Total embodied carbon, A1-A5, B, C
184,620 tCO2e
At baseline± 15,167 tCO2e (8.2%) at one standard deviation
Product stage, A1-A3
128,340 tCO2e
69.5% of total
Construction stage, A4-A5
14,540 tCO2e
7.9% of total
Use stage, B
28,410 tCO2e
15.4% of total
End of life, C
13,330 tCO2e
7.2% of total
Module D, benefits beyond the boundary
-9,240 tCO2e
Reported separately, never netted against the total
Biogenic carbon: 1,840 tCO2e reported separately, not netted against fossil GWPScenario: Baseline
Life cycle stage waterfall
Carbon by package
A1-A3A4-A5BC
TU-03 Tunnel Lining
78,410
42.5%
ST-01 Station Box
44,120
23.9%
EW-01 Earthworks
27,870
15.1%
TR-01 Track and Systems
21,880
11.9%
UT-01 Utilities
12,340
6.7%
Material hotspots
Ranked by contribution to total GWP
| Material | Package | Quantity | GWP factor | Total tCO2e | % of total | Data quality |
|---|---|---|---|---|---|---|
| Precast segmental lining, C50/60 | TU-03 | 42,180 m3 | 1.488 tCO2e/m3 | 62,780 | Manufacturer EPD | |
| Reinforcement bar, grade 500, all packages | All | 39,400,000 kg | 0.762 kgCO2e/kg | 30,020 | Manufacturer EPD | |
| Structural steel sections, S355 | ST-01 | 4,120,000 kg | 2.310 kgCO2e/kg | 9,520 | Industry average | |
| In-situ concrete, C40/50 base slab | ST-01 | 18,470 m3 | 0.394 tCO2e/m3 | 7,280 | Manufacturer EPD | |
| Diesel plant, bulk excavation | EW-01 | 486,000 m3 | 0.0134 tCO2e/m3 | 6,510 | Generic | |
| Shotcrete primary lining | TU-03 | 11,620 m3 | 0.446 tCO2e/m3 | 5,180 | Industry average | |
| Grid electricity, tunnel ventilation | TU-03 | 14,900,000 kWh | 0.312 kgCO2e/kWh | 4,650 | Manufacturer EPD | |
| Ductile iron pipe, DN600 | UT-01 | 4,210 m | 0.610 tCO2e/m | 2,570 | Generic | |
| Rail, 60E1 profile | TR-01 | 1,240,000 kg | 0.850 kgCO2e/kg | 1,054 | Manufacturer EPD | |
| Bituminous surfacing, station approach | ST-01 | 8,940 t | 0.097 tCO2e/t | 870 | Industry average | |
| All other materials (312 items) | All | - | mixed | 54,186 | Mixed |
Carbon by discipline
Structural
118,420
64.1% of total
Track
21,880
11.9% of total
Earthworks
17,300
9.4% of total
Geotechnical
14,680
8.0% of total
Utilities
12,340
6.7% of total
Assumptions applied
Transport, A4
82 km road average, 32 t articulated, 62% load factor
Construction wastage, A5
4.5% applied to all concrete and steel lines
Reference study period
60 years, shared with the LCCA so carbon and cost are comparable
Grid emission factor
0.312 kgCO2e per kWh in 2026, declining to 0.088 by 2075
Biogenic carbon
Reported separately, not netted
Characterisation
TRACI 2.1, GWP 100 year AR6
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3,412 lines, 7 conversion rules, 94 open review flags
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Six TRACI 2.1 categories beyond carbon