Some of the techniques used for biomass cultivation are:

13.2.2.1 Photoautotrophic Production

This form of cultivation takes place when algae utilize an energy source (light) and a carbon source (inorganic carbon) to form carbohydrates through a process termed as photosynthesis. This is the most general method used for cultivating algae and results in the formation of algal cells with lipid content ranging from 5 to 68 % depending on the algal specie being cultivated. If algae are cultivated for oil produc­tion, then the prime advantage of using this cultivation technique is to utilize carbon dioxide to meet the carbon requirement.

13.2.2.2 Heterotrophic Production

In this method, the algal specie is grown on a carbon substrate like glucose thus eliminating the need of light energy. This process can be performed in a reactor with a small surface to volume ratio. A much higher degree of growth control is achieved and harvesting budget is lowered due to production of high-density cells. The set-up cost is negligible but more energy is used as compared to the process utilizing light energy because photosynthetic processes are utilized to form the carbon source on which the algae are grown. Studies have shown that heterotrophic method of bio­mass production has a higher yield and cells have higher lipid content (55 % as compared to 15 % in autotrophic cells).