1
The following document is supplementary material for the paper:
2
Paton, Maier and Dandy, Including adaptation and mitigation responses to climate change in a multi-
3
objective evolutionary algorithm framework for urban water supply systems incorporating GHG
4
emissions
5
Submitted to Water Resources Research, December 19, 2013
6
1
7
As the local catchment reservoirs and their associated water treatment plants (WTPs) were existing
8
features of Adelaide’s southern water supply system, only ongoing GHG emissions were accounted
9
for, namely the energy required for treatment at the WTPs and those associated with chemical use.
10
GHG emissions associated with the replacement of Happy Valley WTP in 2041 and Myponga WTP
11
in 2043 (see section 1 of auxiliary material on economic costs) could not be accounted for due to the
12
absence of data.
13
The power required at Happy Valley WTP was assumed to be 100 kWh/ML, while for Myponga
14
WTP it was assumed to be 140 kWh/ML (see section 1 of auxiliary material on economic costs).
15
While there is an absence of case-specific data for the GHG emissions associated with chemicals for
16
Adelaide’s WTPs, Racoviceanu et al. [2007] found that 94% of energy usage is attributable to
17
operation, 5% is attributable to chemical manufacturing and 1% to chemical transportation, which was
18
similar to a study by Tarantini and Ferri [2001] that estimated chemical manufacturing accounted for
19
10% of energy usage and chemical transportation was insignificant. Consequently, the power rates of
20
100 kWh/ML and 140 kWh/ML for each of the water treatment plants were assumed to account for
21
94% of energy, with 6% attributed to chemical manufacturing and transport. Consequently, for Happy
22
Valley and Myponga WTP, GHG emission estimates were based on energy requirements of 106.4
23
kWh/ML and 148.9 kWhh/ML, respectively. These energy intensities were multiplied by the GHG
24
emissions factor of 0.73 kgCO2-e/kWh and the volume of water treated at each WTP to calculate the
25
total emissions attributable to treatment energy for the local catchment reservoirs.
Local Catchment Reservoirs
26
2
27
The River Murray was an existing Adelaide southern system supply source, so it was not necessary to
28
account for capital GHG emissions associated with the Murray Bridge-Onkaparinga (MBO) pipeline.
29
Consequently, only ongoing GHG emissions of River Murray supply were accounted for, which
30
included GHG emissions of treating the water at Happy Valley WTP (see section 1) and GHG
31
emissions due to pumping. As per the estimation of costs, GHG emissions due to pumping were
32
derived from first principles, using the Darcy-Weisbach head loss equation and the pump power
33
equation (see Eq. 2 and Eq. 3 in section 2 of auxiliary material on economic costs). The pump power
34
was then converted to kWh, based on 24-hour operation, before being converted to GHG emissions
35
using the GHG emission rate of 0.73 kgCO2-e/kWh, which is the latest full fuel cycle emission factor
36
estimate for purchased electricity by South Australian end users [Department of Industry Innovation
37
Climate Change Science Research and Tertiary Education, 2013]. For example, if the River Murray
38
supplied 50GL/yr, the GHG emissions associated with electricity to pump River Murray water would
39
be 1.1 kgCO2-e/m3 or 55,000 tCO2e-/yr.
40
3
41
3.1 Capital GHG Emissions – Desalination Plant
42
The capital GHG emissions for the desalination plant were attributed to the materials, electricity, and
43
diesel used to construct the main plant and onsite power facilities. SA Water [2009] estimated
44
quantities and resulting GHG emissions for these resources for the 50 GL/yr proposed Adelaide
45
desalination plant and proposed that there would be minimal additional construction energy for the
46
100 GL/yr plant because the 50 GL/yr plant was designed for an upgrade to 100 GL/yr capacity.
47
Consequently, an indicative 10% of capital GHG emissions was added to the GHG emissions reported
48
by SA Water [2009] (Table 1), to represent the additional buildings for process equipment that were
49
required for the 100 GL/yr capacity plant.
