🎓 Lesson 15
D5
Emissions Accounting: Scope 1 & 3 Allocation for Haul Operations
Scope 1 emissions are the direct pollution from diesel trucks you operate, while Scope 3 emissions include the indirect pollution from making the diesel fuel and maintaining those trucks — both matter when measuring your haul fleet’s true climate impact.
🎯 Learning Objectives
- ✓ Calculate Scope 1 CO₂e emissions from haul truck fuel consumption using standardized emission factors
- ✓ Allocate Scope 3 upstream emissions for diesel fuel using well-to-tank (WTT) factors and fuel lifecycle data
- ✓ Explain the boundary decisions that determine whether maintenance, tire wear, or component manufacturing fall under Scope 3 Category 1 (purchased goods) or Category 11 (use of sold products)
- ✓ Apply GHG Protocol standards to design a transparent, auditable emissions inventory for a mine haul fleet
📖 Why This Matters
Mining companies face increasing regulatory, investor, and community pressure to disclose full carbon footprints — not just tailpipe emissions. A haul fleet may emit 60–80% of a surface mine’s total Scope 1 & 2 emissions, but ignoring Scope 3 (e.g., diesel refining, truck manufacturing) can underestimate total climate impact by 40–70%. Without proper allocation, sustainability reports misrepresent responsibility, risk assessments underestimate decarbonization costs, and electrification ROI calculations become flawed.
📘 Core Principles
Emissions accounting follows the GHG Protocol’s three-scope framework: Scope 1 (direct), Scope 2 (indirect from purchased energy), and Scope 3 (all other indirect). For haul operations, Scope 1 is straightforward — combustion emissions from onboard engines. Scope 3 requires tracing upstream (fuel extraction → refining → distribution) and downstream (maintenance logistics, spare parts, tire production, eventual scrapping). Allocation hinges on two pillars: (1) activity data fidelity (e.g., actual diesel liters dispensed per truck, not estimates), and (2) boundary selection guided by materiality and control — e.g., fuel procurement contracts determine whether WTT emissions are reportable. Tiered methodologies exist: Tier 1 (default factors), Tier 2 (supplier-specific data), and Tier 3 (primary LCA modeling), with mining best practice favoring Tier 2 where feasible.
📐 Scope 1 + Upstream Scope 3 Emissions Calculation
This formula calculates total cradle-to-gate emissions per liter of diesel consumed — combining tailpipe (Scope 1) and upstream fuel production (Scope 3 Category 3). It enables fleet-level carbon intensity reporting (kg CO₂e/L or kg CO₂e/t-km).
Total Diesel-Related Emissions
E_total = F × (EF_Scope1 + EF_WTT)Calculates combined Scope 1 and upstream Scope 3 (Category 3) CO₂-equivalent emissions from diesel fuel use.
Variables:
| Symbol | Name | Unit | Description |
|---|---|---|---|
| E_total | Total emissions | kg CO₂e | Combined Scope 1 and upstream Scope 3 emissions attributable to diesel consumption |
| F | Fuel consumption | L | Total volume of diesel combusted by haul fleet (metered, not estimated) |
| EF_Scope1 | Scope 1 emission factor | kg CO₂e/L | CO₂e emitted per liter of diesel combusted (e.g., IPCC 2006 default = 3.15 kg CO₂e/L) |
| EF_WTT | Well-to-tank emission factor | kg CO₂e/L | Upstream emissions from diesel extraction, refining, and transport (e.g., IEA 2023 global avg = 1.82 kg CO₂e/L) |
Typical Ranges:
Global average diesel WTT: 1.6 – 2.1 kg CO₂e/L
Scope 1 diesel combustion: 3.14 – 3.16 kg CO₂e/L
💡 Worked Example
Problem: A mine’s CAT 797F fleet consumes 12.4 million liters of diesel annually. Using IPCC 2006 default factors and IEA 2023 WTT data, calculate total Scope 1 + upstream Scope 3 CO₂e emissions.
1.
Step 1: Identify knowns — diesel consumption = 12,400,000 L; Scope 1 EF = 3.15 kg CO₂e/L (IPCC 2006, Table 2.3, diesel combustion); upstream WTT EF = 1.82 kg CO₂e/L (IEA Net Zero Roadmap 2023, 'Diesel Well-to-Tank').
2.
Step 2: Apply formula: Total = Consumption × (Scope 1 EF + WTT EF) = 12,400,000 × (3.15 + 1.82).
3.
Step 3: Compute: 12,400,000 × 4.97 = 61,628,000 kg CO₂e = 61,628 t CO₂e.
Answer:
The result is 61,628 t CO₂e, which aligns with typical large open-pit mines reporting 50–80 kt CO₂e/year from haul diesel alone — confirming methodological consistency.
🏗️ Real-World Application
At BHP’s Escondida copper mine (Chile), haul emissions accounting was revised in 2022 to include Scope 3 Category 3 (fuel-related) and Category 1 (spare parts, lubricants) after third-party audit revealed that excluding upstream diesel added ~37% underreporting. Using supplier-provided LCA data for diesel sourced from Petrox (Chilean refiner), they shifted from Tier 1 (IPCC defaults) to Tier 2 factors — reducing uncertainty from ±22% to ±7%. This enabled accurate comparison of battery-electric vs. diesel-haul scenarios, directly influencing their 2025 fleet electrification roadmap.