Every Carbon Stamp engagement follows a structured, three-phase methodology: Identify, Collect, Deliver. This page explains each phase in detail — what we do, why we do it, and how it produces outputs that are accurate, credible, and assurance-ready.
All work is aligned with the GHG Protocol Corporate Standard (for Scope 1 and Scope 2) and the GHG Protocol Corporate Value Chain (Scope 3) Standard for upstream and downstream emissions. These are the most widely used and internationally recognised greenhouse gas accounting standards in the world. Where required, we can also align reporting with ISO 14064-1, but we default to the GHG Protocol as it is more widely adopted across procurement frameworks, supply chain requirements, and voluntary reporting in the UK and globally.
We use UK Government GHG Conversion Factors (published annually by DEECC, formerly DEFRA / BEIS) as our primary emissions factor source.
We apply the operational control consolidation approach for defining organisational boundaries. The GHG Protocol also recognises financial control and equity share approaches; we can apply either where a client's structure requires it, but operational control is the most practical default for SMEs and is the approach specified by most UK procurement frameworks, including PPN 006.
When we say a report is assurance-ready, we mean that our methodology, data sources, assumptions, and calculations are documented to a standard where an independent third party could review and verify them — sample data back to source, check the application of emission factors, and reproduce the headline numbers.
Every calculation on this page rests on a single foundational equation:
Activity Data × Emission Factor = GHG Emissions (tCO₂e)This formula is the foundation of every calculation we perform. Throughout this page, you will see it applied specifically to each emission source — with the relevant activity data type and emission factor identified for each.
Phase 1 — Identify: Defining Boundaries and Scopes
Before any data is collected, we need to understand your business — what you do, how you operate, and which emissions sources are relevant. This phase establishes the foundations of your carbon footprint assessment, ensuring we measure what matters and don't waste your time collecting irrelevant data.
1. The Scoping Call
Every engagement begins with a structured 2-hour scoping call, conducted face-to-face or online with your designated lead (Operations Manager, Facilities Manager, or Sustainability Lead). It is led by our lead consultant and is designed to:
- Understand your business operations, sites, and supply chain at a practical level.
- Define your organisational and operational boundaries — which entities, facilities, and operations are included in the inventory.
- Identify which emission scopes (1, 2, and 3) and which specific Scope 3 categories are relevant.
- Map where data currently sits across your organisation — utility bills with facilities, fuel cards with fleet, procurement records with finance, delivery logs with logistics.
- Surface any data challenges early — gaps, formats, access issues — so we can plan around them before collection begins.
- Establish a clear point of contact and communication plan for the project.
2. Organisational Boundaries
Organisational boundaries determine which entities, facilities, and operations fall within the reporting company's GHG inventory.
We default to the operational control approach: the reporting company accounts for 100% of emissions from operations over which it has operational control. This is the most practical approach for SMEs and is the approach specified by most UK procurement frameworks including PPN 006.
The alternatives — financial control and equity share — are appropriate where a client has joint ventures, complex ownership structures, or specific investor reporting requirements. We can apply either where needed; full guidance on the three approaches is set out in the GHG Protocol Corporate Standard.
3. Operational Boundaries — Scope Selection
The GHG Protocol classifies all emissions into three scopes:
- Scope 1 — direct emissions from sources owned or controlled by the company: company vehicles, on-site fuel combustion (gas boilers), refrigerant leaks, and process emissions.
- Scope 2 — indirect emissions from the generation of purchased electricity, heat, steam, or cooling consumed by the company.
- Scope 3 — all other indirect emissions across the value chain, both upstream (supply chain, employee activities) and downstream (product distribution, use, disposal).
Scope 1 and Scope 2 are always included. Scope 3 categories are assessed for relevance using a structured screening process, described next.
4. Scope 3 Category Relevance Screening
The GHG Protocol defines 15 categories of Scope 3 emissions. Not all are relevant to every business. During the Identify phase, we assess each category against:
- Likely size relative to the company's total anticipated footprint.
