Supplementary materials
1. Analytical Methods
TS and VS of substrates and inoculum were measured in triplicate per sample
according to standard methods [1]. Organic elements (CHNS) were analyzed by an
elemental analyzer (Vario EL cube, Germany). Pressures in the head of digesters were
measured by a 3150 WAL-BMP-Test system pressure gauge (WAL Mess-und
Regelsysteme GmbH, Germany). The volume of biogas produced was calculated
according to ideal gas law [2]. Biogas composition was measured by a 6890A gas
chromatography
(Agilent
Company,
USA)
equipped
with
a
thermal conductivity detector (TCD) and Argon was the carrier biogas at a flow rate
of 30 mL/min. A 1.8 m × 80/100 stainless steel column (All-tech, USA) was used.
The temperatures of the oven, injector port, and detector were 100, 120, and 120 °C,
respectively. Biogas composition was measured every day in the first week, then once
or twice per week until the end of digestion. Measured methane content was linearly
interpolated to determine the daily methane content [2].
2. Statistical Analysis
The significance of biogas and methane production were obtained by using analysis of
variance (one way ANOVA) at α = 0.01 and α = 0.05. Origin 8.0 (OriginLab, USA)
and PASW Statistics 18.0 (IBM, USA) were used for data and graphing analysis.
3. Floating separation tests
Several batch tests were conducted for floating separation. The first one was operated
at room temperature, with MS-OFMSW to water ratio of 1:9, 3:7, and 5:5 (on weight
basis), respectively, and initial mixing. After 30 h floating, different layers were
appeared. Three layers were shown to inert (fixed) materials, water solution, and
organics (machine- and floating-separated OFMSW, MFS-OFMSW) from the bottom
up. As seen in Table S1, with the percentage of MS-OFMSW in water increasing, the
VS/TS ratio of MS-OFMSW increased. Highest VS/TS ratio of 75.2% was found with
MS-OFMSW to water ratio of 1:9. Thus, MS-OFMSW to water ratio of 1:9 was used
for further tests. Then, we found that increasing the temperature could speed up the
generation of floating and sunken layers. In the current study, MFS-OFMSW was
obtained after settling for 2 h with temperature maintain at 50 oC. A 1 L glass cylinder
was used and the MS-OFMSW to water ratio was 1:9 (on weight basis). The VS/TS
ratio for MFS-OFMSW was 81.2% (Table 1).
References:
1. Li, Y.Q., Feng, L., Zhang, R.H., He, Y.F., Liu, X.Y., Xiao, X., Ma, X.X., Chen, C.,
Liu, G.Q.: Influence of inoculum source and pre-incubation on bio-methane
potential of chicken manure and corn stover. Appl. Biochem. Biotechnol. 171,
117-127 (2013)
2. El-Mashad H.M.: Kinetics of methane production from the codigestion of
switchgrass and Spirulinaplatensis algae. Bioresour. Technol. 132, 305-312
(2013)
Table S1 Characteristics of MS-OFMSW and MFS-OFMSW in previous study
Samples
TS, %
VS (%TS)
MS-OFMSW
23.5
54.0
MFS-OFMSW(1:9)*
8.3
75.2
MFS-OFMSW(3:7)*
19.9
60.1
MFS-OFMSW(5:5)*
23.6
52.3
*: MS-OFMSW to water ratio (on weight basis)
Fig. S1. Floating separation test for MS-OFMSW at ambient temperature