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The rapid increase in fossil fuel depletion, environmental degradations, and industrialization have encouraged the need and production of sustainable fuel alternatives. This has led to the increase in interest in biofuels, especially third-generation biofuels produced from microalgae since they do not compete with food and land supplies. However, the global share for these biofuels has been inadequate recently, especially due to the ongoing global pandemic. Therefore, this paper offers a review of the state-of-the-art study of the production field of third-generation biofuel from microalgae. The current review aims to focus on the different aspects of algal biofuel production that requires further attention to produce it at a large scale. It was found that several strategies during the life cycle of algal biofuel production can significantly increase its quality and yield while reducing cost, energy, and other related attributes. This paper also focuses on the challenges for large-scale production of third-generation biofuels pre and post COVID-19 to better understand the barriers. The high cost of this fuel's production and sale tends to be the major reason behind the lack of large-scale production, hence, inadequacy to meet the global need. Third-generation biofuel has so much to offer including many integrated applications and advanced uses in the future fuel industry. Therefore, it is important to cope with the ongoing circumstances and emphasize the future of algal biofuel as a sustainable source. [ABSTRACT FROM AUTHOR]

The treatment of living organisms is a critical aspect of various environmental and industrial applications, ranging from wastewater treatment to aquaculture. In recent years, algal-based hollow fiber membrane bioreactors (AHFMBRs) have emerged as a promising technology for the sustainable and efficient treatment of living organisms. This review provides a comprehensive examination of AHFMBRs, exploring their integration with algae and hollow fiber membrane systems for diverse applications. It also examines the applications of AHFMBRs in various areas, such as nutrient removal, wastewater treatment, bioremediation, and removal of pharmaceuticals and personal care products. The paper discusses the advantages and challenges associated with AHFMBRs, highlights their performance assessment and optimization strategies, and investigates their environmental impacts and sustainability considerations. The study emphasizes the potential of AHFMBRs in achieving enhanced nutrient removal, bioremediation, and pharmaceutical removal while also addressing important considerations such as energy consumption, resource efficiency, and ecological implications. Additionally, it identifies key challenges and offers insights into future research directions. Through a systematic analysis of relevant studies, this review aims to contribute to the understanding and advancement of algal-based hollow fiber membrane bioreactors as a viable solution for the treatment of living organisms. [ABSTRACT FROM AUTHOR]

In the current scenario of energy requirement and the commercialization aspect of algal biofuel and biomass, it is important that means of predicting the production be available. In this paper, the mathematical models are developed for the tubular, bubble column and airlift photobioreactors to predict the productivity of the algal biomass. A modified Monod kinetic equation, incorporating the effect of nutrient and CO2 concentrations, light availability and oxygen built-up, is used to the estimate specific growth rate of the biomass. The light availability inside the reactor is defined in terms of the modified Beer–Lambert's law as a function of distance from the surface where light is incident and the cell mass concentration. This allows a more accurate measurement of the shading effect. The equations are solved for different reactor types and their estimated productivities are successfully validated against values available in published literature. The model predicts comparatively better productivity for the tubular reactor (1.5 g/L day) than the bubble column and airlift reactor (1.42 and 1.35 g/L day respectively) because tubular reactor has shorter light/dark cycles and better light availability. The analysis is also done to identify the effect of nutrient, carbon dioxide, light and hydrodynamics on the overall productivity. [ABSTRACT FROM AUTHOR]

Currently, fossil materials form the majority of our energy and chemical source. Many global concerns force us to rethink about our current dependence on the fossil energy. Limiting the use of these energy sources is a key priority for most countries that pledge to reduce greenhouse gas emissions. The application of biomass, as substitute fossil resources for producing biofuels, plastics and chemicals, is a widely accepted strategy for sustainable development. Aquatic plants including algae possess competitive advantages as biomass resources compared to the terrestrial plants in this current global situation. Bio‐oil production from algal biomass is technically and economically viable, cost competitive, requires no capacious lands and minimal water use and reduces atmospheric carbon dioxide. The aim of this paper is to review the potential of converting algal biomass, as an aquatic plant, into high‐quality crude bio‐oil through applicable processes in Malaysia. In particular, bio‐based materials and fuels from algal biomass are considered as one of the reliable alternatives for clean energy. Currently, pyrolysis and hydrothermal liquefaction (HTL) are two foremost processes for bio‐oil production from biomass. HTL can directly convert high‐moisture algal biomass into bio‐oil, whereas pyrolysis requires feedstock drying to reduce the energy consumption during the process. Microwave‐assisted HTL, which can be conducted in aqueous environment, is suitable for aquatic plants and wet biomass such as algae. [ABSTRACT FROM AUTHOR]

