Production Of Third-generation Biofuels Research Articles

MICROALGAS: UMA ESTRATÉGIA SUSTENTÁVEL NA TRANSFORMAÇÃO E OBTENÇÃO DE COMPOSTOS ORGÂNICOS

MICROALGAE: A SUSTAINABLE STRATEGY IN THE TRANSFORMATION AND OBTAINING OF ORGANIC COMPOUNDS. The present review presents the biotechnological potential of microalgae, highlighting its applications in biofuels, bioremediation, production of bioactive compounds, biocatalysts, and biofertilizers. Microalgae are photosynthetic microorganisms that combine characteristics of plants and heterotrophic microorganisms, such as yeasts, bacteria, and fungi. They can be considered biotechnological agents of extreme versatility and metabolic adaptability. Its photosynthetic efficiency can absorb large volumes of anthropogenic CO2 and convert it into biomass rich in compounds of high biological and energetic value, enabling the development of sustainable bioremediation processes and the production of third-generation biofuels and biofertilizers. In addition, its biomass has aroused interest in obtaining compounds with biological action, such as carotenoids, mycosporine-like amino acids, polyunsaturated fatty acids, sterols, phycocolloids, carbohydrates, and proteins. The biotechnological potential of microalgae does not end with the production and extraction of its biomass. Its dynamic and adaptive metabolism allows its use in the biotransformation of xenobiotic substrates and the production of compounds of chemical and pharmaceutical interest. In this perspective, microalgae have application qualities as a biotechnological platform in developing synergistic processes between the environment, society, and industry, thus contributing to the expansion and use of Green Chemistry and strengthening the circular economy.

Comparison of microalgal hydrochar and pyrochar: production, physicochemical properties, and environmental application.

Microalgal biomass has been considered the third-generation biofuel production feedstock, but microalgae-derived biochar still needs to be thoroughly understood. This study aims to evaluate the production and physicochemical properties of microalgae-derived hydrochar produced by hydrothermal carbonization (HTC) process by comparison with pyrochar produced by dry thermal carbonization (DTC) process for environmental applications. Microalgal biochar was produced with commercially available Chlorella vulgaris microalgae using HTC and DTC processes under various temperature conditions. Pyrochar presented higher pH, ash contents, porosity, and surface area than hydrochar. Hydrochar gave more oxygen-containing functional groups on the surface and higher lead adsorption than pyrochar, making the microalgal hydrochar applicable in soil amendment and various environmental remediations. HTC could be an economically feasible thermochemical process for microalgal biochar production. It can produce hydrochar with high production yield from wet microalgae at low temperatures without a drying process.

Recent Advances in Seaweed Biorefineries and Assessment of Their Potential for Carbon Capture and Storage

Seaweeds are among the most important biomass feedstocks for the production of third-generation biofuels. They are also efficient in carbon sequestration during growth and produce a variety of high-value chemicals. Given these characteristics together with the relatively high carbohydrate content, seaweeds have been discussed as an ideal means for CO2 capture and biofuel production. Though third-generation biofuels have emerged as some of the best alternatives to fossil fuels, there is currently no large-scale production or mainstream use of such liquid fuels due to the many technical challenges and high production costs. The present study describes the concept of coastal marine biorefineries as the most cost-effective and sustainable approach for biofuel production from seaweeds, as well as atmospheric carbon capture and storage (CCS). The suggested refinery system makes use of marine resources, namely seawater, seaweed, and marine microorganisms. Firstly, extensive screening of the current literature was performed to determine which technologies would enable the emergence of such a novel biorefinery system and its merits over conventional refineries. Secondly, the study investigates various scenarios assessing the potential of seaweeds as a means of carbon sequestration. We demonstrate that the removal of 100 Gigatons of excess CO2 using seaweed farms can be achieved in around 4 months to less than 12 years depending on the area under cultivation and the seaweed species. The total bioethanol that could be generated from the harvested biomass is around 8 trillion litres. In addition, high-value chemicals (HVC) that could potentially be recovered from the process represent a considerable opportunity with multi-billion-dollar commercial value. Overall, coastal marine biorefineries have strong potential for a sustainable green economy and represent a rapid approach to climate change mitigation.

