🎓 Lesson 17
D5
Carbon Accounting Across Transport Legs (Scope 1 & 2)
Carbon accounting across transport legs means measuring how much carbon dioxide is released by vehicles and equipment moving materials between mine sites, processing plants, and ports — separating emissions that come directly from fuel use (Scope 1) and those from purchased electricity (Scope 2).
🎯 Learning Objectives
- ✓ Calculate Scope 1 CO₂e emissions for diesel-powered haul trucks using fuel consumption and emission factors
- ✓ Differentiate and allocate Scope 1 vs. Scope 2 emissions across distinct transport legs (e.g., overland haulage vs. port conveyor power)
- ✓ Apply jurisdiction-specific grid emission factors to quantify Scope 2 emissions for rail or port electrification
- ✓ Explain how transport leg boundaries affect regulatory reporting under national frameworks (e.g., Australia’s NGER, EU CSRD)
- ✓ Design a transport-leg-level carbon inventory template compliant with GHG Protocol Corporate Standard
📖 Why This Matters
In modern mining, 30–50% of a mine site’s total operational emissions stem from logistics — not just blasting or processing. Regulatory bodies (e.g., SEC, ASIC, EU Commission) now mandate granular, leg-level carbon disclosure. A single misclassified transport leg — like attributing port conveyor emissions to Scope 1 instead of Scope 2 — can trigger non-compliance penalties, undermine ESG ratings, and distort decarbonization investment decisions. This lesson equips you to map, measure, and manage emissions where they *actually occur* — not where accounting convenience suggests.
📘 Core Principles
Carbon accounting across transport legs rests on three pillars: (1) Physical boundary definition — each leg (e.g., pit-to-crusher haul, crusher-to-rail transfer, rail-to-port, port stacking) must be mapped with clear start/end points and ownership; (2) Emission source classification — Scope 1 covers mobile combustion (diesel, LNG) and stationary fuel use within operational control; Scope 2 covers purchased electricity driving conveyors, rail traction, or port cranes; (3) Jurisdictional fidelity — grid emission factors vary widely (e.g., 0.78 kg CO₂e/kWh in India vs. 0.042 kg CO₂e/kWh in Norway), making location-specific data non-negotiable. Misalignment here is the #1 cause of audit failure in NGER and CDP submissions.
📐 Scope 1 Transport Emissions Calculation
This formula calculates CO₂e emissions from fuel combustion in owned/operated transport assets (e.g., haul trucks, loaders). It uses fuel mass or volume, carbon content, oxidation rate, and global warming potential (GWP) of CO₂ — standardized by IPCC 2006 Guidelines and adopted by all major reporting frameworks.
Scope 1 Transport Emissions (CO₂e)
E = F × EFCalculates total CO₂-equivalent emissions from fuel combustion in transport assets under operational control.
Variables:
| Symbol | Name | Unit | Description |
|---|---|---|---|
| E | Total CO₂e emissions | kg CO₂e | Greenhouse gas emissions expressed in carbon dioxide equivalents |
| F | Fuel consumed | L or kg | Volume or mass of fuel combusted in transport leg |
| EF | Fuel-specific emission factor | kg CO₂e / L (or kg CO₂e / kg) | IPCC- or jurisdiction-approved emission factor for the fuel type |
Typical Ranges:
Diesel haul trucks (ULSD): 2.65 – 2.72 kg CO₂e/L
LNG-powered locomotives: 2.75 – 3.05 kg CO₂e/kg
💡 Worked Example
Problem: A fleet of 24 CAT 797 haul trucks consumes 1.2 million L of ultra-low-sulfur diesel (ULSD) annually moving ore from pit to primary crusher. Calculate annual Scope 1 CO₂e emissions.
1.
Step 1: Identify emission factor for ULSD — IPCC Tier 2 default = 2.68 kg CO₂e/L (includes CO₂, CH₄, and N₂O weighted by GWP-100)
2.
Step 2: Multiply fuel volume by emission factor: 1,200,000 L × 2.68 kg CO₂e/L = 3,216,000 kg CO₂e
3.
Step 3: Convert to tonnes: 3,216,000 kg ÷ 1000 = 3,216 t CO₂e — falls within typical range for mid-sized open-pit operations (2,500–5,000 t CO₂e/year for pit-to-crusher leg)
Answer:
The result is 3,216 t CO₂e, which falls within the typical safe range of 2,500–5,000 t CO₂e/year for this transport leg.
🏗️ Real-World Application
At Rio Tinto’s Pilbara iron ore operations, carbon accounting was segmented into four transport legs: (1) In-pit haulage (Scope 1 diesel), (2) Primary crushing & stockpile conveyors (Scope 2 — WA grid avg. 0.71 kg CO₂e/kWh), (3) Hamersley Rail (Scope 2 — dedicated renewable PPAs reduced factor to 0.12 kg CO₂e/kWh), and (4) Port of Dampier ship loading (mixed Scope 1 marine fuel + Scope 2 grid power). This leg-level breakdown enabled targeted interventions — e.g., shifting 40% of rail traction to wind-powered grid supply cut Scope 2 emissions by 28,000 t CO₂e/year — and satisfied ASIC’s 2023 climate reporting expectations.