Post Removal of Oil/Tar Materials From Biochar and Subsequent Impact On Weathering.

Recent changes in domestic energy policies have mandated increased reliance on renewable energies including bio-energy feedstocks and dedicated non-foodstuff agricultural crops. Currently conversion platforms are still being developed and optimized, however the use of thermo-chemical conversion, including pyrolysis and gasification, appears to be one of the important processes due to its ability to accept a wide range of feedstocks.  This process results in the production of solid residue, referred to as biochar, that contains both carbon and plant nutrients.   The mixed plant response to biochar soil incorporation appear to dependant on feedstock, pyrolysis operating conditions, biochar collection/separation system and soil chemical and physical properties.  These variables influence the near-term fate of biochar nutrient availability and interaction with soil and plant roots.  This study has focused on the influence of residual surface tar and oils on nutrient solubility and biochar physical characteristics.  Select biochars derived from both agricultural and non-agricultural feedstocks were washed with various organic solvents to determine residual oil and tar content and influence on gas/water diffusion, water holding capacity and surface area.  Solvent extractability of biochar oil/tars ranged from 6.6 g kg-1 for hexane to 64.2 g kg-1 for acetone, respectively.   Additionally, the chemical characteristics of the biochars have been evaluated for elemental analysis and functional organic groups.  The influence of tars and oils on the oxidative/weather fate of the biochar will also be presented.