Algae: A potential feedstock for third generation biofuel

Due to increase in population and augmented usage of conventional fuels; raised interest among scientist to find some potential substitute of conventional fuels for sustainable development, because these fuels are limited and also non-renewable. Many alternative fuels such as biodiesel, ethanol, methanol, synthetic fuels, hydrogen, biogas, natural gas, etc. have been used as internal combustion (IC) engines fuels. Liquid biofuels gained lot of attention as alternative to fossil fuels because it can be derived from renewable biomass resources. The first-generation biofuels originate dispute over food versus fuel as most of the feedstocks are edible. In this regard, algae have emerged as a vital source of production of third generation biofuels, such as bioethanol, biohydrogen, biopropane etc. In some cases the oil yield from microalgae are better as compared to several oil producing crops. Microalgae are photosynthetic microorganisms which convert sunlight, water, and carbon dioxide to sugars, from which macromolecules, such as lipids and triacylglycerols can be obtained. In this paper, the detailed information about algae, its cultivation techniques and lipid extraction for the production of biofuels have been discussed. The characterization of the fuel obtained by algae and its application as diesel engine fuel have also covered in this paper.

Improving carbohydrate accumulation in Chlamydomonas debaryana induced by sulfur starvation using response surface methodology.

Most methods that promote carbohydrate production negatively affect cell growth and microalgal biomass production. This study explores, in a two-stage cultivation strategy, in Chlamydomonas debaryana the optimization of certain culture conditions for high carbohydrate production without loss of biomass. In the first stage, the interaction between sodium bicarbonate supplementation, aeration, and different growth periods was optimized using the response surface methodology (RMS). The 3-factor Box-Behnken design (BBD) was applied, and a second-order polynomial regression analysis was used to analyze the experimental data. The results showed that 0.45g L-1 of sodium bicarbonate combined with a good aerated agitation (0.6 L min-1) and a cultivation period of 18days are optimal to produce 5.02g L-1 of biomass containing 43% of carbohydrates.Under these optimized growth conditions, accumulation of carbohydrates was studied using different modes of nutritional stress. The results indicated that carbohydrate content was improved and the maximum accumulation (about 60% of the dry weight) was recorded under sulfur starvation with only a 14% reduction in biomass as compared to control. This study showed promising results as to biomass production and carbohydrate yield by the microalgae C. debaryana in view of production of third-generation biofuels.

3D bioprinting on cathodes in microbial electrosynthesis for increased acetate production rate using Sporomusa ovata

Microbial Electrosynthesis (MES) is emerging as a promising technology for the decarbonization of the economy. The use of CO2 as a feedstock, i.e. through carbon capture and utilization, can create attractive business opportunities for the production of third generation biofuels. Achieving highly efficient electron transfer from the cathode to microbes is one of the main challenges hindering the development of MES reactors. It is, therefore, essential to improve biofilm growth for enhanced electron-transfer during bioconversion.In this study we show the first use of 3D bio-printing for microbial electrosynthesis systems, creating a “synthetic biofilm”, containing Sporomusa ovata. The synthetic biofilm greatly improves the acetate production rate while drastically decreasing start-up time. Using H-cell reactors, poised at −0.8 V vs Ag/AgCl, with a synthetic biofilm printed on a carbon cloth electrode, an average acetate productivity of 47±5.1 g day−1 m−2 (0.31±0.55 g L−1 day−1) with a maximum productivity of 104 g day1 m−2 (0.68 g L−1⋅day−1) was achieved. This is an order of magnitude higher than typical S. ovata production rates, and 2–3 fold higher than reactors using specialized cathodes. Start-up of MES reactors typically require days, whereas a high production rate was achieved almost directly after the start-up (±40 h) using the synthetic biofilm. Cyclic voltammetry data showed H2 formation occurred at much higher potentials than in the control reactors, (approx. −550 mV vs. −950 mV for controls). Imaging showed that the synthetic biofilm allowed for dense growth of S. ovata cells at the cathode, increasing electron transfer efficiency and potentially improving the bio-catalyzation of H2.

