Characterization of Biochars Produced Under Different Pyrolytic Conditions and Their Implications to Improve Soil Quality.

Biochar amendments of degraded Oxisols by pre-Columbian inhabitants of the Amazonian basin markedly improved their fertility.  This captured the attention of international organizations who propose to adapt this technology to degraded soils in other regions.  This strategy requires an understanding of how biochar pyrolysis affects its chemical characteristics because some recalcitrant biochars may take millennia to improve soil quality.  Biochar pyrolysis can occur at either high (500 to 700°C) or low (250 to 400°C) temperature.  High temperatures produces material with high surface area and carbon structures in condensed polymeric aromatic structures; this material is resistant to microbial degradation.  Biochars produced at low temperatures can contain more aliphatic carbons and may be less resistant to microbial degradation.  Thus, the pyrolysis process can be customized to produce designer biochars for improving soil quality.  Biochars were produced from four different feedstocks by pyrolysis at high and low temperatures and the material characterized for elemental and functional groups using titration and spectroscopic techniques.  Preliminary results showed that a switchgrass biochar pyrolyzed at a lower temperature (250°C) retained more oxygen functional groups and had greater total acidity than higher temperature biochar (500°C).  Biochars are being examined in laboratory incubation experiments to ascertain the influence of high and low pyrolysis temperatures on soil physical and chemical characteristics.