How to Calculate Scope 1 Emissions: A Step-by-Step Guide

 

Why Scope 1 Matters

Scope 1 emissions are the direct greenhouse gases (GHGs) released from sources your company owns or controls. They’re often the easiest to measure and reduce, making them a critical starting point for any carbon accounting strategy.

Examples of Scope 1 emissions are:

• Fuel combustion in company vehicles (gasoline, diesel)
• On-site boilers, furnaces, or generators (natural gas, coal)
• Fugitive emissions (refrigerant leaks, methane from waste)

If your business operates vehicles, machinery, or heating systems, you’re producing Scope 1 emissions—and regulators (like the SEC and EU) are increasingly requiring disclosure.

Step 1: Identify Your Scope 1 Emission Sources

Compile Emissions Inventory

Before calculating Scope 1 emissions, you need a complete inventory of all direct emission sources in your operations. This "mapping" process ensures you don’t overlook significant contributors (like fugitive methane or backup generators).

Category	What to Look For	Common Examples
Stationary Combustion	Fuel burned in fixed equipment	Boilers, furnaces, backup generators (natural gas, diesel, coal)
Mobile Combustion	Fuel burned in vehicles/equipment you own or lease	Company cars, delivery trucks, forklifts, construction equipment (gasoline, diesel)
Process Emissions	GHGs released during industrial processes (non-combustion)	Cement production (CO₂ from limestone), semiconductor manufacturing (PFCs)
Fugitive Emissions	Unintentional leaks of GHGs from equipment or systems	Refrigerant leaks (HVAC), methane from pipelines or landfills

Conduct a Facility Walkthrough

• Who to involve: Facility managers, maintenance staff, fleet operators.
• What to document: To prepare the inventory list.
• Fuel types used (e.g., natural gas, propane, diesel).
• Equipment lists (e.g., boiler models, vehicle registrations).
• Potential leak points (e.g., refrigerant lines, gas valves).

Tip: Take photos and tag locations on a facility map for reference.

Review Operational Records

Cross-check your walkthrough with:

• Fuel purchase receipts (identify diesel, gasoline, natural gas volumes).
• Equipment maintenance logs (e.g., refrigerant recharge records = leaks).
• Utility bills (e.g., natural gas consumption for heating).

Identify "Hidden" Sources

These are often missed but can be significant:

• Emergency generators (test runs consume fuel).
• Off-road vehicles (e.g., farm tractors, airport ground support equipment).
• Employee-owned assets (e.g., leased vehicles under company control).

Red flag: If you operate in cold climates, include fuel for space heating.

Use a Scope 1 Mapping Template

Create a simple spreadsheet to log sources:

Source Type	Location	Fuel/Process	Data Source	Notes
Boiler #1	Main factory	Natural gas	Utility bills (m³)	2,000 m³/year
Delivery van (ID: 45)	Logistics	Diesel	Fuel card (liters)	5,000 L/year
HVAC system	Office building	R-410A refrigerant	Maintenance logs (kg)	1.5 kg leaked last year

Step 2: Collect Activity Data

Collecting accurate activity data is where carbon accounting gets real. This step transforms your mapped emission sources (from Step 1) into quantifiable numbers.

Activity data refers to the measurable inputs that generate emissions. Think of it as the "raw ingredients" for your carbon calculations:

Emission Source	Activity Data Needed	Units	Where to Find It
Diesel fleet	Liters of diesel consumed	Liters or gallons	Fuel cards, invoices, odometer logs
Natural gas boiler	Cubic meters (m³) of gas	m³ or therms	Utility bills, submeters
Refrigerant leaks	kg of refrigerant added	kg	HVAC maintenance records

Golden Rule: Always track data in the same units as your emission factors (e.g., liters for diesel, kg for refrigerants).

For example:

1. Fuel Consumption (Mobile & Stationary Combustion)

• Company Vehicles:
• Source: Fuel purchase records, GPS fleet data, odometer readings.
• Pro Tip: If exact data is missing, estimate using:

Fuel Used (L)=Distance Traveled (km)/Vehicle Efficiency (km/L)

*(Example: A van drives 10,000 km/year at 10 km/L → 1,000 L diesel/year)*

• On-Site Generators/Boilers:
• Source: Utility bills, fuel delivery receipts, hour meters.
• Watch For: Backup generators (often overlooked but used during outages).

2. Process Emissions (Industrial Activities)

• Data Needed: Material inputs/outputs (e.g., limestone used in cement production).
• Sources:
• Production logs (e.g., "X tons of raw material consumed").
• Chemical inventories (e.g., ammonia used in refrigeration).

3. Fugitive Emissions (Leaks & Venting)

• Refrigerants:
• Source: HVAC service records.
• No Records?: Use default leak rates (e.g., 10% of total charge per year).
• Methane (Oil/Gas):
• Source: Leak detection surveys, EPA’s GHGRP reports.

With activity data in hand, you’re ready for Step 3: Applying Emission Factors—where we turn liters and kWh into CO₂e.

Step 3: Apply Emission Factors

An emission factor (EF) is a standardized value that tells you:

"How much greenhouse gas is released per unit of activity?"

