Hypothesize other methods to either increase the oil content of microalgae or to grow greater amount of microalgae for biodiesel production

Aside from open pond growing algae and vertical closed loop production of micro-algae, another method to increase the oil content of micro-algae  is through a closed- drum production.  In this method, the indoor bioreactor plants will be grown in a huge round drum under an ideal or suitable environment that could produce maximum level of algae, which in turn yields large amounts of oil for biodiesel.

what are the choices?