Independent parallel pyrolysis kinetics of extracted proteins and lipids as well as model carbohydrates in microalgae

Microalgae offer unique potentials for developing advanced biorefineries, including third-generation biofuel production, wastewater treatment, and animal and aquaculture feed production. The thermodegradation of protein, lipid, and carbohydrates plays a vital role in the thermochemical conversion of microalgae for biofuel production. This work aims to investigate the kinetics and the interaction of extracted protein and lipid as well as model carbohydrates from microalgae to assist the development of microalgae conversion techniques, which have not been studied so far. Thermogravimetric analysis is integrated with an independent parallel reaction (IPR) and particle swarm optimization (PSO) method to explore the pyrolysis kinetics of three constituents (protein, lipid, and carbohydrates). The calorific values of the three constituents show that protein (5.33 MJ·kg−1) is not a suitable biofuel feedstock. In contrast, lipid (34.22 MJ·kg−1) and carbohydrates (15.37–15.84 MJ·kg−1) are considered as potential feedstocks for liquid and solid biofuel production, respectively. The pyrolysis processes suggest that the thermodegradation extent follows the order of carbohydrates > protein > lipid. The application of the IPR-PSO method on the pyrolysis kinetics of microalgae in three pseudo-components obtains a high fit quality (>96%) for all cases, indicating that the method is suitable to predict the kinetics parameters of the three constituents of microalgae. The effect analysis reveals that the synergistic effect accounts for about 50% of the total mass of the thermodegradation process of model carbohydrates, occuring at 200–320 °C. Meanwhile, the theoretical and experimental thermogravimetric analysis curve of combination of the three constituents suggests that there are four regions detected, including strong synergistic effect, weak antagonistic effect, weak synergistic effect, and strong antagonistic effect, respectively.

Aggregation-induced emission luminogens for lipid droplet imaging.

Lipid droplets (LDs) are evolutionarily conserved organelles involved in energy homeostasis and versatile intracellular processes in different cell types. Their importance is ubiquitous, ranges from utilization as the biofunctional components to third-generation biofuel production from microalgae, while morphology and functional perturbations could also relate to the multiple diseases in higher mammals. Biosynthesis of lipids can be triggered by multiple factors related to organismal physiology and the surrounding environment. An early prediction of this might help take necessary actions toward desired outcomes. In vivo visualization of LDs can give molecular insight into regulatory mechanisms and the underlying connections with other cellular structures. Traditional bioprobes for LDs detection often suffer from different dye-specific limitations such as aggregation-caused quenching and self-decomposition phenomena that hinder the research advancement. The emergence of lipid-specific nanoprobes with aggregation-induced emission (AIE) attributes in recent years is promising in remunerative characteristics with defined bioimaging properties. By utilizing the easy synthetic techniques and exploiting the unique physical features of these molecules, highly selective, stable, biocompatible and facile fluorescent probes could be fabricated for lipid detection. This chapter will provide up-to-date insight into the recent advances in lipid-specific AIE-based probes to enhance the opportunities for basic research related to the distinct roles of LDs in living organisms.

Values and Drawbacks of Biofuel Production From Microalgae

Increased energy consumption leads to a reduction in limited nonrenewable resources called fossil fuels. Due to this fact, researchers look for alternative energy sources to satisfy the need of the current generation without compromising the ability of future generations to meet their needs. As a result, nowadays the production of energy from biological sources is highly applicable and takes advantage of fossil fuel due to the limited impact on the environment. On the other hand, food cost, land use for some other purposes, and carbon emissions have risen due to the increased production of first-generation bioethanol. Even though the second-generation bioethanol from lignocellulose agricultural waste solved this problem, it again faced difficulties-to-overcome technological barriers. This, in turn, pushed researchers to come up with another alternative called the third-generation biofuel production. The renewed promise is held in microalgae biomass as an alternative feedstock. This review deals with the important aspects of biofuel production from algae as a renewable resource. The production processes and their merits and demerits of algae capacity in producing biofuel are also discussed.