- Risk exposure — regulatory, reputational, or financial.
- Materiality to stakeholders — customers, investors, tender requirements, sector expectations.
- Influence — whether the company can realistically drive reductions.
Categories included are documented with reasoning. Categories excluded are also documented, with a clear justification for exclusion. We never silently omit categories.
In Phase 2 (Collect) we walk through each of the 15 Scope 3 categories in detail — what they cover, what activity data we collect, and how we calculate the associated emissions.
5. Deliverable from This Phase
A scoping document / operational boundaries roadmap that the client reviews and approves before data collection begins. This document confirms:
- Which scopes and categories are in scope.
- What data is needed and where it will come from.
- Any known data gaps or challenges and how we plan to address them.
- The project timeline and key milestones.
Phase 2 — Collect: Gathering Activity-Based Data
This phase involves collecting primary activity data for every emission source identified in Phase 1. It is the most detailed part of our process — and the part that most directly determines the accuracy and credibility of your carbon footprint.
We prioritise activity-based data — real-world consumption figures such as kilowatt-hours (kWh), litres of fuel, kilometres travelled, kilograms of material purchased, and tonnes of waste disposed. Activity-based data produces materially more accurate results than spend-based estimation, often by an order of magnitude.
Where a client cannot immediately provide activity data for a specific source, we work with them to obtain it — contacting their energy supplier, requesting data from their waste contractor, or restructuring how procurement records are kept. We treat data gaps as problems to solve, not reasons to fall back on financial proxies.
Activity Data × Emission Factor = GHG Emissions (tCO₂e)Below, for each scope and category, we show the specific form this formula takes — identifying exactly what activity data we collect and which emission factors we apply.
Scope 1 — Direct Emissions
Scope 1 covers all direct GHG emissions from sources that are owned or controlled by the reporting company.
Stationary combustion
Natural gas, heating oil, LPG, or other fuels burned on-site.
Data collected: kWh or litres from utility bills or meter readings.
Applied factors: DEECC fuel-specific gross calorific value factors, published annually.
kWh (gas) × DEECC natural gas EF = tCO₂eLitres (fuel) × DEECC fuel-specific EF = tCO₂eMobile combustion — company vehicles
Fuel consumed by vehicles owned or operated by the company.
Data collected: Litres of fuel purchased (petrol, diesel, LPG) — our preferred method, materially more accurate than distance-based calculation. If fuel records are unavailable, we use distance travelled by vehicle type as a secondary approach.
Litres (fuel) × DEECC fuel-type EF = tCO₂ekm travelled × DEECC vehicle-type EF (per km) = tCO₂eFugitive emissions
Leaks or releases of refrigerant gases from air conditioning, refrigeration, or heat pump systems.
Data collected: Refrigerant type (e.g., R410A, R134a) and quantity of top-ups or recorded leaks (kg).
kg (refrigerant) × GWP of refrigerant = tCO₂eGWP values sourced from IPCC AR5 / AR6, as published in DEECC conversion factors.
Process emissions
Direct emissions from industrial or manufacturing processes (e.g., chemical reactions that release CO₂ as a by-product). Relevant for manufacturers; calculated from process-specific activity data where applicable. Documented as excluded for service-based businesses where not relevant.
Scope 2 — Indirect Emissions from Purchased Energy
Scope 2 covers indirect emissions from the generation of purchased electricity, heat, steam, or cooling consumed by the reporting company.
Purchased electricity
Data collected: kWh consumed, from utility bills or meter readings.
We report using the location-based method as our default — applying the UK national grid average emission factor. This reflects the average carbon intensity of the electricity grid supplying the reporting company.
