Abstract: A method for cultivation of photosynthetic micro-organisms such as micro-algae, photobacteria, and similar organisms, through circulation within tubes made of transparent plastic material of the suspension of said organisms in an appropriate culture medium, envisages: carrying out agitation/mixing of said suspension in the culture medium in said tubes in a pulsed and non-continuous way; separating the biomass produced from the culture medium by means of sifting with a system of differential-inclination sieves; introducing C02 with total dissolution thereof inside the tubes in which the suspension of said micro-organisms in their own culture medium circulates, introducing also buffer solutions in said culture medium; extracting the oxygen produced in the photosynthesis in a natural way by means of skimmers distributed along the tubes traversed by the culture medium; controlling the temperature inside the tubes in order not to reach temperatures that are harmful to the growth of the photosynthetic micro-organis