Impact of microalgal-based carbon encapsulated iron nanoparticles on anaerobic digestion performance

This study investigates the application of microalgal-based carbon-encapsulated iron nanoparticles to enhance anaerobic digestion performance. The nanoparticles were synthesized via hydrothermal carbonization using iron nitrate and algal biomass grown on the liquid fraction of municipal digestate. Their physicochemical properties were characterized through ICP-OES, TEM, SEM-EDX, and XRD to assess morphology, elemental composition, total and zero valent iron concentration, and crystalline phases. The nanoparticles were supplemented at different doses (100 mg·L −1 , 500 mg·L −1 , and 1000 mg·L −1 ) to semi-continuous lab-scale anaerobic digesters fed on municipal sludge. Biomethane production increased by 23.3 %, 16.7 %, and 22.2 % for the 100, 500, and 1000 mg·L −1 doses, respectively, while biogas production increased by 31.9 %, 18.9 %, and 26.5 % compared to the corresponding Control. Microbial community analysis revealed that nanoparticles induced dose-dependent structural shifts, with enrichment of methanogenic families such as Methanoregulaceae, while overall microbial richness remained stable.