Biochar Degradation in Soils: The Overlooked Processes

Presented by Kurt Spokas on August 8, 2014

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Kurt Spokas' Abstract

Recent data collected from both artificially and naturally weathered biochars suggest that a potential significant pathway of biochar disappearance is through physical breakdown of the biochar structure. Through scanning electron microscopy (SEM), we characterized this physical weathering which increased the spacing between the graphite sheets due to the expansion accompanying water sorption and freeze-thaw, as well as desiccation and rewetting. As these sheets expand (exfoliate) this further accelerates physical break-down of the biochar. The micro- and nano-scale biochar particles resulting from this physical disintegration are still carbon-rich particles with no detectable alteration in the O:C ratio of the carbon structure, but are now easily suspended and moved by infiltration. There is a need to understand how to produce a biochar that is resistant to physical degradation in order to maximize the long-term C-sequestration potential of biochar in the soil system.