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The increase in global temperature calls for ambitious action to reduce the release of greenhouse gases into the atmosphere. The transportation sector contributes up to 25% of the total emissions released, mainly from the burning of vehicle fuel. Therefore, scientists from all around the world are focusing on finding a sustainable alternative to conventional vehicle fuel. Biofuel has attracted much attention, as it shows great potential for the replacement of traditional fossil fuels. However, the main bottlenecks of biofuel are the ongoing controversial conflict between food security with biofuel production. Therefore, this study focuses on a sustainable extraction of lipids from microalgae for the production of biofuel using a liquid biphasic flotation system coupled with sugaring-out method. This is the first study to combine the methods of liquid biphasic flotation system with the sugaring-out technique. It represents a holistic study of optimum and effective conditions needed to extract lipids from the system and to understand the reliability of sugar solution as the agent of cell disruption. At the 15-min flotation time, 150 g/L of fructose solution with a 1:2 mass separating agent-acetonitrile ratio successfully extracted up to 74% of lipid from Chlorella sorokiniana CY-1. Two types of fatty acid methyl esters were recovered from the study, with C5:0 being the main component extracted. [ABSTRACT FROM AUTHOR]

• Modified BG-11 and Zarrouk media successfully grew Spirulina with similar dry biomass. • Aerated air exhibit the optimal biomass productivity for Spirulina cultivation. • After 3 cultivation cycles, biomass productivity decreased from 0.2246 to 0.0802 g/L/d. • Pretreatment methods on recycled medium and rainwater improve biomass productivity. • Economical cost of various pretreatment methods were assessed in this study. The cultivation of microalgae represents a water-intensive process, prompting the need to reduce its water footprint and explore alternative water sources. Therefore, this research work aims to investigate the growth of Spirulina by recycling the culture medium obtained from the post-cultivation process and substituting rainwater resources for the preparation of the culture medium. The effect of pre-treatment methods, specifically microfiltration and UV-light was investigated. These methods were applied to treat the recycled medium and rainwater resources used for Spirulina cultivation. Biomass concentration, biomass productivity and phycocyanin accumulation of Spirulina were examined to assess the Spirulina growth under different pre-treatment conditions. After three cultivation cycles in the recycled medium, biomass productivity decreased from 0.2246 to 0.0802 g/L/d which might be due to high salinity and biological pollutants that inhibit Spirulina growth. However, different pre-treatment methods using microfiltration and UV-light on the recycling medium were found to be effective in increasing biomass productivity from 0.1395 to 0.1861 g/L/d. Additionally, the use of rainwater for Spirulina cultivation was explored. Applying pre-treatment methods to the rainwater, biomass productivity was further improved from 0.3211 to 0.3837 g/L/d. These findings suggest that the use of pre-treatment methods and alternative rainwater resources can improve the biomass productivity of Spirulina and potentially reduce the environmental impact throughout the microalgae cultivation process. [Display omitted] [ABSTRACT FROM AUTHOR]

Microcystis aeruginosa has always been regarded as the main culprit of cyanobacterial blooms in freshwater. However, in recent years, Raphidiopsis raciborskii has gradually replaced M. aeruginosa as the culprit of cyanobacterial blooms in some tropical and subtropical shallow lakes. To reveal which one plays a more dominant role, interactions between cylindrospermospin (CYN)-producing R. raciborskii and microcystins (MCs)-producing or non-MCs-producing M. aeruginosa strains were studied using bialgal cultures at different initial ratios of biomasses of the two species at 25 °C. During the co-cultivation, the M. aeruginosa strains inhibited the growth and heterocyst formation of R. raciborskii filaments, and thus occupied a dominant position during the co-cultivation regardless of the initial biomass ratios in the cultures. In addition, the MCs-producing M. aeruginosa strain contributed to a higher portion of the total biomass and exerted a stronger inhibitory effect on R. raciborskii compared with the non-MCs-producing strain. However, the growth of both MCs-producing and non-MCs-producing M. aeruginosa strains was stimulated by R. raciborskii in the co-cultures compared with M. aeruginosa monoculture, indicating that M. aeruginosa could outcompete R. raciborskii if given enough time, enabling it to develop into the dominant species even in very low initial concentration. To our best knowledge, this is the first report on the loss of heterocyst formation by a species of cyanobacteria that resulted from interactions between two different species of cyanobacteria. These findings indicate that it is difficult for R. raciborskii to replace the dominant position of M. aeruginosa under the experimental environmental condition, and the allelopathic effects of M. aeruginosa on R. raciborskii could significantly contribute to the success of M. aeruginosa. [ABSTRACT FROM AUTHOR]

