We are an certification body for organic farming. We also certify some producers of microalgae, such as Spirulina and Chlorella, in Asia. According to organic standards, only organic fertilizers may be used in such a system. Our certified operators claim they use fertilizers such as soybean meal, but we have more and more doubts if that is possible and plausible at all. So far, I have found a few papers confirming that nutrient uptake from organic sources is less efficient. But these papers were based on research combining mineral and organic fertilizers. So far, I have not found any publication confirming it is possible or impossible to work exclusively with organic fertilizers. Maybe the lack of such papers shows that it simply does not make sense and we are on a completely wrong track? Any reference to papers and/or answer from people who have knowledge / experience in this field are most appreciated!
The organic fertilizer should be the water in which the algae grow naturally. Organic bio-materials can supply nutrients but such materials must be sterile.
Hello, thanks for assisting! But I don't think this is the point. Organic materials must somehow be broken down to their mineral components, for being taken up as nutrients by microalgae. For allowing this breakdown , a community of microorganisms is needed - sterile materials seem to be counterproductive. Anyhow, the water, in which the algae grow, is recycled again and again during 6 months or longer, so you have a kind of "natural" substrate there. But to make clear again my question: I am not seeking advice on HOW this could be done, I want to know if the information given by our clients, makes sense, or they are cheating...
Dear Albrecht, It could be probable to grow your arthrospira in a mixte of organic and inorganic elements, but with exclusive organic elements, I am very doubtful, if it works you will have certainly a slow growth , and don't forget the problem in open pond with contaminants, even at a alkaline pH (9-10).
Thanks, Claude! This is what I had suspected! Can you refer me to any paper I could quote in relation to growth rate with organic substrate?
You can do a research by combining the words arthrospira and mixotrophy (or photoheterotrophy)
Using organic fertilizer as source nutrients in microalgal cultivation actually works fine by my experience. Though not as effective as conventional media
Some researchers or persons used human urine to cultivate spirulina and Ta-dah! you have super organic now! If you visit alibab website and search organic spirulina you will find very cheep organic spirulina. So don't look luxurious names.
Based on my experience, Spirulina does not like any kind of organic material for growth. Organic materials both kill the cells and contaminate the medium.
It is an interesting question. We are not sure to get full yield with organic inputs. But along with biostimulants, organic inputs could help in realising good yield potential.
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