percentage is a determining factor in the application of
microalgae for the production of biodiesel since a large part
is composed of neutral lipids, mainly triacylglycerides
(TAG). The use of industrial textile waste as a biodiesel
production process is a sustainable strategy that reduces
large-scale damage to the wastewater receiving environment
(Salama et al. 2017; Fazal et al. 2018).
Regarding rubber production, carried out through the
transformation of latex, is a large amount of wastewater is
generated, such as washing water, protein whey, non-gelled
latex, lipids, carbohydrates, salts, ammonia, nitrate, phosphorus, and total solids (Udaiyappan et al. 2017). Few
studies have been carried out with microalgae applied to
industrial rubber waste since they are not produced in
abundance in different regions. However, Bich et al. (1999),
Ayyasamy et al. (2008) reported that microalgae consumed
the nutrients contained in the waste by up to 93.4%, with
high biomass productivity and lipid biosynthesis that
improve the production of biofuels (Udaiyappan et al. 2017).
The industrial sewage sludge contains nitrified compounds and inorganic pollutants such as cadmium, copper,
lead, and selenium. According to Lim et al. (2013), the use
of microalgae combined with the symbiotic application with
bacteria improves the denitrification process. Besides this,
increases the performance of the microalgae with high lipid
production. Torres et al. (2017) concluded that the lipid
content is not affected, the contaminants favored the increase
of the biomass, demonstrating that the microalgae integrated
to activated sludge substrates for the simultaneous production of components for biodiesel, simultaneously support the
environmental sector through waste treatment.
About pharmaceutical wastewater, they have a significant
and diverse amount of organic compounds that can remain in
aquatic environments and are persistent in degradation by
microorganisms. However, the use of microalgae has
become a sustainable and comprehensive strategy (Tolboom
et al. 2019). Combined with the subsequent extraction of
microalgae oils to the biodiesel manufacturing from the
biomass produced, a symbiotic system, microalgae, and
bacteria can remove 60–90% of the contaminating compounds (Bai and Acharya 2017; Xiong et al. 2018).
A large group of wastewater includes agro-industrial waste,
such as swine wastewater, milk manure, sugarcane bagasse
hydrolyzate, beer fermentation waste, effluents from palm oil
mill among others (Cheirsilp et al. 2017; Feng et al. 2014;
Levine et al. 2011; Cheng et al. 2018). A common aspect of
this type of waste is the presence of a high concentration of
ammonium and chemical oxygen demand (COD) (20,180 mg
L
−1 ). Thus, the co-culture of microalgae in these residues is a
potential solution (Wang et al. 2015). The technology for
reducing the nutrient load, and having a high accumulation of
lipids, through the facility to tolerate stress, becomes an efficient means for biodiesel manufacturing (Cheng et al. 2018).
Noteworthy, Chinnasamy et al. (2010) reported that the
application of algae in the industrial residues of a carpet
factory could produce approximately 15,000 tons of
microalgae biomass, with the production of up to 4 million
liters of biodiesel, and removal of around 1500 tons of
nitrogen and 50150 tons of phosphorus from this wastewater
a year. Notably, the microalgae are promising for the biodiesel production with the cultivation of low-cost waste,
such as industrial waste. The yield of lipid production and
composition from microalgae has emerged as an attractive
path in large-scale biodiesel production. Additional studies
and explorations of the yield of each strain in different kinds
of waste for the production of biodiesel can promote the
commercialization of this biofuel (Kumar et al. 2020).
5 Challenges of the Bioconversion
of Industrial Waste to Biodiesel
The biodiesel production from microalgae involves upstream
and downstream processing, which includes the unit operations of strain selection, cultivation, harvesting, drying,
extraction, and conversion techniques, as shown in Fig. 1.
Until today, the technology to transform microalgal biomass
into biodiesel is technically feasible but uneconomical at
commercial scale. The economic feasibility of any
microalgae-based process depends on the choices of methods for each unit operation in the upstream and downstream
phases.
The most significant challenges to improve the economic
viability of any microalgae-based process are related to three
main aspects: (i) improve cultivations productivity; (ii) reduce the energy demand for the downstream processing,
especially for harvesting, drying, and oil extraction; and
(iii) explore the full potential of microalgal biomass in a
multi-product biorefinery concept (Cuevas-Castillo et al.
2020). The first challenge includes selecting the strain,
finding a low-cost cultivation medium, prioritizing industrial
wastes, and choosing the most suitable cultivation system.
Downstream processing of microalgae biodiesel represents
about 60% of the total production cost of the biofuel, so in
the second approach, more economical and integrated techniques are required for the main steps of the process. The last
issue refers to process design strategies that not only aim a
single product but also to a whole valorization of all biomass
fractions.
The first, and critical, step in microalgae-based processes
for biodiesel production, or any other product is the choice
of the microalgae strain to be grown (Borowitzka 2013;
Aravantinou et al. 2013). To date, there are more than
158,300 strains cataloged, according to algaebase.org, each
with its characteristics and requirements. Due to this large
number of species available, a robust selection is challenging
112
R. R. Dias et al.
microalgae for the production of biodiesel since a large part
is composed of neutral lipids, mainly triacylglycerides
(TAG). The use of industrial textile waste as a biodiesel
production process is a sustainable strategy that reduces
large-scale damage to the wastewater receiving environment
(Salama et al. 2017; Fazal et al. 2018).