50
River Murray
Desalination
51
52
Table 1: Estimated GHG emissions for a 100GL/yr desalination plant based on values reported by SA Water [2009]
for the Adelaide desalination plant
GHG emissions (tCO2-e)
Resource
Electricity
Diesel
Concrete
Steel
Stainless Steel
Aluminium
Copper
Significant Plastics
Minor and Unknown GHG emissions
Total
3,289
12,148
20,306
23,058
1,760
431
1,181
1,071
8,017
71,262
53
Using the ongoing GHG emissions derived for desalination plants (see section 3.3), a 100 GL/yr
54
(≈274 ML/day) plant would have operational GHG emissions of about 394,000 tCO2-e/yr.
55
Consequently, as capital GHG emissions are estimated at approximately 71,000 tCO2-e/yr (Table 1),
56
capital GHG emissions would equate to about 0.9% of total GHG emissions over the plant’s lifetime
57
(assuming a lifetime of 20 years [SA Water, 2009]). This percentage is smaller than that reported by
58
GHD Fitchner [2005], as they estimated that 5% of total GHG emissions were attributable to
59
materials and the construction phase for an RO plant. However, the 5% estimate by GHD Fitchner
60
[2005] was for desalination plants in Sydney, so the value for Adelaide of 0.9% was used to estimate
61
the capital GHG emissions for each desalination capacity (Table 2). For ongoing GHG emission
62
calculations of the desalination plant, see section 3.3.
63
Table 2: Capital GHG emissions for the different desalination plant capacities
Plant Capacity (ML/day)
100
150
200
250
300
350
400
450
500
Capital GHG emissions (tonnesCO2e-)
25,887
38,830
51,773
64,717
77,660
90,603
103,547
116,490
129,443
64
3.2 Capital GHG Emissions – Transfer Pipeline
65
Capital GHG emissions associated with materials for the mild steel cement lined (MSCL) pipeline
66
and construction of the pipeline were accounted for; however, GHG emissions associated with the
67
materials for the pumps were considered insignificant and thus were excluded from the inventory
68
based on the fact that for the Murrumbidgee to Googong MSCL pipeline (12km, 1.0m diameter), the
69
materials and transport of the pumps only constituted 35 tCO2-e or 0.1% of total capital GHG
70
emissions [ACTEW Corporation, 2009].
71
For the GHG emissions associated with the cement and steel of the pipeline, nominal diameters were
72
assumed with the cement and steel thicknesses detailed in Table 3 to estimate the volume of cement
73
and steel for each pipeline design (Table 3). Assuming a density of 2,300 kg/m3 for cement and 7,850
74
kg/m3 for steel, and applying the emission factors of 3.5 GJ/t for cement and 32 GJ/t for steel
75
[Investor Group on Climate Change, 2007], the resulting GHG emissions for the cement and steel of
76
the pipeline were derived (Table 3).
77
78
Table 3: Pipe diameter, cement and steel thickness and volumes of materials and resulting GHG emissions for the
12km MSCL transfer pipeline designed for the different desalination plant capacities
Plant
Capacity
(ML/day)
100
150
200
250
300
350
400
450
500
Internal
Pipe
Diameter
(m)
Cement
thickness
(mm)
Mild steel
thickness
(mm)
Cement
Volume
(m3)
0.90
1.13
1.20
1.30
1.45
1.50
1.60
1.75
1.75
19
25
25
25
25
25
25
25
25
8
9.5
10
11
11
13
13
13
13
285
424
475
564
627
766
815
889
889
Mild
GHG
steel
emissions
volume
for steel
(m3) and cement
(tCO2e-)
658
1,084
1,155
1,249
1,390
1,437
1,532
1,673
1,673
15,607
23,378
26,081
30,787
34,187
41,365
44,015
47,991
47,991
Total GHG
emissions
including
diesel and
vegetation
clearance
(tCO2e-)
23,107
30,878
33,581
38,287
41,687
48,865
51,515
55,491
55,491
79
For the construction of the Adelaide desalination plant transfer pipeline, SA Water [2009] estimated
80
that 1650 m3 of diesel would be required, resulting in GHG emissions of 4,698 tCO2e-. In addition to
81
diesel and steel, other major GHG emissions were expected to be from vegetation clearance and
82
concrete, which were expected to contribute 1,932 tCO2e- and 954 tCO2e-, respectively [SA Water,
83
2009]. Consequently, an additional 7,500 tCO2e- were added to the GHG emissions for steel and
84
cement to account for other GHG emissions involved in the construction of the pipeline. Due to
85
insufficient data, these GHG emissions were not scaled for the different sized pipelines.
