The improvement in methane production, nutrient removal, and heavy metal passivation during anaerobic digestion of chicken manure: The role of modified porous materials

With the expansion of poultry farming, large amounts of unabsorbed nutrients and heavy metals (HMs) in chicken manure are released, causing environmental pollution. Anaerobic digestion (AD), as a common, harmless, and resourceful treatment method, faces challenges with high-concentration harmful substances, necessitating improvements in the treatment effect. This study explored the application of a modified external porous passivator (EPP) in the AD of chicken manure (CM) and corn straw (CS), focusing on pH adjustment, methane production, nutrient element removal, and heavy metal (HM) passivation. There were 9 kinds of modified EPP prepared by loading Mg, Fe, and humic acid (HS) onto the surfaces of attapulgite (AT), biochar (BC), and zeolite (ZO) using the impregnation-baking method. Modifications with Fe- and HS-modified EPP significantly increased methane yields by up to 76.52%. Mg-modified EPP excelled in removing nitrogen (N) and phosphorus (P), with reductions exceeding 47.69% for total nitrogen (TN), 31.95% for total ammonia nitrogen (TAN), 78.55% for total phosphorus (TP), and 83.76% for total phosphate (TPS). Mg modifications notably improved passivation efficiencies for Cu and Zn to 12.03% and 24.73%. Structural modifications, chemical enhancements from new elemental incorporations, and changes in surface charge, significantly boosted adsorption capacities for nutrients and heavy metals (HMs). These improvements underscore the potential of modified EPP in optimizing AD processes, offering substantial benefits in energy recovery and environmental pollution mitigation.