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Abstract: High-cost downstream process is a major bottleneck for producing microalgal biodiesel at reasonable price. Conventional lipid extraction process necessitates biomass drying process, which requires substantial amount of energy. In this regard, lipid extraction from wet biomass must be an attractive solution. However, it is almost impossible to recover lipid directly from wet microalgae with current technology. In this study, we conceived osmotic shock treatment as a novel method to extract lipid efficiently. Osmotic shock treatment was applied directly to wet Chlamydomonas reinhardtii biomass with water content >99%, along with both polar and non-polar organic solvents. Our results demonstrated that osmotic shock could increase lipid recovery approximately 2 times. We also investigated whether the presence of cell wall or different cell stages could have any impact on lipid recovery. Cell wall-less mutant stains and senescent cell phase could display significantly increased lipid recovery. Taken together, our results suggested that osmotic shock is a promising technique for wet lipid extraction from microalgal biomass and successfully determined that specific manipulation of biomass in certain cell phase could enhance lipid recovery further. [Copyright &y& Elsevier]

Superior carbon fixation rate of microalgae compared to terrestrial biomass offers a significant opportunity to build a reliable carbon supply chain for carbon source. Extremophilic microalgae, Galdieria sulphuraria (G. sulphuraria), is further underscored by its exceptional adaptability to harsh environments such as wastewater. This study proposed a strategy to efficiently utilize carbon in G. sulphuraria and to valorise metallic industrial waste, particularly red mud (RM), through co-pyrolysis. To improve the eco-friendliness, CO 2 was used as a reactive gas medium in pyrolysis system. Use of CO 2 in single-stage pyrolysis of G. sulphuraria leads to the enhanced formation of CO through gas-phase reactions (GPRs) of it with volatile matter (VM). Specifically, CO 2 partially oxidize VM while reduce into CO. From single-stage co-pyrolysis of G. sulphuraria with RM, RM accelerated the reaction kinetics for GPRs between CO 2 and VM, leading to the increased formation of syngas from 27.5 to 37.6 mmol compared to N 2 environment. From multi-stage co-pyrolysis, an additional heat source (700 °C) facilitated the GPRs induced by CO 2 , increasing evolution syngas from 37.6 to 73.8 mmol compared to single-stage co-pyrolysis under CO 2 environment. RM‑carbon composites (RMCs) from co-pyrolysis of G. sulphuraria with RM under N 2 /CO 2 environments was utilized as a catalyst in thermally induced transesterification. Both RMCs exhibited superior performance over commercial silica. In specific, both RMCs resulted in higher biodiesel yields of >95.0 wt% at 300 °C, compared to commercial silica (biodiesel yield of 16.6 wt% at corresponding reaction temperature). Such performance of RMCs in thermally induced transesterification could be improved by the modification of their surface properties but its related study was not conducted in this stage. A series of experimental findings propose that co-pyrolysis of G. sulphuraria and RM creates opportunities to maximise syngas production and fabricate red mud‑carbon composites to enhance biodiesel conversion efficiency. [Display omitted] • Tolerance to harsh conditions makes Galdieria sulphuraria a reliable carbon source. • Co-pyrolysis of microalgae and red mud waste produces iron-carbon composite. • CO 2 -assisted pyrolysis improves CO formation, promoting syngas production. • Iron-carbon composite catalyzes in thermally induced transesterification reaction. [ABSTRACT FROM AUTHOR]