Estimates show that there are over 30,000 different strains of algae. While such a large number might indicate exceptional potential for energy production from algae, in reality, only a small percentage of these could be used to derive energy in an economically sustainable manner. There are a number of reasons behind this fact and these will be detailed in this chapter.

1. Algae strain selection, while likely to be a resource intensive step, is critical for the success of algae energy business.
2. There are known species of microalgae that contain high oil content and macroalgae species that are high in carbohydrates.
3. Some of the strains suggested by NREL suited for efficient fuel production are the diatoms and the green algae.
4. It is estimated that there are over 30,000 strains of algae, and hence choosing the most suitable strain for a specific type of culture medium and for a desired type of final energy product could be a resource intensive exercise.
5. Choosing the most suitable algal strain needs consideration of parameters, such as the end products available, energy yield, performance in mass culture, and complexity of structure.
6. While microalgae are currently the more preferred choice owing to their high oil content, macroalgae have their advantages as well, and thus could be considered in future as a biofuel feedstock.