Biochar contribution in greenhouse gas mitigation and crop yield considering pyrolysis conditions, utilization strategies and plant type ‐ A meta-analysis

Context or problem: Fertilizers have the potential to release greenhouse gases (GHGs) and applying biochar, could drastically change fertilizers' scenario in the environment. However, the efficiency of biochar regarding its operation and interaction with organic and chemical fertilizers on GHG emission, and crop productivity has received many contradictory reports. Objective or research question: This study aims to conduct a comprehensive meta-analysis to evaluate the effects of biochar utilization strategies and key variables on GHG emissions and crop productivity. Methods: A meta-analysis was performed using six groups of effective variables including different biochar utilization strategies (sole (B), combined with chemical fertilizers (BCF), combined with organic fertilizers (BOF)), type of feedstock, pyrolysis temperature, application rate, soil texture, and plant types. Also, various GHG emission factors and crop yield were considered as the affected factors. Results: The results showed that the B strategy reduced N2O and CH4 emissions by 16.3 % and 10.1 %. Also, BCF and BOF showed a positive effect size in terms of N2O with 62.9 % and 11.3 % increases. The highest CO2 emission was related to manure-based biochars with a 12.1 % positive effect size. Moderate pyrolysis temperature (400–550 °C) showed the best efficiency in reducing overall carbon intensity per crop yield (GHGI) with a 14.9 % decrease. Also, the highest global warming potential (GWP) was obtained from the > 20 t ha−1 biochar application rate. Applying biochar in sandy soil causes a notable increase in CO2 emission with a 22.1 % positive effect size. The highest GWP was related to the application of biochar in vegetable cultivation with a 20.8 % increase. Conclusions: Soil texture and pyrolysis processing significantly impact soil GHG emissions when biochar is applied with fertilizers. Implications or significance: Expanding our understanding of the relationships among soil GHG emissions, organic fertilizers, and biochar could assist in increasing plant yield and net zero amending approaches.