Algal biomass is a promising renewable feedstock for biofuel production that does not compete with food crops or require complex pretreatment like lignocellulosic biomass. This study examined biofuel production from two algae: Alkalinema pantanalense (cyanobacteria) and Chlorella vulgaris (green alga). Although there was no significant difference in their biomass, A. pantanalense showed a higher carbohydrate content (204.96 mg L−1) than C. vulgaris (156.07 mg L−1). To maximize reducing sugar release, three pretreatments were tested: thermotacidic, biological using the new fungal isolate Trichoderma longibrachiatum , and biological with nanoparticles. Biological pretreatment with Mg Zn ferrite nanoparticles (MZF-nps) at 60 mg L−1 concentration gave the best results, significantly enhancing cellulase, β-glucosidase and filter paper cellulase activities by 20.94 % (A. pantanalense) and 18.63 % (C. vulgaris). For biohydrogen production, the co-culture of Klebsiella pneumoniae and Enterobacter cloacae resulted in faster fermentation and improved hydrogen evolution compared to individual cultures. A. pantanalense and C. vulgaris yields were 35.1 mL g−1 and 26.6 mL g−1 dry weight, with maximal cumulative production of 2478 mL L−1 and 1845 mL L−1, respectively. Optimized Saccharomyces cerevisiae bioethanol fermentation conditions included 72 h incubation, 5 % inoculum, 30 °C, pH 5 under shaking condition, yielded 11.2 g L−1 (A. pantanalense) and 7.2 g L−1 (C. vulgaris). Furthermore, MZF-nps hydrolysate significantly increased bioethanol production, by 4.2-fold (A. pantanalense) to 32.45 g L−1 and 3.48-fold (C. vulgaris) to 28.6 g L−1, compared to thermoacidic pretreatment. In summary, biological pretreatment demonstrates the potential of algal biomass as a renewable feedstock for sustainable biofuel production. • Algal biomass is a promising renewable feedstock for biofuel production. • Biological pretreatment with nanoparticles increased fermentable sugars and biofuel yields. • Optimized fermentation conditions improved bioethanol yields from algal biomass. • MZF-NP increased bioethanol production up to 4.2-fold over thermoacidic pretreatment. • Co-culturing bacteria improved biohydrogen yield from algal biomass over individual strains. [ABSTRACT FROM AUTHOR]

Bioethanol is attracting increasing attention as a sustainable alternative to fossil fuels. Depending on the feedstock, it is classified into four generations. First-generation bioethanol, sourced from food crops, has higher feedstock costs but lower processing costs; however, it may lead to food scarcity. Second-generation bioethanol uses low-cost lignocellulosic feedstocks and can be adopted widely. However, despite the technological development in second-generation bioethanol, cost of processing is still high, making second-generation bioethanol uncompetitive with gasoline. Third-generation bioethanol primarily relies on algae, while fourth-generation bioethanol uses genetically modified algae to enhance bioethanol yield. Current bioethanol production mainly comes from the first-generation route, while second-generation bioethanol is slowly taking off. Third- and fourth-generation bioethanol production is still in the lab and pilot stages. This review critically discusses and summarizes recent advancements in all four generations of bioethanol production. It highlights significant findings regarding different raw materials, processing methods, process parameters, and microorganisms involved. Further, the paper delves into the economic viability and current deployment status of various bioethanol production routes by summarizing the techno-economic analysis done and some of the commissioned plants, along with their technology readiness level. The current challenges associated with different routes are outlined while offering insights into future perspectives. [Display omitted] • Critical analysis of developments in bioethanol synthesis across diverse feedstocks. • Factors influencing different generations of bioethanol production are outlined. • Pretreatment methods aiding in enhanced bioethanol yield. • Explores economic viability and deployment status across all bioethanol generations. • Highlights challenges faced and pinpoint critical factors for process improvements. [ABSTRACT FROM AUTHOR]

The microalgae Chlorella vulgaris and Tetraselmis chuii offer several attractive attributes as aquaculture feed. Biomass production of C. vulgaris and T. chuii is relatively expensive because it requires high operation and substrate cost. Use of food industry waste is one of the promising solutions to reduce the substrate cost. In this research the impact of diverse concentration was filtered and centrifuged, food wastewater (FWW) was scrutinized as an alternative intermediate for microalgal bioremediation, lipid yield and cell growth. C. vulgaris had superior lipid accumulation and cell growth at 75% level and T. chuii had enhanced lipid accumulation and cell growth at 75% with the most explicit growth rate (0.27 d− 1) and maximum biomass formation rate (0.1–0.18 gL− 1 d− 1) and lipid content (33.80 ± 0.88% and 35.04 ± 2.05%) respectively. The microalgae cells not only improved with FWW feeding and the level of COD (80.97–66.17%), BOD (81.13–66.81%), TN (55.88–22.06%) and certain heavy metals like zinc (99.72–99.52%) manganese (72.09–65.17%) nickel (50.68–34.41%), NO3N (50.68–42.59%) ferric (57.14–65.71%) cadmium (83.51–86.64%) lead (48.83–97.21%) and arsenic (55.13–55.00%) were efficiently removed from FWW at different dilution concentrations. C18:0/C18:1 were the major fatty acids in lipids which show a vast potential of microalgae for biodiesel fabrication and instantaneous bioremediation procedure using FWW. [ABSTRACT FROM AUTHOR]

