Emission Factors for Australian Mining: Scope 1, 2 & 3 Factors You Actually Need

Australian mining sits at an unusual intersection of GHG reporting requirements: mandatory NGER facility reporting for large operators, voluntary CDP and TCFD disclosures for listed companies, and increasingly, Scope 3 disclosure requirements driven by lender and investor expectations. The emission factors needed across these three contexts differ, and the complexity compounds quickly.

This guide is written from direct experience calculating GHG inventories for large Australian open-cut and underground mining operations, where the difference between the right and wrong emission factor can represent hundreds of thousands of tonnes of CO2-e on a single site's inventory.

For the foundational concepts behind emission factors and how they work, see our emission factors explained guide. For the decision framework on which factor to use in a given context, see our emission factor selection guide.

Why mining GHG reporting is different

Mining operations have an emission profile that doesn't resemble most other industries. Several distinctive features drive how you need to approach emission factor selection:

• Diesel dominance. For most hard rock and open-cut operations, diesel combustion is the single largest emission source — often 60-80% of total Scope 1 emissions. The haul truck fleet, excavators, drills, and support equipment on a large mine site collectively consume diesel at a scale comparable to a small city's transport fleet.
• Explosives as a reportable source. Every blasting operation produces greenhouse gas emissions. ANFO and emulsion explosives generate CO2 and N2O during detonation. This is a NGER-reportable Scope 1 source that is frequently omitted or underreported in practice.
• Remote electricity supply. Many Australian mining operations are located far from NEM grid connections. Off-grid diesel generation, private SWIS connections, or remote grid tie-ins create electricity emission reporting situations not covered by simple state-level factors.
• Fugitive emissions from coal and gas. For coal and conventional gas operations, methane releases during extraction dwarf other emission sources. Methane's high global warming potential makes small volume escapes enormously significant in CO2-e terms.
• Scale of Scope 3. For coal, LNG, and iron ore producers, the downstream use of sold products generates Scope 3 emissions many times larger than all Scope 1 and 2 combined. A thermal coal producer's Category 11 emissions typically exceed its entire operational footprint by an order of magnitude.

Scope 1: Diesel, explosives, and fugitive emissions

Diesel combustion

Diesel is the workhorse fuel of Australian mining. Both stationary (generators, pumps) and mobile (haul trucks, excavators, drills) diesel consumption are reported as Scope 1 under NGER. The NGA Factors include separate factors for stationary combustion and mobile combustion — though for most mining applications, the values are closely aligned.

At the scale of a large open-cut operation consuming 50-100 million litres of diesel annually, a 1% error in the diesel emission factor represents 1,278-2,556 tCO2-e. That's not a rounding error — it's a material variance in an annual NGER report.

Practical note on fuel measurement: NGER permits both direct metering and fuel purchase records as the basis for activity data. Fuel purchase records are simpler but introduce timing differences between purchase and consumption. For facilities with significant diesel storage, metered consumption is more accurate for the reporting period.

Explosives

This is the most commonly missed Scope 1 source in mining NGER reports. Every tonne of explosive detonated on site produces reportable greenhouse gas emissions — primarily from the decomposition of ammonium nitrate (the nitrogen source in ANFO and emulsion explosives), which generates N2O during detonation.

N2O has a global warming potential of 265 (AR5) — meaning even small quantities of N2O generate significant CO2-e. A large mine site detonating 10,000 tonnes of ANFO annually has a non-trivial explosives emission footprint that must be included in the NGER report.

In an assurance review of a major coal mine's NGER report, I found that explosives emissions had been omitted entirely for three consecutive years. The facility had reported only diesel and electricity. When explosives were included, total Scope 1 emissions increased by approximately 4%. That's above any reasonable materiality threshold and represents a compliance gap.

Fugitive emissions from coal and gas mining

For coal mines, fugitive methane emissions from coal seams are the largest Scope 1 source at many operations — larger than diesel, larger than explosives. The NGA Factors include coal mine methane emission factors differentiated by:

• Mining method: Surface (open-cut) vs underground mining generate very different methane release profiles. Underground mining involves active ventilation of methane-laden air; open-cut mining exposes coal seams to the atmosphere progressively.
• Coal rank and basin: Methane content varies significantly by coal seam. High-volatile bituminous coals in the Bowen Basin (Queensland) have very different methane characteristics than lower-rank coals in the Hunter Valley.
• Post-mining emissions: Coal continues to degas after mining. The NGA Factors include factors for crushed and milled coal in stockpiles, and for coal being transported — methane continues to be released during these stages.

For gas mining (conventional and unconventional), fugitive emissions from well completions, equipment venting, and pipeline leaks are the primary concern. These are also covered in the NGA workbook with activity-specific factors.

