Environmental Engineering Reference
In-Depth Information
Table 17. Comparison of proposed scenarios according to some energy
and environmental performance indicators.
Scenario 1
Scenario II
Scenario III
Scenario IV
CF WtE + HF
AD
CF GAS + HF
AD
CF PYR + HF
AD
MSW WtE
Waste mass flow rate
[kg waste/h]
14.344
14.344
14.344
14.344
LHV [kJ/kg waste]
10.127
10.127
10.127
10.127
Entering power [kW]
40.350
40.350
40.350
40.350
Net power output [kW]
8.896
8.369
6.275
10.450
Efficiency [%]
22
21
16
26
Energy source saving
[TOE/year]
16.075
15.122
11.338
18.882
Specific energy
production [kWh/kg
waste]
0,62
0,62
0,72
0,53
Gross CO
2
emission
[tCO
2
/year]
107.960
84.815
85.852
85.852
Avoided CO
2
emission
[tCO
2
/year]
-34.417
-32.377
-24.276
-40.400
Net CO
2
emission
[tCO
2
/year]
73.543
52.437
61.576
45.425
Gross specific CO
2
emission [kg
CO
2
/kWh]
1,56
1,3037
1,75
1,05
Net specific CO
2
emission [kg
CO
2
/kWh]
1,06
0,80
1,26
0,56
Gross specific CO
2
production [tCO
2
/t
waste]
0,96
0,77
0,78
0,78
Net specific CO
2
production [tCO
2
/t
waste]
0,66
0,47
0,56
0,41
On the contrary the pyrolysis process, coupled with syngas energy recovery in a
reciprocating engine, can reach quite high performances in terms of efficiency and energy
recovery. However, today the pyrolysis technology is not yet competitive in reference to
commercial industrial scale installations for waste treatment, since its application to the
biomass sector (small sizes) in still in development.
The possibility of coupling the thermal treatment, for the combustible fraction, with the
anaerobic digestion, for the humid fraction, allows keeping efficiency and energy recovery
levels similar to the MSW WtE case, with two additional benefits. The first one is related to
the lower CO
2
production, due to lower carbon transformation in the biological process. The
second one is related to the possibility of obtaining incentive pay for the energy produced
from anaerobic digestion, since this is acknowledged as a renewable source, while energy
from WtE is not, at least in some countries (as in Italy for example).
