Carbon Dioxide Emissions From Biochar and Biochar Amended Soil.

Biochar, a solid co-product of thermochemical bioenergy systems, has gained attention as a potential means of carbon sequestration.  However little additional information is needed concerning the stability biochar carbon in soils.  The objectives of this study were to determine the mineralization of biochar C in soil relative to crop residues from which it was derived. Biochars were developed from gasification and pyrolysis of corn stover and corn cob feedstocks respectively.  Biochars or feed stocks were applied to soils at a rate of 20 g kg-1 and incubated in sealed containers for 12 weeks.  Carbon dioxide concentrations in headspace gas was determined weekly and delta 13C was determined every 3 weeks.  Carbon evolution from biochar and feedstocks was determined based on the 13C signature of the substrates relative to the soil.  Biochar mineralization was negligible, indicating that it is a stable C form.  Furthermore, biochar application did not affect soil organic matter degradation.  These results suggest that biochar applications could be a method of C sequestration in soil.