Konstruktion av en fotobioreaktor för odling av alger : ett småskaligt försök

Sammanfattning: The prevailing food and energy crisis of the world, due to the declining reserves of fossil energy and a never ending rise of consumption, forces us to look into new fields to supply our energy demand. The boom of bio energy is criticized, as food crops are used to provide biodiesel and ethanol and the volumes are ridiculously small to supply world demand. Algae are one of the world’s oldest life forms and exist in many different phyla, providing a great variety to choose from, for different purposes. Cultivating microalgae offer a way to produce energy at great volumes without competing with food production and at the same time the algae offer a way to use our expensive nutrients in a more efficient way, besides this the algae are carbon dioxide neutral since their carbon source can be supplied by the atmosphere and the additional energy required can be supplied by algal oil or other renewable sources. Constructing a small photobioreactor for laboratory use offers a simple way of testing different algae. Using drainage water to cultivate algae in a photobioreactor could offer a way to enhance nutrition use efficiency in agriculture. This thesis consists of two experiments, growing microalgae in drainage water from a clay soil and cultivating algae for maximal growth. Both experiments were performed in our photobioreactor. The algae cultivated in drainage water showed no growth, probably due to very low levels of nitrogen released from the clay soil. To obtain more growth we added nutrients in increasing doses in the second experiment. The treatments with high nutrient levels showed the highest levels of biomass but the nutrients had to be added gradually to avoid osmotic stress. However the treatments with a small nutrient supply produced more biomass per unit of applied nutrients than treatments with high doses of applied nutrients. The results show that a drainage water rich in nutrients, perhaps from a sand soil, should be used to obtain algal growth. To grow high levels of biomass, nutrients have to be added continuously and to obtain fast growth, a large amount of nutrients have to be added.