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

•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.