Effect of biochar amendment on soil greenhouse gas emissions: A meta-analysis

Background/Question/Methods

Biochar is carbon-rich charcoal that is produced when biomass is burned in the absence of oxygen. Biochar application to soils has many benefits, such as increased carbon sequestration, improved soil fertility, raised crop yields, and held moisture. However, how biochar amendments to soils affect greenhouse gas (GHG) emissions is largely unclear, especially for a comprehensive evaluation at a global scale. In this study, we have conducted a meta-analysis of 91 papers with 552 paired comparisons to examine the responses of three main GHGs (CO₂, CH₄ and N₂O) emissions to biochar amendment. 

Results/Conclusions

Our results show that biochar application significantly increased soil CO₂ emission by 22.14%, but decreased N₂O emission by 30.92% and did not affect CH₄. As a consequence, biochar application significantly increased global warming potential (GWP) due to the large stimulation of CO₂ emission with great contribution to GWP. Interestingly, the responses of CO₂, CH₄ and N₂O emissions to biochar amendment would be affected by amount of biochar addition, pyrolysis temperature of biochar, biochar types (from woody and herbaceous materials), soil and biochar pH, but experimental duration did not impact GHGs emissions. Our results as revealed can be helpful for making a more rational strategy towards wide-spread adoption of biochar as a soil amendment for climate change mitigation.