86
3.3 Ongoing GHG Emissions – Desalination Plant
87
GHG emissions of the operating desalination plant were based on GHG emissions associated with
88
electricity required for treatment; chemicals; membrane and plant replacement. Assuming the plant
89
was running at full capacity, the electricity required for power was assumed to be 5.0 kWh/m3 (see
90
Section 3.3 of auxiliary material on economic costs). GHG emissions for chemicals, membranes and
91
diesel were based on those for the proposed 50 GL/year Adelaide desalination plant, which were
92
estimated to be 26,771 tonnesCO2e-/yr, 1,773 tonnesCO2e-/yr and 41 tonnesCO2e-/yr, respectively [SA
93
Water, 2009]. The GHG emissions of these three components were relatively small compared with
94
those associated with power, which contributed to 92.7% of the ongoing GHG emissions (Table 4).
95
The percentage breakdowns are very similar to other published percentage breakdowns (Table 4) and
96
were consequently applied to all desalination plant capacities to determine total ongoing GHG
97
emissions (Table 5).
98
Table 4: Ongoing GHG emission breakdown for the major desalination operating processes
GHG emissions (% of Total Ongoing GHG emissions)
Power
Chemicals
Membranes
Other
92.7
6.8
0.5
negligible
92.1
7.0
<0.1
95.0
99
100
4.0
1.0
Source
[SA Water, 2009]
[Biswas, 2009]
[Mrayed and Leslie,
2009]
Table 5: GHG emissions attributed to power, chemicals, and membranes for each desalination plant capacity
(assuming the plant operated at full capacity)
Desalination
Plant Capacity
(ML/day)
100
150
200
250
300
350
400
450
500
Power (tCO2e-/yr)
Chemicals (tCO2e/yr)
Membranes
(tCO2e-/5yrs)
Total (tCO2e-/yr)
133,316
199,974
266,633
333,291
399,949
466,607
533,265
599,923
666,581
9,779
14,669
19,559
24,449
29,338
34,228
39,118
44,007
48,897
3,595
5,393
7,191
8,988
10,786
12,584
14,381
16,179
17,977
143,815
215,722
287,629
359,537
431,444
503,352
575,259
647,166
719,074
101
The GHG emissions associated with membrane replacement were applied every five years (Table 4)
102
and were independent of the amount of water the desalination plant produced. Furthermore, the GHG
103
emissions associated with plant replacement were accounted for once in 2030 and were estimated to
104
be the same as the initial capital GHG emissions (see Table 2, section 3.1). However, GHG emissions
105
associated with power and chemicals depended on the amount of water supplied by the desalination
106
plant. Energy consumption was computed based on the 5.0 kWh/m3 rate, resulting in a linear scaling
107
of GHG emissions for power with volume of water supplied. Similarly, the GHG emissions associated
108
with chemicals were scaled linearly, for example, if 25 ML of water were produced per day by the
109
250 ML/day plant, 10% of the chemical GHG emissions would be accounted for, while 50% of the
110
chemical GHG emissions would be accounted for if water was produced at the rate of 125 ML/day.
111
While accredited green power has been assigned to power the Adelaide Desalination Plant, in this
112
case study renewable energy was not assumed to run the desalination plant. This was appropriate
113
because (1) the renewable energy for the desalination plant is being sourced from South Australia’s
114
electricity grid, so technically renewable energy is not directly powering the desalination plant; (2) SA
115
Water have elected to purchase renewable energy to cover the electricity requirements of the
116
desalination plant but have not chosen to do so for other water sources, thus creating bias for one
117
water source over another from a GHG emissions point of view; and (3) by using the same factors, the
118
unit GHG emissions derived for each water source truly reflect the electricity required to power the
119
water sources, rather than reflecting the source of electricity for each water source. Consequently, the
120
same GHG emission rate of 0.73 kgCO2-e/kWh was applied to all water sources for the purposes of
121
this case study, including the desalination plant.
