Table 8.5 presents the reported H 2 yield and production rate from typical food
processing industry wastes such as rice winery, coffee drink manufacturing, noodle,
potato processing, sugar, molasses, apple pomace, vinasse manufacturing, olive mill
wastewater, olive pulp, and cheese whey. The variation in the chemical composition
of the waste and its degree of complexity increased the variability and conflict
among different studies conducted on the same waste. Promising yields (mol/mol
hexose) have been reported from waste such as sugar factor (2.6), apple pomace
(2.3), rice winery (2.1), and coffee drink (1.8).
3.3.1 Molasses
Sugar production from beet generates waste which contains molasses, beet pulp, and
cutoffs (beet top and beet leaves). Production of a tonne of beet sugar generates 0.33
tonne of beet pulp, 0.53 tonne of grass cutoffs [165], and liquid waste (molasses)
from sugar extraction processes. Molasses is a syrup which contains around 45%
sugar [166] with COD and BOD content of about 55 and 27.5 g/L, respectively
[167]. Around 55% of the total solids in molasses are organic [167]. Table 8.6 gives
some of the reported yields of H 2 produced in mesophilic and thermophilic dark
fermentation of molasses in batch and continuous reactors.
Molasses wastewater has been used for continuous production of H 2 in a
mesophilic (35
C) CSTR enhanced by granular activated carbon; at an HRT of
6 h, a 4–8 kg COD molasses wastewater/m
3 /d produced H 2 at a rate of 5.9 L/d
[176]. Similarly, a yield of 87.0 mL H 2 /g COD and an H 2 production rate of 42.7 mL
Table 8.6 Hydrogen yield from molasses wastewater
Substrate
Type of
operation
Temperature
(
C)
H 2 yield
H 2
production
rate
References
Molasses
wastewater
EGSBR
Mesophilic
1.95 mol/mol hexose
142 mL/g COD
0.71 L/L/h
[168]
Molasses
wastewater
Batch
Mesophilic
4.71 mmol/g COD
removed
[169]
Molasses
Continuous Mesophilic
0.2 L/L/h
[170]
Molasses
Continuous Mesophilic
5.57 L/L reactor/d
[171]
Molasses
wastewater
Batch
Thermophilic 190 mL/g COD
0.04 L/g
VSS/h
[172]
Molasses
Continuous Mesophilic
25 mol/mol
sucrose
[173]
Molasses
CSTR
Mesophilic
2.1 mol/mol
hexose
[174]
Molasses
wastewater
CSTR
Mesophilic
2.41 L/L/d
[175]
8 Biohydrogen of Industrial Waste
343
processing industry wastes such as rice winery, coffee drink manufacturing, noodle,
potato processing, sugar, molasses, apple pomace, vinasse manufacturing, olive mill
wastewater, olive pulp, and cheese whey. The variation in the chemical composition
of the waste and its degree of complexity increased the variability and conflict
among different studies conducted on the same waste. Promising yields (mol/mol
hexose) have been reported from waste such as sugar factor (2.6), apple pomace
(2.3), rice winery (2.1), and coffee drink (1.8).
3.3.1 Molasses
Sugar production from beet generates waste which contains molasses, beet pulp, and
cutoffs (beet top and beet leaves). Production of a tonne of beet sugar generates 0.33
tonne of beet pulp, 0.53 tonne of grass cutoffs [165], and liquid waste (molasses)
from sugar extraction processes. Molasses is a syrup which contains around 45%
sugar [166] with COD and BOD content of about 55 and 27.5 g/L, respectively
[167]. Around 55% of the total solids in molasses are organic [167]. Table 8.6 gives
some of the reported yields of H 2 produced in mesophilic and thermophilic dark
fermentation of molasses in batch and continuous reactors.
Molasses wastewater has been used for continuous production of H 2 in a
mesophilic (35
C) CSTR enhanced by granular activated carbon; at an HRT of
6 h, a 4–8 kg COD molasses wastewater/m
3 /d produced H 2 at a rate of 5.9 L/d
[176]. Similarly, a yield of 87.0 mL H 2 /g COD and an H 2 production rate of 42.7 mL
Table 8.6 Hydrogen yield from molasses wastewater
Substrate
Type of
operation
Temperature
(
C)
H 2 yield
H 2
production
rate
References
Molasses
wastewater
EGSBR
Mesophilic
1.95 mol/mol hexose
142 mL/g COD
0.71 L/L/h
[168]
Molasses
wastewater
Batch
Mesophilic
4.71 mmol/g COD
removed
[169]
Molasses
Continuous Mesophilic
0.2 L/L/h
[170]
Molasses
Continuous Mesophilic
5.57 L/L reactor/d
[171]
Molasses
wastewater
Batch
Thermophilic 190 mL/g COD
0.04 L/g
VSS/h
[172]
Molasses
Continuous Mesophilic
25 mol/mol
sucrose
[173]
Molasses
CSTR
Mesophilic
2.1 mol/mol
hexose
[174]
Molasses
wastewater
CSTR
Mesophilic
2.41 L/L/d
[175]
8 Biohydrogen of Industrial Waste
343