Think of it like a nutrition label for carbon:

• 1 gallon of gasoline = 8.89 kg CO₂e (like "1 cookie = 200 calories")
• 1 kWh of grid electricity = 0.5 kg CO₂e (varies by energy source)

 They’re derived from scientific research by authoritative bodies:

1. Government Agencies
• EPA (U.S.): GHG Emission Factors Hub
• DEFRA (UK): Conversion Factors Database
2. International Organizations
• IPCC (UN): Default factors in their Guidelines
• IEA: Fuel-specific factors for energy

Convert fuel/activity data into CO₂ equivalents (CO₂e) using standardized emission factors.

Example Calculation: Diesel-Powered Fleet

1. Activity Data: 10,000 liters of diesel consumed
2. Emission Factor (EPA): 2.68 kg CO₂e per liter
3. Total Emissions:

10,000 L×2.68 kg CO₂e/L = 26,800 kg CO₂e (26.8 metric tons)

Note: If using biofuels, adjust for biogenic CO₂ (often counted as carbon-neutral).

 

Step 4: Account for Fugitive Emissions

Fugitive emissions are unintentional greenhouse gas leaks from equipment, pipelines, or industrial processes. Unlike combustion (which releases CO₂ predictably), fugitives escape unexpectedly—often as potent gases like methane (CH₄) or refrigerants, which can be hundreds to thousands of times worse for global warming than CO₂.

Key Characteristics of Fugitive Emissions

Feature	Why It Matters
Unintentional	Not from burning fuel, but from leaks, evaporation, or faulty equipment
High Global Warming Potential (GWP)	Methane = 28x CO₂; some refrigerants = 3,000–14,000x CO₂
Often Overlooked	Hard to detect without sensors, but can dominate your carbon footprint

Example: A single supermarket’s HVAC refrigerant leak can emit more CO₂e than its entire electricity use for a year.

Common Sources of Fugitive Emissions

1. Refrigerants (AC units, freezers)
• Gases: HFCs (R-404A), CFCs, HCFCs
• GWP: Up to 3,922x CO₂ (for R-404A)
2. Oil & Gas Systems
• Methane leaks from pipelines, valves, fracking
• GWP: Methane = 28x CO₂ over 100 years (but 84x over 20 years!)
3. Landfills
• Decomposing organic waste → methane
4. Industrial Processes
• Chemical manufacturing, mining (venting of gases)

Often overlooked, fugitive emissions (e.g., refrigerants) can have high global warming potential (GWP).

How to Calculate Fugitive Emissions (Pre-Example Primer)

The formula adjusts for gas type and leak rate:

Fugitive Emissions (kg CO₂e) = Leak Amount (kg)×GWP

Variables:

• Leak Amount: Measured via:
• Maintenance records (e.g., "Added 5 kg refrigerant this year")
• Infrared cameras or sensors (for methane)
• GWP: From IPCC or EPA tables (e.g., R-134a = 1,430x CO₂)

Example Calculation (Refrigerant Leak)

(This sets up your later detailed calculation.)

Scenario: A grocery store’s walk-in freezer uses R-404A refrigerant.

1. Leak Detected: 3 kg lost over a year
2. GWP of R-404A: 3,922 (from IPCC)
3. Calculation:

3 kg×3,922 = 11,766 kg CO₂e

Equivalent to driving a gas car 30,000 miles!

 

Step 5: Sum All Sources for Total Scope 1 Emissions

Now that you’ve calculated emissions for each individual source (e.g., vehicles, boilers, refrigerant leaks), it’s time to roll them up into your total Scope 1 footprint. This is where your carbon accounting comes together—but accuracy is critical.

Create a master table compiling all calculated emissions. Use this structure:

Emission Source	Activity Data	Emission Factor	Emissions (kg CO₂e)
Diesel fleet (10,000 L)	10,000 L diesel	2.68 kg CO₂e/L	26,800
Natural gas boiler (5,000 m³)	5,000 m³ natural gas	1.96 kg CO₂e/m³	9,800
Refrigerant leak (R-404A)	2 kg leaked	GWP = 3,922	7,844
Total Scope 1 Emissions			44,444 kg CO₂e

Note: Always include units (kg CO₂e or metric tons CO₂e) for clarity.

Take note of common mistakes before finalizing:

• Double-counting: Did you account for the same fuel in both mobile and stationary combustion?
• Unit mismatches: e.g., mixing liters and gallons, or kg and tons.
• Missing sources: Did you include backup generators, off-road equipment, or fugitives?

Quick Audit Tip:
Compare your total to previous years or industry benchmarks. If your emissions seem abnormally high/low, revisit calculations.

Conclusion: Why Mastering Scope 1 Emissions Matters

Calculating your Scope 1 emissions isn’t just a compliance exercise—it’s the foundation for credible climate action. By following this step-by-step guide, you’ve learned how to:

1. Map all direct emission sources (from boilers to refrigerant leaks).
2. Collect precise activity data (no more guesswork).
3. Apply scientifically validated emission factors.
4. Sum your total footprint accurately—avoiding costly oversights.

As the old adage goes:

“What gets measured gets managed.”

Now that you’ve measured, it’s time to act. Stay tuned for our next guide on Scope 2 emissions—where we’ll tackle the hidden footprint in your electricity bill.