Sugar contents and oligosaccharide mass profiling of selected red seaweeds to assess the possible utilization of biomasses for third-generation biofuel production

In the present study, we report the sugar contents and oligosaccharide mass profiles of Kappaphycus alvarezii (Doty) Doty ex Silva, Solieria robusta (Greville) Kylin, Gracilariacorticata (J. Agardh), and Gracilariacorticata v. cylindrica Børgesen. Sugar contents in the biomasses of the studied seaweeds indicated that they represent potential sources of raw material for biofuel conversion. Fractionation improved the sugar yield by loosening cell wall components. A Fourier-transform infrared spectroscopy (FTIR) analysis of different cell wall fractions revealed differences in their structural components. Fractionation exposed and released some of the functional groups, depending on the harshness of treatments. However, variable carbohydrate moieties were observed in each fraction. A MALDI TOF-TOF MS analysis of cell wall revealed a complex and dynamic network of polymers in cell walls. K. alvarezii produced the greatest number of oligosaccharide units, followed by S. robusta, G. corticata v. cylindrica and G. corticata. The cell wall of seaweeds was similar to the polymers in the cell wall of higher plants, which indicated the potential to utilize seaweed biomasses for biofuel production. To the best of our knowledge, the present study is the first to report the oligosaccharide mass profiling (OLIMPs) of red seaweeds. A further detailed analysis of the sugar composition of the cell wall and a linkage analysis of OLIMPs would provide detailed structural information. Present results confirmed the potential utilization of red seaweed biomass as an alternative for biofuel production and potential of red seaweed species to be developed as new industrial crops under blue revolution program.

Cultivation of Oily Microalgae for the Production of Third-Generation Biofuels

Biofuel production by oleaginous microalgae is a promising alternative to the conventional fossil fuels. Many microalgae species have been investigated and deemed as potential renewable sources for the production of biofuel, biogas, food supplements and other products. Oleaginous microalgae, named for their ability to produce oil, are reported to store 30–70% of lipid content due to its metabolic properties under nutrient starvation conditions. This review presents the assortment of the research studies focused on biofuel production from oleaginous microalgae. The new methods and technologies developed for oleaginous microalgae cultivation to improve their biomass content and lipid accumulation capacity were reviewed. The production of renewable, carbon neutral, bio-based or microalgae-based transport fuels are necessary for environmental protection and economic sustainability. Microalgae are a significant source of renewable biodiesel because of their ability to produce oils in the presence of sunlight more efficiently than that of crop oils. This review will provide the background to understanding the bottlenecks and the need for improvement in the cultivation or harvesting process for oleaginous microalgae.

Bioethanol production from microalgae polysaccharides.

The worldwide growing demand for energy permanently increases the pressure on industrial and scientific community to introduce new alternative biofuels on the global energy market. Besides the leading role of biodiesel and biogas, bioethanol receives more and more attention as first- and second-generation biofuel in the sustainable energy industry. Lately, microalgae (green algae and cyanobacteria) biomass has also remarkable potential as a feedstock for the third-generation biofuel production due to their high lipid and carbohydrate content. The third-generation bioethanol production technology can be divided into three major processing ways: (i) fermentation of pre-treated microalgae biomass, (ii) dark fermentation of reserved carbohydrates and (iii) direct "photo-fermentation" from carbon dioxide to bioethanol using light energy. All three technologies provide possible solutions, but from a practical point of view, traditional fermentation technology from microalgae biomass receives currently the most attention. This study mainly focusses on the latest advances in traditional fermentation processes including the steps of enhanced carbohydrate accumulation, biomass pre-treatment, starch and glycogen downstream processing and various fermentation approaches.

