Carbon Accounting Guide: Scope 3 Category 6 – Business Travel

Business travel sits in Scope 3, Category 6 under the GHG Protocol and covers trips undertaken by employees for work in vehicles and services not owned by the company (for example, commercial flights, trains, taxis and hotels). It excludes commuting to and from work and travel using company‑owned vehicles, which fall under other categories.

Below is a simple, step‑by‑step guide that can be used inside a corporate sustainability team. The focus is on distance‑based calculations, with spend‑based as a fallback.

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Step 1 – Define What Counts as Business Travel

Before touching data, agree clear boundaries so everyone collects the same thing.

Under Scope 3, Category 6 Business Travel typically includes:

• Air travel (domestic and international) for meetings, conferences and client visits
• Land travel such as rail, bus, taxi, ride‑hailing and hire cars used for work trips
• Hotel stays associated with those trips (nights per room)

A simple way to phrase the boundary is: “Travel for work, not to work, in non‑company vehicles or third‑party services.” This helps keep it aligned to Scope 3.6 and avoids mixing employee commuting or company‑owned vehicles.

Question for you: In your organisation, what types of travel and accommodation would you include in Scope 3 business travel, and are there any grey areas you’d need to clarify?

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Step 2 – Map Your Data Sources

Next, identify where business travel information actually lives. Typical sources are:

• Travel management company (TMC) reports: itineraries, routes, distances, cabin class
• Expense system: employee‑claimed flights, trains, taxis, hotels
• Internal booking tools or corporate card statements: payments for travel and accommodation

Aim to capture, at minimum, for each trip: travel mode (air, rail, car, taxi, bus, hotel), origin and destination (or distance), date, and any relevant details such as flight cabin class or vehicle type. Strong data mapping at this stage makes the calculation later much smoother.

Question for you: Which systems in your company could realistically provide most of the business travel data, and what important fields do they already capture?

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Step 3 – Choose Your Calculation Method (Distance vs Spend)

The GHG Protocol allows several methods; for business travel, two are most practical:

Distance‑based method (preferred)

• Activity data: kilometres travelled (or passenger‑kilometres) per mode
• Emission factor: kg CO₂e per kilometre for each mode (for example, short‑haul flight economy, UK rail, taxi)
• Formula:$$\text{Emissions} = \text{Distance} \times \text{Emission factor}$$

This method is more accurate and better for reduction planning because it directly relates to how far and how people travel.

Spend‑based method (fallback)

• Activity data: amount spent on business travel per mode (for example, “£X on air travel”)
• Emission factor: kg CO₂e per unit of currency (for example, kg CO₂e per £ spent on flights)
• Formula:$$\text{Emissions} = \text{Spend} \times \text{Emission factor}$$

Spend‑based is useful when distances are missing or fragmented, but it is less precise and harder to link to behavioural change.

Question for you: Given the data you typically see, do you think your organisation is more ready for a distance‑based approach, a spend‑based approach, or a hybrid – and why?

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Step 4 – Clean and Categorise Your Travel Data

Now take the raw data and organise it by mode and type so you can apply the right emission factors.

1. Split by transport type and hotels
   • Air travel: domestic, short‑haul, long‑haul; cabin class if available (economy, premium economy, business, first)
   • Rail travel: national rail vs metro or light rail if factors differ
   • Road travel: hire cars by size or fuel type; taxis; buses
   • Hotels: country of stay and nights per room
2. Standardise units
   • Convert all distances to kilometres
   • For group journeys by public transport, calculate passenger‑kilometres:$$\text{Passenger‑kilometres} = \text{Distance} \times \text{Number of passengers}$$
3. Handle missing data
   • If cabin class is missing, use a documented rule (for example, assume economy or apply an average factor)
   • If flight distance is missing, estimate using route distance look‑ups or average sector distance by route type (for example, typical short‑haul European flight distance)

Every assumption should be documented so your inventory is transparent and can be refined over time.

Question for you: When you think about your current travel data quality, what do you expect will be the biggest data gaps you’d have to handle with assumptions?

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Step 5 – Match Activity Data with Emission Factors

Once your data is cleaned, link it to appropriate emission factors from recognised sources (such as national government conversion factors, ICAO tools, or environment‑extended input–output databases).

