PNNL

Abstract

A fundamental understanding of biodegradability is central to elucidating the role(s) of pyrogenic organic matter (PyOM) in biogeochemical cycles. Since microbial community and ecosystem dynamics are driven by net energy flows, then a quantitative assessment of energy value versus energy requirement for oxidation of PyOM should yield important insights into their biodegradability. We used bomb calorimetry, step-wise isothermal thermogravimetric analysis (isoTGA) and 5-year in-situ bidegradation data, to develop energy-biodegradability relationships for a suite of plant- and manure-derived PyOM (n = 10). The net energy value (?E) for PyOM was between 4.0 and 175 kJ mol-1; with manure-derived PyOM having the highest ?E. Thermal-oxidation activation energy (Ea) requirements ranged from 51 to 125 kJ mol-1, with wood-derived PyOM having the highest Ea requirements. We propose a return-on-investment (ROI) parameter (?E/Ea) for differentiating short-to-medium term biodegradability of PyOM and deciphering if biodegradation will most likely proceed via co-metabolism (ROI