The pursuit of carbon neutrality confronts the twofold challenge of meeting energy demands and reducing pollution. This review article examines the potential of gasifying plastic waste and biomass as innovative, sustainable sources for hydrogen production, a critical element in achieving environmental reform. Addressing the problem of greenhouse gas emissions, the work highlights how the co-gasification of these feedstocks could contribute to environmental preservation by reducing waste and generating clean energy. Through an analysis of current technologies, the potential for machine learning to refine gasification for optimal hydrogen production is revealed. Additionally, hydrogen storage solutions are evaluated for their importance in creating a viable, sustainable energy infrastructure. The economic viability of these production methods is critically assessed, providing insights into both their cost-effectiveness and ecological benefits. Findings indicate that machine learning can significantly improve process efficiencies, thereby influencing the economic and environmental aspects of hydrogen production. Furthermore, the study presents the advancements in these technologies and their role in promoting a transition to a green economy and circular energy practices. Ultimately, the review delineates how integrating hydrogen production from unconventional feedstocks, bolstered by machine learning and advanced storage, can contribute to a sustainable and pollution-free future. [Display omitted] • ML enhances hydrogen yield from plastic waste and biomass gasification. • Co-gasification of waste boosts emission reduction and energy sustainability. • Review highlights innovative, eco-friendly hydrogen storage solutions. • Economic viability of gasification methods affirmed for green economic transition. • Future research direction for hydrogen production via gasification. [ABSTRACT FROM AUTHOR]

Mariculture of the economically important seaweed will likely be affected by the combined conditions of ocean acidification that resulting from increasing CO2 rising and decreased light levels, especially under high culture intensity and high biomass accumulation. To examine this coupling effect on the photosynthetic performance of Sargassum fusiforme seedlings, we cultured seedlings of this alga under different light and CO2 levels. Under low light conditions, elevated CO2 significantly decreased the photosynthesis of S. fusiforme seedlings, including a decreased photosynthetic electron transport rate. Seedlings grown under the low light intensity exhibited higher photosynthetic rates and compensation irradiance, and displayed higher photosynthetic pigment contents and light absorption than seedlings grown under high light intensity, providing strong evidence of photosynthetic acclimation to low light. However, the captured light and energy were insufficient to support photosynthesis in acidified seawater regardless of increased dissolved inorganic carbon, resulting in declined carbohydrate and biomass accumulation. This indicated that S. fusiforme photosynthesis was more sensitive to acidified seawater in its early growth stage, and strongly affected by light intensity. Future research should evaluate the practical manipulation of biomass accumulation and mariculture densities during the early culture period at the CO2 level predicted for the end of the century. [ABSTRACT FROM AUTHOR]