Typical factor choices:

• Air travel
  • Factors differ by distance band (domestic, short‑haul, long‑haul) and cabin class, and may include an uplift for non‑CO₂ climate impacts such as contrails
  • Usually expressed in kg CO₂e per passenger‑kilometre, per band and cabin class
• Rail, bus, taxi, hire cars
  • Rail and bus: kg CO₂e per passenger‑kilometre, often varying by region or electricity mix
  • Taxis and hire cars: kg CO₂e per vehicle‑kilometre, sometimes broken down by fuel type or vehicle size
• Hotels
  • Factors expressed in kg CO₂e per room‑night, ideally by country or hotel type
  • For shared rooms, count room‑nights rather than number of guests

Where factors cover multiple greenhouse gases (CO₂, CH₄, N₂O), they are generally already converted into CO₂ equivalents (CO₂e), so you can report results directly in CO₂e.

Question for you: In your current practice, which emission factor source do you rely on most, and what would you need to check to ensure it aligns with GHG Protocol guidance?

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Step 6 – Calculate Emissions Per Mode and Trip

Now apply the basic calculations to each record and then aggregate.

Air travel

For each flight:

$$\text{Emissions}_\text{flight} = \text{Distance}_\text{km} \times \text{EF}_\text{kg CO₂e per passenger‑km}$$

Sum all flights to get total air travel emissions for the reporting period.

Rail, bus and taxi

For passenger transport:

$$\text{Emissions}_\text{trip} = \text{Passenger‑km} \times \text{EF}$$

Sum separately for rail, bus and taxi to see mode‑specific footprints.

Hire cars

For each car trip:

$$\text{Emissions}_\text{trip} = \text{Vehicle‑km} \times \text{EF}_\text{per vehicle‑km}$$

Group by vehicle type (for example, compact petrol, diesel SUV, EV) if you want more insight.

Hotels

Per stay:

$$\text{Emissions}_\text{stay} = \text{Room‑nights} \times \text{EF}_\text{kg CO₂e per room‑night}$$

Sum across all hotel stays for the year.

For spend‑based calculations, the structure is similar but uses spend instead of distance:

$$\text{Emissions}_\text{mode} = \text{Spend}_\text{mode} \times \text{EF}_\text{kg CO₂e per currency unit}$$

Question for you: If you were to pilot this in one business unit, which travel mode would you start with for a test calculation, and why?

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Step 7 – Aggregate, Attribute and Report

Once calculations are complete, bring them together in a way that supports reporting and decision‑making.

Common views:

• By GHG category: total Scope 3, Category 6 business travel emissions in tonnes CO₂e
• By mode: air vs rail vs road vs hotels, to identify hotspots
• By business dimension: department, country, cost centre, or project, depending on how your organisation manages responsibility

Effective disclosure will describe:

• The boundary and what was included in Scope 3.6
• The calculation methods (distance‑based vs spend‑based) and emission factor sources
• Key assumptions, data coverage, and plans to improve data quality over time

This keeps the inventory aligned with key GHG Protocol principles such as relevance, completeness, consistency, transparency and accuracy.

Question for you: When you think about how leaders in your company consume sustainability information, which breakdown of business travel emissions (for example, by mode, by region, by function) would most help drive behavioural change?

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Step 8 – Use the Results to Drive Reduction

The value of Scope 3.6 data is in the actions it can inform.

Typical strategies include:

• Encouraging modal shift from air to rail where practical, or combining trips to reduce flight frequency
• Introducing policies that prioritise virtual meetings, particularly for internal travel and short meetings
• Setting internal approval thresholds for high‑emission trips (for example, long‑haul business‑class flights)
• Engaging airlines, hotels and your TMC on lower‑carbon options and better data provision
• Embedding travel‑related KPIs into budgets or performance metrics

Using a consistent calculation framework year on year allows you to track whether policies and behaviour changes are actually reducing emissions.

Question for you: If you had a clear annual Scope 3 business travel footprint broken down by mode, what is one practical policy or behaviour change you would propose first in your organisation?

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Sources and Further Reading

• GHG Protocol – Technical Guidance for Calculating Scope 3 Emissions (including Category 6: Business Travel)
  https://ghgprotocol.org/scope-3-calculation-guidance-2
• GHG Protocol – Category 6: Business Travel guidance (Scope 3 Standard supporting documents)
  https://ghgprotocol.org
• UK Government GHG Conversion Factors for Company Reporting (for UK‑specific emission factors by mode)
  https://www.gov.uk/government/collections/government-conversion-factors-for-company-reporting
• ICAO Carbon Emissions Calculator (for flight‑specific emission estimates)
  https://www.icao.int/environmental-protection/CarbonOffset/Pages/default.aspx
• Practical examples of business travel calculation methodologies (e.g. university or corporate Scope 3 guidance documents)
  Example: https://squake.earth/blog/how-to-calculate-scope-3-6-emissions-from-business-travel