**5. Commercial scale up**

High cost of biomass production and subsequent extraction processes have limited the progress of upscaling of microalgae for commercial fuel and other value-added products. The technoeconomic analyses reported thus far have a wide variation in the cost estimates, primarily due to non-existence of standardized cost assumptions across different geographic locations. For example, in a study conducted in the US, production of microalgal biomass is estimated at \$4.92/ kg with current technology status [145]. In another study conducted in Europe, production cost was estimated to be €4.95, 4.16, and 5.96/kg of biomass from open ponds, horizontal tubular and flat panel photobioreactors, respectively [146]. Even the biomass production cost drops down to \$0.5/ kg, still scaling-up of microalgae

for standalone production of biofuel is economically infeasible due to swift competition with fossil fuel [145]. Hence, cost reduction and integration of additional revenue generation steps could help in successful scale-up.

While microalgae are primarily sought-after for biodiesel production through utilization of lipids, valorization of other components through a biorefinery approach, as proposed in many studies might enhance the chances of commercialization. Microalgae are traditionally utilized for food and feed, cosmetics, nutraceutical and pharmaceutical applications because of the presence of high content of protein, carbohydrate, pigments, antioxidants, ω-3 fatty acids and other industrially important chemicals. Extraction of these compounds as co or byproducts can improve the overall process economics [147, 148]. In microalgal biorefinery, valorization of different components of microalgae biomass is achieved through a series of unit operations for extraction, purification and biomass conversion [149]. Based on the type of the primary product being extracted, biorefineries can be classified as energy driven or material driven biorefinery. In energy driven biorefinery, oil for biofuel is extracted first, and the de-oiled biomass is used for extraction of value-added products or in a bioconversion processes like fermentation, anaerobic digestion, pyrolysis, hydrothermal liquification (HTL) etc. The best possible sequence of extraction of compounds for valorization of biomass can be evaluated through cost effectiveness assessment (CEA), which is the ratio of total outcomes from a biorefinery to the total cost of producing products [150]. Also, for successful biorefinery scheme, the net energy ratio (NER) assessment is important. It is the ratio of energy output over energy input and should be greater than unity. Higher the values of CEA and NER are, higher would be the feasibility of that biorefinery scheme [148, 150].

Several microalgae biorefineries have been proposed and tested in the literature but their implementation at large scale is still far from reality. **Table 1** summarizes some of the recent biorefinery approaches reported in the literature and **Figure 4** represents various possible biorefinery approaches. Razon and Tan (2011) evaluated a biorefinery for production of biodiesel and biogas from *Haematococcus pluvialis* and *Nannochloropsis* [161]. The NER was less than one for both the cases indicating negative energy balance, even when best performance estimates were taken for unit operations. However, economics of the system can be improved if cultivation is integrated with waste-water plant, thus eliminating the need for chemical fertilizers. Also, wet extraction should be followed thus saving on drying cost [161]. Similarly, Andersson et al. (2014) evaluated the biodiesel and biogas production through integration of cultivation with waste-water treatment plant, flue gas as carbon source and excess heat from industrial cluster. Production of biodiesel and biogas in biorefinery scheme resulted in net positive outcome compared to biogas alone [162]. In another biorefinery approach, Ansari et al. (2015) evaluated lipid extracted algae (LEA) for its use as protein or reducing sugar source and observed comparable yields of these products from whole algae and LEA as source material. Also, oven drying over sun drying and microwave assisted lipid extraction resulted in highest lipid yield compared to other methods tested [154]. In another study first protein was recovered from *Botryococcus braunii* under alkaline conditions, followed by lipid extraction for biodiesel and finally spent biomass was used for bio-oil production through pyrolysis. This biorefinery process resulted in 10% protein recovery, 2% lipid recovery and 33% bio-oil recovery. Bio-oil being obtained in this scheme was at neutral pH and hence non-corrosive for combustion engines but bio-oil recovery from spent biomass was less than that of whole algae. Due to poor recovery of lipids, their extraction step can be omitted and scheme can be simplified [153]. Recently, in *Chlorella vulgaris* biorefinery, where protein extraction was integrated with pyrolysis, extraction under alkaline condition (12 pH) at

