Mitigating biochar phytotoxicity via La (Lanthanum)-participation in pyrolysis

Yang Lia, b#, Yanqi Yanga, b, Fei Shena, b*, Gang Yanga, b, Yanzong Zhangb, Shihuai Denga, b, Jing Zhanga, b, Yongmei Zengb, Yaodong Huc

a Institute of Ecological and Environmental Sciences, Sichuan Agricultural University, Chengdu, Sichuan 611130, P.R. China

b Rural Environment Protection Engineering & Technology Center of Sichuan Province, Sichuan Agricultural University, Chengdu, Sichuan 611130, P.R. China

c College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, P.R. China

Supplementary Table 1 The oak sawdust composition

Raw materials / Cellulose (%) / Hemicellulose (%) / Lignin (%) / Extractive (%) / Ash (%) / FC*
(%) / VM#
(%) / C
(%) / H
(%) / O
(%)
Oak sawdust / 52.2 / 16.0 / 21.5 / 4.36 / 0.66 / 12.7 / 78.0 / 50.1 / 6.6 / 42.4
* FC refers to fixed carbon, and # VM refers to volatile matter

Supplementary Table 2Maximum allowed threshold values of trace elements established according to IBI Biochar Standards (Version 2.0)

Trace elements / IBI Biochar Standards (Version 2.0)
maximum allowed thresholds (mg kg-1):
Pb / 70-500
Cd / 1.4-39
Cr / 64-1200
Cu / 63-1500
Ni / 47-600
Zn / 200-7000

Supplementary Table 3 Pyrolysis product list obtained from the quantification of major peaks in the pyrograms of aqueous extract of BC and La-BC,with peak height, tentative assignment and relative proportions (expressed as % of total quantified peak area, average values of two replicates).

BC (AE) / La-BC (AE)
Tentative assignment / Molecular
formula / Peak height / Relative proportions % / Tentative assignment / Molecular
formula / Peak height / Relative proportions %
1 / Acetic acid, 3,6-Dioxa-2,4,5,7-tetrasilaoctane, 2,2,4,4,5,5,7,7-octamethyl- / C10H30O2Si4 / 59825 / 6.4 / Dibutyl phthalate / C16H22O4 / 71424 / 80.9
2 / Benzamide, N-ethyl-4-(1-methylethyl)-N-(phenylmethyl) / C19H23NO / 60917 / 6.3 / 1,2-Benzenedicarboxylic acid diisooctyl ester / C24H38O4 / 8840 / 19.1
3 / Ethanedioicacid, bis(trimethylsilyl) ester (9CI) / C8H18O4Si2 / 103499 / 9.0
4 / Dibutyl phthalate / C16H22O4 / 198890 / 9.4
5 / 17-Pentatriacontene / C35H70 / 65585 / 6.3
…
∑(Organic compoungds) 29 / 2

Supplementary Table 4The contents of 16 USEPA (United States Environmental Protection Agency)PAHs in BC and La-BC

PAHs / BC
mg kg-1 / La-BC
mg kg-1 / IBI biochar standards V2.0
mg kg-1 (IBI 2014)
Naphthalene (NAP) / 0.93 / 0.11 / Range of maximum allowed thresholds (sum of 16 US EPA PAHs)
6-300
Acenaphthylene (AC) / 0.18 / 0.01
Acenaphthene (ACN) / 0.15 / 0.02
Fluorene (FL) / 0.08 / 0.05
Phenanthrene (PHE) / 0.13 / 0.01
Anthracene (AN) / 0.13 / 0.01
Fluoranthene (FLA) / 0.06 / n.d.
Pyrene (PY) / 0.14 / n.d.
Benzo(a)anthracene (B(a)A) / 0.21 / n.d.
Chrysene (CHR) / 0.05 / n.d.
Benzo[b]fluoranthene (B(b)F) / n.d / n.d.
Benzo[k]fluoranthene (B(k)F) / n.d. / n.d.
Benzo[a]pyrene (B(a)P) / n.d. / n.d.
Indeno[1,2,3-cd]Pyrene (I(123cd)P) / n.d. / n.d.
Dibenz[a,h]anthracene (D(ah)A) / n.d. / n.d.
Benzo[g,h,i]perylene (B(ghi)P) / n.d. / n.d.
∑PAHs / 2.06 / 0.21

# n.d.indicates the content was not detected by GC-MS.

Supplementary Table 5 SEM-EDS results of BC and La-BC

/ Element / Weight (%) / Atom (%) / Compound (%) / Formula
C / 72.0 / 83.6 / 0.0
Mg / 7.4 / 4.3 / 12.3 / MgO
Ca / 11.2 / 3.9 / 15.7 / CaO
O / 9.4 / 8.2
BC / Total:100
/ Element / Weight (%) / Atom (%) / Compound (%) / Formula
C / 22.5 / 61.1 / 0.0
La / 66.1 / 15.6 / 77.6 / La2O3
O / 11.4 / 23.3
La-BC / Total:100

Supplementary Fig. 1 FT-IR spectral of the employed biochars

The results from the FT-IR analysis showed no difference between BC and La-BC. The spectrum of two biochar samples were both characterized by 3 principal bands, at wave numbers 1409, 1590, and 3412 cm−1.Correspondly, these bands indicate bending stretching of –CH2, aromatic C＝O ring stretching of both acidic and basic groups, and phenolic hydroxyl stretching, respectively. The result is similar to a previous study on wheat straw biochar. (Li et al., 2014) And the elemental composition and ratio of BC and La-BC was found to be 76.5% C, 0.4% N, 3.4% H, 16.6% O, 0.217 O/C ratio and 70.0% C, 0.5% N, 3.4% H, 23.2% O, 0.331 O/C ratio, respectively (see Supplementary Table 2). The low H/C molar ratios of BC and La-BC (0.044 and 0.049, respectively.), indicating high levels of aromaticity and carbonization.(Chen et al., 2008) As expected, ash content in La-BC (9.0%) was higher in contrast to BC, which was perhaps due to the content of La increase. N2-BET result with the surface area of La-BC was 24.9 m2g-1, which was promoted 223.4% compared with that of BC (see Supplementary Table 2). Overall, the difference ash and N2-BET results in two biochars displayed that adsorption ability and mechanisms of La-BC may be potentially different form the BC. Additionally, VM content in La-BC was greatly reduced by 47.9% in contrast to that of BC (16.9%). Based on the result, the carbonization degree of biochar can be greatly promoted by LaCl3-involvment, implying the La-BC will be more beneficial to carbon sequestration.

Supplementary Fig.2 Images of the total ion chromatograms from the thermal desorption GC/MS analysis of BC and La-BC. “AES” in this figure refers to the aqueous extractive solution.

References

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IBI Biochar Standards Version 2.0 (2014) Standardized product definition and production testing guidelines for biochar that is used in soil, The International Biochar Initiative

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*Corresponding author. Address: 211 Huimin Road, Wenjiang District, Chengdu, Sichuan, 611130, P.R. China; Tel./fax: +86-28-86293178; E-mail:; # Present address: Institute of Agriculture and Environment, Private Bag 11222, Massey University, 4442 Palmerston North, New Zealand