Environmental Engineering Reference
In-Depth Information
C. Landfill Gas Yield
Methane yield is defined as the total amount of methane generated per unit weight (dry or
wet) of MSW (El-Fadel et al. 1996a). The methane yield is a function of waste composition.
Eleazer et al. (1997) found that the methane yield increased as cellulose and hemicelluose
content increased. The methane yield was reviewed by El-Fadel et al. (1996a). There are two
approaches for estimating this yield: theoretical and experimental
The
Theoretical approach
uses the stoichiometric and biodegradability methods to
estimate the gas yield. The
stoichiometric method is based on several assumptions, such as
whether or not complete degradation of waste has occurred; the degradation product only
includes CH
4
and CO
2;
the balance of substrates and nutrients is available at all times in all
places in the landfill, and no portion of the degraded matter is utilized into cell growth (Ham
1979). The following equation is commonly used to estimate the theoretical landfill gas yield:
.
⎛
b
c
3
d
e
⎞
⎛
a
b
c
3
d
e
⎞
C
H
O
N
S
+
a
−
−
+
+
H
O
⇒
+
−
−
−
CH
+
⎝
⎠
⎝
⎠
a
b
c
d
e
2
4
4
2
4
2
2
8
4
8
4
[1]
a
b
c
3
d
e
⎛
⎞
−
+
+
+
CO
+
d
NH
+
e
H
S
⎝
⎠
2
3
2
2
8
4
8
4
Table 4. Typical Concentrations of VOCs Compounds in Landfills Gases
Concentration, ppbV (Part per billion per volume)
Compound
Median
Mean
Maximum
Acetone
0
6,838
240000
Benzene
932
2057
39000
Chlorobenzene
0
82
1640
Chloroform
0
245
12000
1,1-Dichloroethane
0
2801
36000
Dichloromethane
1150
25694
620000
1,1-Dichloroethene
0
130
4000
Diethylene chloride
0
2835
20000
trans-1,2-Dichloroethane
0
36
850
Ethylene dichloride
0
59
2100
Ethyl benzene
0
7334
87500
Methyl ethyl ketone
0
3092
130000
1, 1, 1-Trichloroethane
0
615
14500
Trichloroethylene
0
2079
32000
Toluene
8125
34907
280000
1, 1, 2, 2-Tetrachloroethane
0
246
16000
Tetrachloroethylene
260
5244
180000
Vinyl chloride
1150
3508
32000
Styrenes
0
1517
87000
Vinyl acetate
0
5663
240000
Xylenes
0
2651
38000
(Source: Tchobanouglous et al., 1993)
