Hydrochar-enhanced hydrogen production from cassava industrial waste residue using <i>Enterobacter Aerogenes MTCC 2822</i>

Hydrogen gas (H₂) is a promising renewable resource, and its production from organic waste has gained significant attention as an alternative to traditional energy sources. This study investigates hydrogen production from cassava industry waste residue (CWR) by incorporating hydrochar-supported nanoparticles (HSNPs) containing nickel (Ni) and iron (Fe) nanoparticles (NPs). Ni and Fe₂O₃ NPs were synthesised through the hydrothermal carbonisation (HTC) method and analyzed for their impact on biohydrogen production. The results indicated a maximum volumetric hydrogen production rate of 1013 mL/gCWR, with a substrate degradation efficiency of 80%. Addition of 0.5 mol Ni–Fe₂O₃ hydrochar was found to be optimal which enhanced the overall cumulative hydrogen production by 41.015%, and higher COD removal efficiency by 90% was obtained as compared to hydrochar without additives. The toxicity of NPs was assessed through bacterial viability, which examined various loading concentrations of NPs in a glucose medium. The findings revealed that supplementing hydrochar-supported NiO and Fe₂O₃ NPs within an optimal range for CWR can significantly improve hydrogen productivity. Additionally, HSNPs can enhance hydrogenase activity and electron transfer efficiency, which are beneficial to bio-H₂ evolution. However, excessive HSNP addition may be toxic to microbes and further inhibit H₂ production. This study presents an effective method for promoting the evolution rate of H₂ gas.