Environmental Engineering Reference
In-Depth Information
generation capacity; LFG generation rate constant. In the case of Scholl Canyon model and
modified first order model, calculation have been performed separately for group of waste
components with different biodegradation velocity, using values for potential LFG generation
capacity and LFG generation rate constant reported in Table 3. Also, for these two models, a
lag time was considered, as reported in Table 3.
Concerning the modified first order model, assumed values for the rise phase gas
generation rate constant (s) are reported in Table 3 (Youcai et al., 2002).
The LandGEM model does not offer the possibility of considering different velocities of
biodegradation for different materials, hence single average values were introduced for
potential gas generation capacity and gas generation rate constant, as reported in Table 3. It is
not possible to introduce lag time in the software.
The amount of waste landfilled yearly is reported in Table 4. The analysed site is a
landfill for non-hazardous waste with an overall capacity of about 3.700.000 m
3
located in
central Italy. Values until seventh year are real data collected on-site, while values between
after eighth year are assumed according to the hypothesis of filling up the site authorised
capacity within the ninth year (last year of operation).
Table 4. Amount of waste landfilled yearly in the analysed site
Year
Waste [t]
Year
Waste [t]
1
171.929
7
278.634
2
263.606
8
240.000
3
260.453
9
240.000
4
315.214
10
240.000
5
246.159
11
240.000
6
259.896
The triangular model requires as inputs: amount of waste landfilled yearly; maximum gas
production rate (Q
LFG,max
); time at which gas production starts (t
0
); time at which the peak rate
of gas production occurs (t
max
); time at which gas production finishes (t
end
).
The maximum gas production rate (Q
LFG,max
) was obtained from the total amount of
produced LFG i.e. potential gas generation capacity (L
0
) used for the other models, from
equation (1) according to:
(14)
2
L
Q
=
0
t
−
t
LFG
,
max
end
0
Also in this model calculations have been performed separately for group of waste
components with different biodegradation velocity, adding up the results to obtain overall
LFG production. Assumed values for start time, peak rate time, end time and maximum LFG
production rate for each group of waste components with different biodegradation velocity,
are summarised in Table 5.
The results obtained applying the different models, according to the assumed inputs, are
shown in Figures 4, 5, 6 and 7. Figure 8 shows the comparison of results obtained from the
different applied models.
