Scope Emissions Calculation Guide
Complete guide to Scope 1, 2, and 3 emissions calculation for UK SRS compliance. GHG Protocol methodologies, emission factors, and calculation frameworks for sustainability reporting.
Overview of Scope Emissions
The Greenhouse Gas (GHG) Protocol categorises emissions into three scopes to provide a framework for comprehensive carbon accounting. UK SRS requires reporting of Scope 1 and 2 emissions, with Scope 3 required where material.
Scope 1: Direct Emissions
Direct greenhouse gas emissions from sources owned or controlled by your organisation.
Sources of Scope 1 Emissions
- Stationary combustion: Fuel burning in boilers, furnaces, turbines
- Mobile combustion: Company-owned or controlled vehicles, aircraft, ships
- Fugitive emissions: Refrigerant leaks, natural gas leaks
- Process emissions: Chemical reactions, industrial processes
Calculation Methodology
Emissions = Activity Data × Emission Factor × Global Warming Potential
Example: Natural Gas Consumption
- Activity Data: 100,000 kWh natural gas consumed
- Emission Factor: 0.18316 kg CO₂/kWh (BEIS 2024)
- Calculation: 100,000 × 0.18316 = 18,316 kg CO₂
- Result: 18.3 tonnes CO₂
Scope 2: Indirect Energy Emissions
Indirect emissions from purchased electricity, heat, steam, and cooling consumed by your organisation.
Scope 2 Categories
- Location-based: Uses average emission factors for electricity grids
- Market-based: Uses emission factors from specific electricity suppliers
UK Electricity Calculation
Location-Based Method
- Activity Data: 50,000 kWh electricity purchased
- Grid Factor: 0.193 kg CO₂/kWh (UK grid 2024)
- Calculation: 50,000 × 0.193 = 9,650 kg CO₂
- Result: 9.7 tonnes CO₂
Market-Based Method
- Renewable electricity: 0 kg CO₂/kWh (with valid certificates)
- Supplier-specific factor: Use supplier's generation mix
- Residual mix factor: For uncertified electricity
Scope 3: Other Indirect Emissions
All other indirect emissions in your value chain, including upstream and downstream activities.
Scope 3 Categories
Upstream Activities
- Category 1: Purchased goods and services
- Category 2: Capital goods
- Category 3: Fuel- and energy-related activities
- Category 4: Upstream transportation and distribution
- Category 5: Waste generated in operations
- Category 6: Business travel
- Category 7: Employee commuting
- Category 8: Upstream leased assets
Downstream Activities
- Category 9: Downstream transportation and distribution
- Category 10: Processing of sold products
- Category 11: Use of sold products
- Category 12: End-of-life treatment of sold products
- Category 13: Downstream leased assets
- Category 14: Franchises
- Category 15: Investments
Common Scope 3 Calculations
Business Travel (Category 6)
- Activity Data: 10,000 km business travel by car
- Emission Factor: 0.16 kg CO₂/km (average UK car)
- Calculation: 10,000 × 0.16 = 1,600 kg CO₂
- Result: 1.6 tonnes CO₂
Purchased Goods (Category 1)
- Spend-based: £ spend × emission factor per £
- Activity-based: Physical quantity × emission factor
- Supplier-specific: Data from suppliers
UK-Specific Guidance
BEIS Emission Factors
Use UK government conversion factors published annually by the Department for Business, Energy and Industrial Strategy (BEIS).
Key UK Factors (2024)
- Grid electricity: 0.193 kg CO₂e/kWh
- Natural gas: 0.18316 kg CO₂e/kWh
- Petrol: 2.196 kg CO₂e/litre
- Diesel: 2.512 kg CO₂e/litre
UK SRS Requirements
- Scope 1 & 2: Mandatory for all in-scope companies
- Scope 3: Required where material (>40% of total)
- Biogenic carbon: Report separately
- Location and market-based: Report both Scope 2 methods
Calculation Best Practices
Data Collection
- Primary data preferred: Direct measurement where possible
- Consistent boundaries: Align with financial reporting
- Regular updates: Use current emission factors annually
- Documentation: Maintain calculation methodologies and assumptions
Quality Assurance
- Data validation: Check for errors and outliers
- Uncertainty assessment: Understand data limitations
- Third-party review: Independent verification where required
- Continuous improvement: Enhance data quality over time
Common Challenges
Data Availability
- Scope 3 data gaps: Limited supplier information
- Estimation methods: Use proxy data and industry averages
- Data collection systems: Implement robust tracking processes
Materiality Assessment
- Screening approach: Initial assessment using estimates
- Quantitative thresholds: Focus on categories >5% of total
- Qualitative factors: Consider stakeholder expectations
Getting Started
Begin your emissions calculation by establishing organisational boundaries and identifying your most significant emission sources across all three scopes.
UK SRS Compliance GuideImplementation Timeline
Resources
- GHG Protocol: Corporate Accounting and Reporting Standard
- BEIS: Government conversion factors for company reporting
- SECR: Streamlined Energy and Carbon Reporting guidance
- UK SRS S2: Climate-related disclosure requirements