Algae Oil Fuel

While oil extraction from algae currently can be a costly process, algae remains the most promising bio source when compared with other potential candidates because it can produce 15,000 to 80,000 liters of vegetable oil a year per hectare. This is impressive when compared with only 120 liters of oil per year for a hectare of corn.

With new extraction processes being explored and older methods refined, and when used with high energy content algae, these processes are approaching cost effectiveness making algae an exciting prospect for fuel self sufficiency.

Oil extraction processes currently being explored include the following:

* Expression/Expeller Press – this is the simplest and most common method involving mechanical crushing or “pressing” out oil from dried algae. The physical attributes of the algae strain determine the type of press used. While this method alone generally produces about 70-75% of the oil, a higher percentage can be recovered if chemical solvents are added to the process.
* Chemical methods are inexpensive and are regularly used in other industries. Chemical extraction methods include:
o Hexane Solvents – Hexane is the least costly and most popular solvent. While it can be used alone for extraction, more than 95% of oil can be extracted if cyclohexane is mixed with the pulp resulting from the mechanical press/expeller. The oil dissolves in the cyclohexane solvent and the pulp is filtered out. Distillation separates the oil from the remaining solvent.
o Soxhlet extraction – A Soxhlet extractor is an apparatus that employs repeated washing with a solvent, in this case hexane or ether. After extraction, a rotary evaporator may be used to remove the solvent.
o Supercritical fluid extraction – this method can produce the highest purities and concentrations. When a gas is heated and compressed to the point that it possesses the properties of both a liquid and a gas, it is referred to as a “supercritical fluid”. Carbon dioxide is liquefied for use as the solvent for oil extraction from algae.

# Osmotic shock – If a high saline solution is used to grow algae and then the harvested sludge is dumped into distilled water, a sudden reduction in osmotic pressure causes cells to burst. Oil can then be skimmed off the surface.
# Enzymatic extraction – This is probably one of the most costly methods and involves the application of enzymes to degrade cell walls.
# Ultrasonic-assisted extraction – ultrasonic sound waves create cavitation bubbles in solvents. These bubbles collapse to create shock waves strong enough to damage the cell walls, releasing their contents into the solvent. Almost all of the oil can be extracted with this method but special equipment is required to maintain pressure and temperature.