# Highly efficient biomethane production from chicken manure and municipal organic solid waste using magnetite: converting waste into energy

## TL;DR

This study shows that adding magnetite improves biomethane production from chicken manure and organic waste, offering a new way to boost energy recovery from waste.

## Contribution

The study demonstrates that magnetite addition enhances biogas and biomethane yields in anaerobic digestion of chicken manure and organic waste.

## Key findings

- Magnetite at 200 mg/L increased biomethane production to 1081.99 mL CH4/gVS.
- Optimal S/I ratio of 1 gVS-S/gVS-I with 2:1 CM:MOSW mix maximized biogas and biomethane.
- Magnetite addition improved TS and VS removal efficiency at 100 mg/L loading.

## Abstract

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.