TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Method: In obtaining biocrude, in the step of at least partial evacuation of the reactor culture, it is vacated between 5 and 50% of the crop. In the step of at least partial evacuation of the reactor culture, it is displaced approximately 10% of the crop. Prior to the feeding stage of gas comprising CO2 into the reactor, the method is carried out a pre-treatment consisting of at least one of the following treatments: substantial elimination SOx, NOx, and humidity and temperature adaptation of the gas at a range of 30 to 40 degrees C. Photosynthesis is carried out under turbulent and under natural light exposure. After the stage at least partial evacuation of the reactor culture, the culture is acidified and evacuated to a pH between 3.5 and 8. Cultivation is evicted acidified to a pH between 6 and 8. Acidification is carried out by adding to the culture at least one acidifying agent selected from CO2, CO2 and air mixture, strong or weak acids or its combination. Acidification is carried out by adding to growing a mixture of CO2 and air. After the step of at least partial evacuation of the reactor culture, separation of the solid fraction containing biomass and the liquid fraction containing carbonates and/or bicarbonates is performed by at least one technique selected from filtration, centrifugation, flocculation, electrocoagulation, ultrasonic, evaporation, decantation or its combination. Separation of carbonate and/or bicarbonates resulting from the liquid fraction at least partial evacuation of the reactor cultivation is carried out by precipitation of carbonate salts caused by the addition for at least one alkali. Anaerobic fermentation stage comprises an anaerobic fermentation, where biomass has a solids concentration of 1 to 50% and at a temperature between 10 and 165 degrees C. Biomass has a solids concentration of 5 to 12% and anaerobic fermentation takes place at a temperature between 30 and 75 degrees C. Anaerobic fermentation takes place at a temperature of about 38 degrees C. Anaerobic fermentation step is carried out a sub-stage homogenization or cavitation of the biomass subjected to pressure between 1 bar and 2500 bars. The biomass is subjected to a pressure between 250 and 1200 bars. The method is repeated between 1 and 5 times. The thermochemical decomposition stage fermented biomass is done by heating it to a temperature of 240 to 340 degrees C and a pressure of 10 to 20 MPa. After anaerobic fermentation step and before thermochemical decomposition stage, the method comprises separating from the biomass resulting from the anaerobic fermentation an aqueous fraction containing ammonium salts, which is returned back to the reactor. The species of microalgae capable of photosynthesis is selected from Chloroficea, Bacilliarioficea, Dinoficea, Criptoficea, Crisoficea, Haptoficea, Prasinoficea, Rafidoficea, and Estigmatoficea. The gas comprising CO2 and fed to the reactor relevant is exogenously the atmosphere or endogenously generated gas. The exogenous component of appropriate CO2 gas comprises a cement or similar industry. The gas comprising CO2 also contains other greenhouse gases. The method further comprises a final stage of refining biocrude.