+DHA demand and supply amounts to 1.1 million tonnes, suggesting that fish only contribute 15% of the global demand of these nutrients.
Krill, an alternative source for these omega-3 polyunsaturated fatty acids (PUFAs), currently contributes only 0.3% of the demand, whereby production could possibly be increased to supply 8–9%.
Some microalgae species contain a high quantity of omega-3 PUFAs with concentrations comparable with those found in fish oil.
In addition, the quality of proteins from microalgae has been shown to be equal to that of proteins from soybean.
Some microalgae species show a wide range of high-value nutrients such as vitamins, carotenoids, phycobilins, polysaccharides, and sterols.
MLU researchers began comparing different cultivation scenarios of the Nannochloropsis sp. and P. tricornutum microalgae species in comparison to the cultivation of fish.
Scenarios included borosilicate glass and acrylic glass as photobioreactor (PBR) materials, two different tube diameters, and three different cultivation seasons.
“One of the things we did was to compare the carbon footprint of nutrients from microalgae and fish,” explains Dr Toni Meier, fellow study team member and head of the Innovation Office nutriCARD at MLU.
“We also analysed how much both food sources increase the acidification and eutrophication in water bodies.
"However, if we compare the environmental effects in relation to the amount of omega-3 fatty acids produced, fish from aquaculture comes off far worse," adds Schade.
Carbon dioxide production
In these scenarios, carbon dioxide production was also considered with the environmental impact of selected fish species obtained from systematic literature research.
Life cycle assessment was also used to look at global warming potential, acidification, eutrophication, cumulative energy demand, water footprint, and land use.
Microalgae biomass as a source of EPA and DHA, and protein was found to have similar or lower environmental impacts than fish fillet from wild capture and aquaculture production when carbon dioxide was modelled as an avoided burden.
The research team also found microalgae production that included the full burden of carbon dioxide production still caused similar or lower environmental impacts than aquaculture fish.
Distinct microalgae species can influence results if the comparisons are based on nutritional values, the study says with the team concluding that the recommended daily intake of 250–500 mg EPA+DHA, would make microalgae an “advisable nutrient source to lessen environmental pressures on marine ecosystems.”
“Microalgae should not and cannot completely replace fish as a food source,” adds Dr Meier. “But if microalgae could be established as a common food, it would be another excellent environmentally friendly source of long-chain omega-3 fatty acids."
“Several algae are already used as a food supplement in powder or tablet form and as an additive to foods such as pasta or cereals.
“It would be a way to reduce the current gap in the global supply of omega-3 fatty acids. At the same time, it would provide considerable relief to the world’s oceans.”
Source: Journal of Applied Phycology
Published online ahead of print: doi.org/10.1007/s10811-020-02181-6
“Distinct microalgae species for food—part 2: comparative life cycle assessment of microalgae and fish for eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and protein.”
Authors: S. Schade, G. I. Stangl & T. Meier