Microalgae-based Biorefinery Research Articles

Two-Step Macromolecule Separation Process with Acid Pretreatment and High-Shear-Assisted Extraction for Microalgae-Based Biorefinery

A simple two-stage extraction and recovery method for macromolecules from microalgae biomass, termed CASS (concentrating the microalgae solution, acid pretreatment, high-shear-assisted lipid extraction, and separation), was developed. This method effectively processed the wet biomass of Chlorella sp. ABC-001 at a moderately low biomass concentration (50 g/L). The optimal conditions were acid pretreatment with 5 wt.% H2SO4 at 100 °C for 1 h, followed by high-shear extraction using hexane at 3000 rpm for 30 min. The acid pretreatment hydrolyzed carbohydrates and phospholipids, disrupting the cell wall and membrane, while high-shear mixing enhanced mass transfer rates between solvents and lipids, overcoming the hydraulic barrier at the cell surface. Within 10 min after completing the process, the extraction mixture achieved natural phase separation into water, solvent, and biomass residue layers, each enriched with carbohydrates, lipids, and proteins, respectively. The CASS process demonstrated high esterifiable lipid yields (91%), along with substantial recovery of glucose (90%) and proteins (100%). The stable phase separation prevented emulsion formation, simplifying downstream processing. This study presents the results on cell disruption, optimal acid treatment concentration, and high-shear mixing to achieve macromolecule separation, expanding the lipid-centric microalgal process to a comprehensive biorefinery concept.

Bicarbonate concentration influences carbon utilization rates and biochemical profiles of freshwater and marine microalgae.

Selecting the optimal microalgal strain for carbon capture and biomass production is crucial for ensuring the commercial viability of microalgae-based biorefinery processes. This study aimed to evaluate the impact of varying bicarbonate concentrations on the growth rates, inorganic carbon (IC) utilization, and biochemical composition of three freshwater and two marine microalgal species. Parachlorella kessleri, Vischeria cf. stellata, and Porphyridium purpureum achieved the highest carbon removal efficiency (>85%) and biomass production at 6gL-1 sodium bicarbonate (NaHCO3), while Phaeodactylum tricornutum showed optimal performance at 1gL-1 NaHCO3. The growth and carbon removal rate of Scenedesmus quadricauda increased with increasing NaHCO3 concentrations, although its highest carbon removal efficiency (∼70%) was lower than the other species. Varying NaHCO3 levels significantly impacted the biochemical composition of P. kessleri, S. quadricauda, and P. purpureum but did not affect the composition of the remaining species. The fatty acid profiles of the microalgae were dominated by C16 and C18 fatty acids, with P. purpureum and P. tricornutum yielding relatively high polyunsaturated fatty acid content ranging between 14% and 30%. Furthermore, bicarbonate concentration had a species-specific effect on the fatty acid and chlorophyll-a content. This study demonstrates the potential of bicarbonate as an effective IC source for microalgal cultivation, highlighting its ability to select microalgal species for various applications based on their carbon capture efficiency and biochemical composition.

Algal biomass based bio-refineries: Concurrent pre-treatment strategies and perspectives for sustainable feedstock

The quest for viable and scalable biofuel sources has been at the forefront of scientific innovation for the past three decades. Due to its rich chemical constituents, microalgal biomass has emerged as a pivotal sustainable and scalable feedstock for biorefineries. This comprehensive review critically analyzes the different types of microalgae feedstock, concurrent extraction technologies, bio-pre-treatment procedures, and the key chemical and physical parameters influencing lipid formation and algal biofuel production. We propose a novel approach of photo-initiated culturing of algal biomass using photobioreactors (PBRs) to address the limitations of concurrent space and time-related constraints. The innovative photo bio-refinery strategy presented herein aims to enhance sustainability factors while minimizing emissions, catering to the needs of futuristic non-electric vehicles. A comparative quality analysis of microalgae-derived biofuel against conventional fossil fuels and other biofuels is conducted, considering chemical, environmental, economic, and social perspectives. Furthermore, we elucidate the efficacy of bio-pre-treatment strategies such as dehydration, hydrothermal liquefaction, pyrolysis, and gasification in optimizing biofuel production. The proposed photo biorefineries exhibit the potential to yield a diverse range of value-added products, including biodiesel, biogases, bio-fertilizers, bio-pesticides, bio-alcohols, dyes, proteins, carotenoids, and drug vitals. This review provides a comprehensive framework for the development of sustainable and efficient microalgae-based biorefineries, paving the way for a greener and more economically viable future in the biofuel industry.

