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Supporting information
Biomethane production by typical straw anaerobic
digestion: deep insights of material compositions and
surface properties
Xiaohu Dai a, b, #, Yu Hua a, #, Rui Liu a, Shuxian Chen a, Huiping Li c, Lingling Dai
a, b, Chen Cai a, b, *
a State Key Laboratory of Pollution Control and Resources Reuse, College of
Environmental Science and Engineering, Tongji University, Shanghai, 200092, China
b Shanghai Institute of Pollution Control and Ecological Security, Shanghai,
200092, China
c College of Environmental and Chemical Engineering, Shanghai University of
Electric Power, Shanghai, 200090, China
Number of Tables: 4
Number of Figures: 1
Pages: 7
# Equally contributing authors
*Corresponding author:
Tel.: +86-15645026232
1
Table S1 Basic characteristics of straws and seeding granular sludge
Project
TS
(%Fresh
weight)
VS
(%Dry
weight)
Crude
protein
(% Dry
weight)
Carbon
content
(%Dry
weight)
Nitrogen
content
(%Dry
weight)
Hydroge
n content
(%Dry
weight)
Oxygen
content
(%Dry
weight)
Rice
straw88.86±0.04 85.92±0.08 8.69±0.01 32.63 1.39 4.63 39.35
Sweet
sorghum
straw
94.79±0.66 89.71±0.72 4.79±0.04 33.71 0.77 6.72 40.07
Wheat
straw95.38±0.37 81.41±0.11 5.69±0.02 37.96 0.91 4.00 40.32
Corn
straw96.42±0.46 82.04±0.08 7.38±0.09 37.97 1.18 5.73 39.16
Seeding
granular
sludge
5.84±0.28 85.40±0.71 40.25±0.01 34.93 6.44 5.14 25.02
3
Table S2 Reaction equation of anaerobic digestion of four kinds of straws
Reaction equationTheoretical
CH4 %
Measured
CH4 %
Rice
straw49.22 40.30
Sweet
sorghum
straw
61.47 50.00
Wheat
straw45.92 36.20
Corn
straw53.87 43.00
4
Table S3 Main functional groups of the RS, SSS, WS and CS samples
Wave
number
(cm-1)
Functional groups
Rice
stra
w
Sweet
sorghum
straw
Wheat
straw
Corn
straw
1
3580-3550
3460-3405
3375-3340
3310-3230
Free OH (6) and OH (2), weakly
absorbed water
O (2) H…O (6) intramolecular
hydrogen bonds
O (3) H…O (5) intramolecular
hydrogen bonds in cellulose
O (6) H…O (3) intramolecular
hydrogen bonds in cellulose
3417 3419 3420 3421
22989-2920
2850-2835
Symmetric CH stretching in aromatic
methoxyl groups and in methyl and
methylene groups of side chains
Asymmetric CH stretching in aromatic
methoxyl groups and in methyl and
methylene groups of side chains
2919
2850
2919
2850
2919
2850
2919
2850
3 1740-1720 C=O stretch in unconjugated ketones 1736 1735 1733 ND
4 1650-1635Water associated with lignin or
cellulose1640 1637 1637 1635
51610-1590
1515-1505
C=C stretching of the aromatic ring(S)
C=C stretching of the aromatic ring(G)
ND
1516
1607
1515
ND
1511
ND
1516
6 1470-1455 CH2 in pyran ring symmetric scissoring 1453 1461 1460 ND
7 1430-1422 C-H asymmetric deformation in -OCH 1424 1423 1425 ND
8 1375-1365 CH bending in cellulose I and cellulose 1374 1377 1375 1381
5
II and hemicellulose
9 1335-1320
C1-O vibrations in S derivatives,
CH in-plane bending in cellulose I and
cellulose II
1322 1319 1320 1320
1
01250
Guaiacyl ring breathing, C-O linkage in
guaiacyl aromatic methoxyl groups1245 1250 1244 ND
1
11205-1200
OH in-plane bending in cellulose I and
cellulose II1202 1203 1202 ND
1
2
1166
898Si-O-Si telescoping vibration peak
1159
899
1163
898
1161
899
1160
902
1
31128-1100
Aromatic C-H in-plane deformation
(typical for S units),1104 1106 1105 ND
1
41060-1015
C-O valence vibration mainly from C
(3)–O (3) H1052 1052 1038 1034
1
5
664
610Trans-state bending vibration of O-N-O
666
606
660
597669 ND
ND: not detected
6
Table S4 Energy balance and economic potentials of present study a
MaterialsRice straw (RS)
Sweet sorghum
straw (SSS)
Wheat straw (WS)
Corn straw (CS)
Unit
Total organic content (m)
76.35 85.04 77.65 79.10 %Fresh weight
Methane yield (VCH4) 161.74 182.74 265.98 335.67 m3 Mg-1
Total content in methane (E)
1.13(4.07)
1.43(5.13)
1.89(6.82)
2.43(8.77)
MWh Mg-1
(GJ Mg-1)- electric energy (for
sale)0.45 0.57 0.76 0.97 MWh Mg-1
- heat energy (for sale) 1.95 2.46 3.27 4.21 GJ Mg-1
Profits from energy sold:
- electric 67.50 85.50 114.00 145.50United States
dollar(USD)
- heat 24.38 30.75 40.88 52.63Total profit 91.88 116.25 154.88 198.13Cost of 1 Mg 17 17 17 17Net total profit 74.88 99.25 137.88 181.13
a The energy value of biogas produced from straw fermentation bases on methane
content. The calculation of amount of energy produced was based on Equation (8).
E = 1·m·VCH4·WeCH4 (8)
Where E: amount of energy produced from material, MWh; m: total organic content,
%; VCH4: volume of biomethane produced from 1Mg of substrate, m³ Mg-1; WeCH4:
energy value of methane, 0.00917MWh m-3. Considering the energy transformation,
the calculated amount of energy has to be recalculated by coefficients: ηe = 0.4
(electric efficiency of co-generation unit) and ηt = 0.48 (themal efficiency).
The price of straw as well as other substrates for biomethane production were taken
from the actual market data. The price for electric and heat energy was taken from the
published literature (Zbytek et al., 2016).
7
Fig. S1 The surface morphology observation of four typical straws by scanning
electron microscope:
(a) Corn straw; (b) Wheat straw; (c) Sweet sorghum straw; (d) Rice straw.
Corn straw(a-2)
Wheat straw(b-1)
Wheat straw(b-2)
Sweet sorghum straw(c-1)
Sweet sorghum straw(c-2)
Rice straw(d-1)
Rice straw(d-2)
Corn straw(a-1)
8
