A green fresh water algae will now take up the fight with marigolds; but not to embellish the flower beds, but to produce a compound not many have given thought to, the orange carotenoid lutein. Lutein is used both in food supplements, animal feed and cosmetics – and it is very expensive.

The idea behind BioBUF is to use residues to create new value chains through fermentation and microalgae production. It is not only biomass for energy purposes, but also biomass that can be refined to high-value products. One example is are carotenoid pigments produced by microalgae. Carotenoids are powerful antioxidants and lutein is one of them. Joshua Mayers has investigated several species of algae and has finally found one that both produces large amounts of biomass as well as has a high content of lutein.

–About one percent of the dry weight of a microalgae consists of carotenoids, of which up to 30 to 40 percent can be lutein. This is much more than in marigolds, which is the main plant lutein is currently extracted from. If algae in bioreactors could be cultivated using the same surface as used for marigold, it is likely to have a higher yield from the algae cultivation, says Joshua Mayers.

Whether or not it will be economically and environmentally sustainable, depends on many factors, including if costs for the growth medium to the cultivation can be reduced by using nutrients from waste water from the different industrial processes. If the natural light is insufficient and additional light is required, this would of course have large effect on energy demand, and thereby costs. Alongside experimental work in BioBUF, a life cycle assessment is being performed to compare the environmental impact of marigold cultivation with algae cultivation to help determine if algal lutein is a viable product. Marigolds demand fertilizing and large amounts of water. The aim of the algae cultivation is that the only external supply is electricity required to drive the bioreactor, to harvest and to extract the pigment. Everything else, such as heat and nutrients, must be derived from other processes in the BioBUF refinery concept, otherwise it may become too expensive.

Joshua Mayers and Eva Albers, the algae group leader, cultivate the selected algae specie at lab-scale. By growing in high-throughput well plates, he can in a short time test a large amount of different conditions to examine when the largest amount of biomass is produced. He also tests how the algae’s pigment production can be enhanced. Limiting the availability of nutrients stresses the algae, and since the pigment is part of the algae’s antioxidative protection mechanism, the production might increase. However, this is of course a fine act of balance. If the algae is too stressed, the growth will be jeopardized and the cultivation might even die.

If pigments eventually will be extracted in a large scale, algae production must be scaled up. But this is not covered by the scope of the BioBUF project.

– Our task is to look at the opportunities, and that it is possible to integrate algae cultivation with the other processes in the BioBUF refinery concept, and by doing so the use of residues is maximized and wastes of, for example, heat and other residues are minimized. It is hoped this approach will generate an environmentally and economically sustainable biorefinery.