Environmental Engineering Reference
In-Depth Information
the effective utilisation time of the equipment. Table 14 summarises the construction phases
and the depreciation times assumed. The interest rate used is 6,5%.
On the basis of the LFG collected yearly in the two considered cases, it is possible to
estimate the appropriate size and number of reciprocating engines required every year to use
the LFG energy content, assuming to apply LFG collection and energy recovery until about
95% of total LFG is produced. Considering a reciprocating engine average life of ten years, it
is possible to calculate the overall number and combination of engines required.
The engine selection has been based on existing models (Jenbacher), using relative large
size engine in the high LFG production period and small size engines in the final LFG
production. Table 15 summarises the engine number used for each of the considered case.
Table 13. Investment and operation costs for the different considered plants
Equipment
Landfill with leachate
recirculation
Conventional landfill
with vertical collection
system
Bottom impermeabilisation [€]
4.957.803
4.957.803
Collection system (leachate and LFG) [€]
750.000
460.000
Capping [€]
1.816.809
1.816.809
Table 14. Assumed construction phases and the depreciation times
Equipment
Construction phases
Depreciation time [years]
Bottom impermeabilisation
All placed at the beginning
8
Capping
All placed at the closing time
1
Flare
Life time of 1 flare
10
Landfill with leachate recirculation
Collection/recirculation system is placed at three different
moments
At the beginning
After 2 year
After 5 years
Collection system
8
6
3
At the beginning
After 2 year
After 5 years
8
6
3
Conventional landfill with vertical collection system
Collection system
Collection system is placed at
the beginning
Landfill operation time = 8
years
From the electric energy conversion efficiency of the considered engines (143 kW -
34,3%; 625 kW - 38,7; 836 kW - 38,8) it is possible to evaluate the electricity production
and assuming an electric energy selling price of about 0,13 €/kWh, it is possible to estimate
the gain from electricity sell. The estimation of electricity production also took into account
the energy conversion efficiency lowering when energy input is less than nominal size.
