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•P. tricornutum cultivated under natural conditions in Chile was characterized.•Real process data was used to scale-up the biorefinery scenarios.•Three P. tricornutum based ...biorefinery process configurations were proposed.•Integrated biorefinery for biofuels and high-value compounds revealed advantageous.
Microalgae are a rich source of proteins, carbohydrates and lipids, among other components, and thus, are considered to be the next generation biomass. However, in order to enhance the economic viability of its industrial production, all biomass components need to be valorized, requiring a multi-product biorefinery. Thus, this work proposes and conceptually analyses biorefinery processes for valorizing Phaeodactylum tricornutum for biofuels and high-value compounds, based on real data from a pilot-scale process. The algal biomass was biochemically characterized and the production was scaled-up to an industrial approach to analyze three biorefinery configurations, based on a 18 ton·year−1 of microalga biomass. The biomass revealed a composition of 7.85 wt% carbohydrates, 38.40 wt% proteins, 9.08 wt% lipids, 0.86 wt% fucoxanthin and 5.19 wt% biosilica. The biorefinery process addressed for biofuels production has an estimated annual production of 1.72, 0.35 and 1361 m3·year−1 of respectively biodiesel, bioethanol and biomethane. The biorefinery addressed for high-value compounds yields 0.18, 0.93 and 6.95 ton·year−1 of respectively fucoxanthin, biosilica and protein. The biorefinery designed for valorizing full microalgae biomass, showed to be more beneficial for promoting a circular economy. Biorefinery approach is useful for making sound and profitable decisions regarding microalgae bioproducts.
In either unicellular or multi-cellular form, microalgae are photosynthetic microorganisms, mainly known for being part of the human diet in several world regions. More recently, they have been in ...the spotlight of researchers, not only because of their nutritional value, but also due to their high value-added components. This work reviews five microalgae genera: Dunaliella, Botryococcus, Chlamydomonas, Chlorella and Arthrospira, considered among the most promising for commercial biotechnological applications. The analysis shows that, although the research paradigms are generally shared among species, parameterization changes of culture environment and stress conditions, several applications can be envisaged for the cultivated species, which is discussed in this work. Besides, several applications in which these microalgae are being widely used, or are intended to be used, are analyzed and discussed. The potential applications depend on the type of metabolites found in each microalgae species, which is discussed in this work, giving examples of application and describing methods for their cultivation, harvesting and biomass processing. Thus, in addition to being used in human diet supplementation, microalgae can be used as ingredients for animal feed, medicines, cosmetics pigments, biofuels, bioplastics and biostimulants.
•Five microalgae genera considered most promising for commercial applications.•Type of metabolites found in each microalgae species.•Different methods for cultivation, harvesting and biomass processing.•Microalgae promising commercial applications.
•Bio-refineries are an adequate framework to process organic waste materials.•Spent coffee grounds can be completely utilized in a bio-refinery to obtain high-value products.•A full set of high value ...products, biofuels and bioenergy can be obtained in a SCG bio-refinery.•Significant challenges still exist to develop and implement waste based bio-refineries.
Although normally seen as a problem, current policies and strategic plans concur that if adequately managed, waste can be a source of the most interesting and valuable products, among which metals, oils and fats, lignin, cellulose and hemicelluloses, tannins, antioxidants, caffeine, polyphenols, pigments, flavonoids, through recycling, compound recovery or energy valorization, following the waste hierarchy. Besides contributing to more sustainable and circular economies, those products also have high commercial value when compared to the ones obtained by currently used waste treatment methods. In this paper, it is shown how the bio-refinery framework can be used to obtain high value products from organic waste. With spent coffee grounds as a case study, a sequential process is used to obtain first the most valuable, and then other products, allowing proper valorization of residues and increased sustainability of the whole process. Challenges facing full development and implementation of waste based bio-refineries are highlighted.
