Use of chemical and physical characteristics to investigate trends in
biochar feedstocks
Fungai Mukome, Xiaoming Zhang, Lucas C.R. Silva, Johan Six, and
Sanjai J. ParikhUniversity of California, Davis
US Biochar Conference, Rohnert Park, CAJuly 2012
What is Biochar?Walnut shell
Wood
Wood chips
Fly ashcarbon-negative.us
Corn stover
Rice Husks Manure
Orange peels
All biochars are not created equal…. (McLaughlin et al. 2009)
• Differ on– pH– Surface area– Ash content– Water holding capacity
• All a function of pyrolysis temperature (highest treatment temperature-HTT), pyrolysis method, residence time and feedstock
– Cation exchange capacity (CEC)– H/C ratio– C/N ratio
Objectives
1. To characterize physical and chemical properties of various biochars (mostly commercially available)
2. To determine if trends exist for biochar properties that can be related to feedstock material, which can serve to develop guidelines for biochar use.
Objectives 1
• Physical properties:– Moisture content– Ash content– BET Surface area– Surface morphology
• Chemical properties:– Elemental content– H and C content– pH– Cation exchange capacity– Surface basicity and acidity– Surface functionality (ATR-FTIR and Raman)
Twelve biochars were analyzed
Char Source MaterialPyrolysis Temp (°C)
Ash (wt %)
BET Surface Area (m2/g)
Type (Hysteresis)
BC_ A Turkey litter 700-800 64 21.8 aPs. II (H3) BC_Bb Walnut shell 900 40.4 227.1 Ps. II (H4) BC_C Inoculated material unavailablec 15.5 95.9 Ps. II (H4)
BC_D Soft wood 600-700 2.4 25.2 Ps. II (H4) BC_E Wood + Algal digestate 600-700 6.4 2 Ps. II (H3) BC_F Wood 510 3 165.8 Ps. II (H4) BC_G Wood 410 2.6 2.8 Ps. II (H3) BC_H Wood chips 500-650 17 4.9 Ps. II (H3) BC_I Wood chips unavailable 5 164.1 Ps. II (H4) BC_J Wood chips unavailable 2.8 153.1 Ps. II (H4) BC_K Wood chips unavailable 5.5 154.4 Ps. II (H4) BC_L Wood chips unavailable 4.2 301.6 Ps. II (H4)
a Ps.II = Pseudo Type IIb Unknown, not willing to provide or proprietary c Not commercially available
Physical properties
WoodNon-wood
SEM images of three biochars showing a) a char with type H3 hysteresis loop b) a char with type H4 hysteresis loop and c) a char with high ash content.
c) BC_Ba) BC_G b) BC_F
10µm100µm60µm
Type II isotherms - capillary non-porous or macroporous adsorbents and represent monolayer-multilayer adsorption.
Lower surface areas (BC_J,BC_H, BC_A and BC_G) - Type H3 hysteresis loops - lack of microporosity, plate-like particles and slit shaped pores.
Higher surface area - (BC_L, BC_K, BC_J, BC_I, BC_F) - Type H4 hysteresis loops- narrow slit-like pores
Scanning Electron Microscopy analysis
CharC
(wt %)N
(wt %)H
(wt %)O
(wt %)PO4-P (wt %)
K (wt %)
S (ppm)
Fe (ppm)
pHw (1:2)
CECa
cmol/kgAcidity
(meq/g)Basicity (meq/g)
BC_A 15.6 0.78 0.83 4.4 6.61 7.05 10720 9191 10.9 24.4 0.08 4.92
BC_Bb 55.3 0.47 0.89 1.6 0.64 9.32 940 1981 9.7 33.4 - 11.71
BC_C 53.3 1.96 3.7 24.3 0.47 1.2 5920 1109 6.8 44.5 1.22 1
BC_D 68.2 0.51 3.66 26.8 0.13 0.26 370 1934 7.5 26.2 1.24 1.02
BC_E 58.1 0.41 4.16 31.7 0.08 0.19 685 3370 6.8 67 1.56 1.22
BC_F 83.9 0.36 1.88 19.8 0.02 0.13 110 505 7.3 12 0.27 0.93
BC_G 65.7 0.21 4.38 23.5 0.02 0.12 50 248 7.1 10 0.83 0.4
BC_H 71.2 0.91 2.88 11.6 0.08 0.72 480 3517 7.9 3.2 0.79 1.01
BC_I 87.3 0.59 2.15 7.4 0.07 0.85 140 203 9.2 9.1 0.41 0.84
BC_J 88 0.44 2.55 14.8 0.02 0.33 60 79 9.5 14.9 0.49 0.87
BC_K 85.4 0.55 2.37 8.9 0.07 0.48 140 606 8.8 3.6 0.6 0.94
BC_L 82.5 0.49 1.64 5.6 0.06 1.02 160 473 9.5 16.5 0.36 1.21
aCEC = Cation exchange capacityb Not commercially available
