Effect of microscale zero-valent iron on biogas and methane production

ABSTRACT

This study investigates the effect of microscale zero-valent iron (mZVI) addition on biogas and methane production under mesophilic (37 ± 1 °C) and thermophilic (55 ± 1 °C) anaerobic digestion conditions. Laboratory-scale reactors were operated with five different mZVI concentrations (0, 1, 4, 8, and 10 g L−1 mZVI) under mesophilic and thermophilic conditions. The highest cumulative biogas production was 201 ± 10 and 135 ± 10 mL at mesophilic and thermophilic temperatures, respectively, at 10 g L−1 mZVI concentration. The maximum CH4 content was 93.53 ± 3.00 and 78 ± 3.00% under mesophilic and thermophilic conditions with 10 g L−1 mZVI, which was 40 ± 3.00% (p < 0.05) and 18 ± 3.00% (p > 0.05) higher than the control group. This indicated that the addition of mZVI made a significant contribution to CH4 conversion under mesophilic conditions compared with thermophilic conditions. Microbial community analysis revealed that mZVI enhanced the relative abundance of bacteria such as Firmicutes and Actinobacteria at the phylum level. In addition, Methanosaeta was the most dominant archaea in all operational conditions. These findings demonstrate that mZVI addition under mesophilic conditions is a promising strategy to improve biogas production and CH4 content in anaerobic digestion systems.