🎓 Lesson 11
D5
Carbon Cost Attribution Framework
Carbon cost attribution framework is a method to assign greenhouse gas emissions to specific mining activities—like drilling, blasting, or hauling—so engineers can measure and reduce the climate impact of each operation.
🎯 Learning Objectives
- ✓ Calculate carbon intensity (kg CO₂e/tonne ore) for a surface blast using fuel, explosive, and equipment data
- ✓ Design a low-carbon blast plan by optimizing explosive selection and energy efficiency against carbon budget constraints
- ✓ Analyze trade-offs between traditional powder factor and carbon-adjusted powder factor (kg CO₂e/kg explosive)
- ✓ Explain how emission factors for ANFO vs. emulsion explosives differ—and why that matters for net-zero planning
📖 Why This Matters
Mining contributes ~4–7% of global CO₂ emissions—and blasting alone accounts for up to 15% of a mine’s operational carbon footprint due to diesel-powered equipment and high-carbon explosives like ANFO. As regulators tighten reporting rules (e.g., IFRS S2, GHG Protocol) and investors demand Scope 3 transparency, engineers must move beyond ‘cost per tonne’ to ‘carbon per tonne’. This framework turns sustainability from an ESG add-on into a core design parameter—just like fragmentation or dilution.
📘 Core Principles
CCAF rests on three pillars: (1) Activity-Based Attribution—emissions are assigned to physical work units (e.g., kWh consumed per m³ of rock broken, kg explosive detonated per bench); (2) Tiered Emission Factors—using ISO 14064-1 compliant default values (e.g., IPCC AR6 for diesel, manufacturer-specific for emulsions) refined with site-specific metering where available; (3) System Boundary Alignment—matching LCA boundaries (cradle-to-gate for explosives, well-to-tank for fuel) with mine planning phases (design → execution → reconciliation). Crucially, CCAF treats carbon not as overhead—but as a *consumable resource* with diminishing returns: doubling explosive mass rarely doubles fragmentation, but *always* increases emissions linearly.
📐 Carbon-Adjusted Powder Factor
This modified powder factor links blasting efficiency directly to carbon impact—replacing mass-based optimization with emissions-aware design. It enables engineers to compare alternatives (e.g., low-energy emulsion vs. high-energy ANFO) on equal carbon footing.
Carbon-Adjusted Powder Factor (CAPF)
CAPF = Σ(m_i × EF_i) / TQuantifies total Scope 1+2 CO₂e emissions from explosives per unit of ore produced.
Variables:
| Symbol | Name | Unit | Description |
|---|---|---|---|
| m_i | Mass of explosive component i | kg | e.g., ANFO, emulsion, primer, boosters |
| EF_i | CO₂e emission factor for component i | kg CO₂e/kg | Source: IPCC AR6 (diesel), manufacturer EPDs (emulsions), or site-specific LCA |
| T | Tonnage of ore fragmented | tonne | Measured post-blast via survey + density calibration |
Typical Ranges:
Tier-1 low-carbon mine: 0.9 – 1.2 kg CO₂e/t
Conventional open-pit operation: 1.3 – 1.8 kg CO₂e/t
💡 Worked Example
Problem: A surface copper mine uses 850 kg of ANFO (emission factor = 3.2 kg CO₂e/kg) and 150 kg of primer (emission factor = 4.8 kg CO₂e/kg) to break 2,400 tonnes of ore. Calculate CAPF and compare to conventional PF.
1.
Step 1: Compute total explosive-related emissions = (850 × 3.2) + (150 × 4.8) = 2,720 + 720 = 3,440 kg CO₂e
2.
Step 2: Compute conventional powder factor = (850 + 150) kg / 2,400 t = 1,000 / 2,400 = 0.417 kg/t
3.
Step 3: Compute CAPF = 3,440 kg CO₂e / 2,400 t = 1.433 kg CO₂e/t
4.
Step 4: Interpret: CAPF of 1.43 kg CO₂e/t exceeds typical benchmark of ≤1.2 kg CO₂e/t for Tier-1 operations—indicating opportunity to switch to lower-carbon emulsion (EF = 2.1 kg CO₂e/kg) or reduce total charge.
Answer:
The CAPF is 1.43 kg CO₂e/tonne ore, which exceeds the industry target of ≤1.2 kg CO₂e/t for low-carbon mines—suggesting a 17% reduction in explosive-related emissions is needed to meet benchmark.
🏗️ Real-World Application
At Newmont’s Boddington Mine (Australia), engineers applied CCAF during blast design optimization in 2022. By substituting 30% of ANFO with low-carbon emulsion (EF reduced from 3.2 to 2.1 kg CO₂e/kg) and adjusting burden/spacing to maintain fragmentation (measured via image analysis), they achieved a 22% drop in blast-related carbon intensity—from 1.58 to 1.23 kg CO₂e/tonne—with no change in dig rate or crusher throughput. This enabled alignment with Newmont’s 2030 Science-Based Target and informed procurement policy for explosives across its portfolio.