133-1 Determining C:N Ratios of the Labile Biochar Fraction.

Poster Number 514

See more from this Division: ASA Section: Environmental Quality
See more from this Session: Agronomic, Environmental, and Industrial Uses of Biochar: I (includes graduate student competition)

Monday, November 16, 2015
Minneapolis Convention Center, Exhibit Hall BC

Santanu Bakshi, Iowa State University, Dept. of Agronomy, Ames, IA, Chumki Banik, Agronomy, Iowa State University, Ames, IA and David A. Laird, Department of Agronomy, Iowa State University, Ames, IA
Abstract:
Most models divide biochar into a labile fraction, which is assumed to be mineralized rapidly, and a recalcitrant fraction, which is assumed to be stable for hundreds or even thousands of years.  The C:N ratio of the labile fraction is important as this ratio determines whether the biochar immobilizes N or is a source of N fertility during the first few years after application as the labile fraction is mineralized. Volatile matter as determined by proximate analysis is commonly assumed to represent the labile fraction of biochar; however, proximate analysis does not provide a ready means of determining the C:N ratio of the volatile matter.  The goal of this study is to evaluate a proposed fractionation scheme for biochar, which allows the C:N ratio of the labile fraction to be determined. Laboratory controlled chemical and spectroscopic analyses will be reported for six biochars produced from four biomass feedstocks (hardwood, soybean, switchgrass and corn stover) using two pyrolysis techniques (slow and fast). All analyses will be done in quadruplicates and will be quantified with respect to total C of biochar. The inorganic C fraction of biochar is determined by CO2 released on reaction with 1M HCl using a 1M NaOH trap. Labile organic C will progressively be extracted in four steps using hot water, 6M, 9M, and 12M H2SO4. All extracted solutions will be analyzed for dissolved organic carbon and nitrogen and the residues will be evaluated separately by proximate and ultimate analysis. Volatile matter as determined by proximate analysis will be compared with the amounts of organic matter extracted using hot water and the various H2SO4 solutions. The C:N ratio and total N extracted with hot water and H2SO4 will be compared with the C:N ratio and total N of the original biochar and the residue after the H2SO4 treatments.

See more from this Division: ASA Section: Environmental Quality
See more from this Session: Agronomic, Environmental, and Industrial Uses of Biochar: I (includes graduate student competition)

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