Combining algal cultivation and biogas (methane) generation is considered to be one of the prospective environmentally feasible options of creating perpetually renewable source of pure energy for industrial and human consumption. Methane and energy generated in anaerobic fermentation facilities can be utilized as replacement for fossil fuel energy, thus reducing greenhouse gas emissions. This is caused by the fact that carbon is a biologically degradable material and algae form an integral part of the carbon cycle. Carbon release into the atmosphere from biogas combustion is utilized by plants for their further growth.
Selection of optimal strain of algae depends on cost, efficiency, growth rate of algae, and difficulties during cultivation. The best cost-effective strain is Chlorella, green algae, because after extraction of lipids further utilization of algae is possible. The anaerobic digestion of Chlorella vulgaris and Chlorella sorokiniana was studied using batch digesters. Standard analysis of chemical oxygen demand (COD), solids, pH were performed. Biogas composition and production were also determined. The conversion of biomass to biogas ranged from 40 - 73 % in COD. In general it is important to select the strain of algae that contains the most of chlorophyll and lipids (reservoir substances of algae).