Validation and optimization of key biochar properties through iron modification for improving the methane oxidation...

Knowledge of various BC properties in stimulating the methane (CH₄) oxidation capacity of landfill cover soil (LCS) is still limited, restricting the optimization of BC performance. To validate key BC properties and seek a feasible way for enhancing BC performance, this study prepared BCs with distinctly varying characteristics through iron (Fe) modification. Then, batch incubation experiments under different CH₄ and oxygen concentrations were conducted. Pore volume, cation exchange capacity (CEC), and surface area of BC collectively accounted for 78.5% of the variances in the microbial community structures, with pore volume being the most important factor. These correlated well with the differences in the CH₄ oxidation capacities among the different BC-amended LCS. At a low ratio of 15% (v/v) in LCS, BCs' pH not affected their performance but homogeneity could be a limiting factor. Fe modification proved a promising approach to more efficiently improve the three key BC properties (especially pore volume) and thus optimize BC performance than increasing pyrolysis temperature did. Fe-modified BCs encouraged a bacterial consortium (methanotroph, methylotrophs, and nitrogen-fixing bacteria) in the soil with significantly improved CH₄ oxidation capacities by up to 26%-74% compared to that of pristine BC.