Algae has a great CO2 biofixation potential that plays crucial role in regulating global carbon cycle and sustaining the ecology. Biosequestration of carbon is more efficient, sustainable, and has broader spectrum than its sequestration via various synthetic means. This study has analyzed the carbon sequestration potential of algae of Uchalli Wetland Complex (UWC) to mimic the natural microalgae function to realize the ecological significance of the complex being an important Ramsar site. The microalgal mats/colonies were sampled from three lakes, i.e., Khabeki, Uchalli, and Jahlar lakes, for consecutive eight months with an interval of 30 days to determine the carbon sequestration potential of the UWC. Maximum percentages of carbon (25.33–31.55%), hydrogen (3.86–4.68%), and nitrogen (2.9–3.45%) in the microalgal mats of Jahlar Lake, whereas highest sulfur content (5.9–7.42%) was observed in microalgal colonies of Khabeki Lake. Growth kinetics depicts maximum biomass productivity (4.5 × 106 avg.) in September while maximum CO2 sequestration (75.7 g−2 month−1) is detected in algal mats of Uchalli Lake. This study explored an undiscovered carbon sequestering potential of about 108.6 g−2 month−1 of algae of UWC that is certainly assistive in combating the climate change. Pearson's correlation generated significant relationships among different studied parameters at 0.01 and 0.05 levels. Statistical analysis by ANOVA with respect to lakes showed significant values (p = 0.000–0.003) of pH, salinity, carbon, nitrogen, hydrogen, sulfur, CO2 fixed, C/N, and C/H. [ABSTRACT FROM AUTHOR]

Featured Application: Anaerobic co-digestion of waste biomass in a two-stage anaerobic process was successful, and sequential production of biohydrogen and biomethane was realized, minimizing waste disposal and realising additional energy output for possible replacement of fossil fuels in a green way. Green and sustainable economies have recently become a key issue in long-term growth and well-being. Co-digestion of various waste materials in an eco-friendly way through biogas production has become the preferred method for their utilization and valorization. The possibility of hydrogen and methane yield maximization depends on the most suitable alkali reagent for pretreatment of waste lignocellulosic material, which was revealed in batch tests to determine the hydrogen production potential. The mixture for digestion consisted of pretreated wheat straw mixed with waste algal biomass in a ratio of 80:20 (w/w). The maximum hydrogen yield was achieved after applying sodium hydroxide thermoalkaline pretreatment, with a two-fold higher yield than the untreated control. Hydrogen production was stable and methane was not present in the resultant gas. The influence of the hydraulic retention time (HRT) on the maintenance of cascade installation was studied. The maximum daily concentration of hydrogen was achieved at an HRT of 2 days—42.5% H2—and the maximum concentration of methane was 56.1% at an HRT of 6 days. Accumulation of volatile fatty acids was registered in the first step and their depletion was noted in the second one. The obtained values of the cellulose content demonstrated that it was utilized by up to 2.75% in the methanogenic bioreactor at the end of the process. Metagenomics analyses revealed the bacteria Thermocaproicibacter melissae (44.9%) and Clostridium cellulosi (41.9%) participated in the consortium, accomplishing substrate hydrolysis and acidogenesis in the first stage. Less in abundance were Thermoanaerobacterium butyriciformans, Calorimonas adulescens, Pseudomonas aeruginosa and Anaerocolumna chitinilytica. Methanogenesis was performed by an archaeon closely related to Bathyarchaeota (99.5%) and Methanobacterium formicicum. The most abundant bacterial strains in the methanogenic fermenter were Abyssalbus ytuae (30%), Proteiniphilum acetatigenes (26%) and Ruficoccus amylovorans (13%). [ABSTRACT FROM AUTHOR]