Synergistic and stepwise treatment of resveratrol and catechol in Haematococcus pluvialis for the overproduction of biomass and astaxanthin

To increase the production of biomass and astaxanthin from Haematococcus pluvialis to meet the high market demand for astaxanthin, this study recruited two typical and negligible phytohormones (namely resveratrol and catechol) for the stepwise treatments of H. pluvialis. It was found that the hybrid and sequential treatments of resveratrol (200 μmol) and catechol (100 μmol) had achieved the maximum astaxanthin content at 33.96 mg/L and 42.99 mg/L, respectively. Compared with the hybrid treatment, the physiological data of H. pluvialis using the sequential strategy revealed that the enhanced photosynthetic performance via the Calvin cycle by RuBisCO improved the biomass accumulation during the macrozooid stage; meanwhile, the excessive ROS production had occurred to enhance astaxanthin production with the help of NADPH overproduction during the hematocyst stage. Overall, this study provides improved knowledge of the impacts of phytohormones in improving biomass and astaxanthin of H. pluvialis, which shed valuable insights for advancing microalgae-based biorefinery.

Biochemical trade-offs and opportunities of commercialized microalgae cultivation under increasing carbon dioxide

Microalgae's exceptional photosynthetic prowess, CO2 adaptation, and high-value bioproduct accumulation make them prime candidates for microorganism-based biorefineries. However, most microalgae research emphasizes downstream processes and applications rather than fundamental biomass and biochemical balances and kinetic under the influence of greenhouse gases such as CO2. Therefore, three distinctly different microalgae species were cultivated under 0% to 20% CO2 treatments to examine their biochemical responses, biomass production and metabolite accumulations. Using a machine learning approach, it was found that Chlorella sorokiniana showed a positive relationship between biomass and chl a, chl b, carotenoids, and carbohydrates under increasing CO2 treatments, while Chlamydomonas angulosa too displayed positive relationships between biomass and all studied biochemical contents, with minimal trade-offs. Meanwhile, Nostoc sp. exhibited a negative correlation between biomass and lipid contents under increasing CO2 treatment. The study showed the potential of Chlorella, Chlamydomonas and Nostoc for commercialization in biorefineries and carbon capture systems where their trade-offs were identified for different CO2 treatments and could be prioritized based on commercial objectives. This study highlighted the importance of understanding trade-offs between biomass production and biochemical yields for informed decision-making in microalgae cultivation, in the direction of mass carbon capture for climate change mitigation.

Evaluation on microalgae for the production of bio-chemicals and electricity

Recent advancement in biophotovoltaic systems using microalgae, coupled with biorefinery approach, would improve economy-feasibility in production. The major concern is its commercial strength in terms of scalability, strain selection and extraction procedure cost. It must compete with conventional feedstocks such as fossil fuels. This project proposes to enhance the economic feasibility of microalgae-based biorefinery by evaluating their performance for bio-electricity, bio-diesel and carotenoids production in a single cycle. The first part of the study was to construct and select a Bio-bottle Voltaic (BBV) device that would allow microalgae to grow and produce bioproducts, as well as generate the maximum current output reading derived from the microalgae's photosynthesis process. The second phase consisted of a 25-day investigation into the biorefinery performance of six different microalgal species in producing bio-electricity, bio-diesel and carotenoid in a prototype BBV device. The prototype BBV device with aluminium foil and pencil lead as its anode and cathode produced the highest carotenoid and biodiesel component production from the two microalgae tested, according to the results of the first phase of the experiment. In the second portion of the study, Scenedesmus dimorphus and Chlorella vulgaris were identified as the two microalgae most capable of maintaining their growth throughout the experiment. The maximum current reading observed for C. vulgaris was 653 mV. High Performance Liquid Chromatography analysis showed four major carotenoid compounds found which were Neoxanthin, Cantaxanthin, Astaxanthin and 9-cis antheraxanthin, and the highest carotenoid producer was C. vulgaris which recorded at 1.73 μg/mL. C. vulgaris recorded as the most alkanes producer with 22 compounds detected and Heptacosane and Heneicosane as the two major biodiesel compounds found in the extracts. Evaluation of C. vulgaris data showed that it has enormous potential for microalgal biorefinery candidates. Further ongoing research and development efforts for C. vulgaris will improve the economic viability of microalgae-based industries and reduce reliance on depleted fossil fuels.

