What is a photobioreactor?

A photobioreactor consists of transparent tubes in which algae are grown. Normally tubes are arranged horizontally, or vertically, and the algae-water in the tubes are circulated continuously. A problem in open ponds was that, the ponds were deep, and so the algae would not get enough exposure to sunlight. Tubes have typical diameters of 10-15 centimeters, thereby increasing the percentage of algal volume receiving adequate sunlight. This is CellPharm's photobioreactor:

 

What are the steps to get oil from the algae you harvest from ponds or photobioreactors?

You first take the wet algae from the pond/photobioreactor, which looks something like this:

Then you dry the algae, till you get a dry powder like this :

Drying can by done in the sun in warm countries, or by using heaters. Then you have to seperate the oil from algal cake which is done using an expeller or press. ( similar to the device by which people make extract fruit juice in IIT Kharagpur). Extraction can also be done by hexane solvent oil extraction or Super Critical Fluid extraction. The cake coming out of BioKing's oil press(left) and the oil:

The cake can be sold for making fertilizers and pharmaceuticals. The oil is sold to biodiesel refineries.