Microalgae biochar as an acidic catalytic support for ethyl ester synthesis

Microalgae are valued in the industrial, commercial, and scientific sectors for their bioactive and functional content, which includes lipids, carotenoids, proteins, and fatty acids. The residual biomass can be converted into biochar, which has significant commercial potential due to its high adsorption capacity and suitability as a support for heterogeneous catalysts, enabling the development of sustainable and cost‐effective integrated biorefinery platforms. In this study, Spirulina maxima was cultivated in Zarrouk medium using bubble column photobioreactors. After cultivation, the biomass was harvested by filtration. Phycocyanin pigments were extracted using a sodium buffer solution. The residual biomass was pyrolyzed in a muffle furnace (10 °C min −1 , 310 °C, 60 min) to produce biochar. This biochar was impregnated with heteropolyacid molybdenum (HPA‐Mo) and its catalytic potential was studied in the transesterification reactions of macaw palm oil. A 2 2 central composite factorial design was used to assess the effects of impregnation concentration (2–10 mM) and catalyst loading (20–40% w/w). Results showed that low impregnation concentration (2 mM) and biochar catalyst loadings above 40% (w/w oil) achieved effective conversion into ethyl esters, reaching 70%.