The analysis of total solids (TS) and volatile solids (VS) for each inoculum was conducted according to the EPA standard methods . Nutrient analysis for ammonium (NH₄⁺), phosphate (PO₄³⁻), potassium (K⁺), and iron (Fe) was performed using a spectrophotometer in conjunction with the HACH Lange LCK cuvette test system. Gas samples were collected daily from the reactors and analyzed for H₂, CO, CO₂, N₂, and CH₄ using gas chromatography (GC, 7890A, Agilent Technologies, Santa Clara, CA, USA). Volatile fatty acid (VFA) concentrations were measured weekly using gas chromatography (7890B, Agilent Technologies, Santa Clara, CA, USA). Detailed procedures for sample collection, preparation, and analysis are described in a previous study .