**471**

*Recent Advances in Algal Biomass Production DOI: http://dx.doi.org/10.5772/intechopen.94218*

**products**

Carotenoids; Bio hydrogen

Biodiesel; Bioethanol

bio-oil

Lipid; Protein/ Reducing sugars

Nitrogen as NH4

Biohydrogen

biodiesel

Pigments; Fatty

acids

+

**Remarks Reference**

[151]

[152]

[153]

[154]

[155]

[156]

[157]

[158]

CO2 super critical fluid extraction plus ethanol (20 wt.%) could extract 45% (dry weight basis) of lipids and recover 70% of

Dark fermentation of left-over biomass by *E. aerogenes* yielded maximum 60.6 mL

Enzymatic saccharification of de-oiled biomass followed by fermentation resulted in the yield of 0.14 g ethanol/g residual biomass equivalent of 82% of the

Protein extraction followed by bio-oil

Neutral pH was found in bio-oil from

Sun drying resulted in poor outcome.

Electrocoagulation and solar drying reduced the energy requirements by 90% for harvesting and dewatering. 0.12 g/100 g dry biomass of total pigments with 56% free astaxanthin, 16% beta-carotene & 5% of lutein and

Fermentation of residual biomass produced hydrogen yield of 47 mL/g d.w. Carotenoid extraction with acetone is expensive and hydrogen yields have to improve by increasing sugar content in the biomass through altered cultivation

Whole algal slurry after acid pretreatment is directly used for ethanol fermentation. No losses of fermentable sugars in the solids, which are otherwise separated from

the sugar rich supernatant. \$0.95/ GGE cost reduction in biofuel

100% EtOH and 2 min.

Green processes: pressurized liquid extraction (PLE) and microwave-assisted solvent extraction (MAE) were evaluated for extraction of bioactive compounds. Optimum extraction conditions were 50°C, 100% EtOH, 20 min for PLE, while optimum conditions for MAE were 30°C,

Higher recovery of fucoxanthin enriched with EPA were obtained with PLE method.

75% recovery of energy in SCWG process and 100% recovery of N from lipid

Microwave assisted extraction from oven dried samples provided highest lipid yield. Protein and reducing sugar yield comparable in lipid extracted algae vs.

the pigments

recommended.

whole algae.

microalgal biomass.

extracted hydrochar.

canthaxanthin.

practices.

production.

H2/g Dry biomass of alga.

theoretical fermentation yield.

**Microalgae Biorefinery** 

*Nannochloropsis sp.* Biodiesel;

*Botryococcus braunii* Protein; lipid;

*Nannochloropsis sp.* Lipid; fuel gases;

*Spirogyra sp.* Carotenoids;

*Scenedesmus acutus* Bioethanol;

*Phaeodactylum tricornutum*

*Dunaliella tertiolecta*

*Scenedesmus obliquus*

#### *Recent Advances in Algal Biomass Production DOI: http://dx.doi.org/10.5772/intechopen.94218*

*Biotechnological Applications of Biomass*

scheme [148, 150].

for standalone production of biofuel is economically infeasible due to swift competition with fossil fuel [145]. Hence, cost reduction and integration of additional