Chemical properties
WoodNon-wood
Aromatic
Aliphatic/Functionalized
C=O
C=CC-H
C-O, C-H
C-O
FTIR: Fourier Transform Infrared Spectroscopy
Greater aromaticity in wood derived biochar
1800 1600 1400 1200 1000 800 600Wavenumber (cm-1)
BC_L
BC_K
BC_J
BC_I
BC_H
Abso
rban
ce BC_E
BC_D
BC_C
BC_A
BC_B
BC_F
BC_G
Char
xAromatic C-H (744cm-1)
xAliphatic ether (1029cm-1)
xAliphatic CH3 (1417cm-1)
xAromatic C=C (1587cm-1)
xAromatic carbonyl
(1690cm-1)
BC_A - 2.9 1 0.21 0.02BC_B - 1.1 2.2 - - BC_C 0.53 3.6 0.38 0.69 0.39BC_D 0.63 2.67 2.46 2.6 1.2BC_E 0.27 2.83 2.2 2.05 0.94BC_F 1.2 2.09 1.7 2.3 0.28BC_G 1.2 2.16 0.83 1.5 0.4BC_H 1.12 1 1.71 1.78 0.41BC_I 1 1.2 1.83 1.98 0.38BC_J 0.71 1.67 0.27 1.41 0.36BC_K 1.05 1.17 1.6 1.9 0.36BC_L 1.1 1.01 1.05 1.22 0.12x. Ratios of peak intensities relative to the aromatic C-H stretch at 870cm-1 common to all spectra
1000 1200 1400 1600 1800
BC_A
BC_C
BC_J BC_K BC_L
BC_B BC_I BC_F
BC_G BC_H
BC_D BC_E
Inte
nsity
Wavenumber (cm-1)
Char Aliphatic ether (1029cm-1)
yRaman Id/Ig
BC_A 2.9 0.4BC_B 1.1 0.34BC_C 3.6 0.76BC_D 2.67 0.58BC_E 2.83 0.65BC_F 2.09 0.4BC_G 2.16 0.25BC_H 1 0.83BC_I 1.2 0.68BC_J 1.67 0.72BC_K 1.17 0.59BC_L 1.01 0.71
y. Ratio of peak intensities of the Carbon D (1350cm-
1) and G (1690cm-1) bands in Raman spectra
D band(aromatic)
G band(aliphatic & olefinic)
• ID - sp2 disordered C atoms in aromatic ring structures• IG - sp2 disordered C atoms in aliphatic and olefinic molecules•Approximates sp2: sp3 ratio in amorphous carbon
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0G G
G
G
G
G
GG
GG
G
GG
GG
G
G
GG
G
L
L
L
L
M N
N
P
P
P
PP
P
PP P
WW
WW
W
WW
WWW
WWWWWW WWW
W
WWW
WW
G
NW
W
W
KJ
I
E
D
C
H
A
B
G
F
y = 1.805x + 0.190R2 = 0.83
H/C
atom
ic ra
tio
O/C atomic ratio
y = 2.182x + 0.198R2 = 0.88
0.0 0.1 0.2 0.3 0.4 0.50.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Literature Study biochar (inset)
L
Objective 2 1. Sharma et al. Fuel 2004, 83, 1469-1482.2. Keiluweit et al. Environmental Science & Technology 2010, 44, 1247-1253.3. Zheng et al. Journal of Hazardous Materials 2010, 181, 121-126.4. Cao, X. et al. Bioresource Technology 2010, 101, 5222-5228.5. Özçimen et al. Renewable Energy 2010, 35, 1319-1324.6. Jindarom et al. Chemical Engineering Journal 2007, 133, 239-246.7. Chan et al. Soil Research 2008, 46, 437-444.8. Azargohar et al. Applied Biochemistry and Biotechnology 2006, 131, 762-773.9. Wu et al. Industrial & Engineering Chemistry Research 2009, 48, 10431-10438.10. Toles et al. Bioresource Technology 2000, 71, 87-92.11. Van Zwieten et al. Plant and Soil 2010, 327, 235-246.12. Chen, B. and Chen, Z. Chemosphere 2009, 76, 127-133.13. Major et al. Plant and Soil 2010, 333, 117-128.14. Argudo, M. et al. Carbon 1998, 36, 1027-1031.15. Hammes et al. Applied Geochemistry 2008, 23, 2113-2122.16. Chun et al. Environmental Science & Technology 2004, 38, 4649-4655.17. Mahinpey et al. Energy & Fuels 2009, 23, 2736-2742.18. Rondon et al. Biology and Fertility of Soils 2007, 43, 699-708.19. Abdullah, H. and Wu, H. Energy & Fuels 2009, 23, 4174-4181.20. Cheng, C.-H and Lehmann, J. Chemosphere 2009, 75, 1021-1027.21. Spokas et al. Chemosphere 2009, 77, 574-581.22. Steiner et al. J. Environ. Qual. 2009, 39, 1236-1242.23. Busscher et al. Soil Science 2010, 175, 10-14.24. Brewer et al. Environmental Progress & Sustainable Energy 2009, 28, 386-396.25. Novak et al. Annals of Environmental Science 2009, 3, 195-206.26. Novak, J. M. and Reicosky, D. C. Annals of Environmental Science 2009, 3, 179-193.27. Singh et al. J. Environ. Qual. 2010, 39, 1224-1235.