Rural farms are typically energy-intensive facilities with relatively low energy efficiency. In this sector, the introduction of renewable energies and integrated resource management technologies has ...been slower than in the domestic and industrial sector. The introduction of renewable energy sources was an important step in the past, but they are currently insufficient, as they do not allow for adequate energy management. The development of new solutions with integrated energy control is especially attractive for these installations as they present the least limitations in terms of space and adaptation to new technologies.
This work describes a solution that was developed and implemented in a farm located in central Portugal. The results show that 83.2% reduction in energy from the grid can be achieved, with 5527 kg CO2 savings, and the return on investment (of € 32,434) is about 8 years. However, this period can be shortened if evolutionary options are taken, such as upgrading to electric driven agricultural equipment.
Low indoor air quality is an increasingly important problem due to the spread of urbanization. Because people spend most of their time inside, poor indoor air quality causes serious human health ...issues, resulting in significant economic losses. In this work, the current state of affairs is presented and analyzed, focusing on the current problems and the available solutions to improve the quality of indoor air, and the use of nature-based solutions. These involve the cultivation of microalgae in closed photobioreactors. In these systems, photosynthetic organisms can capture CO2 and other pollutants generated in indoor environments, which they use to grow and develop biomass. Several possible layouts for the implementation of microalgae-based indoor air cleaning systems are presented, taking into account the systems that are currently available at a commercial scale. A critical analysis of the microalgae indoor purification systems is presented, highlighting their advantages and disadvantages, and suggesting potential improvements and future lines of research and development in the area.
Active nickel phase dispersed in a carbon dioxide sorbent is used together with a zinc oxide promoter in the BRM. The 13X zeolite structure of the support used disappears at elevated temperatures, ...inducing moderate Ni crystal sizes and thus disfavoring reaction activity. However, the high-loaded catalyst with larger Ni particle sizes seems to be compensated by the presence of a ZnO promoter. Results show that the Ni-ZnO-13X based catalyst is adequate to perform the BRM reaction.
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•13XZnO20Ni17-u shows promising results for syngas production via BRM reaction.•Higher temperature increases catalyst activity.•Molar ratios of hydrogen-to-carbon monoxide are close to two at high temperatures.•Absence of inert gas in the feed did not influence catalyst activity and selectivity.•50–60% CO2 conversion was achieved at a maximum operating temperature of 800 °C.
Ennoblement of carbon dioxide, particularly the one produced by anaerobic digestion or by biomass combustion, is a motivation to develop novel or improving already existing processes. In this context, an interesting idea is to use carbon dioxide combined together with methane and water. Therefore, bi-reforming of methane (BRM) for syngas production appears to be a good choice. In this work, BRM was studied over a Ni-catalyst supported on a ZnO-doped zeolite 13X in the temperature range 300 to 900 °C. This material was deeply characterized by different techniques. The pure zeolite 13X shows relative good sorption capacity for CO2 at low temperatures (<100 °C). The ZnO phase introduced on zeolite 13X did not show a significant improvement for BRM, while 13X zeolite material impregnated with Ni and ZnO showed promising activities, achieving CO2 conversions in the range of 50–60% at a maximum operating temperature of 800 °C and atmospheric pressure. The results obtained suggest that ZnO acts as an oxygen supplier when methane is activated by surface nickel, thus destabilizing the feed in the following order: methane, water and carbon dioxide. The influence of the operating conditions in the reactants conversion and products distribution was also analyzed, and it can be concluded that the molar ratios of hydrogen-to-carbon monoxide are close to two at high temperatures.