122
3.4 Ongoing GHG Emissions – Transfer Pipeline
123
The operating GHG emissions for the transfer pipeline were attributed to the electricity required to
124
power the transfer of water. The power required to pump the water was estimated using first
125
principles, as illustrated in Section 2 of auxiliary material on economic costs. The power requirements
126
were then multiplied by the electricity GHG emission factor of 0.73 kgCO2-e/kWh and assuming 24-
127
hour continuous pumping. The maximum annual GHG emissions associated with pumping water from
128
Port Stanvac to Happy Valley for each desalination plant capacity are reported in Table 6. GHG
129
emissions associated with pump replacement were excluded, as they were negligible compared with
130
GHG emissions associated with pumping: the materials for pumps were estimated to be in the order of
131
35 tCO2-e (see section 3.2), equating to 0.04-0.21% of the maximum annual GHG emissions required
132
for pumping (Table 6). Maintenance for the pipeline was also assumed to have negligible GHG
133
emissions and was thus not included in estimating GHG emissions.
134
Table 6: Maximum Pump Power and Maximum Annual GHG Emissions for the transfer pipeline
Desalination Plant Capacity
(ML/day)
100
150
200
250
300
350
400
450
500
Maximum Pump
Power (Watts)
2620
3679
5175
6540
7533
9064
10,227
11,011
12,779
Maximum Annual GHG emissions
(tCO2e-)
16,765
23,541
33,116
41,851
48,205
58,000
65,445
70,461
81,774
135
4
Rainwater Tanks
136
4.1 Capital GHG Emissions
137
Capital GHG emissions were attributed to the rainwater tank, pump, pipes, fixtures, and installation of
138
materials to site, while the transport of the rainwater tank system to site was not accounted for, as this
139
was expected to vary considerably for each house. When greater than 50% roof connectivity was
140
selected, capital GHG emissions for indicative lengths of PVC pipe to connect the extra roof area
141
were also accounted for. However, there was no differentiation in capital GHG emissions when water
142
was used for different end uses because there was insufficient data to accurately determine the
143
materials required to plumb in different end uses. This was also difficult to estimate given that house
144
layouts vary considerably.
145
The rainwater tanks were assumed to be made from high density polyethylene (HDPE). To estimate
146
the GHG emissions associated with using HDPE for the tanks, the volume of HDPE for each tank
147
(Table 7) was first estimated for each tank size using middle-of-the-range diameters sourced from a
148
number of rainwater tank suppliers in Adelaide (Table 7), their corresponding heights (Table 7) and
149
assuming that the thickness of the base was 10mm and the thickness of the sides and tops were either
150
5mm (1.0-7.5 m3 tank) or 7.5mm (10.0-27.0 m3). These values were then converted to GHG
151
emissions (Table 7) assuming a density of 950 kg/m3, an embodied energy factor of 75.2 MJ/kg (20.9
152
kWh/kg) [Piratla et al., 2012] and the GHG electricity conversion rate of 0.73 kgCO2e-/kWh. The
153
resulting GHG emissions for the southern system in 2010 (Table 7) were therefore estimated by
154
multiplying these GHG emissions by the number of houses in 2010 (260,261 houses).
155
Table 7: Diameter, height, volume of HDPE and GHG emissions for different sized rainwater tanks
Size
(m3)
Diameter
(m)
Height
(m)
1.0
2.0
3.0
4.0
5.0
7.0
10.0
15.0
22.5
27.0
0.93
1.30
1.50
1.83
1.84
2.00
2.55
2.50
3.70
3.85
1.72
2.00
2.00
1.75
2.15
2.42
2.35
3.10
2.50
3.10
Volume of HDPE
for single tank
(m3)
0.035
0.061
0.074
0.090
0.102
0.123
0.243
0.282
0.426
0.508
GHG emissions for
single tank (kgCO2e-)
512
880
1067
1300
1478
1784
3513
4091
6171
7360
Total GHG emissions for
southern system in 2010
(tCO2e)
133,150
229,045
277,608
338,411
384,665
464,308
914,418
1,064,695
1,606,188
1,915,500
156
Parkes et al. [2010] concluded that there is a lack of good quality data for estimating the embodied
157
energy for components of rainwater tank systems. However, they report that a generic electro-
158
mechanical pump for rainwater harvesting once installed has GHG emissions of 184 kgCO2e-.
