4.4 Strategy IV: Integration of Microalgae into Other
Processes and Circular Economy
In recent years, the importance of the new concepts for biorefineries and in particular for microalgae’s has been highlighted. Biorefinery obeys the principles of a
circular economy in the sense that all waste streams are valued (Mohan et al. 2016a)
promoting the use/transformation of secondary or residual streams into value-added
products (Yuan et al. 2015). It includes the use of: (i) wastewater as nutrient source
(Barr and Landis 2017; Delrue et al. 2016; Gouveia, et al. 2016; Olguin 2012;
Queiroz et al. 2013; Zhu 2015), (ii) digestate from a wastewater treatment of the
pulp and paper industry to internally recycle the nutrients for microalgae cultivation; this is an example that leads to a notably lower cost of microalgae biomass
production (Kouhia et al. 2015) or (iii) gaseous waste streams with high CO 2
content (Moncada et al. 2014; Wiesberg et al. 2017).
On the other hand, in all the above-mentioned studies, the potential of
microalgae for producing different forms of bioenergy and chemicals has been
presented as separated concepts that are not integrated into the first and second
biorefineries in multiproduct portfolios. Recently, it has been recognized that the
biorefinery concept plays an important role in the future development of a bio-based
economy and integration of the first-, second-, and third-generation biorefineries has
been recently proposed to develop a complete bioindustry (Moncada et al. 2014).
That work analyzed the integration of microalgae into a second-generation sugarcane biorefinery, including the joint production of sugar, ethanol, and electricity, by
introducing the cultivation of microalga Chlorella to use CO 2 -rich streams derived
from fermentation and cogeneration systems and subsequently produce biodiesel,
glycerol, sugar, fuel ethanol, heat, and power. Table 5 shows the concept of
incorporation of microalgae into other biorefinery or production schemes. These
scenarios are as diverse as the existing types of biomass; some works include
microalgae in pulp and paper industry or sugar cane biorefineries for treatment and
valorization of effluents, using combustion gas or wastewater as presented in
Table 5.
It is important to note that under this scenario, the possibility of biorefinery
schemes is infinite. Despite the complexity it involves, the biorefinery needs to
promote a circular economy to achieve viability (Mohan et al. 2016a, b). In the
proposals, the concept of biorefining for one single product was abandoned.
4.5 Design Strategy and Current Status
In order to conceptualize a biorefinery, the sequence of decisions includes
(Toledo-Cervantes and Morales 2014): (1) microalgae rich in target products.
(2) cultivation conditions and operation strategies, (3) conversion processes of
whole microalgae/defatted microalgal biomass to biofuels, (4) biomass harvesting,
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Processes and Circular Economy
In recent years, the importance of the new concepts for biorefineries and in particular for microalgae’s has been highlighted. Biorefinery obeys the principles of a
circular economy in the sense that all waste streams are valued (Mohan et al. 2016a)
promoting the use/transformation of secondary or residual streams into value-added
products (Yuan et al. 2015). It includes the use of: (i) wastewater as nutrient source
(Barr and Landis 2017; Delrue et al. 2016; Gouveia, et al. 2016; Olguin 2012;
Queiroz et al. 2013; Zhu 2015), (ii) digestate from a wastewater treatment of the
pulp and paper industry to internally recycle the nutrients for microalgae cultivation; this is an example that leads to a notably lower cost of microalgae biomass
production (Kouhia et al. 2015) or (iii) gaseous waste streams with high CO 2
content (Moncada et al. 2014; Wiesberg et al. 2017).
On the other hand, in all the above-mentioned studies, the potential of
microalgae for producing different forms of bioenergy and chemicals has been
presented as separated concepts that are not integrated into the first and second
biorefineries in multiproduct portfolios. Recently, it has been recognized that the
biorefinery concept plays an important role in the future development of a bio-based
economy and integration of the first-, second-, and third-generation biorefineries has
been recently proposed to develop a complete bioindustry (Moncada et al. 2014).
That work analyzed the integration of microalgae into a second-generation sugarcane biorefinery, including the joint production of sugar, ethanol, and electricity, by
introducing the cultivation of microalga Chlorella to use CO 2 -rich streams derived
from fermentation and cogeneration systems and subsequently produce biodiesel,
glycerol, sugar, fuel ethanol, heat, and power. Table 5 shows the concept of
incorporation of microalgae into other biorefinery or production schemes. These
scenarios are as diverse as the existing types of biomass; some works include
microalgae in pulp and paper industry or sugar cane biorefineries for treatment and
valorization of effluents, using combustion gas or wastewater as presented in
Table 5.
It is important to note that under this scenario, the possibility of biorefinery
schemes is infinite. Despite the complexity it involves, the biorefinery needs to
promote a circular economy to achieve viability (Mohan et al. 2016a, b). In the
proposals, the concept of biorefining for one single product was abandoned.
4.5 Design Strategy and Current Status
In order to conceptualize a biorefinery, the sequence of decisions includes
(Toledo-Cervantes and Morales 2014): (1) microalgae rich in target products.
(2) cultivation conditions and operation strategies, (3) conversion processes of
whole microalgae/defatted microalgal biomass to biofuels, (4) biomass harvesting,
124
P.-L. Gorry et al.