Abstract: Steam-activation increased CH₄ emission of stover biochar but decreased it for wood biochar by 14%^–70%. Biochar generally increased CH₄emission but reduced N₂O emission by 10%–41%. Emission of N₂O was 17% lower for maize-stover biochar compared to Eucalyptus-wood biochar, and 3% lower for 350°C compared to 550°C pyrolysis temperature. Emission of CH₄ was 21% higher for activated stover biochar compared to Eucalyptus-wood biochar and 10% lower for 350°C compared to 550°C pyrolysis temperature. No difference in net CO₂equivalent was observed among biochar grades.