Integrating microalgae growth in biomethane plants: Process design, modelling, and cost evaluation

The integration of microalgae cultivation in anaerobic digestion (AD) plants can take advantage of relevant nutrients (ammonium and ortho-phosphate) and CO2 loads. The proposed scheme of microalgae integration in existing biogas plants aims at producing approximately 250 t·y−1 of microalgal biomass, targeting the biostimulants market that is currently under rapid expansion. A full-scale biorefinery was designed to treat 50 kt·y−1 of raw liquid digestate from AD and 0.45 kt·y−1 of CO2 from biogas upgrading, and 0.40 kt·y−1 of sugar-rich solid by-products from a local confectionery industry. An innovative three-stage cultivation process was designed, modelled, and verified, including: i) microalgae inoculation in tubular PBRs to select the desired algal strains, ii) microalgae cultivation in raceway ponds under greenhouses, and iii) heterotrophic microalgae cultivation in fermenters. A detailed economic assessment of the proposed biorefinery allowed to compute a biomass production cost of 2.8 ± 0.3 €·kg DW−1, that is compatible with current downstream process costs to produce biostimulants, suggesting that the proposed nutrient recovery route is feasible from the technical and economic perspective. Based on the case study analysis, a discussion of process, bioproducts and policy barriers that currently hinder the development of microalgae-based biorefineries is presented.

A step forward in sustainable pesticide production from Amphidinium carterae biomass via photobioreactor cultivation with urea as a nitrogen source

This study addresses the problem of replacing nitrate and ammonium with urea as a greener nitrogen source in the mass cultivation of the microalga Amphidinium carterae for the development of amphidinol-based phytosanitary products. To solve this problem, a nuclear magnetic resonance assisted investigation evaluated the effect of nitrogen sources on growth and metabolic profiles in photobioreactors. Urea-fed cultures exhibited growth kinetics comparable to nitrate-fed cultures (µmax = 0.30 day−1, Pbmax = 43 mgL-1day−1). Urea-fed cultures had protein, lipid, and carbohydrate contents of 39.5%, 14.5%, and 42.4%, respectively, while nitrate-fed cultures had 27.9 %, 17.5% and 48.1%, respectively. Metabolomics revealed nitrogen source-dependent metabotypes and a correlation between amphidinols and polyunsaturated fatty acids. The amphidinol-to-nitrogen yield coefficient in urea-fed cultures (135 mg/g) was approximately 2.5 times higher than in nitrate-fed cultures. The potent antiphytopathogenic activity exhibited by extracts from urea-fed cultures underscores the potential of urea as a sustainable nitrogen source in microalgae-based biorefineries.

The High-Value Product, Bio-Waste, and Eco-Friendly Energy as the Tripod of the Microalgae Biorefinery: Connecting the Dots

A bio-based circular economy is fundamental to catalyzing the transition to a new economic model that thrives well within the planet’s ecological limits. The microalgae biorefinery, which consists of converting biomass into multiple products, operates in light of the principles of a circular economy. Therefore, as the pivot of a new economic paradigm that aims to promote ecological robustness, the main scope and motivation of this article are to use life cycle assessment to scrutinize the environmental sustainability of a microalgae-based biorefinery system. We assume β-carotene as the flagship of the microalgae industry and evaluate the sustainability metrics and indicators of two residual products: bulk oil and defatted biomass. The role of the use of renewable energy in the unit operations of the biorefinery was also evaluated. The results of this study show that waste products contribute an almost insignificant fraction of the ecological footprint and the cost and energy demand of the microalgae-based biorefinery. It is also confirmed from the results that the transition from coal-based energy to renewable is the most realistic path to production with significantly lower emissions. In sum, the consolidation of the microalgae biorefinery seems to be just around the corner, and our highlights can help make this a successful route.

Integrated microalgae-based biorefinery for wastewater treatment, industrial CO2 sequestration and microalgal biomass valorization: A circular bioeconomy approach

Integrated microalgae-based biorefinery for wastewater treatment, industrial CO2 sequestration and microalgal biomass valorization: A circular bioeconomy approach

Techno-economic analysis of a microalgae-based biorefinery network for biofuels and value-added products

Biorefineries have the potential to become economically competitive through the exploitation of all biomass conversion scenarios. This study presents a technoeconomic assessment of a microalgal biorefinery for the integrated production of biodiesel, biobutanol, and co-products acetone, ethanol, and glycerol. Pre-treatment stages include acid hydrolysis (AH) and solvent extraction (SX), in two different processing networks (Configuration 1: AH followed by SX; Configuration 2: SX followed by AH). The lowest Minimum Fuel Selling Price (MFSP) was attained by Configuration 1 ($2.11/kg total biofuel), which was 75 % and 11 % lower than the single-fuel biobutanol and biodiesel conversion scenarios, respectively. Sensitivity analysis showed that the feedstock costs, inlet rate, and solvent usage (SX), have the greatest effect on the MFSP. Results also showed that the selling price of biobutanol is highly sensitive to fluctuations in biodiesel prices, which may have implications on a growing fuels market with unpredictable supply and demand.