utilization of lipids, valorization of other components through a biorefinery approach, as proposed in many studies might enhance the chances of commercialization. Microalgae are traditionally utilized for food and feed, cosmetics, nutraceutical and pharmaceutical applications because of the presence of high content of protein, carbohydrate, pigments, antioxidants, ω-3 fatty acids and other industrially important chemicals. Extraction of these compounds as co or byproducts can improve the overall process economics [147, 148]. In microalgal biorefinery, valorization of different components of microalgae biomass is achieved through a series of unit operations for extraction, purification and biomass conversion [149]. Based on the type of the primary product being extracted, biorefineries can be classified as energy driven or material driven biorefinery. In energy driven biorefinery, oil for biofuel is extracted first, and the de-oiled biomass is used for extraction of value-added products or in a bioconversion processes like fermentation, anaerobic digestion, pyrolysis, hydrothermal liquification (HTL) etc. The best possible sequence of extraction of compounds for valorization of biomass can be evaluated through cost effectiveness assessment (CEA), which is the ratio of total outcomes from a biorefinery to the total cost of producing products [150]. Also, for successful biorefinery scheme, the net energy ratio (NER) assessment is important. It is the ratio of energy output over energy input and should be greater than unity. Higher the values of CEA and NER are, higher would be the feasibility of that biorefinery

While microalgae are primarily sought-after for biodiesel production through

Several microalgae biorefineries have been proposed and tested in the literature but their implementation at large scale is still far from reality. **Table 1** summarizes some of the recent biorefinery approaches reported in the literature and **Figure 4** represents various possible biorefinery approaches. Razon and Tan (2011) evaluated a biorefinery for production of biodiesel and biogas from *Haematococcus pluvialis* and *Nannochloropsis* [161]. The NER was less than one for both the cases indicating negative energy balance, even when best performance estimates were taken for unit operations. However, economics of the system can be improved if cultivation is integrated with waste-water plant, thus eliminating the need for chemical fertilizers. Also, wet extraction should be followed thus saving on drying cost [161]. Similarly, Andersson et al. (2014) evaluated the biodiesel and biogas production through integration of cultivation with waste-water treatment plant, flue gas as carbon source and excess heat from industrial cluster. Production of biodiesel and biogas in biorefinery scheme resulted in net positive outcome compared to biogas alone [162]. In another biorefinery approach, Ansari et al. (2015) evaluated lipid extracted algae (LEA) for its use as protein or reducing sugar source and observed comparable yields of these products from whole algae and LEA as source material. Also, oven drying over sun drying and microwave assisted lipid extraction resulted in highest lipid yield compared to other methods tested [154]. In another study first protein was recovered from *Botryococcus braunii* under alkaline conditions, followed by lipid extraction for biodiesel and finally spent biomass was used for bio-oil production through pyrolysis. This biorefinery process resulted in 10% protein recovery, 2% lipid recovery and 33% bio-oil recovery. Bio-oil being obtained in this scheme was at neutral pH and hence non-corrosive for combustion engines but bio-oil recovery from spent biomass was less than that of whole algae. Due to poor recovery of lipids, their extraction step can be omitted and scheme can be simplified [153]. Recently, in *Chlorella vulgaris* biorefinery, where protein extraction was integrated with pyrolysis, extraction under alkaline condition (12 pH) at

revenue generation steps could help in successful scale-up.

**470**



*All the studies mentioned are conducted at lab scale.*

#### **Table 1.**

*Experimental demonstration of microalgal biorefinery approaches.*

#### **Figure 4.**

*Possible microalgal biorefinery approaches (dotted line: Alternate route, HTL: Hydrothermal liquification, HTC: Hydrothermal carbonization, SCWG: Super critical water gasification, BPFS: Bioplastic feed stock, stillage: Fermentation broth after removal of ethanol, extracted stillage: Broth after extraction of ethanol and lipids, spent biomass: Deproteinized and de-oiled biomass).*

50°C for 90 min followed by sonication resulted in 80% protein recovery. Bio-oil obtained from protein extracted biomass was better in quality and comparable in quantity with whole algal biomass extraction. Based on technoeconomic analysis, it was proposed that the extracted protein if used for food application then the profit can increase by 1.51 USD/ kg of microalgae biomass [159]. Lu and Savage (2015) processed *Nannochloropsis* slurry through hydrothermal carbonization (HTC) and resultant hydrochar was further used for lipid extraction. Lipid extracted residual char was converted into fuel gases through a process called super critical water gasification and almost complete recovery of N as NH4 + was achieved, which can be used for nutrient recycling. This scheme is attractive as multiple products can