If the client procures renewable electricity via a REGO-backed tariff, we also calculate and report using the market-based method, which can reflect a lower or zero emissions factor for that purchased electricity. We present both results where applicable, as recommended by the GHG Protocol Scope 2 Guidance.
kWh (electricity) × UK grid average EF = tCO₂ekWh (electricity) × supplier-specific / residual mix EF = tCO₂ePurchased heat, steam, or cooling
kWh consumed from district heating or third-party heat / cooling supply. Relevant for businesses purchasing heat from an external network; excluded with documentation if not applicable.
kWh (heat / cooling) × DEECC heat / cooling EF = tCO₂eScope 3 — Value Chain Emissions
Scope 3 encompasses all indirect emissions across a company's value chain — both upstream (in the supply chain and from employee activities) and downstream (from the distribution, use, and end-of-life treatment of sold products). The GHG Protocol Corporate Value Chain (Scope 3) Standard defines 15 distinct categories. Each is collapsed below — click any to expand.
Upstream categories
Category 1 — Purchased Goods and Services
What it covers: Emissions from the extraction, production, and transportation of goods and services purchased by the reporting company in the reporting year.
What we collect: Quantity and type of key purchased materials in physical units (kg, litres, units, metres). For significant service-based procurement, we work with suppliers to obtain their own carbon data or use sector-specific factors where a physical unit can be defined.
Our approach: We avoid spend-based estimation for this category. Where supplier-specific data is unavailable, we apply DEECC material-specific emission factors (e.g., kgCO₂e per kg of specific plastic resin, steel, paper, aluminium) to the quantity purchased.
Typical relevance: Almost always relevant. Typically the largest Scope 3 category for manufacturers, product companies, and retailers.
kg (material purchased) × material-specific EF = tCO₂eCategory 2 — Capital Goods
What it covers: Emissions from the extraction, production, and transportation of capital goods purchased — machinery, vehicles, buildings, IT equipment, furniture.
What we collect: Type, quantity, and material composition of capital purchases in the reporting year.
Typical relevance: Often excluded for SMEs where capital purchases are infrequent or immaterial. Always documented with justification if excluded.
Units / kg (capital item) × capital goods EF = tCO₂eCategory 3 — Fuel- and Energy-Related Activities Not Included in Scope 1 or 2
What it covers: Upstream emissions from the extraction, production, and transportation of fuels and energy purchased by the reporting company — commonly known as "well-to-tank" (WTT) emissions — plus transmission and distribution (T&D) losses for electricity.
What we collect: The same kWh and fuel consumption data already collected for Scope 1 and 2. No additional collection is required — we apply the relevant WTT and T&D factors from DEECC.
Typical relevance: Always included when Scope 1 and 2 are reported.
kWh / litres (same as Scope 1 & 2) × WTT or T&D EF = tCO₂eCategory 4 — Upstream Transportation and Distribution
What it covers: Transportation and distribution of purchased products from tier-1 suppliers to the reporting company, in vehicles not owned or controlled by the company.
What we collect: Weight of goods (tonnes), distance (km), mode of transport (road, rail, sea, air). Where exact distances are unavailable, we calculate them from origin / destination postcodes or port data.
Our approach: Tonne-km emission factors from DEECC, applied by transport mode.
Typical relevance: Relevant for businesses with significant inbound logistics — manufacturers, distributors, retailers with physical supply chains.
Tonnes × km × tonne-km EF (by mode) = tCO₂eCategory 5 — Waste Generated in Operations
What it covers: Disposal and treatment of waste generated by the company's own operations during the reporting year.
What we collect: Weight of waste by type (general, mixed recycling, food / organic, hazardous, construction) and disposal method (landfill, incineration with / without energy recovery, open- or closed-loop recycling, composting, anaerobic digestion).
Our approach: DEECC waste disposal emission factors, applied by waste type and disposal route.
Typical relevance: Relevant for most businesses; materiality varies. Larger proportion for manufacturers and food / beverage businesses.
Tonnes (waste) × waste-type & disposal-route EF = tCO₂eCategory 6 — Business Travel
What it covers: Transportation of employees for business-related activities, in vehicles not owned or controlled by the company.
What we collect:
- Flights: origin / destination, haul type (domestic, short-haul, long-haul), class of travel.
- Rail: journey distance or route.
- Taxi / ride-hailing: distance or journey logs.
- Private car (grey fleet): mileage claimed, fuel type, engine size.