Scope 2: State-by-state electricity factors

Scope 2 reporting for mining operations is complicated by two factors: geographic diversity (large operators span multiple states) and remote supply situations (many sites are off-grid or on private networks).

NEM-connected operations

For mine sites connected to the National Electricity Market (NEM), the NGA Factors provide state-level Scope 2 emission factors. These are updated annually to reflect the changing generation mix in each state. The 2025 NGA factors (approximate values, always verify in the current workbook):

The difference between a Queensland and a Tasmanian electricity factor is approximately 4.7-fold. Using the wrong state factor — or blending across states without disaggregating electricity consumption — introduces very large errors. For operations spanning multiple states, you must apply the correct state factor to each state's consumption separately.

Off-grid operations

Mine sites operating on diesel generators do not use NGA electricity emission factors. The diesel consumed by those generators is reported as a Scope 1 stationary combustion source using the NGA diesel stationary combustion factor. The "electricity" produced by the generator is an intermediate step, not a reportable emission source.

This is a crucial distinction: if you apply an electricity emission factor to the kWh output of a diesel generator, you'll undercount emissions — because the electricity factor is calculated for a generation mix that includes significant renewable content. Your generator is running on 100% diesel.

Private network arrangements and remote grid connections

Some large mining operations have private transmission infrastructure connecting to the grid at a single point, or arrangements with private generators. For NGER, the relevant factor is determined by the actual source of the electricity:

• If sourced from the state NEM grid via a private network: use the state NEM factor
• If sourced from a dedicated diesel generator: report as Scope 1 stationary combustion
• If sourced from a gas-fired power station (captive or contracted): the gas consumption at the station is a Scope 1 source; the electricity itself may still require a Scope 2 factor for transmission losses depending on the arrangement

Scope 3: The categories that actually matter

The GHG Protocol defines 15 Scope 3 categories. For Australian mining, the majority of the inventory value sits in a handful of these. Understanding which categories are material — and which emission factors apply — is critical for credible voluntary disclosures.

Category 1 — Purchased goods and services

For mining, the most material purchased goods are typically: steel (structural steelwork, pipework, rails), wear parts and grinding media, explosives (the upstream manufacturing emissions of the explosives you combust as Scope 1), tyres (a significant cost centre and significant emission source), and reagents and chemicals.

The NGA Factors do not include spend-based or mass-based factors for these categories — you'll need to use DEFRA's Category 1 spend-based factors, or Ecoinvent lifecycle data for a more detailed treatment. DEFRA publishes material-specific factors for steel, aluminium, plastics, and many other common inputs that are applicable to Australian procurement despite the UK origin of the database.

The upstream explosives note: When you purchase ANFO, you create Scope 3 Category 1 emissions from the manufacturing of that ammonium nitrate and fuel oil. Then when you detonate it, you create Scope 1 emissions from the combustion. Both need to be accounted for — a point frequently missed in mining Scope 3 inventories.

Category 3 — Fuel- and energy-related activities

This category captures the upstream emissions associated with extracting, processing, and transporting the fuels and electricity you use — emissions that aren't counted in Scope 1 or 2 themselves. For a diesel-intensive mining operation, the upstream extraction, refining, and transport of the diesel supply chain adds approximately 15-20% to the Scope 1 diesel combustion figure.

The NGA Factors include upstream (Scope 3) emission factors for the major fuels used in Australian operations. This is one of the most under-utilised parts of the NGA workbook in mining GHG reports — required for NGER in some contexts, and increasingly expected in voluntary disclosures.

Category 4 — Upstream transportation and distribution

Inbound freight of consumables, equipment, and parts to remote mine sites is often substantial. For a Pilbara iron ore operation, for example, the freight required to supply the mine with explosives, tyres, reagents, and maintenance equipment involves significant road, rail, and sometimes air freight. DEFRA's freight emission factors (per tonne-km) are the most practical source for this category where no Australian-specific factor applies.

Category 11 — Use of sold products

This is the defining Scope 3 category for coal, gas, and LNG producers — and the one that attracts the most attention from investors and NGOs. Category 11 captures the greenhouse gas emissions from the downstream combustion of the products you sell.

For thermal coal, this means the CO2 emitted when your coal is burned in power stations, typically in Asia. The NGA Factors include Scope 3 emission factors for sold coal products, which can be combined with production volume data to estimate Category 11 emissions.

For metallurgical coal, the situation is more complex: coking coal produces CO2 in steelmaking blast furnaces, but the emissions occur in a process context where the coal serves as both a fuel and a reductant. The NGA Factors provide guidance on how to treat this.

A large Australian coal producer's Category 11 Scope 3 emissions from downstream combustion of sold coal can exceed 50 million tCO2-e per year — against total Scope 1 and 2 emissions of perhaps 3-5 million tCO2-e. The sold product emissions dwarf operational emissions by an order of magnitude, which is why Category 11 is the primary focus of investor and regulatory attention for coal producers.

