Domestic cultivation of a highly nutritious micro-algae
Spirulina is a micro-algae, more precisely a spiral cyanobacterium of about ¼ millimetres. It has thrived in hot, desert regions for more than three billion years. At the origin of plant and animal life, Spirulina has largely contributed to the creation of the earth's atmosphere by producing oxygen from carbon dioxide. If it is of particular interest to us today it is because it is also a super-food. Spirulina's rich constitution is due to the fact that its cell wall is made of protein. On the other hand, in the plant world, the cells have a cellulose wall, which is difficult to digest. Spirulina also has a high concentration of vitamins and iron. This ideal composition and its ease of assimilation make spirulina a food supplement coveted by great athletes. But Spirulina is sold expensive while it is simple and quick to grow. Its yield is very good: on the same space Spirulina produces five hundred times more protein than a cattle breeding. In the same way it takes about 13,500 litres of water to produce one kg of bovine proteins whereas only 2,500 litres are needed for micro-algae. Numerous associations and NGOs (Univers la Vie, Antenna, etc) cultivate it to fight against famine and malnutrition in the world. It exists in its natural state around the tropical belt (Peru, Mexico, Chad, Ethiopia, Madagascar, India...) and even in France, in the Camargue. The family culture makes it possible to integrate spirulina into its daily diet. The French Spirulina Federation recommends a consumption of fifty grams of fresh spirulina per day, or about 10 grams of dry spirulina. In this objective of local production, it is necessary to have 1m² of cultivation basin per person.
The growing medium
Spirulina lives naturally in volcanic lakes, rich in salt and bicarbonate of soda, with a high PH, close to 10. This is its environment but not its food, as fish do not feed on sea salt. In the culture of spirulina, the objective is to recreate as close as possible the native environment of spirulina. In its natural state, Spirulina is rarely taken except by pickers and flamingos. In pond the harvests are much heavier, it is thus necessary to regularly bring food to the culture to allow its renewal. In the culture of spirulina, it is thus necessary to dissociate the culture environment from the living environment and the food:
culture medium = living environment + food
The development environment.
Spirulina lives naturally in warm climates. When the temperature of its living environment is below 18°C, it hibernates. From 20°C it starts to develop. From 30°C its production intensifies strongly. At 37°C, the optimal temperature of the environment, the population increases by a quarter every eight hours. Above 42°C, spirulina dies. In France, outdoor cultivation, with a translucent cap, is possible from mid-April. The deep green colour of spirulina is obtained by photosynthesis. For this, spirulina needs a strong luminosity but not a long exposure to the sun. It is important to shake the pool to prevent the spirulina on the surface from burning and to allow the deep ones to benefit from the light. The culture must be 20cm deep maximum so that all the spirulina can benefit from good sunlight.
One of the health indicators of spirulina is its concentration. To measure it there is a very simple instrument: the Spirumeter or Secchi disk. It is a white disc at the end of an axis graduated in centimetres. The concentration of spirulina is measured by dipping the disc into the culture solution. When the disc disappears, the graduation on the surface is read, the Secchi concentration index. The lower the index, the more concentrated the spirulina is. For a healthy spirulina, the concentration should be between 2 and 4. At 2 it is very concentrated, it can be harvested. At 4 it is at its minimum cultivation concentration, for example after a harvest.
This tutorial is produced in collaboration with Gilles Planchon, a specialist in the domestic culture of spirulina, trainer and researcher on the natural living environments of microalgae.Find here the video tuto and the construction of a basin of family culture.
Medium of culture.
Medium of culture
Seeding, cultivation and maintenance
WARNING If tap water: Shake (pump or bubbler) during ½ day: the chlorine in the water evaporates and the limestone precipitates with the bicarbonate of soda, when the living medium is transferred to the pool, the limestone remains at the bottom of the canister. If rainwater: filter
The rich composition of spirulina comes from its diet, it is mainly composed of nitrogen, phosphorus, potassium, magnesium and iron. The food used in the family culture can be of mineral or natural origin. Mineral fertilizers obtained by chemical synthesis or by the exploitation of natural deposits are less ecological than natural food produced locally. Both preparations are presented.
Mineral Food The components of this preparation are agricultural fertilizers, they must be water-soluble. They can be found in agricultural cooperatives or garden stores. For about 10 litres of food (Milieu LIB from the book La Spiruline pour Tous - Culture Familiale') :
Natural food The components of the mineral food are found in ideal proportions in the urine . By adding a solution of iron oxide or "juice of rusty nails" spirulina benefits from a local and organic food ideal for its productivity and resistance. The high pH and salinity of the culture medium reduces the risk of contamination. However, only "organic" urine should be used, from people with a healthy diet (non-smokers, without medication or contraceptives). Human urine is now widely used in agriculture and many studies exist on the subject . For 1 litre of urine-based food:
Jus de clous rouillés : pour 1litre de jus de clou
WARNING Prepare the iron solution at least 10 days before the starting date of spirulina culture. If you leave the nails more than 10 days in the solution, the iron oxide concentration will rise. It will be necessary to dilute the juice with water.