Wastewater treatment and simultaneous production of value-added products with microalgae represent a sustainable alternative. Industrial wastewater, characterized by high C/N molar ratios, can naturally improve the carbohydrate content in microalgae without the need for any external source of carbon while degrading the organic matter, macro-nutrients, and micro-nutrients. This study aimed to understand the treatment, reuse, and valorization mechanisms of real cooling tower wastewater (CWW) from a cement-processing industry mixed with domestic wastewater (DW) to produce microalgal biomass with potential for synthesis of biofuels or other value-added products. For this purpose, three photobioreactors with different hydraulic retention times (HRT) were inoculated simultaneously using the CWW-DW mixture. Macro- and micro-nutrient consumption and accumulation, organic matter removal, algae growth, and carbohydrate content were monitored for 55 days. High COD (> 80%) and macronutrient removals (> 80% of N and P) were achieved in all the photoreactors, with heavy metals below the limits established by local standards. The best results showed maximum algal growth of 1.02 g SSV L−1 and 54% carbohydrate accumulation with a C/N ratio of 31.24 mol mol−1. Additionally, the harvested biomass presented a high Ca and Si content, ranging from 11 to 26% and 2 to 4%, respectively. Remarkably, big flocs were produced during microalgae growth, which enhanced natural settling for easy biomass harvesting. Overall, this process represents a sustainable alternative for CWW treatment and valorization, as well as a green tool for generating carbohydrate-rich biomass with the potential to produce biofuels and fertilizers. [ABSTRACT FROM AUTHOR]

Chlorella vulgaris is of great importance in numerous exploratory or industrial applications (e.g., medicals, food, and feed additives). Rapid quantification of algal biomass is crucial in photobioreactors for the optimization of nutrient management and the estimation of production. The main goal of this study is to provide a simple, rapid, and not-resource-intensive estimation method for determining the algal density of C. vulgaris according to the measured parameters using UV–Vis spectrophotometry. Comparative assessment measurements were conducted with seven different methods (e.g., filtration, evaporation, chlorophyll a extraction, and detection of optical density and fluorescence) to determine algal biomass. By analyzing the entire spectra of diluted algae samples, optimal wavelengths were determined through a stepwise series of linear regression analyses by a novel correlation scanning method, facilitating accurate parameter estimation. Nonlinear formulas for spectrometry-based estimation processes were derived for each parameter. As a result, a general formula for biomass concentration estimation was developed, with recommendations for suitable measuring devices based on algae concentration levels. New values for magnesium content and the average single-cell weight of C. vulgaris were established, in addition to the development of a rapid, semiautomated cell counting method, improving efficiency and accuracy in algae quantification for cultivation and biotechnology applications. [ABSTRACT FROM AUTHOR]

Benthic algae and autotrophic seston are important bases of stream food webs, and several different environmental factors may influence their biomass. We explored how benthic algae and autotrophic seston biomass (using chlorophyll-a as a proxy for algal biomass) were associated with stream temperature, channel width, canopy cover, stream cardinal orientation, benthic macroinvertebrate functional feeding group abundance, salmonid biomass, and water velocity in 16 small, fish-bearing streams in the temperate rainforest of the Olympic Peninsula in Washington State, USA, in the summer of 2020. We performed a mixed-effects regression analysis of extracted chlorophyll-a (chl-a) and then used model averaging to determine significant (α = 0.05) algal–environmental associations for benthic algae and autotrophic seston separately. We found that benthic algae chl-a concentration increased significantly with stream temperature (p = 0.0085) and decreased significantly with water velocity (p = 0.0053). For autotrophic seston, we found that chl-a concentration increased significantly with benthic macroinvertebrate predator abundance (p = 0.0007) and stream temperature (p = 0.0160). This study underscores the need to consider a broad range of environmental variables when making research and management decisions concerning stream ecology. [ABSTRACT FROM AUTHOR]

In the past years, a series of initiatives on biotechnology research have been launched, which were focused on investigating methods to improve productivity and metabolic processes related to biomass production, as well as for bio-refining biomass to produce biofuels or other valuable products from the food and pharmaceutical sectors. Advanced techniques of the biological systems electromagnetic stimulation with radiation from various frequency domains are increasingly being studied and applied in practice. This paper analyses the physiological response of the algal species of Chlorella sorokiniana exposed to the DC and AC electric fields generated at low frequencies in the range of 10 Hz - 10 kHz and for the different electric field intensities. Through a series of algal suspension exposures in the electric field of well-defined parameters, the cell growth rate for the exposed samples was analysed, as compared to the samples unexposed in the electric field. The experimental results were interpreted in terms of cellular mechanisms identified on theoretical studies and can be applied in the perspective of the development of more efficient biotechnological processes. [ABSTRACT FROM AUTHOR]

