Optimized culture technologies are the key elements to regulate the effective cost of production of algal biomass for biogas production. There are various approaches for cultivation of algae, starting from solutions that are technically advanced in which the procedure is methodically checked and measured, to the low expected methods con­sisted of open tanks. Algal biomass is usually taken from the natural, degraded and eutrophic water bodies for the production of biogas (Zhong et al. 2012).

There are two processes by which algae is grown, (1) open culture system and (2) closed systems (also named as photobioreactors). In the course of the Second World War, Germans were the first, who comprehended the idea of growing algae in open ponds. Before that, algae were cultivated and used as food supplements. For CO2 reduction, mass harvesting of algae was initiated by a bunch of staff at Carnegie Institute in Washington when industrial development originated (Burlew 1953). Algae were commercially produced during early 1970s and late 1970s in Israel, Eastern Europe, and Japan. It was cultivated as nutritious diet in open ponds during 1970s period. Lake Chadand and Lake Texcoco in Africa were the main sources of production of Spirulina specifically for the families living in these zones. Cultivation of algae was also influenced by food and nutritious requirement of people living in these area. For water management in the United States, algal open pool system was established and the recovered enriched algal biomass was then transformed into methane, which was considered as the chief energy source (Burlew 1953). With the passage of time, in the aquaculture field, algal biomass production was considered as the most important (Muller-Feuga 2000). Algae have gained a lot of attention in recent years because of its capaci­ties in chemical production (Borowitzka 1999; Lorenz and Cysewski 2000) and also due to its use as the food supplement by both animals and humans (Dallaire et al. 2007). Some other applications of algae include the biosorption of heavy metals (Wilde and Benemann 1993; Lodeiro et al. 2005; Karthikeyan et al. 2007) and fixation of CO2 (Benemann 1997; Sung et al. 1999; Chae et al. 2006). There are certain advantages of closed system as compared to open pond system. The recommendations for photobioreactors have been made from laboratory to indus­trial scale. Because of the improved customized and controlled cultivation set­tings, closed photobioreactors have gained a lot of attention than open pond system. Adulteration can be avoided and greater algal biomass production can be attained in closed photobioreactor. A large number of photobioreactors have been examined for biomass production and cultivation of algae but only a limited num­ber of them are able to use solar energy. The main hindrance in the algal biomass production is the deficiency of effective photobioreactors. Transferal of photobio­reactor and detailed study of certain parts of hydrodynamics is essential for the improvement of algal biomass production. Characteristics of maximum number of open-air photobioreactors include uncovered illuminating areas. Flat and cylin­drical photobioreactors are considered favorable apart from facing the difficulty in surmounting the photobioreactor up. There are bioreactors that have better scaling ability but their usage in open-air cultures is restricted due to having less illuminating exterior. Such bioreactors include airlift, stirred tank, and bubble — column (Prajapati et al. 2013).