•A review of microalgae thermochemical conversion to bioliquids was carried out.•We focused on pyrolysis and hydrothermal liquefaction for biocrude/biofuels.•Original experimental research on ...microalgae pyrolysis was also carried out.•Starvation does not impact significant on the energy content of the biocrude.•This result is relevant for designing full scale microalgae production plants.
Advanced Biofuels steadily developed during recent year, with several highly innovative processes and technologies explored at various scales: among these, lignocellulosic ethanol and CTO (Crude Tall Oil)-biofuel technologies already achieved early-commercial status, while hydrotreating of vegetable oils is today fully commercial, with almost 3.5Mt/y installed capacity worldwide. In this context, microalgae grown in salt-water and arid areas represent a promising sustainable chain for advanced biofuel production but, at the same time, they also represent a considerable challenge. Processing microalgae in an economic way into a viable and sustainable liquid biofuel (a low-cost mass-product) is not trivial. So far, the most studied microalgae-based biofuel chain is composed by microorganism cultivation, lipid accumulation, oil extraction, co-product valorization, and algae oil conversion through conventional esterification into Fatty Acids Methyl Esters (FAME), i.e. Biodiesel, or Hydrotreated Esters and Fatty Acids (HEFA), the latter representing a very high quality drop-in biofuel (suitable either for road transport or for aviation). However, extracting the algae oil at low cost and industrial scale is not yet a mature process, and there is not yet industrial production of algae-biofuel from these two lipid-based chains. Another option can however be considered: processing the algae through dedicated thermochemical reactors into advanced biofuels, thus approaching the downstream processing of algae in a completely different way than separation. The present work examines the possible routes for thermochemical conversion of microalgae into liquid biofuels, distinguishing between dry-processes (namely Pyrolysis, PO) and wet-processes (near critical-water HydroThermal Liquefaction, HTL). A literature review on algae-HTL was carried out, distinguishing between batch and continuous experiments, and compared to original results from algae pyrolysis. In particular, pyrolysis was carried out on both starved (lipid-accumulated) and non-starved microalgae. Typical composition of major products is given for both PO and HTL, comparing the main characteristic of the products.
Major engineering advantages and challenges in thermochemical conversion of algae into liquid biofuels were identified and discussed for both processes, in view of the production of a transport biofuel and the full exploitation of this renewable feedstock in energy and biorefinery complexes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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•Different microalgal cultivation systems are comprehensively reviewed.•Modern approaches for enhancing microalgal lipid accumulation are discussed.•Harvesting, lipid extraction and ...transesterification methods are discussed.•Techno-economic and environmental impacts of microalgal biodiesel are presented.•Real case scenarios for large-scale microalgal biodiesel production are summarized.
Biodiesel is considered a promising alternative to conventional fuels in response to increasing global energy demands, and it also contributes to reduced environmental emissions. Microalgae is a potential resource for qualitative biodiesel production due to its high specific growth rate, ability to accumulate significant quantities of intracellular lipids, potential to utilize wastewater as a cultivation medium and less cropland requirement compared to conventional oil crops. However, the commercialization of microalgae biodiesel largely depends on the energy and cost-efficiency of the microalgae cultivation system. Moreover, optimization of cultivation systems and strain improvement in microalgae are promising strategies to enhance the growth rate and lipid productivities. This review provides a comprehensive overview of the various microalgae cultivation systems, focusing on the recent developments, including the genetic engineering perspectives in improving microalgae growth and lipid productivity, techno-economic analysis, and real case studies for microalgal biodiesel production. The review paper also summarizes the microalgae harvesting and lipid extraction processes, transesterification methodologies, quality of microalgae biodiesel, and environmental concerns associated with the large-scale production of microalgae biodiesel.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Globalized approach towards heavy oil emulsions from colloid science to industry.•Prevalence of bitumen emulsions; their shared mechanism and antithetical roles.•Complexity of heavy oil emulsions ...lies in oversimplification of heavy oil types.•“Intelligent” chemical application as a solution to the heavy oil emulsion paradox.
