Waste-to-Value Biochar from Agricultural and Woody Residues: Global Drivers of Crop Yield Enhancement and Greenhouse Gas Mitigation

Abstract

The use of agricultural and woody residues in the circular economy is being implemented more actively, and biochar can be suggested as one of the areas of integration linking waste management with agronomic and environmental impacts. This study quantified the overall effects of residue-derived biochar on crop yield and greenhouse gas response ratios (CO₂, N₂O, and CH₄), compared straw- and wood-derived feedstocks, and examined key climatic, soil, and management drivers associated with response variability. A quantitative secondary analysis was conducted using a global treatment–control dataset. Effects were expressed as log response ratios and converted to percentage change for interpretation. Overall means and confidence intervals were estimated, and feedstock-specific summaries were calculated. Multivariable ordinary least squares regression models with centered predictors assessed associations with climate variables, soil properties, pyrolysis temperature, biochar application rate, nitrogen input, and their interaction. Biochar application was associated with a 10.17% increase in crop yield and significant reductions in N₂O (−21.43%) and CH₄ (−14.83%), while CO₂ responses were not statistically significant. Yield responses were positively associated with biochar rate and soil organic carbon and showed a significant interaction with nitrogen input. Variability in N₂O responses was linked to climatic factors, soil pH, pyrolysis temperature, and nitrogen rate. These results imply that biochar can be used to convert agricultural and woody residues into biochar and aid productivity and lower some greenhouse gases, with results that depend on the environmental conditions and the intensity of management.