159
Furthermore, they estimated that excluding the tank and pump, all other initial rainwater tank
160
components (e.g. pipes and fixtures) once installed contributed another 143 kgCO2-e. The applicability
161
of these data to this case study is questionable, considering the study is from the United Kingdom and
162
applies to a single household with a header tank, rather than a direct feed (as is assumed for this case
163
study). However, in lieu of any other data regarding embodied energy estimates for components of
164
household rainwater tank systems, these data were used with 327 kgCO2e- being added to the capital
165
GHG emissions of the rainwater tanks in Table 7.
166
To estimate the GHG emissions associated with redirecting more roof runoff into the rainwater tank,
167
indicative lengths of PVC pipe were assumed, with a diameter of 90mm and wall thickness of 1.9mm.
168
Similar to estimating the GHG emissions from using HDPE for the rainwater tanks, the volume of
169
PVC was thus estimated, and then converted to GHG emissions assuming a density of 1390 kg/m3, an
170
embodied energy factor of 74.9 MJ/kg (20.8 kWh/kg) [Piratla et al., 2012] and the GHG electricity
171
conversion rate of 0.73 kgCO2e-/kWh (Table 8). While for larger tanks these additional GHG
172
emissions only constituted a small proportion of the capital GHG emissions (e.g. 0.4%-1.5% for the
173
27.0 m3 tank), for the smaller tanks they added considerably to the capital GHG emissions (e.g. 5.1%-
174
17.8% for the 1.0 m3 tank).
175
Table 8: Length, volume of, and GHG emissions associated with the PVC pipe for the different roof connectivities
Roof
Connectivity
0.6
0.7
0.8
0.9
Length
(m)
2.5
5.0
7.5
10.0
Volume
(m3)
0.0013
0.0026
0.0039
0.0053
GHG emissions for
single tank (kgCO2e-)
28
56
83
111
Total GHG emissions for southern
system in 2010 (tCO2e)
7,223
14,447
21,670
28,894
176
4.2 Ongoing GHG Emissions
177
Ongoing GHG emissions for rainwater tanks were attributed to electricity use of the pump and
178
replacement of the tank and pumps. However, no replacement GHG emissions associated with pipes
179
nor fixtures were accounted for, as these were assumed to have a lifetime greater than the planning
180
horizon. Similarly, no GHG emissions associated with maintenance were accounted for due to a lack
181
of data. The electricity use of the pump was determined from the average energy intensity of the
182
pump (Table 9), which, as explained in section 4.2 of the auxiliary material on economic costs, was
183
dependent on the end use (a decision variable in the case study). To transfer these values to GHG
184
emissions, the energy intensities were multiplied by the volume of rainwater supplied and the GHG
185
emission rate of 0.73 kgCO2-e/kWh. For example, if 50 m3 was supplied to the garden and laundry in a
186
year, the annual GHG emissions associated with pumping would be about 45 kgCO2e- per household
187
and about 11,700 tCO2e- for the whole of the southern system in 2010. As the rainwater tanks were
188
assumed to have a lifetime of 25 years, replacement GHG emissions for the tanks were accounted for
189
and were assumed to be the same as the initial capital GHG emissions (see section 4.1). Similarly, 184
190
kgCO2e- was accounted for when the pump was replaced every 10 years (see section 4.1).
191
Table 9: Energy intensities of the pump for different harvested rainwater end uses
Harvested Rainwater End Use
Garden only
Garden & Toilet
Garden, Toilet, & Laundry
Garden & Laundry
Garden, Laundry, & Hot Water
Garden & Hot Water
Garden, Hot Water, & Toilet
Garden, Toilet, Laundry, & Hot Water
Energy Intensity (kWh/m3)
1.20
1.50
1.45
1.23
1.25
1.24
1.44
1.41
192
5
Stormwater Schemes
193
5.1 Capital GHG Emissions
194
The capital material and construction GHG emissions for the stormwater schemes were attributed to
195
the materials and construction of the wetland, Aquifer Storage and Recovery (ASR) wells, and the
196
distribution network. The GHG emissions associated with pumps were not considered, given that
197
GHG emissions for pumps of large pipelines were found to be negligible compared to other capital
198
GHG emissions and the operating GHG emissions of pumps (see section 3.4).