**473**

**6. Conclusions**

*Recent Advances in Algal Biomass Production DOI: http://dx.doi.org/10.5772/intechopen.94218*

reduced [163].

be extracted efficiently and use of HTC process in the beginning eliminates the energy intensive step of drying for lipid extraction [155]. Dong et al. (2016) tested another biorefinery approach, where *Scenedesmus acutus* slurry was subjected to fermentation after acid pretreatment at 155°C for 15 min. Ethanol was recovered through distillation of fermentation broth and lipids were recovered from stillage by solvent extraction. Advantage of this approach was that monomeric sugar was fully utilized in the fermentation process as sugar-rich liquor was not separated from solid residues post pretreatment. Also, using whole cell algal slurry (post pretreatment) for fermentation resulted in microalgal biofuel cost reduction by \$0.95/GGE [157]. In another study, production of bioplastic feed stock (BPFS) and biofuel were integrated in algal biorefinery. Open raceway pond (ORP) cultivation followed by utilization of dried biomass as BPFS was found to be the most economical with minimum selling price (MSP) estimated to be \$970/ ton. Other scenarios, were, lipid extraction or fractionation prior to use of biomass as BPFS. These biorefineries with an estimate of MSP of \$1370 and \$1460/ ton of lipid extracted or fractionated biomass, respectively, were proposed to be competitive if cultivation cost is

Though biorefinery concept gives greater product and economic flexibility, the technologies needed for processing of residual streams of microalgae biomass are still in nascent stages of development and hence many biorefinery models are faced with technoeconomic hurdles. Cultivation, harvesting and drying are highly cost and energy intensive steps and needs substantial innovations and advancements to improve economics. Economics of downstream processing steps, which include cell disruption, extraction, purification and biomass conversion are not thoroughly assessed and reported, moreover, technology for multiproduct extraction is neither fully mature nor evaluated at large scale [164]. The economic analyses reported on biorefineries thus far are mostly based on small scale studies and limited knowledge on end-to-end biorefinery trials at large scale, affects the reliability of economic analysis [162]. Other significant challenges in successful implementation of microalgae biorefineries are; consistent availability of algal biomass, variation in microalgal composition based on cultivation conditions and strain specificity. Therefore, adequate control of cultivation parameters and selection of appropriate strain is important. When biorefinery products are intended for food industry, then the production process from cultivation to final product should adhere to regulations set by regulatory agencies in respective geographic locations [149]. Product stability

is another key challenge and must be ensured throughout the storage period.

process economically viable and environmentally sustainable.

**6.1 Will algal biomass production ever be economically viable?**

In conclusion, though microalgae are an excellent feedstock for implementation of biorefinery approaches, a concerted effort is still needed to make the production

Though microalgae technologies have evolved tremendously in the past decade and have shown greater promise as renewable feedstocks for food, fuel and other high value products, their commercial scale production is still in its infancy. Companies like Sapphire Energy, Aurora Biofuels, Solazyme, and Algenol started with the aim of producing biofuel from algae at a large scale but could not sustain their operations due to economic infeasibility. Some companies have stopped the operations, while others changed their focus to produce algae for food or other nonfuel products. Considering the technoeconomic analysis of fuel production from

#### *Recent Advances in Algal Biomass Production DOI: http://dx.doi.org/10.5772/intechopen.94218*

*Biotechnological Applications of Biomass*

**Microalgae Biorefinery** 

*All the studies mentioned are conducted at lab scale.*

*Experimental demonstration of microalgal biorefinery approaches.*

**products**

*Chlorella vulgaris* Protein; bio-oil Hydrolysis with sonication under alkaline

*Chlorella vulgaris* Lutein; Protein Pulse electric field treatment enhanced

application.

process.

yield and 57% purity.

economically viable.

