Algal biodiesel production with engineered biochar as a heterogeneous solid acid catalyst.

• Efficiency of acidified biochar catalyst for transesterification was evaluated. • Peanut shell biochar pyrolyzed at 400 °C showed best catalytic efficiency. • Yield of biodiesel was influenced by the operational parameters. • Maximal biodiesel yield of 94.91% was obtained with significant FAMEs. • 16.83% of oleic acid and 12.15% palmitic acid was present in algal biodiesel. This study evaluates the use of engineered biochar as a heterogeneous solid acid catalyst for transesterification of algal oil derived from a native microalgal consortium. Biochar derived from sugarcane bagasse, coconut shell, corncob and peanut shell were evaluated for catalytic activity following surface modification. Peanut shell pyrolyzed at 400 °C with the sulfonic acid density of 0.837 mmol/g having 6.616 m2/g surface area was selected for efficient catalysis. The efficiency of transesterification was evaluated with 1–7 wt% catalyst loading, methanol: oil ratio of 6:1 to 30:1 at 55–85 °C over 2–8 h. Biodiesel yield of 94.91% was obtained with 5 wt% catalyst loading, MeOH: oil ratio of 20:1 at 65 °C after 4 h. Spectral analysis of algal biodiesel showed the presence of functional groups corresponding to esters. GC–MS analysis revealed the prominent presence of palmitic and oleic acids, further advocating the suitability of the technology for commercial application. [ABSTRACT FROM AUTHOR]