199
For the wetlands and ASR wells, GHG emissions were attributed to the concrete and steel used in
200
their construction and the excavation of soil required to create the wetlands and wells. The amount of
201
concrete and steel used in a wetland’s outlet structure was estimated from data supplied in
202
supplementary material by Moore and Hunt [2013]. Specifically, values for the mass of concrete and
203
mass of steel per square metre (1.90 kg/m2 and 0.02 kg/m2, respectively) were derived by dividing the
204
mass of concrete and steel estimated by Moore and Hunt [2013] for their case study wetland by its
205
area. For this case study, these rates were then applied to the total wetland area for the stormwater
206
schemes and converted to GHG emissions using the emission factors of 1.3 GJ/t and 32 GJ/t for
207
concrete (30 MPa) and steel, respectively (Table 10) [Investor Group on Climate Change, 2007]. In
208
the study by Moore and Hunt [2013], GHG emissions associated with the PET plastic trays used to
209
package wetland seedlings were also accounted for; however, these were found to constitute less than
210
2% of the wetland material GHG emissions, so they were neglected.
211
Table 10: Wetland area, mass of concrete and steel estimated for each wetland, and corresponding GHG emissions
Stormwater
Scheme
Brownhill-Keswick
Sturt Creek
Field River
Pedler Creek
Total Wetland
Area (ha)
49.72
50.4
25.26
40.03
Mass of
Concrete (kg)
944,051
956,962
479,620
760,063
Mass of Steel (kg)
10,070
10,208
5,116
8,107
GHG Emissions
(tCO2e-)
265
268
135
213
212
The volume of concrete used for the ASR wells was calculated by multiplying the number of wells for
213
each stormwater harvesting scheme (Table 11) [Wallbridge and Gilbert, 2009] by the volume of
214
concrete used in each well, which was estimated by assuming a well height of 150 m, an outside
215
diameter of 500 mm, and a wall thickness of 50 mm. Using the emission factor for concrete (30MPa)
216
of 3.2 GJ/m3 [Investor Group on Climate Change, 2007], the GHG emissions for the concrete used for
217
the wells was subsequently estimated (Table 11).
218
Table 11: Materials and construction GHG emissions for the ASR wells
Stormwater Scheme
Brownhill-Keswick
Sturt Creek
Field River
Pedler Creek
Number of
wells
73
80
5
30
Volume of Concrete
(m3)
409
448
28
168
Material GHG Emissions
(tCO2e-)
213
233
15
87
219
For excavation energy (Table 12), the volumes of the wetlands and ASR wells were multiplied by the
220
assumed density of soil of 1250 kg/m3, and the energy required for excavation of 0.1 MJ/kg [Alcorn,
221
2003]. This energy was then multiplied by the emissions associated with the diesel used in excavation,
222
which was estimated at 69.2 kgCO2-e/GJ [Department of Industry Innovation Climate Change Science
223
Research and Tertiary Education, 2013], to obtain the final estimates of GHG emissions for wetland
224
construction (Table 12). The relatively greater number of GHG emissions associated with
225
construction (Table 5.3) compared with those associated with materials (Tables 5.1 and 5.2) for the
226
wetlands was expected, considering Moore and Hunt [2013] found that construction of stormwater
227
wetlands accounted for the majority of capital GHG emissions.
228
Table 12: Wetland and ASR construction GHG emissions for each stormwater scheme
Stormwater Scheme
Brownhill-Keswick
Sturt Creek
Field River
Pedler Creek
Total Wetland &
ASR Well
Volume (m3)
729,430
739,686
365,927
573,464
Total Energy for
Excavation (GJ)
Construction GHG Emissions
for Wetland (tCO2e-)
91,179
92,461
45,741
71,683
6,310
6,398
3,165
4,960
229
For the distribution network, pipes were assumed to be made from high density polyethylene (HDPE),
230
have a pressure rating of 600 kPa, an outside diameter of 280mm, and a wall thickness of 10.8 mm.
