Environmental Engineering Reference
In-Depth Information
Table 8.5
Calculation and stoichiometry of methane fermentation
Biomass
Organic
Gas production(Nm
3
/
kg-VS
degradation
)
CH
4
(%)
Carbohydrate
(C
6
H
10
O
5
)
n
+ nH
2
O→3nCH
4
+ 3nCO
2
0.83
50.0
Protein
C
16
H
24
O
5
N
4
+ 14.5H
2
O→8.25CH
4
+ 3.75
CO
2
+ 4NH
4
+
+ 4HCO
3
−
0.764
68.8
Lipid
C
50
H
90
O
6
+ 24.5H
2
O
→34.75CH
4
+ 15.25CO
2
1.425
69.5
Cooking scrap
C
17
H
29
O
10
N + 6.5H
2
O→9.25CH
4
+ 6.75
CO
2
+ NH
4
+
+ HCO
3
−
0.881
57.8
Cattle manure
C
22
H
29
O
10
N + 6.5H
2
O→9.25CH
4
+ 6.75
CO
2
+ NH
4
+
+ HCO
3
−
0.970
56.0
Kitchen garbage
C
46
H
73
O
31
N + 14H
2
O→24CH
4
+ 21CO
2
+ NH
4
+
+ HCO
3
−
0.888
53.3
Sewage sludge
C
10
H
19
O
3
N + 5.5H
2
O→6.25CH
4
+ 2.75C
O
2
+ NH
4
+
+ HCO
3
−
1.003
69.4
Chicken manure
C
7.5
H
12.4
O
4.8
NS
0.13
+ 4.15 H
2
O→3.7
CH
4
+ 2.8 CO
2
+ NH
4
+
+ HCO
3
−
+ 0.13
H
2
S
0.75
63.5
The characteristics of cattle manure are summarized in Table
8.8
. In addition,
the average performance of cattle manure fermentation is shown in Fig.
8.11
, and
the whole process including dewatering and waste water treatment is illustrated in
Fig.
8.12
. As shown in Fig.
8.11
, the average biogas yield from cattle manure fer-
mentation was 37.7 m
3
/m
3
inf
(60.1 % CH
4
content), with the extent of reduction in
total solids (TS) reaching 32.3 % in the digested sludge. The bio-methane has been
converted into heat or electric energy with benefits for the farmers (Table
8.7
).
8.4.4
Chicken Manure
With the increase in intensive and mechanized poultry breeding industries, large
amounts of waste are being produced. Annually, about 13 million t of chicken ma-
nure (CM) is generated in Japan, which corresponds to 65 % of total food processing
waste. Based on the characteristic of CM (Table
8.9
), methane fermentation of
chicken manure allows for bioenergy recovery as well as minimizing the waste,
and has distinct advantages over conventional treatments, as illustrated in Fig.
8.13
.
A laboratory scale CSTR reactor (Fig.
8.14
) has been developed with an average
performance shown in Fig.
8.15
for both ammonia-stripped CM and raw CM. Be-
low total ammonia nitrogen concentrations of 5000 mg/L, the process can deliver a
steady performance. Methane fermentation of CM has a number of benefits as a ma-
nure treatment technology, including greenhouse gas emissions and odor reduction,
increased nutrient availability, and reduced pathogen risk. However high organic
nitrogen content leads to increases in volatile fatty acid production at the expense
of methane. In one proposed design, CM 10 t/day feed with total solids of 10 % in
