• Energy Research

Marine macroalgae have attracted significant interest as a viable resource for biofuel and value-added chemical production due to their abundant availability, low production costs, and high carbohydrate and lipid content. The growing awareness of socio-economic factors worldwide has led to a greater consideration of marine macroalgae as a sustainable source for biofuel production and the generation of valuable products. The integration of biorefinery techniques into biofuel production processes holds immense potential for fostering the development of a circular bioeconomy on a broad scale. Extensive research was focused on the technoeconomic and environmental impact analysis of biofuel production from macroalgal biomass. The integrated biorefinery processes offers valuable pathways for the practical implementation of macroalgae in diverse conversion technologies. These studies provided crucial insights into the large-scale industrial production of biofuels and associated by-products. This review explores the utilization of marine macroalgal biomass for the production of biofuels and biochemicals. It examines the application of assessment tools for evaluating the sustainability of biorefinery processes, including process integration and optimization, life cycle assessment, techno-economic analysis, socio-economic analysis, and multi-criteria decision analysis. The review also discusses the limitations, bottlenecks, challenges, and future perspectives associated with utilizing macroalgal biomass for the production of biofuels and value-added chemicals.

The present research was mainly focused on the production of biodiesel from Annona squamosa oil using a synthesized Ni-doped CaO nanocatalyst. The optimization of the transesterification reaction parameters was studied through response surface methodology. The highest biodiesel yield of 99.1% was achieved with the optimized conditions of 7.86% catalyst concentration, 442 RPM, 15.19:1 molar ratio of methanol to oil, reaction temperature of 55.8°C and reaction time of 63.3 min. The results obtained from reaction kinetics study showed a good fit with a first-order kinetic model. The activation energy and R2value were determined to be 53.7 kJ/mol and 0.90, respectively. The synthesized Ni-doped CaO nanocatalyst was characterized using Scanning Electron Microscope with Energy Dispersive X-ray Spectroscopy which confirms the presence of nickel, calcium and oxygen. Also, the average size of the nanocatalyst was found to be 48.79 nm. The Fourier Transform–Infrared Spectroscopy results showed the occurrence of functional groups such as C-H and C = O bonds in the synthesized Ni-doped CaO nanocatalyst. The presence of fatty acid methyl esters in the produced biodiesel was analyzed through Gas Chromatography-Mass Spectrometry analysis. The obtained results from the current study provides the possibility and insights for sustainable biodiesel production and a greener environment.

In this study, biodelignification and enzymatic hydrolysis of elephant grass were performed by recombinant and native strain of Trichoderma reesei, respectively. Initially, rT. reesei displaying Lip8H and MnP1 gene was used for biodelignification with NiO nanoparticles. Saccharification was performed by combining hydrolytic enzyme produced with NiO nanoparticles. Elephant grass hydrolysate was used for bioethanol production using Kluyveromyces marxianus. Maximum lignolytic enzyme production was obtained with 15 µg/L of NiO nanoparticles and initial pH of 5 at 32 °C. Subsequently, about 54% of lignin degradation was achieved after 192 h. Hydrolytic enzymes showed elevated enzyme activity and resulted in 84.52 ± 3.5 g/L of total reducing sugar at 15 µg/mL NiO NPs. About 14.65 ± 1.75 g/L of ethanol was produced using K. marxianus after 24 h. Thus, dual strategy employed for conversion of elephant grass biomass into fermentable sugar and subsequent biofuel production could become potential platform for commercialization.

The present study investigated the synthesis of sodium alginate encapsulated magnetic graphene oxide (SAMGO) beads from Strychnous Potatorum seeds. The synthesized SAMGO beads were investigated for adsorptive removal of nickel from aqueous solution. The synthesized SAMGO beads were characterized for surface morphology, functional groups, magnetic property and phase identification using SEM, FT-IR, VSM and XRD analysis. The optimization process involving the SAMGO beads for adsorptive removal of nickel resulted in maximum removal rate under the conditions of contact time – 15 min, SAMGO bead dose – 10 mg/50 mL of solution, nickel ion concentration – 50 mg/L, pH-9 and temperature of 30 °C. Adsorption of nickel onto SAMGO beads was well studied by pseudo-second-order kinetic studies. Also, the adsorption equilibrium study was well fitted towards Freundlich isotherm ( R2 = 0.99). The findings from the regeneration studies demonstrated that the selected desorbing agents, 0.5 M HCl and 0.5 M EDTA were well-suited for desorption. After five experimental cycles, the desorption efficiency decreased by only 10.93% and 7.76% using 0.5 M HCl and 0.5 M EDTA, respectively indicating that the SAMGO beads for reusability. The synthesized SAMGO beads have shown potential to reuse, nontoxic green adsorbent with maximum removal rate.

Biodiesel is considered to be an economical and eco-friendly substitute to fossil fuels. The present research was focused on the synthesis of potassium doped biochar catalyst from wood dust waste. The synthesized activated biochar catalyst was subjected to characterization using various techniques such as FT-IR, SEM-EDAX, XRD analysis which showed possible higher catalytic efficiency. The microalgae Chlorella vulgaris oil was used for the biodiesel production through transesterification reaction using the synthesized potassium doped biochar catalyst. The reaction parameters were optimized using statistical methods and the optimized conditions were found to be of 5.46% of catalyst dosage, 10.39:1 of methanol to algal oil ratio, 61.41 °C of temperature and 75.3 min of time with the highest biodiesel yield of 91.9%. The reaction kinetics was studied and it was found to follow the first-order kinetics with an activation energy of 12.18 KJ/mol. The catalyst reusability study exhibited higher catalytic performance until fourth cycle. Overall, the utilization of microalgae as a biofuel source and industrial waste as a catalyst contributes to sustainable biodiesel production and promotes a greener environment by reducing dependency on fossil fuels and minimizing industrial waste.