Quantification of Bioavailable Polycyclic Aromatic Hydrocarbons in Biochars.

Mounting concerns regarding fossil fuels and anthropogenic carbon emissions have resulted in an increased interest in biofuels. Biofuels provide a sustainable energy source as well as a potential mechanism for mitigating climate change. Although more studies are necessary in order to ensure sustainability, biofuels may result in an overall carbon negative process through soil application of biochar, a byproduct of pyrolysis. Biochar has potential to add organic carbon and sequester carbon in soil; however, the contaminants present in biochar may negatively affect the environment. This study quantified concentrations of total and bioavailable polycyclic aromatic hydrocarbons (PAHs) found in the biochar of feedstocks that underwent slow pyrolysis at 400, 550, and 700 degrees Celsius and biochars produced by gasification at 1100 degrees C. Total concentrations of PAHs were measured using Soxhlet extractions and gas chromatography-mass spectrometry. Bioavailable concentrations were determined using polyoxymethylene passive samplers and Soxhlet extractions of lettuce and soybeans grown in biochar-amended soils. The results of this study will provide information on the potential bioaccumulation of PAHs in crops and will allow researchers to assess public health risks associated with biochar amendment to agricultural fields. Policy makers will be able to use the results to determine the potential of biochar amendment as a clean development mechanism under the Kyoto Protocol.