A Theoretical Model for GHG Emissions Due to Biochar Application in Tropical Agricultural Soils

Biochar, a pyrolysis product, has the potential to reduce greenhouse gas (GHG) emissions while increasing the soil water holding capacity. The purpose of this paper is to model biochars GHG emission based on its applied dose, its pH value, pyrolysis temperature and soil texture. Poultry manure and sugarcane straw biochar produced at two temperatures (350 and 650 degrees C), were applied in three doses (12.5, 25, and 50 Mg ha(-1)), to sandy and clayey soils at two soil pH values (original 7.5 and adjusted to 5.5). The concentrations of CO2, CH4 and N2O were determined using gas chromatography. Increasing the biochar pyrolysis temperature and reducing the soil pH to 5.5 reduced the CO2, CH4, and N2O emissions from the soil. The mitigating effect of biochars was more evident in the sandy soil, since the clayey soil was highly buffed. The CO2 emission, explained negatively by the variables soil texture and biochar pH and positively by the variables pyrolysis temperature and biochar dose, had the final equation: CO2 = 82.28 - 0.05Cclay - 0.08pH + 6.98Tpyrolysis + 0.64Dbiochar (R-2 = 0.65).