Conceptual Design of an Autotrophic Multi-Strain Microalgae-Based Biorefinery: Preliminary Techno-Economic and Life Cycle Assessments

Microalgae represent a promising solution in addressing the impacts associated with the current agricultural and manufacturing practices which are causing irreparable environmental damage. Microalgae have considerable biosynthetic potential, being a rich source of lipids, proteins, and high-value compounds. Under the scope of the H2020-BBI MULTI-STR3AM project, an innovative large-scale production system of valuable commodities for the food, feed, and fragrance sectors is being developed on the basis of microalgae, reducing costs, increasing the scale of production, and boosting value chain sustainability. In this work, we aimed to create a process model that can mimic an industrial plant to estimate mass and energy balances, optimize scheduling, and calculate production costs for a large-scale plant. Three autotrophic microalgae strains (Nannochloropsis sp., Dunaliella sp. and Spirulina sp.) were considered for this assessment, as well as the use of locally sourced CO2 (flue gas). The developed process model is a useful tool for obtaining the data required for techno-economic analysis (TEA) and life cycle assessment (LCA) of industrial biorefinery-based processes. Nannochloropsis sp. was the most economic option, whereas Dunaliella sp. was the most expensive strain to produce due to its lower productivity. Preliminary environmental assessments of the climate change impact category revealed that water recirculation and the use of flue gas could lead to values of 5.6, 10.6, and 9.2 kgCO2eq·kgAFDW−1 for Nannochloropsis sp., Dunaliella sp., and Spirulina sp., respectively, with electricity and NaCl as the main contributors. The obtained data allow for the quantification of the production costs and environmental impacts of the microalgal biomass fractions produced, which will be fundamental for future comparison studies and in determining if they are higher or lower than those of the replaced products. The process model developed in this work provides a useful tool for the evaluation and optimization of large-scale microalgae production systems.

A Two-Tier Superstructure Model for Optimization of Microalgae-Based Biorefinery

Microalgae have attracted great research interest as a feedstock for producing a wide range of end-products. However, recent studies show that the tight processing integration technology for microalgae-based biorefinery makes production less economical and even has a negative impact on sustainability. In this study, a new two-tier superstructure optimization design methodology is proposed to locate the optimal processing pathway. This model is developed based on the decomposition strategy and the relationship-based investigation, coupling an outer-tier structure with an inner-tier structure, wherein the outlet flows of the middle stages is relaxed and then an appropriate level of redundancy for designing the processing is provided. Two scenarios are developed to compare the most promising biorefinery configurations under two different design option favors. By solving the mixed integer nonlinear programming model with the objective functions of maximizing the yield of the desired products and maximizing the gross operating margin, the optimization results obtained show the ability of this framework to provide the promising configurations and cost-effectiveness of microalgae-based biorefinery. Compared with Scenario 1, the optimized solutions in Scenario 2 feature a gross operating margin increase up to 27.09% and an increase in product yield up to 25.00%. The proposed method improves the original huge computing scale and ensures economics without simplifying the processing pathways.

Emerging trends in the pretreatment of microalgal biomass and recovery of value-added products: A review

Microalgae are a promising source of raw material (i.e., proteins, carbohydrates, lipids, pigments, and micronutrients) for various value-added products and act as a carbon sink for atmospheric CO2. The rigidity of the microalgal cell wall makes it difficult to extract different cellular components for its applications, including biofuel production, food and feed supplements, and pharmaceuticals. To improve the recovery of products from microalgae, pretreatment strategies such as biological, physical, chemical, and combined methods have been explored to improve whole-cell disruption and product recovery efficiency. However, the diversity and uniqueness of the microalgal cell wall make the pretreatment process more species-specific and limit its large-scale application. Therefore, advancing the currently available technologies is required from an economic, technological, and environmental perspective. Thus, this paper provides a state-of-art review of the current trends, challenges, and prospects of sustainable microalgal pretreatment technologies from a microalgae-based biorefinery concept.

