"Solvent extraction by hexane is the most common choice for extraction of oil/lipids from algae. However, hexane is not the best choice of solvent for algae oil extraction because of the need to market byproducts for human and animal consumption. Oil and hexane from the solvent extraction process are separated by distillation/evaporation which is an energy intensive operation. Presence of explosive hexane vapors in the oil processing plant is also a serious safety concern. Extraction of algae oil with alcohols (e.g. ethanol) will eliminate the emission and toxicity issues. However, energy consumption for alcohol recovery/separation is significantly high because alcohols boil at higher temperature and latent heat of alcohols is 2-2.5 times higher than hexane."

http://www.sbir.gov/sbirsearch/detail/3221 

Is there any other alternative method to extract oil from Algae?

Suggest at http://www.cleantick.com/questions/q/is-hexane-solvent-extraction-the-best-method-for-algae-oil