from Nannochloropsis sp. biomass when supercritical CO 2 was used, and they
observed an increase of 36% when ethanol was added as co-solvent; in this case, the
global recovery was around 85% for lipids, and 70% of pigments. Ethanol allows
faster extraction and is suitable for feed and nutraceutical applications. The main
advantage of SFE with CO 2 is the use of a nontoxic, cheap, safe, and chemically
inert solvent at adequate critical temperature and pressure. Water is another good
candidate for SFE being nontoxic and cheap, but high pressure and temperature
necessary to reach its critical point involve higher energy costs than SFE with CO 2 .
On the other hand, innovative solvent-free methods such as osmotic pressure or
isotonic (also called ionic) solvent have started to be investigated (Ranjith Kumar
et al. 2015). They are eco-friendly, since they avoid the use of toxic solvents, have
lower energy consumption, and are considered cheaper alternatives (Adam et al.
2012). Ionic liquids, nonaqueous salt solutions that comprise an organic cation and
Table 3 (continued)
Extraction
techniques
Advantages
Disadvantage
References
Deep eutectic
solvents (DESs)
Safe, cheap, multi
eutectic fluid system
(two or more
solvents),
biodegradable,
nontoxic, production
of such solvents is
inexpensive,
extensive polarity
Promising results
where demonstrated,
application area needs
to be defined
Jeevan Kumar et al.
(2017), Jeong et al.
(2015), Paiva et al.
(2014)
Fluorous solvents
Nontoxic,
hydrophobic and
lipophobic, inert in
nature, employed for
trace metals extraction
and fractionation of
oils, phase easily split
up
Lipid extraction
through fluorous
solvents needs to be
studied
Horváth (1998),
Jeevan Kumar et al.
(2017)
Acid and alkaline
hydrolysis
High efficiency, fast
Use of high
concentration of acids
or alkaline
Dong et al. (2016),
Jeevan Kumar et al.
(2017), Roux et al.
(2017)
Conventional solvent extraction
Extraction in
Soxhlet apparatus
High efficiency, easy
to scale up thanks to
its simple operating
system, safety
Toxicity
Halim et al. (2012a),
Michalak and
Chojnacka (2014)
Solid–liquid
extraction (SLE)
Easy to scale up
Toxicity
Michalak and
Chojnacka (2014)
Liquid–liquid
extraction (LLE)
Easy to scale up
Toxicity
Michalak and
Chojnacka (2014)
5 Microalgae Biorefineries for Energy …
105
observed an increase of 36% when ethanol was added as co-solvent; in this case, the
global recovery was around 85% for lipids, and 70% of pigments. Ethanol allows
faster extraction and is suitable for feed and nutraceutical applications. The main
advantage of SFE with CO 2 is the use of a nontoxic, cheap, safe, and chemically
inert solvent at adequate critical temperature and pressure. Water is another good
candidate for SFE being nontoxic and cheap, but high pressure and temperature
necessary to reach its critical point involve higher energy costs than SFE with CO 2 .
On the other hand, innovative solvent-free methods such as osmotic pressure or
isotonic (also called ionic) solvent have started to be investigated (Ranjith Kumar
et al. 2015). They are eco-friendly, since they avoid the use of toxic solvents, have
lower energy consumption, and are considered cheaper alternatives (Adam et al.
2012). Ionic liquids, nonaqueous salt solutions that comprise an organic cation and
Table 3 (continued)
Extraction
techniques
Advantages
Disadvantage
References
Deep eutectic
solvents (DESs)
Safe, cheap, multi
eutectic fluid system
(two or more
solvents),
biodegradable,
nontoxic, production
of such solvents is
inexpensive,
extensive polarity
Promising results
where demonstrated,
application area needs
to be defined
Jeevan Kumar et al.
(2017), Jeong et al.
(2015), Paiva et al.
(2014)
Fluorous solvents
Nontoxic,
hydrophobic and
lipophobic, inert in
nature, employed for
trace metals extraction
and fractionation of
oils, phase easily split
up
Lipid extraction
through fluorous
solvents needs to be
studied
Horváth (1998),
Jeevan Kumar et al.
(2017)
Acid and alkaline
hydrolysis
High efficiency, fast
Use of high
concentration of acids
or alkaline
Dong et al. (2016),
Jeevan Kumar et al.
(2017), Roux et al.
(2017)
Conventional solvent extraction
Extraction in
Soxhlet apparatus
High efficiency, easy
to scale up thanks to
its simple operating
system, safety
Toxicity
Halim et al. (2012a),
Michalak and
Chojnacka (2014)
Solid–liquid
extraction (SLE)
Easy to scale up
Toxicity
Michalak and
Chojnacka (2014)
Liquid–liquid
extraction (LLE)
Easy to scale up
Toxicity
Michalak and
Chojnacka (2014)
5 Microalgae Biorefineries for Energy …
105