The possible use of microalgae as a new alternative for biogas upgrading has already been discussed in various precedent studies. Apart from this, microalgae have numerous applications, that make their cultivation economically advantageous. So, the purpose of this thesis is to identify the best microalgal accretion conditions, using a planar photobioreactor and LEDs with variable intensities. Two different illumination intensities were used during the experiment: 33 and 57 PAR. Observing trends of pH, CO2, oxygen, nitrogen and temperature, it is possible to monitor microalgal production and respiration. Furthermore, a correlation between optical density (OD) and dry weight was found, in order to evaluate microalgae growth.