The basin was filled with the living environment in the previous stage. Now it is time to bring in the food:
The culture medium is ready to welcome spirulina, you just have to get some. It is possible to get spirulina from anyone who has a family culture. It is also possible to contact a producer near you to know if he can supply fresh or concentrated spirulina (Gilles Planchon can make shipments to France). One kilogram of fresh pressed spirulina normally costs around 50€.
With freshly pressed spirulina, cultivation can begin as early as the harvesting phase, for this purpose a large quantity of unwashed spirulina must be introduced directly into the basin. It can be kept for 3 to 5 days in a refrigerator. It takes about 500g of freshly pressed spirulina to seed a 500 litre basin. A concentration of about 4cm will be obtained with a spirum meter. The first harvest will be possible one week later.
WARNING Foam indicates an increase in protein so spirulina that breaks: let it rest and shake more gently.
It is possible to seed his pond with concentrated spirulina. Unlike pressed spirulina, spirulina has not been separated from its living environment. It has a very high concentration, it must be quickly transferred to its new growing basin. It should not remain more than 12 hours in transfer.
It is also possible to start the spirulina culture with a smaller volume and grow it to the final volume of the basin. Under ideal conditions, it takes 30 days to go from one litre of culture to 500 litres. The growth phase is more economical because very little spirulina is needed at the beginning. The growing phase can start indoors from the beginning of April.
Spirulina needs a lot of light but should not be left in direct sunlight for long periods of time. For this, it makes the growing medium stir regularly during the day. The simplest solution is to use an aquarium pump, which can be found in pet shops. An ideal pump should be able to move the volume of the pond in one hour. In our case, the pump has a flow rate of 1000l/hour for a 500 litre pond.
TIP For small volumes, stirring can be done by hand, with a strainer, at least four times a day.
Check the concentration of spirulina regularly, ideally once a day.
With the heat of the pond, the water evaporates but the food, salt and baking soda remain in the pond.
REMINDER Tap water can be calcareous, it must be softened or use rainwater or osmosis water (see Preparing the culture medium: the living environment)..
Spirulina needs a lot of light but not direct exposure to strong sunlight.
WARNING If the spirulina is exposed to strong luminosity while the culture medium is at low temperature, for example at the end of winter, there is a risk of photolysis (the spirulina breaks and dies). Shade the pond when the culture medium is cool.
Over time the basin becomes loaded with organic matter (dead spirulina, other algae...). In order to keep a healthy growing environment, it is necessary to replace ¼ once or twice a year:
When the outside temperature becomes too low for the crop (pond temperature below 18°C), the crop must be overwintered.
When you buy spirulina or for winter storage, you can put part of it, pressed but not washed, in the refrigerator. It can be put back into culture by following the rapid sowing phase.
TIP Harvesting is more efficient in the morning. As long as the basin has not been agitated, the spirulina is in patches on the surface of the basin TIP.
TIP With a 1000/hour pump and a 500-litre tank, you can filter up to 125 litres, i.e. about 8 minutes of pumping time.
WARNING Check the concentration during the harvesting phase, shake the basin and take a jug, the concentration must remain above 4. If the concentration is lower, stop harvesting and shade.
WARNING Once the spirulina is harvested, avoid touching it by hand, its culture medium (high concentration of salt and baking soda) protected it from bacterial aggression.
WARNING Spirulina breathes at night, it should not be fed in the evening. Favour harvests in the morning.
Vous pouvez télécharger une fiche pédagogique créée par le Low-tech Lab à l'occasion de l'exposition "En Quête d'un Habitat Durable" dans la partie "Fichiers" du tutoriel (onglet au niveau de la section "Outils-Matériaux")
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For more information on the family culture of Spirulina :
For strains, materials and products necessary for spirulina cultivation as well as registration for training courses:
For the basin construction :
Other references :
Si vert : présence de chlorelle : ajouter du sel dans le milieu de culture Si marron : forte concentration de spiruline morte : ombrer
ATTENTION Une fois la spiruline récoltée, éviter de la toucher à la main, son milieu de culture (forte concentration de sel et de bicarbonate de soude) la protégeait des agressions bactériennes
Nourriture minérale, 200 ml pour 100 grammes de spiruline fraiche pressée ou Nourriture organique, 200 ml d’urine et 10 ml de solution de fer pour 100 grammes de spiruline fraiche pressée