n= 85
van Krevelen diagram of a) selected biochar (from literature) and b) 12 study biochar (inset)
A algae G grass L hull M manure N nutshell P pomace W wood
Change in ash content as a function of pyrolysis temperature of biochar
0 100 200 300 400 500 600 700 800 900 1000
0
10
20
30
40
50
60
70
80
A
A
A
A
A
A
A
G GG
G
G
G
G
G
G
G G
G
L
LL
L
M
M
M
M
M
M
M
M
NN NN
N
N
P P P P P PP P P
P
W W W WWWW
WWWW
WW
WW
W
W WW
W
WWW W
Temperature (oC)
A algaeG grassL hullM manureN nutshellP pomaceW wood
Ash
con
tent
(%)
100 200 300 400 500 600 700
0
5
10
15
20
25
30
HHH
H
H
H HH
H
S S S S SS
S
S
S
H HardwoodS Softwood
Ash
con
tent
(%)
Temperature (oC)
Change in ash content as a function of pyrolysis temperature of biochar derived from hard and softwood
Change in the C/N ratio as a function of pyrolysis temperature of biochar derived from hard and softwood.
0 100 200 300 400 500 600 700 800 900 1000
10
100
1000
AAAAAAA
G GG
GG G
G
G
G
G
GGG
G G
G
G
LLL
L
LL
MM
M
M
M
M
M
MM M
MM
NN
N
P P P P PP P P P
WW
W
W
W
W
W
W
W
WW
WWW
WWWW
W
W
W
WW
W
W
WW
WW
W
W
W
WW
WW
A algaeG grassL hullM manureN shellP pumiceW wood
J ra
tio
J (oC)
0 100 200 300 400 500 600 70010
100
1000
HHHH
H H HH
H
H HH H
SS S S
SS
S
S SS
SSS
SS
H hardwoodS softwood
C/N
ratio
Temperature (OC)
Change in the C/N ratio as a function of pyrolysis temperature of biochar
100 200 300 400 500 600 700 800 900 1000
1
10
100
G
G
G
G
G
G
G
G
G
G
G
G
G
G
G
G
G
G
G
L
L
M MN
N
N
N
P
P
P P
PP
P
P
P
P
WW
WW
W
WW
WW
W
W
WWW
W
W
W
WW
W
WW
W
W
W
WW
W
W
G grassL hullM manureN nutshellP pumiceW wood
(Sur
face
are
a (m
2 g-1)
Temperature
100 200 300 400 500 600 700
1
10
100
HHHH
H
HH
H
H
SS
S
S
S
S S
SS
S
S
S
S
(Sur
face
are
a (m
2 g-1) H Hardwood
S Softwood
Temperature (oC)
Change in the surface area as a function of pyrolysis temperature of biochar
Change in surface area as a function of pyrolysis temperature of biochar derived from hard and softwood
Box plots showing differences in a) ash content and b) C/N ratios, but not in c) surface area across the different feedstocks. The grey boxes show the range from first to third quartiles, with the median dividing the interquartile range, into two boxes for the second and third quartiles. Letters show significant differences (p<0.05) according to a one-way ANOVA followed by Tukey (HSD) multiple means comparison
Suggested guidelines
Characteristic Suggested guideline
Ash content grass ≈ manure >> nut shells, pomace and wood(hard wood > soft wood)
C/N ratio wood >> grass> pomace> manure(soft wood > hard wood)
Surface area temperature dependent(soft wood > hard wood)
Property Agroecosystem consideration
Ash content Hydrophobicity and retention of agrochemicals
C/N ratio Initial Immobilization of soil N
Surface area Sorption of pesticides, herbicides and heavy metals, sites for fungal and microbial colonization
Acknowledgements
• Xiaoming Zhang • Lucas C.R. Silva • Johan Six• Sanjai J. Parikh• UC Davis Agricultural Sustainability Institute (ASI) Junior Faculty Award
• David and Lucile Packard Foundation
Email:[email protected]
Effects of biochar• Improves
– water holding capacity– nutrient retention– soil fertility – agricultural yield– greenhouse emission (GHG) mitigation
• However many other studies have shown – no increase in crop yields, – increased GHG emissions,– unintended “liming” of soils.
• Results often linked to the properties of the biochar used, application rate, soil type and climate.