Polyurethanes (PUs) are commonly used chemicals in various industries and are conventionally produced by the reaction of polyols and diisocyanates. However, synthetic petroleum-based polymers are non-biodegradable and resulting in issues like waste disposal, risks to aquatic and terrestrial ecosystems. In this study, a novel microalgal protein-based ultraviolet (UV) curing polyurethane acrylate (PUA) was prepared with hexanediol diacrylate (20% HDDA) precursor, amino acid oligomers, and photoinitiator (Irgacure 184). Experimental conditions for the synthesis of precursors were studied and their chemical structures were confirmed by FT-IR, 1HNMR, 13CNMR, and differential scanning calorimetry (DSC). The absorption peak at 1695 cm−1 confirmed the formation of a urethane bond. For instance, the obtained polyurethane acrylate coating (PUA) possessed a glass transition temperature (Tg) of 122 ℃, tensile strength, modulus of 19.1 MPa, 465 MPa, and lower elongation break (6%). While using reactive diluents, the coating compositions showed significant enhancement of mechanical, physical, and chemical resistance properties. In general, this work offered a simple bio-scheme of reactions to prepare a sustainable microalgal-based PU coating that could be applied in the coating industry with improved properties. [ABSTRACT FROM AUTHOR]

The paper describes the anaerobic digestion of biomass of microalgae and bacteria from the treatment of wastewater from municipal sources and malt house. During the three series of experiments the influence of primary sludge addition, type of biomass and the substrate to inoculum ratio on anaerobic digestion and biogas production was investigated. The results showed that the composition of the substrate plays an important role. Digesters with added primary sludge reached stationary phase faster than without added sludge digesters but the specific biogas production was not higher. Regarding the suitable substrate to inoculum ratio the most suitable ratio is 2:1 (inoculum:biomass). Biomass from municipal wastewater treatment produced up to 186 L kg OM at 2:1 ratio of inoculum to biomass. Substrate from malt house wastewater treatment produced less biogas, 126 L kg OM at 2:1 ratio of inoculum to biomass. Methane content in the gas at the end of the experiment varied between 60 and 75 %. [ABSTRACT FROM AUTHOR]

Mediterranean rivers are subjected to strong seasonality with drought during the hot season and extreme flows in autumn-winter. In particular, drought episodes and water scarcity alter the river morphology, with repercussions on primary production and the trophic chain. In this paper, we aimed at analysing the different responses in terms of chlorophyll a content of the three main photosynthetic groups composing stream periphyton, namely diatoms, cyanobacteria and green algae. This work was conducted in the Ligurian Alps (NW-Italy) on five oligotrophic streams (Argentina, Impero, Merula, Quiliano, and Vallecrosia), similar in terms of physico-chemical parameters. We measured chlorophyll a content of diatoms, cyanobacteria and green algae by means of an in situ fluorimetric probe (BenthoTorch®). Data were collected from April to October 2014 in: 1) impacted sites, where the water scarcity was exacerbated by human pressure; 2) control sites. We applied Generalized Linear Mixed Models to investigate the response of total chlorophyll a and its relative proportions among the three algal groups in relation to the following environmental predictors: water depth, flow velocity, canopy shading, microhabitat isolation, sampling season, dissolved oxygen, temperature, pH, nutrients, and macrophyte coverage. Results showed an opposite response of diatoms and green algae. Diatoms were favoured in the control sites and under moderate flow conditions, while the probability of green algae presence was higher in the impacted sites and during the drought season. Cyanobacteria showed a response similar to green algae, preferring warm, isolated pools typical of the drought period. Diatoms proved to be the most sensitive to drought. More specifically, we found out that percentages of diatoms below 51% with respect to total benthic chlorophyll a indicate high hydrological disturbance. This study provides the first evidence that the proportion of chlorophyll a produced by diatoms can be a suitable indicator for monitoring programs aiming at determining the effects of water scarcity on river ecosystems. [ABSTRACT FROM AUTHOR]

The paper investigated the feasibility of biomethane (bio-CH4) production from the anaerobic co-digestion of the microalgae Scenedesmus quadricauda (S. quadricauda) and thickened waste activated sludge (TWAS). The concept was tested in bench-scale anaerobic digesters by varying the proportions of volatile solids (VS) loading from S. quadricauda and TWAS and two critical operational parameters, temperature and alkalinity. The CH4 production for the various S. quadricauda and TWAS proportions ranged from 234 to 318 mL/g of chemical oxygen demand (COD) digested and 329 to 530 mL/g of VS digested at 35 °C. The reductions in total solids (TS), COD, and VS ranged from 25 to 44%, 46 to 53%, and 40 to 53%, respectively. Temperature had a significant effect on CH4 production, lower temperatures greatly reduced CH4 production. No significant difference in CH4 production was observed for experiments conducted at alkalinity levels of 70, 1630, and 3200 mg/L as CaCO3. [ABSTRACT FROM AUTHOR]

