AlgaeOil Extraction

Algae slush

Algae Oil Extraction

Oil extraction from algae is a hotly debated topic currently because this process is one of the more costly processes which can determine the sustainability of algae-based biodiesel. In terms of the concept, the idea is quite simple: Extract the algae from its growth medium (using an appropriate separation process), and use the wet algae to extract the oil. (Note: The algae need not be dried before oil extraction)

There are three well-known methods to extract the oil from oilseeds, and these methods should apply equally well for algae too:

1. Expeller/Press
2. Hexane solvent oil extraction
3. Supercritical Fluid extraction

Expeller/Press

Expression/Expeller press-When algae is dried it retains its oil content, which then can be "pressed" out with an oil press. Many commercial manufacturers of vegetable oil use a combination of mechanical pressing and chemical solvents in extracting oil. While more efficient processes are emerging, a simple process is to use a press to extract a large percentage (70-75%) of the oils out of algae

Hexane Solvent Method

Algal oil can be extracted using chemicals. Benzene and ether have been used, but a popular chemical for solvent extraction is hexane, which is relatively inexpensive. The downside to using solvents for oil extraction are the inherent dangers involved in working with the chemicals. Benzene is classified as a carcinogen. Chemical solvents also present the problem of being an explosion hazard.

Algae tanks

Hexane solvent extraction can be used in isolation or it can be used along with the oil press/expeller method. After the oil has been extracted using an expeller, the remaining pulp can be mixed with cyclo-hexane to extract the remaining oil content. The oil dissolves in the cyclohexane, and the pulp is filtered out from the solution. The oil and cyclohexane are separated by means of distillation. These two stages (cold press & hexane solvent) together will be able to derived more than 95% of the total oil present in the algae.