A process for producing biomass and products derived thereof by means of cultivating unicellular algae in aqueous medium fed with a CO 2 current in a set of photobioreactors, comprising: - injecting a current of sea, salty or fresh water into the photobioreactors as a culture medium for the algae, previously enriched with nutrients, microfiltered and disinfected, - injecting a strain of at least one species of unicellular algae into the photobioreactors, and putting said strain in contact with the enriched water current under light conditions for the culture to grow by means of photosynthesis; - injecting a current of gases containing CO 2 into the photobioreactors, characterised in that it further comprises - extracting part of the algae culture from the photobioreactors, storing in a accumulation tank and sending to a separate unit to extract the biomass by means of mechanical and/or chemical separation, such that the obtained biomass has a humidity degree comprised between 50 % and 90 %; - subjecting the wet biomass to decantation and/or cavitation in a separate unit in order to extract part of the lipids and/or fatty acids and other added-value products along with a first reject, passing the remaining biomass on to the following step; - subjecting the remaining biomass from the preceding step to direct, low-temperature, thermal liquefaction in a separate unit in order to produce a biocrude and a second reject, all this at a temperature comprised between 250 °C and 350 °C and a pressure comprised between 150 and 210 bar, both limits included, for a time comprised between 1 and 120 minutes; - recovering the rejects from both the step of lipid, fatty acid and other added-value product extraction and the subsequent step of thermochemical treatment under subcritical conditions, storing each reject in separate chambers and subjecting to physicochemical treatment based on adjusting salinity, pH, microfiltration, disinfection and addition of nutrients, for subsequent reintroduction into the culture. - injecting a current of sea, salty or fresh water into the photobioreactors as a culture medium for the algae, previously enriched with nutrients, microfiltered and disinfected, - injecting a strain of at least one species of unicellular algae into the photobioreactors, and putting said strain in contact with the enriched water current under light conditions for the culture to grow by means of photosynthesis; - injecting a current of gases containing CO 2 into the photobioreactors, - extracting part of the algae culture from the photobioreactors, storing in a accumulation tank and sending to a separate unit to extract the biomass by means of mechanical and/or chemical separation, such that the obtained biomass has a humidity degree comprised between 50 % and 90 %; - subjecting the wet biomass to decantation and/or cavitation in a separate unit in order to extract part of the lipids and/or fatty acids and other added-value products along with a first reject, passing the remaining biomass on to the following step; - subjecting the remaining biomass from the preceding step to direct, low-temperature, thermal liquefaction in a separate unit in order to produce a biocrude and a second reject, all this at a temperature comprised between 250 °C and 350 °C and a pressure comprised between 150 and 210 bar, both limits included, for a time comprised between 1 and 120 minutes; - recovering the rejects from both the step of lipid, fatty acid and other added-value product extraction and the subsequent step of thermochemical treatment under subcritical conditions, storing each reject in separate chambers and subjecting to physicochemical treatment based on adjusting salinity, pH, microfiltration, disinfection and addition of nutrients, for subsequent reintroduction into the culture.