Highly efficient biomethane production from chicken manure and municipal organic solid waste using magnetite:...

The aim of this study is to investigate the effect of magnetite (Fe₃O₄) addition on biogas and biomethane production in the anaerobic treatment of chicken manure (CM) and municipal organic solid waste (MOSW). Batch experiments were conducted under mesophilic conditions using different substrate-to-inoculum (S/I) ratios (0, 1, 2, and 4 g VS-S/g VS-I) and magnetite concentrations (50, 100, 200, 400, and 600 mg L⁻¹). The highest biogas and biomethane production was obtained in the S/I = 1 gVS-S/gVS-I, 2:1 (CM: MOSW) reactor and were 2910.5 ± 199.4 mL CH₄/gVS and 1718.03 ± 117.73 mL CH₄/gVS, respectively. At different magnetite concentrations, the highest biogas and biomethane production occurred at 200 mgL^-1 magnetite loading rate, 1842.7 ± 112.0 mL CH₄/gVS and 1081.99 ± 65.78 mL CH₄/gVS, respectively. The highest total organic carbon (TOC) and total nitrogen (TN) concentrations were determined at S/I = 4, 2:1 (CM: MOSW) gVS-S/gVS-I loading ratio, while the highest TS and VS removal efficiency was determined at S/I = 1 gVS-S/gVS-I, 2:1 (CM: MOSW) ratio and 100 mgL^-1 magnetite loading ratio. When the microbial distribution was examined, the first five dominant species (W5, S1, Coprothermobacter, Treponema and Fervidobacterium) did not change after the addition of magnetite. The findings demonstrate the positive effects of magnetite addition on biogas and biomethane production, providing significant insights for the development of new strategies to enhance anaerobic digestion processes.