28
2 High-Efficient Anaerobic Fermentation Technology of Organic …
HE
PE
BU
PR
AC
FA
0
2
4
6
8
10
12
Control-HS Control-MSAcid-HS Acid-MS Alkali-HSAlkali-MSEnzyme-HSEnzyme-MS
0
10
20
30
40
50
60
70
80
90
100
Individual VFA (%)
Pretreatments
Rmax
Rm(mL/h)
Fig. 2.12 Percentage of individual VFA accounting for the total VFAs and R m in response to
different pre-treatments with the combined hydrogen/methane production process
ranked the first in the hydrogenogenic stage according to the analysis on the VFA
compositions in the two stages, while propionic acid was the leading product after
the methanogenic stage. Most of the soluble metabolites of the pre-treatments with
alkali and enzyme comprised butyrate and acetate, as evaluated by GC (which in
combination held 99.4 and 98.7% separately of the overall soluble metabolites in
the two pretreatments). The result indicated that a fermentation based on butyric
acid happened in the hydrogenogenic stage. For the pre-treatments with acid, the
soluble metabolites consisted of acetate, ethanol and butyrate, which totally held a
proportion of 99.6% of the overall soluble metabolites. This composition implied
that bothe fermentation processes based on ethanol and butyric acid took place in the
hydrogenogenic systems. Nevertheless for the pre-treatments with acid, fermentation
using butyric acid was the primary metabolic pathway. Moreover, it was observed
that the control test led to the highest concentrations of lactic acid (3.84 g/L) in comparison with those in all other pre-treatments after the hydrogenogenic stage. This
probably threatened the efficiency of anaerobic digestion after the hydrogen production. The soluble metabolites, particularly butyrate and acetate acids displayed
dramatically reducing concentrations in the methanogenic stage, while the percentage of propionic acid was higher than that of all pre-treatments in the hydrogenogenic
stage.
2 High-Efficient Anaerobic Fermentation Technology of Organic …
HE
PE
BU
PR
AC
FA
0
2
4
6
8
10
12
Control-HS Control-MSAcid-HS Acid-MS Alkali-HSAlkali-MSEnzyme-HSEnzyme-MS
0
10
20
30
40
50
60
70
80
90
100
Individual VFA (%)
Pretreatments
Rmax
Rm(mL/h)
Fig. 2.12 Percentage of individual VFA accounting for the total VFAs and R m in response to
different pre-treatments with the combined hydrogen/methane production process
ranked the first in the hydrogenogenic stage according to the analysis on the VFA
compositions in the two stages, while propionic acid was the leading product after
the methanogenic stage. Most of the soluble metabolites of the pre-treatments with
alkali and enzyme comprised butyrate and acetate, as evaluated by GC (which in
combination held 99.4 and 98.7% separately of the overall soluble metabolites in
the two pretreatments). The result indicated that a fermentation based on butyric
acid happened in the hydrogenogenic stage. For the pre-treatments with acid, the
soluble metabolites consisted of acetate, ethanol and butyrate, which totally held a
proportion of 99.6% of the overall soluble metabolites. This composition implied
that bothe fermentation processes based on ethanol and butyric acid took place in the
hydrogenogenic systems. Nevertheless for the pre-treatments with acid, fermentation
using butyric acid was the primary metabolic pathway. Moreover, it was observed
that the control test led to the highest concentrations of lactic acid (3.84 g/L) in comparison with those in all other pre-treatments after the hydrogenogenic stage. This
probably threatened the efficiency of anaerobic digestion after the hydrogen production. The soluble metabolites, particularly butyrate and acetate acids displayed
dramatically reducing concentrations in the methanogenic stage, while the percentage of propionic acid was higher than that of all pre-treatments in the hydrogenogenic
stage.