**472**

**Figure 4.**

**Table 1.**

50°C for 90 min followed by sonication resulted in 80% protein recovery. Bio-oil obtained from protein extracted biomass was better in quality and comparable in quantity with whole algal biomass extraction. Based on technoeconomic analysis, it was proposed that the extracted protein if used for food application then the profit can increase by 1.51 USD/ kg of microalgae biomass [159]. Lu and Savage (2015) processed *Nannochloropsis* slurry through hydrothermal carbonization (HTC) and resultant hydrochar was further used for lipid extraction. Lipid extracted residual char was converted into fuel gases through a process called super critical water

*Possible microalgal biorefinery approaches (dotted line: Alternate route, HTL: Hydrothermal liquification, HTC: Hydrothermal carbonization, SCWG: Super critical water gasification, BPFS: Bioplastic feed stock, stillage: Fermentation broth after removal of ethanol, extracted stillage: Broth after extraction of ethanol and* 

be used for nutrient recycling. This scheme is attractive as multiple products can

+

**Remarks Reference**

[159]

[160]

conditions yielded high protein recoveries. Scheme is economically feasible if extracted protein is used for food

Profit is 1.51 \$/Kg of microalgae biomass

the lutein (2.2 ± 0.1-fold) and chlorophyll yields (5.2 ± 3.4-fold) compared to nontreated cells single-stage ethanol extraction

Protein extraction cost estimated to be US\$4.16/kg of protein with 50% extraction

Further improvement in yield and purity is needed to make this biorefinery

was achieved, which can

gasification and almost complete recovery of N as NH4

*lipids, spent biomass: Deproteinized and de-oiled biomass).*

be extracted efficiently and use of HTC process in the beginning eliminates the energy intensive step of drying for lipid extraction [155]. Dong et al. (2016) tested another biorefinery approach, where *Scenedesmus acutus* slurry was subjected to fermentation after acid pretreatment at 155°C for 15 min. Ethanol was recovered through distillation of fermentation broth and lipids were recovered from stillage by solvent extraction. Advantage of this approach was that monomeric sugar was fully utilized in the fermentation process as sugar-rich liquor was not separated from solid residues post pretreatment. Also, using whole cell algal slurry (post pretreatment) for fermentation resulted in microalgal biofuel cost reduction by \$0.95/GGE [157]. In another study, production of bioplastic feed stock (BPFS) and biofuel were integrated in algal biorefinery. Open raceway pond (ORP) cultivation followed by utilization of dried biomass as BPFS was found to be the most economical with minimum selling price (MSP) estimated to be \$970/ ton. Other scenarios, were, lipid extraction or fractionation prior to use of biomass as BPFS. These biorefineries with an estimate of MSP of \$1370 and \$1460/ ton of lipid extracted or fractionated biomass, respectively, were proposed to be competitive if cultivation cost is reduced [163].

Though biorefinery concept gives greater product and economic flexibility, the technologies needed for processing of residual streams of microalgae biomass are still in nascent stages of development and hence many biorefinery models are faced with technoeconomic hurdles. Cultivation, harvesting and drying are highly cost and energy intensive steps and needs substantial innovations and advancements to improve economics. Economics of downstream processing steps, which include cell disruption, extraction, purification and biomass conversion are not thoroughly assessed and reported, moreover, technology for multiproduct extraction is neither fully mature nor evaluated at large scale [164]. The economic analyses reported on biorefineries thus far are mostly based on small scale studies and limited knowledge on end-to-end biorefinery trials at large scale, affects the reliability of economic analysis [162]. Other significant challenges in successful implementation of microalgae biorefineries are; consistent availability of algal biomass, variation in microalgal composition based on cultivation conditions and strain specificity. Therefore, adequate control of cultivation parameters and selection of appropriate strain is important. When biorefinery products are intended for food industry, then the production process from cultivation to final product should adhere to regulations set by regulatory agencies in respective geographic locations [149]. Product stability is another key challenge and must be ensured throughout the storage period.

In conclusion, though microalgae are an excellent feedstock for implementation of biorefinery approaches, a concerted effort is still needed to make the production process economically viable and environmentally sustainable.