231
The length of pipeline required for the distribution of harvested stormwater to non-potable industrial
232
and commercial users (Table 13) was estimated from a number of similar stormwater schemes in
233
Adelaide. Specifically, the following equation was derived to estimate pipe length based on the
234
potential yield of the schemes:
235
L  18.108 * Y 0.5681
(1)
236
where L is the length of pipeline (in km) and Y is the potential yield of the stormwater scheme (in
237
GL/yr). Consequently, the volume of HDPE for each of the stormwater scheme distribution networks
238
was estimated and converted to GHG emissions (Table 13) by multiplying the volume of HDPE by its
239
density (950 kg/m3), an embodied energy factor of 75.2 MJ/kg (20.9kWh/kg) [Piratla et al., 2012]
240
and the GHG electricity conversion rate of 0.73 kgCO2e-/kWh. Piratla et al. [2012] estimated that
241
GHG emissions of 2,830.4 kgCO2e- were incurred for installation of a 152.4 m-long, 200 mm-
242
diameter section of pipe buried 1.22 m below the surface. This value converts to an average 18.6
243
kgCO2e-/m of pipe installed. Considering the pipelines for the stormwater distribution in this case
244
study were almost a third larger in diameter than that reported by Piratla et al. [2012], an indicative
245
value for installation of 26 kgCO2e-/m was applied to this case study to estimate GHG emissions for
246
the distribution network installation (Table 13).
247
248
Table 13: Estimated length of pipelines for the stormwater schemes’ distribution network, the corresponding volume
of HDPE required and the resulting GHG emissions associated with the HDPE and installation of the pipeline
Stormwater
Scheme
BrownhillKeswick
Sturt Creek
Field River
Pedler Creek
Length of
Pipeline (km)
Volume of
HDPE (m3)
GHG Emissions for
HDPE (tCO2e-)
GHG Emissions for Pipe
Installation (tCO2e-)
58.5
51.0
31.3
45.5
529.8
461.7
283.1
412.3
7,675
6,688
4,101
5,973
1,522
1,326
813
1,184
249
Total capital GHG emissions for the stormwater harvesting schemes are summarised in Table 14.
250
Table 14: Summary of capital GHG emissions for the stormwater harvesting schemes
Stormwater
Scheme
BrownhillKeswick
Sturt Creek
Field River
Pedler Creek
Wetland and
Well
Materials
478
501
150
300
Capital GHG Emissions (tCO2e-)
Wetland
and Well Distribution Network
Excavation
6,310
6,398
3,165
4,960
9,197
8,014
4,914
7,158
Total
15,985
14,913
8,229
12,418
251
5.2 Ongoing GHG Emissions
252
Ongoing GHG emissions for the stormwater harvesting schemes were based on operating GHG
253
emissions, namely those associated with pumping the stormwater. The wetlands, wells and
254
distribution network were assumed to have lifetimes greater than the planning horizon of 40 years
255
considered, so no GHG emissions associated with replacement were attributed to stormwater
256
harvesting. GHG emissions for pump replacement were also ignored, as these were assumed to be
257
negligible compared with those associated with the electricity required to pump the harvested
258
stormwater.
259
Dandy et al. [2013] estimated that the GHG emissions associated with pumping for a stormwater
260
harvesting scheme (the scheme included a wetland, ASR and distribution to open spaces for
261
irrigation) were approximately 554 MWh for 0.88 GL of stormwater. This translates to a rate of 0.63
262
kWh/m3 or 0.50 kgCO2e-/m3 using the electricity emissions factor of 0.73 kgCO2e-/kWh, which was
263
applied to the yield of the stormwater harvesting schemes to estimate ongoing GHG emissions. For
264
example, if the Brownhill-Keswick scheme produced its maximum yield of 7.9 GL/yr, annual
265
operating GHG emissions for the Brownhill-Keswick scheme would be 3,950 tCO2e-.
266
6
267
268
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