Diatoms are very diverse and highly productive organisms, found in a wide variety of environments. This study aims to analyze the growth and lipid composition of Phaeodactylum tricornutum, cultured ...in an outdoor pilot-scale bubble column photobioreactor under natural conditions in Chile for biodiesel production. Results showed that P. tricornutum cultures reached their highest biomass concentration (0.96 ± 0.04 kg m−3) after 14 days of culturing, at the stationary phase, with a volumetric productivity of 0.13 kg m−3 d−1. Biomass samples showed a total lipid content of 9.08 ± 0.38 wt %. The fatty acid methyl ester analysis revealed a composition of 24.39% C16-C18 fatty acids, 42.34% saturated fatty acids, 21.91% monounsaturated fatty acids and 31.41% polyunsaturated fatty acids. These findings suggest that P. tricornutum oil can be used as an alternative raw material for the production of biodiesel capable of meeting international quality standards.
•An economic and sustainability evaluation of microalgae biodiesel is done.•The most efficient units for the overall process system were considered.•Microalgae sustainability is similar to other ...feedstocks.•Profitability and sustainability depend on lipid content and areal productivity.•Profitability tends to a limit value for large cultivation areas.
This article evaluates the sustainability and economic potential of microalgae grown in brewery wastewater for biodiesel and biomass production. Three sustainability and two economic indicators were considered in the evaluation within a life cycle perspective. For the production system the most efficient process units were selected. Results show that harvesting and oil separation are the main process bottlenecks. Microalgae with higher lipid content and productivity are desirable for biodiesel production, although comparable to other biofuel’s feedstock concerning sustainability. However, improvements are still needed to reach the performance level of fossil diesel. Profitability reaches a limit for larger cultivation areas, being higher when extracted biomass is sold together with microalgae oil, in which case the influence of lipid content and areal productivity is smaller. The values of oil and/or biomass prices calculated to ensure that the process is economically sound are still very high compared with other fuel options, especially biodiesel.
Bioethanol is the most widely used biofuel in the world. Bioethanol production from biomass is a way to reduce crude oil consumption and the environmental pollution. This work aims to evaluate the ...potential environmental impacts of bioethanol production from corn stover obtained from phytoremediation, comparing four different acids (Sulfuric, Nitric, Hydrochloric and Acetic acids) to perform the biomass pre-treatment. The study follows a life cycle thinking perspective, accounting for all the life cycle stages from corn stover grinding, to biomass pre-treatment, enzymatic hydrolysis, fermentation, filtration and ethanol distillation, on a “gate-to-gate” approach. The life cycle inventory was developed using mainly primary data from laboratorial experiments, and complemented whenever necessary with information from literature and from the Ecoinvent V3.0 database available in the SimaPro 8.0.2 software. For the environmental impact assessment, the ILCD Midpoint 2011 methodology was used. Results show that in general, the sulfuric and hydrochloric acids have a better environmental performance than the acetic and nitric acids. Also, results show that pre-treatment, followed by enzymatic hydrolysis are the process steps with the highest relative contribution to the potential environmental impacts. Thus, an improvement analysis should focus on these process steps, for example to reduce fossil energy consumption by implementing renewable energy sources.
•A LCA of ethanol production from corn stover was done, focusing on the acid used in the biomass pre-treatment.•Biomass was obtained from phytoremediation of contaminated soil.•Sulfuric and hydrochloric acids have a better environmental performance when compared with acetic and nitric acids.•Pre-treatment, followed by enzymatic hydrolysis, are the process steps with the largest environmental impacts.
Several microalgae species have been exploited due to their great biotechnological potential for the production of a range of biomolecules that can be applied in a large variety of industrial ...sectors. However, the major challenge of biotechnological processes is to make them economically viable, through the production of commercially valuable compounds. Most of these compounds are accumulated inside the cells, requiring efficient technologies for their extraction, recovery and purification. Recent improvements approaching physicochemical treatments (e.g., supercritical fluid extraction, ultrasound-assisted extraction, pulsed electric fields, among others) and processes without solvents are seeking to establish sustainable and scalable technologies to obtain target products from microalgae with high efficiency and purity. This article reviews the currently available approaches reported in literature, highlighting some examples covering recent granted patents for the microalgae’s components extraction, recovery and purification, at small and large scales, in accordance with the worldwide trend of transition to bio-based products.
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