A Comparative Study of Cu and Zn Passivation by Humic Acid, Fly Ash, Biochar, and Zeolite During Pig Manure Anaerobic Fermentation Process

This study established an anaerobic fermentation system using pig manure/corn straw as substrate to compare the influence on biogas production and Cu and Zn passivation by humic acid (HA), biochar (BC), fly ash (FA), and zeolite (ZS). Results showed that the cumulative gas production was promoted, and the availability of Cu and Zn was decreased substantially with the introduction of passivators. Multiple comparison analysis (LSD) indicated that the passivation rate of Cu in the presence of HA was 41.43