INDEX-BASED LOGISTIC MODELING TO PREDICT SOIL CARBON SEQUESTRATION POTENTIAL OF PYROGENIC CARBONS

We present an entirely new model for predicting the biodegradability, and subsequently the carbon sequestration potential, of pyrogenic organic carbon (pyC) materials in fire-impacted/biochar-amended soils. The model uses the relative stability of the pyC material (R₅₀; to that of graphite), a heterogeneity constant (α; based on the chemistry of the feedstock) and, an index-based kinetic function (β; the environmental driver) to estimate the percentage of pyC remaining after a given time, t (in years). Time, t can be on the decadal, the centurial and millennial time scales. The model was tested with published data from two independent (a 1-year and a 5-year) biochar biodegradation studies and was found to have prediction errors of <10% from the measured pyC-remaining. In addition to the pyC remaining the model facilitates the 1) simple calculation of mean residence time for the pyC material, 2) reconstruction/construction of degradation curves for materials of different stabilities and, 3) development of refined classification scheme to quantitatively rank (and assign monetary value to) the carbon sequestration potential of different pyC materials. The advantages and limitations of the model will be discussed.