Supplemental Material

Criteria to select biochars for field studies based on biochar chemical properties

Catherine E. Brewer1, Rachel Unger2, Klaus Schmidt-Rohr3, Robert C. Brown1*

1Center for Sustainable Environmental Technologies, Iowa State University, Ames, IA 50011

2Department of Agronomy, Iowa State University, Ames, IA 50011

3Department of Chemistry, Iowa State University, Ames, IA 50011

Figure S1. FTIR spectra of switchgrass biochars from slow pyrolysis, fast pyrolysis and O2/steam-blown gasification.

Table S1. NMR C functionality fractions (χfuncitonality),fractions of aromatic edge carbons (χedge) and minimum number of carbons per aromatic cluster(nC,min = 6/χedge,max2), and relative aromatic-to-alkyl proton ratio(Harom/Halk) in biochars.

Biochar # / χC-H / χC-O / χedge,min / χalkyl / χC=O / χedge,max / nC,min / Harom/Halk
1 / 0.32 / 0.14 / 0.46 / 0.12 / 0.11 / 0.70 / 12 / 1.2
2 / 0.33 / 0.15 / 0.48 / 0.22 / 0.11 / 0.81 / 9 / 0.8
3 / 0.38 / 0.18 / 0.56 / 0.52 / 0.16 / 1.23 / 4 / 0.4
4 / 0.34 / 0.18 / 0.52 / 0.47 / 0.14 / 1.13 / 5 / 0.4
5 / 0.12 / 0.07 / 0.19 / 0.11 / 0.07 / 0.37 / 44 / 0.7
6 / 0.31 / 0.08 / 0.39 / 0.08 / 0.01 / 0.47 / 27 / 2.2
7 / 0.27 / 0.16 / 0.43 / 0.17 / 0.11 / 0.70 / 12 / 0.8
8 / 0.24 / 0.12 / 0.36 / 0.08 / 0.07 / 0.52 / 22 / 1.4
9 / 0.29 / 0.11 / 0.39 / 0.08 / 0.06 / 0.54 / 21 / 1.7
11 / 0.11 / 0.09 / 0.19 / 0.12 / 0.08 / 0.39 / 39 / 0.6
13 / 0.37 / 0.07 / 0.44 / 0.05 / 0.02 / 0.51 / 23 / 4.0
14 / 0.26 / 0.12 / 0.39 / 0.11 / 0.06 / 0.56 / 19 / 1.1
15 / 0.25 / 0.10 / 0.35 / 0.08 / 0.06 / 0.49 / 25 / 1.6

Table S2. Concentrations of extractable/exchangeable cations (in units of meq 100g soil-1) present in biochar measured by extracting one sample of each biochar (1.5 g) with 0.5 M ammonium acetate solution (15 ml) adjusted to pH = 7.0 [44]. Filtered solutions were analyzed by inductively-coupled plasma atomic emission spectroscopy (ICP-AES). Analysis of Biochar 13 was repeated to qualitatively evaluate repeatability. BDL = below detection limits.

Biochar # / Ba / Ca / Fe / K / Mg / Mn / Na / Sr
1 / 0.03 / 31 / 0.01 / 25 / 21 / 0.11 / 0.6 / 0.04
2 / 0.03 / 29 / 0.04 / 42 / 22 / 0.10 / 0.2 / 0.03
3 / 0.03 / 28 / 0.06 / 40 / 24 / 0.09 / 0.4 / 0.02
4 / 0.02 / 28 / 0.09 / 44 / 25 / 0.10 / 0.4 / 0.02
5 / 0.01 / 44 / BDL / 18 / 12 / 0.07 / 0.7 / 0.01
6 / 0.01 / 12 / 0.01 / 9 / 5 / 0.08 / 0.3 / 0.01
7 / 0.03 / 20 / 0.01 / 41 / 17 / 0.35 / 0.3 / 0.05
8 / 0.03 / 20 / 0.01 / 35 / 14 / 0.30 / 0.3 / 0.04
9 / 0.03 / 22 / BDL / 45 / 17 / 0.29 / 0.3 / 0.05
10 / 0.06 / 43 / BDL / 71 / 29 / 0.12 / 2.8 / 0.06
11 / 0.05 / 72 / BDL / 59 / 26 / 0.11 / 2.3 / 0.05
12 / 0.02 / 89 / BDL / 53 / 12 / 0.01 / 2.3 / 0.04
13 (1) / 0.01 / 8 / BDL / 9 / 2 / 0.05 / 0.3 / 0.01
13 (2) / 0.02 / 11 / 0.01 / 14 / 3 / 0.08 / 0.3 / 0.01
14 / 0.03 / 15 / BDL / 8 / 2 / 0.06 / 1.0 / 0.02
15 / 0.12 / 42 / BDL / 4 / 1 / 0.33 / 0.3 / 0.08
16 / 0.05 / 32 / BDL / 6 / 4 / 0.27 / 1.4 / 0.04
17 / 0.02 / 6 / 0.01 / 4 / 1 / 0.05 / 1.5 / 0.01