Efficient algal lipid extraction via a green bio-electro-Fenton process and its conversion into biofuel and bioelectricity with concurrent wastewater treatment in a photosynthetic microbial fuel cell†

Third-generation biodiesel produced using carbon-neutral algal feedstock is a promising alternative to meet global energy demands. However, the economic viability of algae-derived biodiesel is severely impacted by poor lipid recovery and taxing downstream processes. In this regard, green Fenton chemistry was employed to disrupt algal cells in a bio-electro-Fenton-assisted photosynthetic microbial fuel cell (BEF-PMFC) by employing different Fenton catalysts for higher lipid recovery. The maximum lipid yield of 39.2% with 98% chlorophyll removal was achieved by homogeneous Fenton oxidation in a Ni–Pd/C catalysed BEF-PMFC after 6 h of reaction at a pH of 3.0, whereas a comparable lipid yield (37.5%) and chlorophyll removal (95%) were attained by a CoFe-AC-driven heterogeneous Fenton oxidation process. Experiments exhibited a maximum of 90% lipid extraction efficiency, which was 1.5-fold higher than that without cell-disruptive wet biomass. Finally, biodiesel synthesised from lipids obtained via BEF conformed to the ASTM D6751-12 standard. The PMFC equipped with the Ni–Pd/C coated cathode generated a maximum power density of 74.5 mW m⁻² and a chemical oxygen demand removal efficiency of 89.2%, which were ca. 2.8 times and 1.2 times higher compared to the control PMFC operated without any catalyst on the cathode. Thus, this investigation paves the way for using a green chemistry-based strategy to assist PMFCs in achieving higher recovery of bioelectricity and lipid recovery with minimal reliance on chemicals.