Microalgae in the greenhouse - for reduced leaching of nutrients and for the production of economically valuable substances
The horticultural industry is an important player in Swedish food production. Fresh produce such as fruits, berries and vegetables is a natural part of a healthy diet. In 2012, a new area was started at the department of Horticulture, SLU, Alnarp, where the possibility to cultivate a new produce, microalgae, is studied. Microalgae are a natural source of valuable substances such as antioxidants and omega-3 fatty acids.
Today a large part of the greenhouse production is performed in hydroponic systems. These systems are based on a nutrient solution containing good quality water which is enriched with macro-and micronutrients. The nutrients will be taken up to a greater or lesser extent by the plant. From the environmental standpoint, it is desirable that the grower closes the system and re-circulates the nutrient solution. However, all growers do not have the possibility to close their systems and even those who primarily use a closed system may periodically have nutrient solution as a waste product. Leakage of the used nutrient solution contributes to the eutrophication and also means an economic loss for growers when the precious nutrients are not used in production.
The used nutrient solution is comparable to a wastewater which also is very rich in nitrogen and phosphorus. The reduction of these nutrients in wastewater by algae is a well established technique that has shown good results. Algae represent a large and diverse group containing both complex multicellular organisms, macroalgae, and microalgae which consists of single-celled organisms. Cultivation of microalgae is a growing industry with great potential, where the focus is not only on reduction of nutrients. There are also applications in food, feed, life sciences and as renewable fuel for the biomass (microalgae) that are produced during the cleaning process. There is a wide diversity of microalgae, and they represent an interesting resource for developing sustainable and economic production systems in horticulture as well as in other industries.
The focus will be on the green algae Chlorella vulgaris, producing polyunsaturated fatty acids, and Haematococcus pluvialis that produce a pigment, astaxanthin. Both of these metabolites have applications in pharmaceutics, food and health food industry when they have been purified from the harvested microalgae. There is also a very important direct use of the harvested microalgae in the feed industry to provide a good fatty acid balance and good pigmentation of fish and eggs.
The used nutrient solution is naturally rich in microorganisms and an important step is to examine how to establish the microalgae. The cultivation must be based on simple and robust methodology and be useful outside of the laboratory and in the greenhouse. The reduction of nutrients and salts are studied parallel with the microalgae growth.
The research is funded by the SLF, Partnership Alnarp, KSLA, Region Skåne and Lundström's Foundation.
Contact person: Malin.Hultberg@slu.se