The leftover oils from the common source of omega-3 supplements, Nannochloropsis salina, make up more than 70-percent of the algae plant and are typically either thrown away or burned but researchers from the University of California have found a way to purify it and turn it into azelaic acid - a building block for flexible polyurethanes.
The study, published in Green Chemistry, even found a way to convert the co-product heptanoic acid into food flavouring and fragrance.
According to the scientists, their process can be performed on oils from multiple algal species, to produce valuable molecules that take part in a chain reaction to form polymers for a highly sustainable source of bio-based plastics. But they chose the N. salina because of its established high production of eicosapentaenoic acid (EPA), a valuable omega-3 oil.
Co-author Michael Burkart said: "We showed that we could take waste products from algae-based omega-3 oil production and convert those into valuable and renewable polyurethane foams. These have all kinds of commercial applications, from flip-flops and running shoe soles, to mattresses and yoga mats. In addition, we prepared a flavouring molecule from the remaining co-product that is valued at over $500 per kilogram.
"Co-production of flexible polyurethanes and renewable solvent from a microalgae oil waste stream."
The process
To start the work, the research team - which included scientists from Division of Physical Sciences, the Division of Biological Sciences and the California Center for Algae Biotechnology at UC San Diego - first found a scale-able, cost-effective pathway to improve the purity of algae oil using simple physical methods along with saponification. This is a process by which oils react with sodium or potassium hydroxide to produce glycerol and a fatty acid salt, or soap.
In addition to the fatty acids, the team identified multiple contaminants in the waste oil. #
Co-author Stephen Mayfield explained: "Unlike plants, which store mainly triacyglycerides, or vegetable oil, in their seeds, microalgae contain a variety of metabolic components that are insoluble in water but freely soluble in the algae oil when extracted. The presence of these pigments inhibits downstream reaction efficiency, therefore their removal is a key process in the production of renewable chemicals from algae oil."
Burkart added: "We are already working with major shoe companies to turn these into commercial products that people will want to buy. We are finding that consumers are concerned about all of the petroleum-based plastic waste we are generating as a society, and our team is rapidly developing solutions for future products. Stay tuned!"
Source: Green Chemistry
Burkart. M., et al
"Co-production of flexible polyurethanes and renewable solvent from a microalgae oil waste stream"