Integrating technical and sustainability perspectives: anaerobic co-digestion from lab to pilot scale using textile wastewater sludge and cattle manure

This study investigated the bioconversion of textile wastewater plant sludge (TWS) and cattle manure (CM) into biogas through co-anaerobic digestion (CAND), focusing on detailed characteristics analyses and ratio optimization. The lab-scale biochemical methane potential experiments were conducted to optimize the ratio of TWS and CM. An optimum TWS: CM ratio of 3:2 was further evaluated in a pilot-scale anaerobic digester with a 1 m(& sup3;) capacity, undergoing continuous monitoring and operation for six months to validate system upscaling and process optimization. The biological analyses of the resultant digestate confirmed the presence of different methanogens and provided insight into co-digestion mechanisms. The elemental analysis revealed the stabilization of the inorganic contaminants of the TWS due to the addition of CM. The critical parameters of the digestion process were also analyzed, i.e., changes in volatile solids, pH, and COD. The comparative Life Cycle Assessment demonstrated that the CAND of TWS outperformed incineration with energy recovery and landfilling with biogas recovery, yielding net-negative impacts for climate change (-57.8 kg CO2-Eq) and fossil energy use (-12 kg oil-Eq). Pilot-scale digestion achieved a biogas yield of 492 NmL/g VS, confirming the feasibility of scale-up despite a reduction relative to batch-scale BMP results.