685
Anaerobic digestion of Eichhornia crassipes was accomplished to enhance
methane production using microwave pre-treatment [75]. Pre-treatment was carried
out at microwave power of 500 W, temperature of 100 °C, 20.1 g/L substrate concentration and 15 min operational time. Using microwave pre-treatment, methane
production was 221 mL/g-sub which was 38.3% higher than the conventional method.
Varanasi et al. [76] have studied the biohydrogen production, biomethanation
and bioelectricity generation from water hyacinth. Biohydrogen was produced in
batch process carried out in a reactor of 500 mL volume at pH of 6.5 and temperature 37 °C with the maximum cumulative H 2 production (904 ± 40.69 mL/L) and
yield (41.38 ± 2.06 L/kg COD). Biomethanation of water hyacinth has been performed in double-jacketed batch reactor having 500 mL volume. Anaerobic environment was maintained by sparging N 2 for 5 min. Temperature was maintained at
37 °C and stirring speed at 280 rpm. The maximum cumulative methane production
was achieved to be 796.73 ± 18.62 mL/L with 35.69 ± 1.24 L/kg COD yield.
Microbial fuel cell (MFC) was incorporated to produce electricity. Carbon felt
coated with WO 3 catalyst as anode and carbon ink-coated anion exchange membrane as cathode were used in the polyacrylic MFC chamber. The batch time for
MFC was 72 h, and the internal resistance was 17–20 Ω. The maximum power
densities in two-stage and three-stage process were obtained as 18.15 ± 0.54 and
16.28 ± 0.65 W/m
3
, respectively. The combined system comprising of three stages
was able to provide the highest energy (60%) in the form of hydrogen, methane and
electricity with 94% of overall COD removal.
Biohydrogen was produced from water hyacinth in batch and continuous process
by Ruen-ngam and Jaruyanon [77] using a batch reactor. The processing conditions
were temperature in the range of 400–500 °C at 50 °C of interval, pressure variation
from 21.2 to 26.8 MPa and 5–30 min variation in reaction time. Biomass ratio was
varied from 2.5% to 15%. The continuous system used for gas production was operated at 0.51 L/h, while maintaining temperature and pressure conditions closed to
supercritical water (T = 374 °C, P = 22 MPa). The H 2 production rate in continuous
system was 0.96 mol/min which could recover energy equivalent to 2.08 Wh/g biomass or 11.43 kWh/mole glucose. The H 2 yield was 2.7 times higher in continuous
system than the batch system.
Water hyacinth was used for producing hydrogen using cellulose and xylanase
enzyme [78]. Sodium chlorite (NaClO 2 ) was added in acidic fermentation process
for lignin deterioration. The concentration of NaClO 2 was varied from 0 to
20 mg/L. The maximum hydrogen yield of 119.6 ± 7.8 mL/g TVS (total volatile
solids) at NaClO 2 concentration of 8 mg/L was obtained which was much more as
compared to 39.7 ± 2.5 mL/g TVS (without NaClO 2 ). A higher concentration of
NaClO 2 (more than 8 mg/L) has caused the death of anaerobes in the fermentation
media showing an adverse impact on performance of the process.
Waste Valorization of Water Hyacinth Using Biorefinery Approach: A Sustainable Route
Anaerobic digestion of Eichhornia crassipes was accomplished to enhance
methane production using microwave pre-treatment [75]. Pre-treatment was carried
out at microwave power of 500 W, temperature of 100 °C, 20.1 g/L substrate concentration and 15 min operational time. Using microwave pre-treatment, methane
production was 221 mL/g-sub which was 38.3% higher than the conventional method.
Varanasi et al. [76] have studied the biohydrogen production, biomethanation
and bioelectricity generation from water hyacinth. Biohydrogen was produced in
batch process carried out in a reactor of 500 mL volume at pH of 6.5 and temperature 37 °C with the maximum cumulative H 2 production (904 ± 40.69 mL/L) and
yield (41.38 ± 2.06 L/kg COD). Biomethanation of water hyacinth has been performed in double-jacketed batch reactor having 500 mL volume. Anaerobic environment was maintained by sparging N 2 for 5 min. Temperature was maintained at
37 °C and stirring speed at 280 rpm. The maximum cumulative methane production
was achieved to be 796.73 ± 18.62 mL/L with 35.69 ± 1.24 L/kg COD yield.
Microbial fuel cell (MFC) was incorporated to produce electricity. Carbon felt
coated with WO 3 catalyst as anode and carbon ink-coated anion exchange membrane as cathode were used in the polyacrylic MFC chamber. The batch time for
MFC was 72 h, and the internal resistance was 17–20 Ω. The maximum power
densities in two-stage and three-stage process were obtained as 18.15 ± 0.54 and
16.28 ± 0.65 W/m
3
, respectively. The combined system comprising of three stages
was able to provide the highest energy (60%) in the form of hydrogen, methane and
electricity with 94% of overall COD removal.
Biohydrogen was produced from water hyacinth in batch and continuous process
by Ruen-ngam and Jaruyanon [77] using a batch reactor. The processing conditions
were temperature in the range of 400–500 °C at 50 °C of interval, pressure variation
from 21.2 to 26.8 MPa and 5–30 min variation in reaction time. Biomass ratio was
varied from 2.5% to 15%. The continuous system used for gas production was operated at 0.51 L/h, while maintaining temperature and pressure conditions closed to
supercritical water (T = 374 °C, P = 22 MPa). The H 2 production rate in continuous
system was 0.96 mol/min which could recover energy equivalent to 2.08 Wh/g biomass or 11.43 kWh/mole glucose. The H 2 yield was 2.7 times higher in continuous
system than the batch system.
Water hyacinth was used for producing hydrogen using cellulose and xylanase
enzyme [78]. Sodium chlorite (NaClO 2 ) was added in acidic fermentation process
for lignin deterioration. The concentration of NaClO 2 was varied from 0 to
20 mg/L. The maximum hydrogen yield of 119.6 ± 7.8 mL/g TVS (total volatile
solids) at NaClO 2 concentration of 8 mg/L was obtained which was much more as
compared to 39.7 ± 2.5 mL/g TVS (without NaClO 2 ). A higher concentration of
NaClO 2 (more than 8 mg/L) has caused the death of anaerobes in the fermentation
media showing an adverse impact on performance of the process.
Waste Valorization of Water Hyacinth Using Biorefinery Approach: A Sustainable Route