An effective method for harvesting of microalga: Coculture-induced self-flocculation

Microalgae are potential candidates for the production of third-generation biofuels, but the high-energy consumption of harvesting biomass makes current commercial microalgal biodiesel production economically unfeasible. Self-flocculation is regarded as a cost-efficient strategy for harvesting microalgae. In this work, a coculture system was developed by the mixotrophic cultivation of two poorly flocculating microalgae, Desmodesmus sp. ZFY and Monoraphidium sp. QLY-1, for self-flocculation of microalgal cells. The flocculation efficiency for harvesting was enhanced to 85.33% with settling for 4 h in coculture, which was better than that in mono-culture (57.98% and 32.45%). Coculture resulted in changes in both the concentration and composition of extracellular polymeric substances (EPS) in the culture, which partially contributed to cell aggregation. The concentration of polysaccharides in LB-EPS ranged from 27.01% and 27.35% in mono-culture to 46.53% in coculture. Moreover, the fine properties of lipid productivity (93.99 mg L−1 d −1) and fatty acid composition in coculture indicated the potential to produce biodiesel within most biodiesel standards.

Prioritization of prospective third-generation biofuel diatom strains

Energy has been playing a pivotal role in the progress and prosperity of a nation. Growing demands with dwindling stock of fossil fuels with the associated greenhouse gas (GHG) footprint and the consequent changes in the climate during the post-industrialization era have necessitated the exploration for sustainable energy alternatives. Biofuels are gaining importance as viable alternatives to fossil fuels during the last decade. Microalgae, especially diatoms, have shown prospects to be viable third-generation biofuel feedstocks, due to its higher lipid productivity, shorter cycling time and ubiquitous presence. This investigation focuses on identifying robust diatom strains that can sustain the vagaries of nature and yield higher lipid. This would avert the imminent risks of contamination associated with pure cultures and higher costs. The current research involved inventorying diatom consortia across diverse lentic and lotic habitats of the Aghanashini estuary with varied levels of nutrients primarily influenced by distribution of flora and fauna to understand the role of environmental parameters and nutrient levels in species composition, community structure. This effort is an essential prelude to phyco-prospecting potential candidates for third-generation biofuel production. The results obtained from the present study provide insights into an optimal habitat conditions, more specifically ideal nutrient concentrations for enhanced growth of different clusters of diatoms, a determining factor for higher biomass and lipid productivity. Multivariate statistical analyses revealed an occurrence of 27 tolerant diatoms species belonging to genera’s Amphora, Cyclotella, Navicula, Nitzschia and Pleurosigma. Linkages of the dominant and productive clusters of diatoms with habitat nutrient concentrations were investigated through agglomerative hierarchical clustering. Probable empirical relationship among varying environmental conditions and corresponding lipid content of diatoms were explored through regression analyses. Investigations of species tolerant to higher nutrient loads and assessment of lipid aided in prioritizing the strains with benefits of phyco-remediation as well as prospects of biofuel.

Bioflocculation as an innovative harvesting strategy for microalgae

Microalgae are a promising new source of biomass for the production of third generation biofuels but, so far, the majority of microalgal biomass has been used for high-value applications. New low-cost technologies are needed to make the production and processing of microalgae economically feasible for low-value applications. A major challenge lies in the harvesting of microalgae, which requires a cost-efficient separation technology. Flocculation, especially bioflocculation, is an attractive low-cost separation technology. Various new bioflocculation strategies have been claimed to generate major advances in cost-efficient harvesting. Here, we review the recent advances in bioflocculation based on algal–bacterial, algal–fungal, or algal–algal interactions within the framework of microalgae biomass harvesting for biofuel production. We also discuss recent advances using infochemicals and genetic engineering for the induction of bioflocculation.

DEVELOPMENT AND EVALUATION OF THERMAL AND CHEMICAL MICROALGAE CELL DISRUPTION METHODS FOR BIOFUELS AND BIOPRODUCTS PRODUCTION

Biomass of microalgae continues under study as promising candidate for novel biofuels and bioproducts, however, microalgae-based processes faces technical bottlenecks related to efficiency of metabolite extraction and transformation. This paper shows the development and evaluation of thermal and chemical cell disruption methods for the extraction of oil from Nannochloropsis sp. as feedstock for the production of third generation biofuels and high value fatty acids, in order to achieve lipid extraction efficiency. The thermal cell disruption process chosen was autoclave, during operation times of 1 and 3 hours at 394.15 K and 103410 Pa. Chemical treatment was based on acid hydrolysis with HCl in concentrations of 0.1, 0.5, 1 and 3 mol L-1. Organosolv Pretreatment was also used with a reaction time of 4.1 hours at 394.15 K and 103410 Pa. Results showed that the thermal and Organosolv cell disruption process increases extraction yields for biomass without pretreatment, but these did not exceed any of the results obtained with acid hydrolysis. Solution 0.5 mol L-1 HCl proved to be the most suitable for cell disruption process. In addition it was determined that the water content in the pretreated biomass, decreases the efficiency of the extraction processes.

