Effect of different particle-size biochar on methane emissions during pig manure/wheat straw aerobic composting: Insights into pore characterization and microbial mechanisms

[Display omitted] •Effects of rice straw biochar (RSB) on manure composting were investigated.•Addition of powdered RSB caused methane emissions to increase by 56.84%.•Addition of granular RSB caused methane emissions to decrease by 22.15%.•Granular RSB increased both the pore volume and connectivity of initial samples.•RSB reduced the methanogen to methanotroph ratio in initial samples. This study explored the effects of different particle sizes of rice straw biochar (RSB) on the methane emissions of pig manure/wheat straw aerobic composting experiments to provide a theoretical suggestion for biochar application. The experiments were conducted with a control group, powder (