Raphidiopsis raciborskii (R. raciborskii) forms harmful cyanobacterial blooms globally, and poses a great threat to the safety of drinking water and public health. There is a great need to develop eco-friendly biological alternative measures to mitigate mass blooms of R. raciborskii. However, previous rare studies on algicidal microorganisms against R. raciborskii restricted this aim. Recently, an algicidal bacterium Streptomyces sp. HY (designated HY) was identified with flavones producing ability, and could remove up to 98.73 % of R. raciborskii biomass within 48 h by directly attacking the cyanobacterium and release of algicidal substances (i.e., flavonoids) with a inoculum ratio of 5 %. Algicidal rate of HY was enhanced by 88.05 %, 89.33 % under dark and light, and full-light conditions respectively, when compared with the dark condition. Its algicidal substances were stable in a broad range of temperature (−80–55 °C) and pH (3−11) conditions, and all treated groups exhibited ≈ 100 % algicidal rate at day 3. HY treatment disrupted the photosynthesis system and triggered serious oxidative stress resulting in severe morphological injury. Thereby, HY treatment significantly affected expression levels of several essential genes (i.e., psbA , psaB , rbcL , ftsZ , recA , grpE), and simultaneously inhibited the biosynthesis and release of cylindrospermopsin. Yet, HY treatment didn't show any toxicity to zebrafish test embryos. Such results indicate that HY is a promising algicidal candidate strain to control global R. raciborskii blooms, and holds great promises for an effective biological measure to sustain water safety. [Display omitted] • Algicidal Streptomyces sp. HY (HY) lysed R. raciborskii cells effectively via direct/indirect attacks. • HY strain produces flavonoids and effectively bio-flocculates R. raciborskii cells. • HY strain kills various R. raciborskii strains regardless of geographic origin and toxin-producing ability. • HY strain dysregulates the expression of several essential genes, and inhibits the biosynthesis and release of CYN. • Algicidal effects of HY strain on R. raciborskii are promoted by oxidative stress and photosystem inhibition [ABSTRACT FROM AUTHOR]

The production of low-cost solid adsorbents for carbon dioxide (CO 2) capture has gained massive consideration. Biomass wastes are preferred as precursors for synthesis of CO 2 solid adsorbents, due to their high CO 2 adsorption efficiency, and ease of scalable low-cost production. This review particularly focuses on waste biomass-derived adsorbents with their CO 2 adsorption performances. Specifically, studies related to carbon (biochar and activated carbon) and silicon (silicates and geopolymers)-based adsorbents were summarized. The impact of experimental parameters including nature of biomass, synthesis route, carbonization temperature and type of activation methods on the CO 2 adsorption capacities of biomass-derived pure carbon and silicon-based adsorbents were evaluated. The development of various enhancement strategies on biomass-derived adsorbents for CO 2 capture and their responsible factors that impact adsorbent's CO 2 capture proficiency were also reviewed. The possible CO 2 adsorption mechanisms on the adsorbent's surface were highlighted. The challenges and research gaps identified in this research area have also been emphasized, which will help as further research prospects. [Display omitted] • Biomass-derived adsorbents for CO 2 capture were reviewed • Different carbon and silicon-based adsorbents were synthesized from biomass • Synthesis condition decides the physicochemical properties of adsorbents • Modification of adsorbents is needed for the improvement of CO 2 uptake • Biomass-derived CO 2 adsorbent with optimized operational condition is needed [ABSTRACT FROM AUTHOR]

Macroalgae, with short growth cycles, and high CO 2 fixation capacity, are third-generation biomass mainstays that play an essential role as a global carbon sink. Macroalgal biochar plays a crucial role in soil improvement, pollutant adsorption, electrodes, and capacitors, and it has already contributed to both ecological and economic fields. However, the physicochemical properties of macroalgal biochar are challenging to control, and the way macroalgal biochar is pyrolyzed and activated largely determines its physicochemical properties and areas of application. In this study, five standard methods (conventional pyrolysis, hydrothermal carbonization, microwave pyrolysis, co-pyrolysis, and drying) for the pyrolysis of macroalgal biochar and two activation methods (physical and chemical) are reviewed to screen for optimal preparation and activation methods under different conditions and in different application contexts. The conventional pyrolysis process is mature and simple, but the yield is low, which is suitable for industrial production. Hydrothermal carbonization can reduce the content of alkali metals in biochar without prior drying. Microwave pyrolysis has low energy consumption and uniform product properties, which is suitable for biochar with high stability requirements. Co-pyrolysis is a low-cost pyrolysis method if suitable co-pyrolysis materials can be found. The drying ash content is high, but the surface performance is weak, which is generally used as pretreatment. From laboratory to practical applications, macroalgal biochar still needs to be investigated in terms of cost reduction, yield improvement, and optimization of preparation and activation methods. • The development of macroalgal biochar resources was reviewed. • Five common pyrolysis methods are compared. • Physical and chemical activation can improve the macroalgal biochar. • Doping with elements enhances its adsorption and electrochemical properties. • Analysis of risk assessment, long-term stability and economic value of macroalgal biochar are needed before practical use. [ABSTRACT FROM AUTHOR]