It is now widely acknowledged that energy from fossil fuels is
unsustainable due to its depleting resources and the build up of
greenhouse gases in the environment [1]. It has therefore become
a common practise to reduce carbon dioxide emissions that result
from human activity. This paves the way for biofuels such as
biodiesel that are both renewable and carbon neutral. In addition,
biodiesel has biodegradable and non-toxic properties which
make it a very promising alternative fuel. The production and use
of biodiesel contributes close to no net carbon dioxide and sulphur
into the atmosphere and emits less gaseous pollutants than
petroleum diesel [2,3]. However, biodiesel from plant crops are
being produced from the same agricultural land as would be cultivated
for food and thus a conflict arises with the food supply.
Alternative sources of triglyceride oils which do not consume agricultural
resources such as arable land and fresh water are therefore
of considerable interest [4,5]. Microalgae as a source of biodiesel
has been extensively researched due to its advantages over traditional
biodiesel feedstocks such as having a high lipid content, being
able to double its biomass after a period of just 24 h [4,6] and having
the ability to grow in arid regions making use of water that is
not suitable for conventional agriculture [5,7]. Unlike other sources
of biodiesel, the demand for a large area of land is significantly
reduced when using microalgae [4,8].
Despite these advantages, broad commercialization of microalgae
sourced biodiesel has been restrained due to the high costs
involved with the process. These high costs are mainly associated
with the dewatering of extremely dilute cultures containing microscopic
algae cells. There are many dewatering techniques that can
be used for microalgae dewatering. These include centrifugation,
gravity sedimentation, filtration and screening, flotation and flocculation
[9–14]. However, each has its disadvantages that affect the
overall economics of the process. An effective microalgae dewatering
process should be workable for all microalgae strains, yield a
product with a high microalgae concentration and require moderate
costs of operation, energy and maintenance. More than one
dewatering step or a combination of dewatering techniques may
be needed in order to concentrate the microalgae into a slurry that
is suitable for biodiesel production. The dewatering of microalgae
It is now widely acknowledged that energy from fossil fuels isunsustainable due to its depleting resources and the build up ofgreenhouse gases in the environment [1]. It has therefore becomea common practise to reduce carbon dioxide emissions that resultfrom human activity. This paves the way for biofuels such asbiodiesel that are both renewable and carbon neutral. In addition,biodiesel has biodegradable and non-toxic properties whichmake it a very promising alternative fuel. The production and useof biodiesel contributes close to no net carbon dioxide and sulphurinto the atmosphere and emits less gaseous pollutants thanpetroleum diesel [2,3]. However, biodiesel from plant crops arebeing produced from the same agricultural land as would be cultivatedfor food and thus a conflict arises with the food supply.Alternative sources of triglyceride oils which do not consume agriculturalresources such as arable land and fresh water are thereforeof considerable interest [4,5]. Microalgae as a source of biodieselhas been extensively researched due to its advantages over traditionalbiodiesel feedstocks such as having a high lipid content, beingable to double its biomass after a period of just 24 h [4,6] and havingthe ability to grow in arid regions making use of water that isnot suitable for conventional agriculture [5,7]. Unlike other sourcesof biodiesel, the demand for a large area of land is significantlyreduced when using microalgae [4,8].Despite these advantages, broad commercialization of microalgaesourced biodiesel has been restrained due to the high costsinvolved with the process. These high costs are mainly associatedwith the dewatering of extremely dilute cultures containing microscopicalgae cells. There are many dewatering techniques that canbe used for microalgae dewatering. These include centrifugation,gravity sedimentation, filtration and screening, flotation and flocculation[9–14]. However, each has its disadvantages that affect theoverall economics of the process. An effective microalgae dewateringprocess should be workable for all microalgae strains, yield aproduct with a high microalgae concentration and require moderatecosts of operation, energy and maintenance. More than onedewatering step or a combination of dewatering techniques maybe needed in order to concentrate the microalgae into a slurry thatis suitable for biodiesel production. The dewatering of microalgae
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