20
2 High-Efficient Anaerobic Fermentation Technology of Organic …
basically consistent with those in anaerobic fermentation of solid phase of kitchen
wastes. According to Fig. 2.7a, the content of hydrogen under each treatment condition firstly increased and then decreased. When hydrothermal hydrolysis was performed at 150 °C for 60 min and added with 40% of waste, the content of hydrogen
was higher than those under other treatment conditions and reached the highest (15%)
at 72 h. In comparison with liquid phase of kitchen wastes, the content of hydrogen
was about 5–6 times that of mixed phase. This indicates that potential of hydrogen production by acidizing mixed phase of kitchen wastes is low to some extent.
In accordance with Fig. 2.7b, the content of methane firstly rose and then tended
to be stable under each experimental condition. Under the hydrothermal hydrolysis
condition at 150 °C for 60 min with 40% of water added, the content of methane
was the highest and reached 58% at 110 h, followed by 55 and 54% of methane
produced under the conditions at 200 and 120 °C for 70 and 50 min with 40% of
water added separately. On the one hand, under such conditions, the inhibition of
high content of oil on fermentation system can be reduced maximally. On the other
hand, hydrothermal hydrolysis pre-treatment improves degree of homogenisation of
mixed phase of kitchen wastes, thus improving methane production in anaerobic fermentation. By comparing anaerobic fermentation of solid, liquid and mixed phases
of kitchen wastes, different properties of materials have different biogas production
efficiencies; liquid phase shows higher potential of hydrogen production, while solid
and mixed phases demonstrate higher potential of methane production.
By using the modified Gompertz model, the kinetic curves of anaerobic hydrogen
and methane production of liquid-phase kitchen wastes were fitted. Based on the
results in Fig. 2.8 and Table 2.1, under all conditions of hydrothermal hydrolysis
pre-treatment, R
2 of the fitted curve of hydrogen production was larger than 0.99,
while that of the fitted curve of methane production was larger than 0.98. After adding
40% of water and being treated at 150 °C for 60 min in hydrothermal hydrolysis, the
highest hydrogen production was only 8.21 mL/g.VS and the maximum potential for
hydrogen production was 23.01 mL. Under this condition, the highest cumulative
Fig. 2.7 Effects of different treatment conditions on hydrogen and methane proportion of kitchen
waste mixed phase anaerobic fermentation
2 High-Efficient Anaerobic Fermentation Technology of Organic …
basically consistent with those in anaerobic fermentation of solid phase of kitchen
wastes. According to Fig. 2.7a, the content of hydrogen under each treatment condition firstly increased and then decreased. When hydrothermal hydrolysis was performed at 150 °C for 60 min and added with 40% of waste, the content of hydrogen
was higher than those under other treatment conditions and reached the highest (15%)
at 72 h. In comparison with liquid phase of kitchen wastes, the content of hydrogen
was about 5–6 times that of mixed phase. This indicates that potential of hydrogen production by acidizing mixed phase of kitchen wastes is low to some extent.
In accordance with Fig. 2.7b, the content of methane firstly rose and then tended
to be stable under each experimental condition. Under the hydrothermal hydrolysis
condition at 150 °C for 60 min with 40% of water added, the content of methane
was the highest and reached 58% at 110 h, followed by 55 and 54% of methane
produced under the conditions at 200 and 120 °C for 70 and 50 min with 40% of
water added separately. On the one hand, under such conditions, the inhibition of
high content of oil on fermentation system can be reduced maximally. On the other
hand, hydrothermal hydrolysis pre-treatment improves degree of homogenisation of
mixed phase of kitchen wastes, thus improving methane production in anaerobic fermentation. By comparing anaerobic fermentation of solid, liquid and mixed phases
of kitchen wastes, different properties of materials have different biogas production
efficiencies; liquid phase shows higher potential of hydrogen production, while solid
and mixed phases demonstrate higher potential of methane production.
By using the modified Gompertz model, the kinetic curves of anaerobic hydrogen
and methane production of liquid-phase kitchen wastes were fitted. Based on the
results in Fig. 2.8 and Table 2.1, under all conditions of hydrothermal hydrolysis
pre-treatment, R
2 of the fitted curve of hydrogen production was larger than 0.99,
while that of the fitted curve of methane production was larger than 0.98. After adding
40% of water and being treated at 150 °C for 60 min in hydrothermal hydrolysis, the
highest hydrogen production was only 8.21 mL/g.VS and the maximum potential for
hydrogen production was 23.01 mL. Under this condition, the highest cumulative
Fig. 2.7 Effects of different treatment conditions on hydrogen and methane proportion of kitchen
waste mixed phase anaerobic fermentation