- Hotel nights: number of nights by country.
Our approach: DEECC business travel emission factors, applied by mode and distance band.
Passenger-km (by mode & class) × DEECC travel EF = tCO₂eNights × DEECC hotel EF (by country) = tCO₂eCategory 7 — Employee Commuting
What it covers: Transportation of employees between home and work, plus emissions from working from home.
What we collect: A structured employee commuting survey capturing mode of transport (car, bus, train, cycling, walking), one-way commute distance, commuting days per week, and working-from-home days per week.
Our approach: Commuting emissions are calculated per employee and aggregated. Homeworking emissions are calculated separately using DEECC homeworking factors.
Typical relevance: Relevant for all businesses with employees. Increasingly significant for hybrid and remote workforces.
km (one-way) × 2 × days per year × mode-specific EF = tCO₂e per employeeWFH days per year × DEECC homeworking EF = tCO₂e per employeeCategory 8 — Upstream Leased Assets
What it covers: Operation of assets leased by the reporting company, where those emissions are not already included in Scope 1 or 2.
What we collect: Energy consumption data for leased assets (offices, vehicles, equipment) where this is not captured under Scope 1 or 2 under the chosen consolidation approach.
Typical relevance: Often excluded for SMEs operating from their own or single-tenancy premises. Documented with justification if excluded.
kWh (leased asset energy use) × relevant EF = tCO₂eDownstream categories
Category 9 — Downstream Transportation and Distribution
What it covers: Transportation and distribution of sold products from the reporting company to the end customer, in vehicles not owned or controlled by the company.
What we collect: Weight of goods dispatched (tonnes), destination (postcodes, regions, or countries), and mode of transport.
Our approach: For clients with large delivery volumes, we build bespoke distance calculation models using postcode-level data (geocoding APIs) and Haversine distance calculations, paired with DEECC tonne-km freight emission factors by transport mode. This allows us to calculate emissions for hundreds of thousands of individual deliveries with high accuracy.
Typical relevance: Relevant for manufacturers, distributors, and any business shipping physical products. Often one of the largest Scope 3 categories for product companies.
Tonnes × km (calculated per delivery) × tonne-km EF (by mode) = tCO₂eCategory 10 — Processing of Sold Products
What it covers: Further processing of intermediate products sold by the reporting company, by downstream companies (e.g., a component manufacturer selling parts that are assembled by a customer).
What we collect: Where relevant, data on the type of processing the sold product undergoes and the associated energy or material inputs.
Typical relevance: Relevant primarily for B2B suppliers of raw materials, semi-finished goods, or components. Excluded with documented justification for finished-product businesses.
kg (product sold) × downstream processing EF = tCO₂eCategory 11 — Use of Sold Products
What it covers: Emissions from the end-use of goods and services sold by the reporting company during their expected lifetime.
What we collect: Product type, energy consumption during use (wattage, expected hours of use), expected product lifetime, and usage patterns.
Typical relevance: Highly relevant for manufacturers of products that consume energy during use (electrical appliances, powered equipment, lighting), and for fuel or chemical products where combustion occurs during use. Can be excluded with justification for passive products (furniture, textiles).
Units sold × kWh per use × uses per lifetime × electricity grid EF = tCO₂eCategory 12 — End-of-Life Treatment of Sold Products
What it covers: Disposal and treatment of products sold by the reporting company, at the end of their useful life.
What we collect: Product material composition (by weight), units sold, and assumed end-of-life disposal route (landfill, recycling, incineration, composting) based on industry data or product-specific assumptions.
Our approach: DEECC waste disposal factors applied by material type and disposal method, scaled by units sold.
kg (material in sold products) × end-of-life disposal EF = tCO₂eCategory 13 — Downstream Leased Assets
What it covers: Operation of assets owned by the reporting company and leased to other entities.
What we collect: Energy consumption or operational data for assets leased out.
Typical relevance: Relevant for businesses leasing out property, vehicles, or equipment. Excluded with documented justification if not applicable.
kWh (leased-out asset energy use) × relevant EF = tCO₂eCategory 14 — Franchises
What it covers: Operation of franchises — applicable only to franchisors.