This paper presents data on methane fermentation of algal biomass containingChlorellasp. andScenedesmussp. The biomass was obtained from closed-culture photobioreactors. Before the process, the algae were subjected to low temperature and pressure pretreatment for 0.0, 0.5, 1.0 and 2.0 h. The prepared biomass was subjected to mesophilic methane fermentation. The amount and composition of the biogas formed in the process were determined. The amount of biogas produced was larger when the biomass was subjected to thermal preprocessing. The proportion of methane in the gas also increased. Extending the heating time beyond 1.0 h did not significantly improve the biogassing effects. [ABSTRACT FROM PUBLISHER]

'Algae Service for LIFE', the project supported by the European Union, seeks to promote best practices in ecological service and the circular economy by implementing innovative complex system of three interlinked elements: i) prototypes for harvesting of cyanobacteria and macroalgae biomass; ii) distant methods for surveying of the blooms and defining hot-spots of algal agglomerations; and iii) restitution of harvesting costs by redesigning of waste algal biomass into valuable products. The current paper describes application of algal biomass part of the project by providing actions in redesigning of harvested waste biomass of cyanobacteria and macroalgae into potential valuable products for sustainable management and recycling of environmental resources. It also highlights the socio-economic aspects of the project and added value of the project for the European Union. [ABSTRACT FROM AUTHOR]

Algal biomass that is represented mainly by commercially grown algal strains has recently found many potential applications in various fields of interest. Its utilization has been found advantageous in the fields of bioremediation, biofuel production and the food industry. This paper reviews recent developments in the analysis of algal biomass with the main focus on the Laser-Induced Breakdown Spectroscopy, Raman spectroscopy, and partly Laser-Ablation Inductively Coupled Plasma techniques. The advantages of the selected laser-based analytical techniques are revealed and their fields of use are discussed in detail. [ABSTRACT FROM AUTHOR]

[Display omitted] • Renewable biofuel production by algal biomass has been discussed in this review. • Two major thermochemical process like pyrolysis and hydrothermal liquefaction are described. • Different pyrolysis and HDL methods in fuel production has been explained. • Temperature, heating rate of the process and product yield have been focused. • Challenges and future benefits of the fuel production using algal biomass is detailed. Renewable and sustainable biofuel production from algal biomass has been explored vigorously due to the owing potential of overcoming the limitations of first and second-generation biofuel feedstocks. Thermochemical conversion technologies are considered promising routes for bioenergy production from algal biomass and have been extensively investigated over the last few years. This paper aims to review the various pyrolysis (slow, fast, and microwave -assisted) processes and hydrothermal liquefaction (HTL) techniques. The fast pyrolysis is involving a higher heating rate and shorter residence time compared to slow pyrolysis. Microwave-assisted pyrolysis (MAP) is considered a highly efficient process due to uniform heating. Due to a high moisture feedstock, the HTL process is considered the most energy-efficient processing option for algal biomass. In all these processes, the process temperature is considered the most critical parameter affecting product yield. This paper provides a detailed analysis and discussion on the effect of temperature and heating rates on the product (biochar, bio-oil, and syngas) yields for various microalgal species. The process details, different approaches, and process conditions investigated, challenges and recent advancements achieved in both technologies have been discussed in detail that provides useful insights to design a sustainable process and understand the process feasibility. [ABSTRACT FROM AUTHOR]

Eutrophication is one of the major emerging challenges in aquatic environment. Industrial facilities, including food, textile, leather, and paper, generate a significant amount of wastewater during their manufacturing process. Discharge of nutrient-rich industrial effluent into aquatic systems causes eutrophication, eventually disturbs the aquatic system. On the other hand, algae provide a sustainable approach to treat wastewater, while the resultant biomass may be used to produce biofuel and other valuable products such as biofertilizers. This review aims to provide new insight into the application of algal bloom biomass for biogas and biofertilizer production. The literature review suggests that algae can treat all types of wastewater (high strength, low strength, and industrial). However, algal growth and remediation potential mainly depend on growth media composition and operation conditions such as light intensity, wavelength, light/dark cycle, temperature, pH, and mixing. Further, the open pond raceways are cost-effective compared to closed photobioreactors, thus commercially applied for biomass generation. Additionally, converting wastewater-grown algal biomass into methane-rich biogas through anaerobic digestion seems appealing. Environmental factors such as substrate, inoculum-to-substrate ratio, pH, temperature, organic loading rate, hydraulic retention time, and carbon/nitrogen ratio significantly impact the anaerobic digestion process and biogas production. Overall, further pilot-scale studies are required to warrant the real-world applicability of the closed-loop phycoremediation coupled biofuel production technology. • Nutrient-rich wastewater is a major cause of eutrophication in water bodies. • Algal biomass harvested from wastewater is a good substrate for biogas production. • Environmental factors affect the anaerobic digestion process. • Limited pilot-scale studies on phycoremediation coupled biogas production. • Algal blooms could be a valuable source for bioenergy production. [ABSTRACT FROM AUTHOR]

