Abstract: According to the proposed method for producing biomass, the organisms or cells in a suspension kept in circulation in a photobioreactor are cultivated with introduction of light and of at least CO2 as a nutrient. For the cultivation, the suspension is introduced via at least one introduction organ in an upper region of a culturing space and its downward movement is slowed down by at least one inner element that has a horizontally extending grid, screen or net structure and that is disposed in the culturing space. The suspension is converted into a plurality of drops on this structure. The drops pass through a drop cycle, by means of which the downward movement of the suspension is slowed down and a particularly intensive exposure of the organisms or cells contained in the nutrient solution to nutrients and light introduced into the reactor is assured.