Heavy oil, commonly defined by high density, viscosity, and heavy components distinguishing it from light oil, has a peculiar nature with respect to emulsification. In this article, we delve into the colloid and interface aspects of heavy oil emulsions and their types (heavy oil-in-water emulsion and water in-heavy oil emulsion) along with their industrial applications and occurrences. We observe the paradoxical roles heavy oil emulsions play at different stages of heavy oil production such as upstream, midstream, downstream (and other related areas). First, indigenous surface-active agents in the heavy oil are discussed along with the upstream efforts to generate chemically stable in-situ oil-in-water emulsion in the reservoir to improve displacement efficiency of heavy oil. Functions of naturally formed heavy oil emulsions encountered at the different stages of thermal recovery applications are also presented. This is followed by the review of mid-stream demulsification and emulsification efforts during the oil processing and production periods. The paper is then finalized with the discussion on the final demulsification attempts in the downstream sector defined by the refining process and wastewater management—along with other relevant areas of oil spill and aquifer remediation. With this comprehensive overview of the roles that heavy oil emulsions play in the heavy oil industry, we hope to interconnect the separate, detached views of heavy oil emulsions existing in distinct heavy oil industry sectors and provide a globalized, big-picture view for enhanced understanding of heavy oil emulsions and their applications. The results from this investigation demonstrate that a comparative approach towards heavy oil emulsions is necessary to bolster a more optimal and dynamic manipulation of functions and properties of heavy oil emulsion throughout the industry.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Fossil fuels are sharing a large portion of energy demand. Conventional energy sources emit a huge amount of greenhouse gas into the atmosphere, which creates energy and environmental challenges for ...the ecosystem. To fulfill the world energy demand and to support environmental as well as economic development in a sustainable way, with the utilization of technological advancement of renewable energy resources, algae are presently believed as most adaptable feedstock materials for bioenergy production. Algae has a high fixation rate of atmospheric carbon dioxide which supports to fast growth rate with high productivity per unit area in the form of renewable algal biomass. The present article aims to elaborate on the three generations of biofuels, sustainable microalgae biomass production, cultivation systems, and a wide range of growth parameters. The microalgae harvesting methods and their challenges are also discussed, with a special focus on lipid extraction methods and future r recommendations. The upstream and downstream processes of microalgae could help to harness the microalgae energy in an eco-friendly manner and will help in achieving overall sustainable development.
•Microalgal biomass is a sustainable feedstock for biofuel and bioproducts.•Optimization of upstream and downstream processes enhance produces of microalgae.•Important biotic and abiotic factors of microalgae cultivation are summarized.•Critical steps of harvesting and transesterification of microalgal are discussed.•The key challenges with future recommendations of algal cultivation are briefed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The organic acids (OAs) market has been expanding due to their versatility and wide range of uses in several industrial applications, thus prompting a transition from chemical to biological ...approaches to generate such high-value products. Nevertheless, downstream processes to separate OAs from the fermentation broth represent, to date, the main cost in biological OAs manufacturing. With the goal of limiting this issue, the present study investigated OAs separation from a lactic acid (LA)-rich fermentation broth through physical, i.e., using ethyl acetate (EA), and physico-chemical, i.e., using tributyl phosphate (TBP), solvent extraction. In addition, the salting-out effect of different salts on OAs recovery was investigated. Among the investigated conditions, a combination of pure TBP and 40% ammonium sulfate ensured the highest LA extraction efficiency of 65%. Besides, mixing TBP with EA (50:50) enabled to maintain the same LA extraction efficiency while reducing the process costs, limiting the toxicity of the chemicals involved, and obtaining an extracted OAs mix with lower co-metabolites, i.e. volatile fatty acids, compared to using pure TBP. Overall, solvent extraction assisted by salting-out agents were shown to be a promising method to separate OAs from a fermentation broth in liquid form, especially for fermentation processes operated at low pH.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This review will discuss, under the Circular Economy and Biorefinery concepts, the performance of the alternative solvents in the downstream process to recover natural pigments in a more sustainable ...way. Conventionally, pigments marketed on an industrial scale are produced through chemical synthesis by using petroleum derivatives as the main raw material. Also, the current production chain of the synthetic dyes is linear, with no solvent recycling and waste generation. Thus, the most promising processes of extraction and purification of natural pigments and strategies on the polishing of the solvents are here reviewed. In this review, the use of alternative solvents, namely, ionic liquids, eutectic solvents, aqueous solutions of surfactants, and edible oils, for recovering natural pigments was reviewed. Works discussing higher extraction yields and selectivity, while maintaining the stability of the target pigments, were reported. Also, a panorama between Sustainability and Circular Economy prospection was discussed for better comprehension of the main advances in the field. Behind the analysis of the works published so far on the theme, the most important lacunas to overcome in the next years on the field were pointed out and discussed. Also, the future trends and new perspectives to achieve the economic viability and sustainability of the processes using alternative solvents will be scrutinized.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Fucoxanthin is a brown-colored pigment from algae, with great potential as a bioactive molecule due to its numerous properties. This review aims to present current knowledge on this high added-value ...pigment. An accurate analysis of the biological function of fucoxanthin explains its wide photon absorption capacities in golden-brown algae. The specific chemical structure of this pigment also leads to many functional activities in human health. They are outlined in this work and are supported by the latest studies in the literature. The scientific and industrial interest in fucoxanthin is correlated with great improvements in the development of algae cultures and downstream processes. The best fucoxanthin producing algae and their associated culture parameters are described. The light intensity is a major influencing factor, as it has to enable both a high biomass growth and a high fucoxanthin content. This review also insists on the most eco-friendly and innovative extraction methods and their perspective within the next years. The use of bio-based solvents, aqueous two-phase systems and the centrifugal partition chromatography are the most promising processes. The analysis of the global market and multiple applications of fucoxanthin revealed that Asian companies are major actors in the market with macroalgae. In addition, fucoxanthin from microalgae are currently produced in Israel and France, and are mostly authorized in the USA.
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