Lake Balaton, a shallow polymictic freshwater lake in Central Europe, became eutrophic in the 1970s. To retain the inorganic nutrients from the main tributary River Zala, a semi-artificial system called the Kis-Balaton Water Protection System (KBWPS) was constructed in the early 1980s. In 2015, the system was reconstructed and modernised, thus offering the opportunity to evaluate the effectiveness of the functional connection between the KBWPS and Lake Balaton over the past 20 years and to compare its impact before and after the reconstruction. To this end, time series data of algal biomass in Lake Balaton between 1999 and 2019 based on Landsat 7 satellite data were analysed. Over the last 20 years, the algal biomass in Lake Balaton showed an increasing trend (0.009 ± 0.011% increase per year), with territorial specificities also observed. No change was noted in the western part, while an increase was recorded in the eastern part of the lake. A significant difference in the rate of algal biomass accumulation was noticed before (annual increase of 0.008 ± 0.019%) and after (0.240 ± 0.306% per year) the KBWPS reconstruction. Given that the largest increase in algal biomass after reconstruction was observed in the outermost KBWPS basin of Lake Balaton, it appears that mesoscale environmental, water balance, or other factors affecting the lake are playing a role in this increase, rather than the KBWPS reconstruction. This research highlights the potential to study aquatic ecosystems using Earth observation techniques, and how mesoscale factors such as changes in the local climate regime or shifts in lake management can greatly impact the trophic state of a large shallow lake. Effectively identifying these factors is crucial in maintaining the proper status of aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Heavy metals, dyes and pharmaceutical pollutants in water environment are considered as serious threat to the human and animal health globally. Rapid development of industrialization and agricultural activities are the major source for eliminating the toxic pollutants into the aquatic environment. Several conventional treatment methods have been suggested for the removal of emerging contaminants from wastewater. Algal biosorption, among other strategies and techniques, is demonstrating to be a limited technical remedy that is more focused and inherently more efficient and helps remove dangerous contaminants from water sources. The different environmental effects of harmful contaminants, including heavy metals, dyes, and pharmaceutical chemicals, as well as their sources, were briefly compiled in the current review. This paper provides a comprehensive definition of the future possibilities in heavy compound decomposition by using algal technology, from aggregation to numerous biosorption procedures. Functionalized materials produced from algal sources were clearly proposed. This review further highlights the limiting factors of algal biosorption to eliminate the hazardous material. Finally, this study showed how the existence of algae indicates a potential, effective, affordable, and sustainable sorbent biomaterial for minimizing environmental pollution. [Display omitted] • Algal biosorption is the economically viable and low-energy technological solution. • Biosorption mechanisms of algal biomass towards hazardous pollutants are discussed. • Functionalized materials derived from algal technology are reviewed. • Limiting factors and reactors involved in algal biosorption were elucidated. • Prospects and recommendations for future works were summarized. [ABSTRACT FROM AUTHOR]

The rising living standards of humans have a high demand for natural resources. Algal biomass has emerged as a substitute for conventional resources obtained from animals and plants. Compositionally, algae constitute extractable carbohydrates, proteins, lipids, and other valuable bioactive compounds (BACs) in abundance. BACs profusely derived from algal biomass include long-chain polysaccharides, fatty acids such as mono- and polyunsaturated fatty acids (MUFA and PUFA), phenols, and proteins. The coupling of wastewater with algae for resource recovery for the BACs extraction can serve as a source of plenteous biochemicals with high industrial values like pigments, polysaccharides, lipids, antioxidants, and growth-promoting compounds. Extracted algal BACs can incorporate in the manufacturing of numerous cosmetic products, pharmaceuticals, and nutraceuticals. The productivity and quality of algal produce are still low relative to their demand. Genetic engineering has emerged as a proven approach to enhance the quality and quantity of algal produces and provide a better avenue for biofuel and value-added chemicals productions. Currently, genetic engineering has grabbed significant attention from researchers, and continuous efforts are encouraged to improve industrially viable algal species that can satisfy future demand. This article focuses on the wide range of BACs derived from algae and wastewater for resource recovery, genetic engineering in algae for BACs, influencing processing parameters for genetic engineered algae, concerns associated with genetic engineered algae, and future perspective. [ABSTRACT FROM AUTHOR]

