Summary of “Extraction of Hydrocarbons from Microalga Botryococcus braunii with Switchable Solvents” by Samori et al.

In a paper published in Bioresource Technology in 2010, Samori et al. examine a new procedure for extracting hydrocarbons from Botryococcus brauniiBotryococcus braunii is a species of colonial, freshwater, green, microalga that holds high potential as a renewable biofuel source.  Samori et al. divide biofuels into first, second, and third generations.  According to the authors of this study, ethanol from sugar cane or corn and biodiesel from seeds are considered first generation biofuels; lignocellulosic fuels based fuels are second generation fuels; and, algae/ microalgae based biofuels are the third generation.  The rationale behind placing algal fuels at the forefront of biofuel sources lies in algae’s more efficient light usage, ability to grow in otherwise unusable areas, potential to multitask by cleaning up waste water flows, and ease of genetic modifications.  Furthermore, biodiesel produced from algae tends to be more readily usable than biodiesel from seed plants.  Drawbacks of algal fuel sources include energy intensive harvesting procedures and high economic costs from pond operation and bioreactors according to Samori et al.  Despite these hindrances, algae-based biofuels are an upcoming and promising source of energy and as such, should be researched.

One of the most challenging aspects of biofuel production is the extraction of lipids or hydrocarbons from the fuel source.  Samori et al. central focus was the comparison of two different SPS systems’ (DBU/ethanol and DBU/octanol), DBU’s, and n-hexane/chloroform/methanol’s lipid extraction efficiencies.  An SPS is a switchable-polarity solvent that is based on DBU; DBU is an acronym for 1,8-diazabicyclo-[5.4.0]-undec-7-ene.  They found that the alcohol used with the DBU is essential to assembling the liquid carbonate anion.  Total hydrocarbon yield was greatest with DBU/octanol (16 ± 2%), second best with DBU alone (15 ± 6%), and third with DBU/ethanol (12 ± 2%); n-hexane yielded only 7.8% (± 3%).  All DBU systems posted fatty acid extraction yields in the 0.6 to 0.7% range, while n-hexane/chloroform/methanol yielded around 2.7%.  After 4 hours, DBU/octanol and DBU/ethanol yielded similar quantities of hydrocarbons—14% and 13%.  The cycle between non-ionic and ionic was done by bubbling CO2 gas through equimolar solutions of DBU/octanol and changing DBU-octylcarbonate salt to its non-polar variant with N2 gas.  A hydrocarbon extraction efficiency of 81% was achieved with ionic/ non-ionic cycling.  Samori et al. concluded that SPS are promising as a “green technology” for hydrocarbon extraction from dried and aqueous growth microalgal.  DBU/octanol had the highest extraction efficiency in both dried and liquid algae samples.  SPS are also promising because they serve as a non-hazardous hydrocarbon extraction method for small biofuel production indistries.

Samori, Chiara, Cristian Torri Giulia Samori, Daniele Fabbri, Paola Galletti, Franca Guerrini, Rossella Pistocchi, and Emilio Tagliavin. 2010. “Extraction of hydrocarbons from microalga Botryococcus braunii with switchable solvents.” Bioresource Technology. 3274-3279.

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