Algal oil can be extracted from microalgae using an effective chemical sol­vent [35]. Hexane, cyclohexane, benzene, ether, acetone, and chloroform have proven to be effective in oil extraction of microalgae paste [36]. Among these, hexane has long been used as an oil extraction solvent in the food industry and is relatively inexpensive. A chemical method is usually faster in terms of extraction speed and requires a lower energy input for the extraction process itself. One of the drawbacks of using chemical solvents for algae oil extrac­tion is the safety issues involved in working with the chemicals. Care must be taken to avoid exposure to chemical vapors and direct contact with the chemical, either of which can cause serious personal injury. Benzene is clas­sified as a carcinogen, and most ethers are highly flammable. Another disad­vantage of using a chemical is the additional cost of recovery of the chemical for reuse in the process.

In a broader classification of algae oil extraction technology, chemical extraction methods include: (1) hexane solvent method, (2) Soxhlet extrac­tion, and (3) supercritical fluid extraction.