The accumulation of CO2 in the atmosphere carries with it severe consequences, and cities are responsible for 70% of CO2 emissions. With this initiative, we address how innovative green architecture can contribute to removing CO2 from the urban area by implementing elements that incorporate microalgae cultivation into architecture. The presented project incorporates two photobioreactor installations filled with water, where microalgae circulate through methacrylate tubes. Used as two architectural elements: a façade that can fix 720 kg of CO2 per year from the atmosphere and produce 400 kg of biomass that can be used as fertilizer in irrigation water; and three artificial trees that can fix 50 kg of CO2 and produce 28 kg of biomass. To test its efficiency, a Life Cycle Inventory was conducted and compared to the amount of CO2 fixed during its lifetime. It was concluded that the system would need 11.11 years to fix the CO2 produced and would have a negative CO2 impact of 27 tons of CO2 during the useful life of its materials. This project is a starting point towards developing a disruptive and experimental alternative with great potential, being the first in Spain and one of the first in the world. [ABSTRACT FROM AUTHOR]

Algal biomass is a prospective feedstock for the eco-sustainable production of many different products with added value, such as meals, feeds, and fuels. The remaining biomass from the algae can be used as raw material and can be transformed into useful secondary products after the important macromolecules have been removed. By optimizing algal biomass hydrolysate utilizing microbial fermentation, several studies demonstrated the generation of bioenergy (bioalcohol, biogas, and biohydrogen) and biochemicals (organic acids and biopolymers). Since the harvest and maintenance of sustainable algal cultivation incur considerable energy and economical prowess, developing products from algae remains a challenge to be countered in commercial applications. This is a typical bottleneck issue when processing algae for fuels or chemicals at the pilot scale. Implementation of integrated algae biorefinery methods can substantially reduce the cost of production and energy consumption. An algae-based green economy can be financially more viable and utilizable, especially for countries with weaker economies. This review's goal is to examine the implementation of integrated biorefineries for the recovery of bioproducts generated from algae and potential applications. In this context, the life cycle analysis and business elements of a unified algal biorefinery are also addressed. [ABSTRACT FROM AUTHOR]

The world's biodiesel demand is rising from day to day due to the urgency to tackle fuel crisis, greenhouse gases (GHG) emissions and climatic changes in the near future. This alternative energy will minimize the dependency on fossil fuels while guarantees a continuous energy supply and upholds the ecosystem sustainability. Malaysia, as a developing country is still finding a suitable green energy source to support the national daily energy consumption without affecting the political stability and socio-economic background. In this article, a realistic effort made by applying microalgal biotechnology for biodiesel production and concurrently mitigating CO2 and other flue gases in the presence of tertiary wastewater. Microalgae produce high amount of biomass feedstock in a short time with less amount of land capacity by using wastewater as the medium to grow. Malaysia is producing variable wastes from both agro-industrial and industrial sectors that can be recycled as a nutrient supply for microalgae. Wastewater that is available in Malaysia comprises high nutrient value compounds that have high amount of nitrogen and phosphorus. The current trend in Malaysia in the biodiesel industry as well as the application of microalgae as a superlative feedstock to replace conventional methods and boost future biodiesel industries are well elaborated in this article. This also includes the opportunities and challenges of Malaysia in cultivating microalgae with stronger technical feasibility and higher turnout in the economy by using the high rate algal pond (HRAP). Apart from that, this review paper illustrates the process of converting waste from five different sources in biofuel production by using microalgae as the intermediate tool. [ABSTRACT FROM AUTHOR]

The food industry is a high consumer of polymer packing materials, sealing materials, and engineering components used in production equipment. Biobased polymer composites used in the food industry are obtained by incorporating different biogenic materials into the structure of a base polymer matrix. Renewable resources such as microalgae, bacteria, and plants may be used as biogenic materials for this purpose. Photoautotrophic microalgae are valuable microorganisms that are able to harvest sunlight energy and capture CO2 into biomass. They are characterized by their metabolic adaptability to environmental conditions, higher photosynthetic efficiency than terrestrial plants, and natural macromolecules and pigments. The flexibility of microalgae to grow in either low-nutrient or nutrient-rich environments (including wastewater) has led to the attention for their use in various biotechnological applications. Carbohydrates, proteins, and lipids are the main three classes of macromolecular compounds contained in microalgal biomass. The content in each of these components depends on their growth conditions. In general, proteins represent 40–70% of microalgae dry biomass, followed by carbohydrates (10–30%) and lipids (5–20%). A distinctive feature of microalgae cells is the presence of light-harvesting compounds such as photosynthetic pigments carotenoids, chlorophylls, and phycobilins, which are also receiving growing interest for applications in various industrial fields. The study comparatively reports on polymer composites obtained with biomass made of two species of green microalgae: Chlorella vulgaris and filamentous, gram-negative cyanobacterium Arthrospira. Experiments were conducted to reach an incorporation ratio of the biogenic material into the matrix in the 5–30% range, and the resulting materials were characterized by their mechanical and physicochemical properties. [ABSTRACT FROM AUTHOR]