Biochar as a Strategy to Mitigate Greenhouse Gases in Degraded Drylands of the Brazilian Semiarid Region: Carbon Stocks and CO₂ Fluxes

Background Biochar can enhance total organic carbon (TOC) stocks and reduce CO 2 emissions in degraded soils. Aims This study assessed the effects of pyrolytic biochars on TOC recovery and CO 2 emissions in a greenhouse experiment. Methods PVC columns (20 cm diameter, 50 cm height) were filled with soil and arranged in a factorial scheme (2 × 4 + 1) with four replicates. Treatments included two biochars: co‐pyrolyzed sewage sludge and cashew pruning (SPB) and cashew bagasse biochar (CBB), applied at 5, 10, 20, and 40 Mg ha −1 , plus a control. CO 2 flux was measured in two additional gas collection events. TOC content and bulk density were analyzed, and carbon stocks (CSs) were calculated. Results The application of 5 and 40 Mg ha −1 of SPB and CBB increased TOC and CSs compared to the control. CO 2 flux fluctuated between samplings, as expected with corn introduction. The highest CO 2 flux initially occurred in SPB40, followed by CBB20, whereas in the second sampling, CBB5 showed the highest flux and CBB20 the lowest. Conclusion These results suggest that SPB and CBB applications improve soil CSs and mitigate CO 2 fluxes, contributing to climate change mitigation and soil restoration.