1. Marianao CP 19390, La Habana, Cuba
Antagonistic effects on methane yield of liquid hot-water pretreated press mud fractions codigested with vinasse
Lisbet Mailin López González a, Ileana Pereda Reyes b, Jörn Budde c, Monika Heiermann c, Osvaldo Romero a, Han Vervaeren d
a University of Sancti Spíritus ‘‘José Martí Pérez’’, Centro de Estudio de Energía y Procesos Industriales (CEEPI), Avenida de los Mártires, 360, 60100, Sancti Spíritus, Cuba
b Instituto Superior Politécnico ‘‘José Antonio Echeverría’’ (Cujae), Centro de Estudio de Ingeniería de Procesos (CIPRO), Calle 114 No e/ Rotonda y Ciclovía,
Marianao CP 19390, La Habana, Cuba
c Leibniz-Institute for Agricultural Engineering Potsdam-Bornim, Max-Eyth-Allee 100, Potsdam, Germany
d Laboratory of Industrial Water and Eco-technology (LIWET), Faculty of Bioscience Engineering, Ghent University Campus Kortrijk, Graaf Karel de Goedelaan 5, B-8500
Kortrijk, Belgium
Concept
Vinasse (V) and press mud are considered the main residues generated in Sugar-distillery complexes. Press mud pretreated by liquid hot water increased the solubilisation of the chemical oxygen demand (COD), and the methane yield. A separated anaerobic digestion of the two fractions is accompanied by significant differences in the kinetics of the hydrolytic/acidogenic and methanogenic stages.
Vinasse
Press mud
Objective
Press mud fractions (liquid and/or solid) as obtained by liquid hot water (LHW) pretreatment were tested for methane yield and combined effects (synergetic, antagonistic or neutral) in co-digestion with V, using a simplex lattice mixture design.
Methods
Press mud was pretreated to 150°C for 20 min. Liquid and solid fractions were blended with vinasse in different proportions, according to a three factor mixture design (Table 1). Methane production was followed by liquid displacement measurement and its composition analysed by gas chromatography.
Assuming that the measured response was dependent on the relative proportions of the components in the mixture, linear to cubic models were used for the analysis of the design.
Table 1. Mixture Compositions for the Experimental Setups
Mixing ratios *
Mixtures V LF SF
100
V67 : LF0 : SF33
66.6
33.3
V67 : LF33 : SF0
V33 : LF0 : SF67
V33 : LF67 : SF0
V33 : LF33 : SF33
V0 : LF67 : SF33
V0 : LF33 : SF67
*Expressed as the COD proportion for each component added in the mixture
Results
Fig. 6. Dependence of methane yield with the pre-treatment severity (Fig. 6. Dependence of methane yield with the pre-treatment severity (
Methane yield
Coefficient
Estimate
Standard Error
p-value
βLF
369 6
βSF
249 βV
271
βLF_SF -2 28
0.940
βLF_V
-416
0.000
βSF_V
-21 25
0.457
βLF_SF_V
-767
202
0.001
δLF_V (LF-V)
-344 62
δLF_SF (LF-SF) 80
0.213
δSF_V (SF-V)
-109
0.097 B
The methane yields obtained experimentally are comparable to the predicted for the full cubic in the case of the mixtures without V and the mixtures without LF.
When V and LF are present, the linear prediction fails, according to the high antagonistic effect found for their interaction.
The methane yields obtained from batch anaerobic digestion tests are 20 %, 36 % and 25 % lower for V67 : LF33 : SF0, V33 : LF67 : SF0 and V33 : LF33 : SF33, respectively, than the attained methane yields considering an additive behaviour. A
LF has the highest positive coefficient.
Antagonistic effect for the mixture of LF and V.
Antagonistic influence for the coefficient βLF_SF_V and δLF_V (LF-V).
Kinetic
The values for k ranged from 0.18 d-1 to 0.39 d-1.
Higher methane production rates are observed for V and most of its blends
The full cubic model (R2adj=95%):
Fig. 1. Three-dimensional mixture surface (A) and contour plot (B) for methane yields (yCH4) obtained from fitted model.
Conclusions
For most mixtures examined, antagonistic effects were found with significant differences when vinasse and liquid fraction are mixed.
The co-digestion of V and the LF of LHW pretreated press mud is not considered a good option.
This research was supported by the VLIR-UOS project entitled “Biogas production from waste from local food, wood and sugar cane industries for increasing self-sufficiency of energy in Sancti Spiritus, Cuba”.
López González et al Antagonistic effects on methane yield of liquid hot-water pretreated press mud fractions codigested with vinasse. Energy Fuels.. DOI: /acs.energyfuels.5b01369