Time-Resolved Kinetic Measurement of Microalgae Agglomeration for Screening of Polysaccharides-Based Coagulants/Flocculants.

Time-resolved monitoring of microalgae agglomeration facilitates screening of coagulants/flocculants (CFs) from numerous biopolymer candidates. Herein, a filtering-flowing analysis (FFA) apparatus was developed in which dispersed microalgal cells were separated from coagulates and flocs formed by CFs and pumped into spectrophotometer for real-time quantification. Polysaccharides-based CFs for Microcystis aeruginosa and several other microalgae were tested. Cationic hydroxyethyl cellulose (CHEC), chitosan quaternary ammonium (CQA) and cationic guar gum (CGG) all triggered coagulation obeying a pseudo-second-order model. Maximal coagulation efficiencies were achieved at their respective critical dosages, i.e., 0.086 g/gM.a. CHEC, 0.022 g/gM.a. CQA, and 0.216 g/gM.a. CGG. Although not active independently, bacterial exopolysaccharides (BEPS) aided coagulation of M. aeruginosa and allowed near 100% flocculation efficiency when 0.115 g/gM.a. CQA and 1.44 g/gM.a. xanthan were applied simultaneously. The apparatus is applicable to other microalgae species including Spirulina platensis, S. maxima, Chlorella vulgaris and Isochrysis galbana. Bio-based CFs sorted out using this apparatus could help develop cleaner processes for both remediation of harmful cyanobacterial blooms and microalgae-based biorefineries.

Marine microalgae as sustainable feedstock for multi-product biorefineries

Marine microalgae accumulate numerous compounds with commercial value including carotenoids, proteins, biopolymers, and lipids, making them attractive feedstocks to produce diverse bioproducts including pharmaceuticals, nutraceuticals, cosmetics, animal feed, and biofuel. With the emerging concepts of “Blue Economy” and “Blue Biotechnology”, marine microalgae can be employed to achieve sustainability in numerous industries. Nonetheless, microalgae-based production processes are still not considered economically feasible owing to the high costs associated with cultivation and biomass processing. To mitigate the costs associated with the production process, the concept of marine microalgae-based biorefining has emerged where a single feedstock is employed to produce several distinct bioproducts, each with commercial value. Marine microalgae-based biorefineries could be made economically feasible by incorporating both high-value and low-value bio-compounds in the production line, whereas utilization of wastewater and flue gases as alternative nutrient sources for the cultivation can make the process more sustainable. Nonetheless, several challenges are associated with marine microalgae-based biorefinery, which necessitate the attention of future researchers to make this concept a reality. Hence, the present review provides a comprehensive discussion on the biorefinery of marine microalgae in view of producing diverse metabolites using a single feedstock while providing valuable insight into the directions of future research.

Microalgae-Based Biorefineries: Challenges and Future Trends to Produce Carbohydrate Enriched Biomass, High-Added Value Products and Bioactive Compounds.

Simple SummaryMicroalgae-based biorefineries allow the simultaneous production of microalgae biomass enriched in a particular macromolecule and high-added and low-value products if a proper selection of the microalgae species and the cultivation conditions are adequate for the purpose. This review discusses the challenges and future trends related to microalgae-based biorefineries stressing the multi-product approach and the use of raw wastewater or pretreated wastewater to improve the cost-benefit ratio of biomass and products. Emphasis is given to the production of biomass enriched in carbohydrates. Microalgae-bioactive compounds as potential therapeutical and health promoters are also discussed. Future and novel trends following the circular economy strategy are also discussed.Microalgae have demonstrated a large potential in biotechnology as a source of various macromolecules (proteins, carbohydrates, and lipids) and high-added value products (pigments, poly-unsaturated fatty acids, peptides, exo-polysaccharides, etc.). The production of biomass at a large scale becomes more economically feasible when it is part of a biorefinery designed within the circular economy concept. Thus, the aim of this critical review is to highlight and discuss challenges and future trends related to the multi-product microalgae-based biorefineries, including both phototrophic and mixotrophic cultures treating wastewater and the recovery of biomass as a source of valuable macromolecules and high-added and low-value products (biofertilizers and biostimulants). The therapeutic properties of some microalgae-bioactive compounds are also discussed. Novel trends such as the screening of species for antimicrobial compounds, the production of bioplastics using wastewater, the circular economy strategy, and the need for more Life Cycle Assessment studies (LCA) are suggested as some of the future research lines.