Category 12 — End-of-life treatment

Less material for mining than for consumer goods industries, but worth considering for tyre disposal (a persistent environmental and emissions issue for large open-cut mines), processing chemicals, and certain by-products.

Fugitive emissions in context: Australia's 2025 inventory data

Australia's National Greenhouse Gas Inventory shows that fugitive emissions from the mining sector — predominantly methane from coal mines — fell by 2.2% in the most recent reporting year. This decline was driven by two factors:

• New carbon capture and storage (CCS) activities at key mining facilities, capturing and destroying methane that would otherwise have been vented or released
• Reduced production from both surface and underground coal mines, reflecting a combination of mine closures, scheduled maintenance downtime, and market conditions

The 2.2% decline is notable but modest in the context of the sector's overall methane footprint. Australian coal mine methane is measured using the ventilation air methane (VAM) methodology for underground mines and surface emission factors for open-cut operations — both covered in the NGA Factors workbook.

For context on what changed in the 2025 NGA Factors specifically, including updated electricity factors and the new hydrogen combustion factors, see our 2025 emission factor updates article.

Practical NGER compliance tips

1. Use the correct NGA workbook for your reporting year

The NGA Factors workbook is updated annually, typically published in August. The 2025 workbook applies to the 2025-26 NGER reporting year (July 2025 to June 2026). Using last year's workbook for the current reporting year is a compliance error — and with factors potentially changing by more than 5%, it's not trivial.

2. Report electricity at state level, not national average

NGER requires state-level electricity factors. If your operation crosses state boundaries, maintain separate electricity consumption records for each state and apply the correct state factor. There is no NGA national electricity average — if you see one being applied, it's wrong.

3. Document your explosives mass and type

NGER records for explosives must include the mass of each explosive type used. "ANFO" and "emulsion explosive" have different NGA factors. If your blasting contractor uses a blend, you need the composition breakdown to apply the correct weighted factor. Your drilling and blasting contractor's records are the primary source — request per-period quantity reports by explosive type.

4. Include Category 3 upstream fuel emissions in voluntary disclosures

Upstream fuel emissions (Category 3) are not always required for NGER but are increasingly expected in CDP questionnaire responses and TCFD-aligned sustainability reports. The NGA workbook includes these factors — use them. It's a relatively simple add-on to a Scope 1 calculation and avoids a common gap being flagged in assurance reviews of voluntary disclosures.

5. Reconcile fuel purchase records to consumption

A common audit finding is a mismatch between fuel purchase volumes and fuel consumption volumes in the NGER report. Purchases and consumption can differ due to inventory changes in site fuel tanks. For NGER, you report consumption, not purchases. Reconcile your opening and closing inventory balances against purchases to derive consumption for the period.

Frequently asked questions

What emission factor do I use for diesel haul trucks?

Use the NGA Factors Scope 1 emission factor for diesel combustion in mobile equipment (non-road mobile machinery). The NGA 2025 factor is approximately 2.556 kg CO2-e per litre. This applies to all diesel-powered mobile equipment on site: haul trucks, excavators, drills, loaders, dozers, and ancillary vehicles. Always verify in the current-year NGA workbook, as factors are updated annually.

Do explosives need to be reported separately in NGER?

Yes. Explosives combustion (detonation) is a distinct, reportable Scope 1 source under NGER. The NGA Factors include specific factors for ANFO, emulsion explosives, and other commercial blasting agents. Report the mass of each explosive type used during the reporting year and apply the corresponding NGA factor. This is a compliance requirement, not optional.

Which electricity factor applies to an off-grid mine site in Western Australia?

Off-grid operations using diesel generators do not use an electricity emission factor. Instead, the diesel consumed by those generators is a Scope 1 stationary combustion source — report it using the NGA diesel stationary combustion factor. The generator's diesel consumption is the reportable activity, not the kWh it produces.

How do I calculate Scope 3 Category 11 for coal sales?

The NGA Factors include Scope 3 emission factors for the downstream combustion of sold coal (thermal and metallurgical). Multiply the tonnage of each coal type sold by the corresponding NGA Scope 3 factor. For international sales, the combustion occurs outside Australia but the emissions are still attributed to the producer under GHG Protocol Scope 3 Category 11 and the GHG Protocol Product Life Cycle Standard.

What are the fugitive emission factors for underground coal mines?

The NGA Factors include methane emission factors for underground coal mine ventilation air, expressed per tonne of coal mined. The factors vary by coal basin and seam gas content — the NGA workbook provides factors differentiated by mining region and coal type. For high-methane seams, site-specific gas content measurements (used in the NGA's detailed calculation method) will produce more accurate results than the simplified default factors.