Regarding rubber production, carried out through the
transformation of latex, is a large amount of wastewater is
generated, such as washing water, protein whey, non-gelled
latex, lipids, carbohydrates, salts, ammonia, nitrate, phosphorus, and total solids (Udaiyappan et al. 2017). Few
studies have been carried out with microalgae applied to
industrial rubber waste since they are not produced in
abundance in different regions. However, Bich et al. (1999),
Ayyasamy et al. (2008) reported that microalgae consumed
the nutrients contained in the waste by up to 93.4%, with
high biomass productivity and lipid biosynthesis that
improve the production of biofuels (Udaiyappan et al. 2017).
The industrial sewage sludge contains nitrified compounds and inorganic pollutants such as cadmium, copper,
lead, and selenium. According to Lim et al. (2013), the use
of microalgae combined with the symbiotic application with
bacteria improves the denitrification process. Besides this,
increases the performance of the microalgae with high lipid
production. Torres et al. (2017) concluded that the lipid
content is not affected, the contaminants favored the increase
of the biomass, demonstrating that the microalgae integrated
to activated sludge substrates for the simultaneous production of components for biodiesel, simultaneously support the
environmental sector through waste treatment.
About pharmaceutical wastewater, they have a significant
and diverse amount of organic compounds that can remain in
aquatic environments and are persistent in degradation by
microorganisms. However, the use of microalgae has
become a sustainable and comprehensive strategy (Tolboom
et al. 2019). Combined with the subsequent extraction of
microalgae oils to the biodiesel manufacturing from the
biomass produced, a symbiotic system, microalgae, and
bacteria can remove 60–90% of the contaminating compounds (Bai and Acharya 2017; Xiong et al. 2018).
A large group of wastewater includes agro-industrial waste,
such as swine wastewater, milk manure, sugarcane bagasse
hydrolyzate, beer fermentation waste, effluents from palm oil
mill among others (Cheirsilp et al. 2017; Feng et al. 2014;
Levine et al. 2011; Cheng et al. 2018). A common aspect of
this type of waste is the presence of a high concentration of
ammonium and chemical oxygen demand (COD) (20,180 mg
L
−1 ). Thus, the co-culture of microalgae in these residues is a
potential solution (Wang et al. 2015). The technology for
reducing the nutrient load, and having a high accumulation of
lipids, through the facility to tolerate stress, becomes an efficient means for biodiesel manufacturing (Cheng et al. 2018).
Noteworthy, Chinnasamy et al. (2010) reported that the
application of algae in the industrial residues of a carpet
factory could produce approximately 15,000 tons of
microalgae biomass, with the production of up to 4 million
liters of biodiesel, and removal of around 1500 tons of
nitrogen and 50150 tons of phosphorus from this wastewater
a year. Notably, the microalgae are promising for the biodiesel production with the cultivation of low-cost waste,
such as industrial waste. The yield of lipid production and
composition from microalgae has emerged as an attractive
path in large-scale biodiesel production. Additional studies
and explorations of the yield of each strain in different kinds
of waste for the production of biodiesel can promote the
commercialization of this biofuel (Kumar et al. 2020).
5 Challenges of the Bioconversion
of Industrial Waste to Biodiesel
The biodiesel production from microalgae involves upstream
and downstream processing, which includes the unit operations of strain selection, cultivation, harvesting, drying,
extraction, and conversion techniques, as shown in Fig. 1.
Until today, the technology to transform microalgal biomass
into biodiesel is technically feasible but uneconomical at
commercial scale. The economic feasibility of any
microalgae-based process depends on the choices of methods for each unit operation in the upstream and downstream
phases.
The most significant challenges to improve the economic
viability of any microalgae-based process are related to three
main aspects: (i) improve cultivations productivity; (ii) reduce the energy demand for the downstream processing,
especially for harvesting, drying, and oil extraction; and
(iii) explore the full potential of microalgal biomass in a
multi-product biorefinery concept (Cuevas-Castillo et al.
2020). The first challenge includes selecting the strain,
finding a low-cost cultivation medium, prioritizing industrial
wastes, and choosing the most suitable cultivation system.
Downstream processing of microalgae biodiesel represents
about 60% of the total production cost of the biofuel, so in
the second approach, more economical and integrated techniques are required for the main steps of the process. The last
issue refers to process design strategies that not only aim a
single product but also to a whole valorization of all biomass
fractions.
The first, and critical, step in microalgae-based processes
for biodiesel production, or any other product is the choice
of the microalgae strain to be grown (Borowitzka 2013;
Aravantinou et al. 2013). To date, there are more than
158,300 strains cataloged, according to algaebase.org, each
with its characteristics and requirements. Due to this large
number of species available, a robust selection is challenging
112
R. R. Dias et al.