DRUM: A New Framework for Metabolic Modeling under Non-Balanced Growth. Application to the Carbon Metabolism of Unicellular Microalgae

Metabolic modeling is a powerful tool to understand, predict and optimize bioprocesses, particularly when they imply intracellular molecules of interest. Unfortunately, the use of metabolic models for time varying metabolic fluxes is hampered by the lack of experimental data required to define and calibrate the kinetic reaction rates of the metabolic pathways. For this reason, metabolic models are often used under the balanced growth hypothesis. However, for some processes such as the photoautotrophic metabolism of microalgae, the balanced-growth assumption appears to be unreasonable because of the synchronization of their circadian cycle on the daily light. Yet, understanding microalgae metabolism is necessary to optimize the production yield of bioprocesses based on this microorganism, as for example production of third-generation biofuels. In this paper, we propose DRUM, a new dynamic metabolic modeling framework that handles the non-balanced growth condition and hence accumulation of intracellular metabolites. The first stage of the approach consists in splitting the metabolic network into sub-networks describing reactions which are spatially close, and which are assumed to satisfy balanced growth condition. The left metabolites interconnecting the sub-networks behave dynamically. Then, thanks to Elementary Flux Mode analysis, each sub-network is reduced to macroscopic reactions, for which simple kinetics are assumed. Finally, an Ordinary Differential Equation system is obtained to describe substrate consumption, biomass production, products excretion and accumulation of some internal metabolites. DRUM was applied to the accumulation of lipids and carbohydrates of the microalgae Tisochrysis lutea under day/night cycles. The resulting model describes accurately experimental data obtained in day/night conditions. It efficiently predicts the accumulation and consumption of lipids and carbohydrates.

Obtaining high value products in a biorefinery topology using microalgae

Resumen en: M icroalgae biomass presents high potential for third-generation biofuel production. It also contains other products whose recovery can contribute to the...

Research on the biodiversity of Western Siberia microalgae for third-generation biofuel production processes

Approaches are considered for the search for novel sources of non-food, renewable raw materials for third-generation biofuel production, namely, microalgae strains inhabiting natural systems of Western Siberia. This regional biodiversity survey is of great interest in connection with the vast habitat areal and the limited research on the properties of microalgae. During the work, a number of strains was isolated; one of them, Chlorella spp. A1125, has the necessary characteristics for cultivation in a pilot photobioreactor, including a maximum lipid productivity of 0.081 g/L (23% of the dry cell weight) with growth in minimal media. The strain is characterized by the content of both saturated fatty acids C16:0 (25%) and unsaturated fatty acids C16:2 (16%) and C18:2 (27%), making it a promising candidate for the third-generation biofuel production.

Use of third-generation biofuels in self-contained power generation systems based on contemporary steam piston engines

An alternative concept is studied for third-generation biofuel production and use in low capacity self-contained cogeneration installations, making it possible to optimize the whole production cycle for conversion of biomass energy into thermal and electrical energy. It is shown that the use of contemporary steam piston engines instead of internal combustion engines in small thermal electric power plants with a capacity up to 1 MW makes it possible to use boiler biofuel prepared by simplified waste-free technology based on energy-efficient low-temperature processes with a marked (by a factor of 1.3–1.5 compared with steam turbines, and by a factor of 1.25–2 compared with diesel power stations) improvement in the efficiency of converting heat of combustion into electrical energy. Development of cogeneration systems of this class makes it possible to reduce the dependence of consumers on natural monopolies in the field of power supply due to the use of local (in this case renewable) fuel resources.