Multi-objective superstructure optimization of a microalgae biorefinery considering economic and environmental aspects

The increasing consumption of fossil fuels has many destructive effects on the environment. The development of a microalgae-based biorefinery is one of the most promising solutions to reduce these adverse effects. In the present study, a superstructure has been proposed to optimize different processing pathways for microalgae-based biofuels production. The proposed multi-objective mixed integer nonlinear programming (MINLP) model was solved in such a way as to minimize the total annualized cost (TAC) and environmental impacts simultaneously. The bi-objective optimization model was converted into a problem with a single objective using the augmented ε-constraint method. The optimal solution ranges were from 20.98 to 154.63 $MM/year for TAC, corresponding to 7.45 × 106 to 1.056 × 107 Points for the environmental impacts of the system. In the present study, the negative environmental impacts have been reduced by 42 percent compared to a base study using more environmentally friendly technological pathways.

Fabrication of poly(ethylene-co-vinyl acetate) (EVA)/biomass composite using residual Chlorella biomass through a sequential biorefinery process

Realization of full-fledged microalgae-based bioeconomy hinges on implementing integrated biorefineries, in which multiproducts are recovered from intact biomass with a minimal amount of waste materials. In particular, existing literature has suggested identifying correct valorization pathways for residual biomass generated following extraction or conversion processes as a key innovation necessary for microalgae-based biorefineries. This study aimed to evaluate the possibility of utilizing different biomass materials recovered from the operation of sequential microalgal biorefinery, through which lipid and carbohydrate portions of intact Chlorella biomass are sequentially removed via solvent extraction (defatting) and dilute acid hydrolysis (desugaring). Three types of biomass materials, including intact Chlorella biomass, were first analyzed for biochemical composition: the results indicated a proportional increase in protein and carbohydrate following the defatting step because of the removal of lipid fraction, while a significant increase in the amount of crude protein was further observed after the saccharification of 100 g/L of dried defatted biomass with varying concentrations of HCl between 0.1 N and 0.5 N. Provided that the results of FTIR analysis suggested a distinctive increase in peaks corresponding to the functional groups of protein in defatted and desugared biomass, the fabrication of poly(ethylene-co-vinyl acetate) (EVA)/biomass composite indicated substantial improvements in the mechanical properties of composites formulated with defatted and desugared biomass compared to the composite fabricated with intact Chlorella biomass at a biomass blend ratio of 30 wt.%. Although lipid extraction seemed to have a minimal influence on the mechanical properties of the composite, the results suggested that the saccharification process can be favorably considered in the design of microalgal biorefinery aiming to produce plastic filler materials. Given that an increase in the acid concentration during the desugaring step did not lead to a commensurable improvement in the mechanical properties of the final composites, continuing efforts are warranted to maximize the overall economic outlook of the biorefinery process simultaneously utilizing both hydrolysate, as well as the leftover residual materials under optimized operation strategies.

The urge of algal biomass-based fuels for environmental sustainability against a steady tide of biofuel conflict analysis: Is third-generation algal biorefinery a boon?

To meet the rising demand for biofuel, food, and feed, as well as pharmaceuticals, microalgal-based biorefinery systems provide various advantages. Because of the worldwide energy crises, the future of microalgal biorefinery is attentively receiving prominence. Despite being renewable and carbon–neutral, microalgal-based technology produces net CO2 emissions. Due to poor market pricing for renewable fuels, current biomass conversion techniques are neither profitable nor long-term viable. The microalgal strain chosen is critical to the experiment's success. A comprehensive approach that considers all three aspects of environmental sustainability is required to successfully address these challenges. The process should never be jeopardized in any way that threatens its long-term viability. The issue of sustainability must therefore be addressed from the outset of every biorefinery project. It is necessary to investigate genetically altered microalgal strains with improved lipid content, light usage efficiency, pigment accumulation, and other features during the design phase of an algal-based biorefinery, among other things. This is due to the recent drop in crude oil prices, as well as the significant capital and investment costs associated with algae cultivation. Dewatering, harvesting, and lipid recovery must all be researched and developed at a low cost. To solve the problem of decreasing biomass productivities at bigger production scales, a new generation of photobioreactor designs, lighting strategies, and nutrient feed systems are required. To be successful, proponents of large-scale microalgae-based biorefineries must integrate social and sustainability sciences into their commercial plans. The current review explores the potential application of algal biomass for the production of biofuels and bio-based products. The variety of processes and pathways through which bioconversion of algal biomass can be performed are described in this review.