Typical relevance: Excluded for non-franchise businesses with documented justification.
Franchise operational data × relevant EFs = tCO₂eCategory 15 — Investments
What it covers: Emissions associated with the reporting company's equity investments, debt investments, project finance, and managed investments.
Typical relevance: Relevant primarily for financial institutions (banks, asset managers, insurers). Excluded for most SMEs with documented justification.
Investment value or share of investee emissions × relevant EF / attribution factor = tCO₂eData Quality and Uncertainty
We assess and document data quality for every emissions source using a tiered approach:
- Tier 1 (highest quality): primary activity data from direct measurement — metered kWh, fuel receipts in litres, weighed waste records, supplier-confirmed quantities. This is what we target for every source.
- Tier 2: primary data with some estimation — partial-year data extrapolated to a full year, distance-based vehicle calculations where fuel data is unavailable, estimated splits of waste streams.
- Tier 3 (lowest quality): secondary data or modelled estimates — industry averages, national statistics, spend-based proxies. Used only as a last resort and clearly flagged as such in the report.
We report the percentage of the total footprint derived from Tier 1 data as a quality metric in every report. For our typical engagements, this figure exceeds 80%.
All assumptions, estimations, extrapolations, and data gaps are documented in the report's methodology appendix. Nothing is hidden.
Phase 3 — Deliver: Reporting, Presentation, and Ongoing Support
1. Carbon Impact Report
We deliver a comprehensive, GHG Protocol-compliant Carbon Impact Report — typically 20–30 pages — that serves as both an internal strategic document and an external-facing proof of your sustainability credentials.
The report includes:
- Executive summary with headline emissions figures.
- Full methodology statement: boundaries, scopes, standards applied, emission factor sources, consolidation approach, and any exclusions with justification.
- Detailed emissions breakdown by scope, by category, and by individual source.
- Year-on-year comparison and trend analysis (for returning clients with a prior baseline).
- Emissions intensity metrics — tCO₂e per £m revenue, per FTE, per unit produced, or whichever metric is most operationally meaningful.
- Data quality assessment (Tier 1 / 2 / 3 breakdown).
- Identified emissions hotspots with context on why they are significant.
- Prioritised reduction recommendations — practical, actionable steps, ranked by impact and feasibility.
The report is designed to be assurance-ready: a third-party auditor could review our methodology, trace data back to source, and verify the calculations independently.
2. Board / Leadership Presentation
Every engagement includes a live presentation of results to the client's leadership team, board of directors, or relevant staff.
This is not a PDF handoff. We walk through the findings in a structured session, explain what the numbers mean in operational terms, highlight where the biggest reduction opportunities sit, and field questions from the team. This ensures the report doesn't sit on a shelf — it becomes a working tool for decision-making.
3. PPN 006 Carbon Reduction Plan — where required
For clients tendering for UK public sector contracts (including NHS Net Zero Supplier Roadmap), we produce a fully compliant Carbon Reduction Plan per the PPN 006 template.
This includes baseline emissions data (Scope 1, 2, and relevant Scope 3), current reporting year emissions, reduction targets aligned with UK net zero commitments, and specific, named reduction measures the company is implementing or plans to implement.
The document is formatted and structured for direct submission to procurement bodies and tender committees.
4. Ongoing Annual Support
Carbon footprinting is not a one-off exercise. We support clients with annual recalculations, enabling year-on-year tracking, target monitoring, base year restatements where necessary (e.g., following structural changes, mergers, or significant data corrections), and continuous improvement of data quality.
Returning client engagements are faster and more cost-effective because the methodology, boundaries, data collection processes, and stakeholder relationships are already established.
See What a Completed Report Looks Like
Want to understand what our Carbon Impact Report looks like in practice? Download an example report to see the level of detail, structure, and insight we deliver to every client.
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Need a definition? Every key term used on this page is defined in our carbon reporting glossary.