Exploring long-term effects of biochar on mitigating methane emissions from paddy soil: a review

Abstract Biochar has been reported to mitigate short-term methane (CH 4 ) emissions from paddy soil. Currently, CH 4 mitigation by biochar has primarily focused on the abundance and variations of methanogens and methanotrophs, and changes in their activities during methane production and consumption. However, long-term effects of biochar on methane mitigation from paddy soil remain controversial. This review overviewed the existing mechanisms for CH 4 mitigation as a result of biochar application. In addition, the two existing opinions on the long-term CH 4 mitigation effect upon biochar application were highlighted. Combining the already explored mechanisms of fresh biochar on CH 4 mitigation from paddy soil and a novel discovery, the potential mechanisms of biochar on long-term methane emission response were proposed. This review also revealed the uncertain responses of biochar on long-term CH 4 mitigation. Therefore, to achieve carbon neutral goal, it is important to further explore the mechanisms of long-term CH 4 mitigation under biochar application.