Business Travel Emissions Tracking for Australian Companies: A Practical Guide

PwC's business travel accounts for 48% of the firm's total Scope 1, 2, and 3 emissions. Not purchased electricity. Not office heating. Flights.

For a company that sells advice, that number should unsettle every sustainability manager reading this. And PwC isn't unusual — Deloitte reports its travel emissions are still only down 51% per full-time employee against its 2019 baseline, after briefly hitting 64% during the COVID years when nobody was flying at all. The rebound is real. Australia's corporate travel services market hit $5.3 billion in 2025, growing at a compound rate of 12.7% over the previous five years. Business travel emissions tracking in Australia went from an afterthought to an urgent Scope 3 problem practically overnight.

We build carbon accounting software. When we started working with professional services and consulting firms, we assumed Scope 2 electricity would be their main headache — it's what we'd seen in construction and property. We were wrong. For firms where the product is people flying to client sites, Scope 3 Category 6 is the number that dominates the disclosure, and it's the one most companies have the worst data on.

Here's the thing that makes this both urgent and solvable: AASB S2 gives you a one-year deferral on Scope 3 reporting. But from your second reporting period, Category 6 business travel becomes a mandatory disclosure if it's material. For any consulting firm, law firm, or accounting practice with more than a hundred staff, it is material. Full stop.

The Rebound Nobody Planned For

During 2020 and 2021, corporate travel basically stopped. Firms discovered video calls worked for a surprising number of things. Emissions dropped 60 to 70% across most professional services companies.

Then 2023 happened. Clients wanted face time again. Partners wanted to be in the room. International travel surged. Australian outbound business travel volumes grew 12.4% in the first half of 2025 compared to 2024, with Q1 alone up 19% year-on-year. The United States accounts for 24.1% of all international business trips from Australia, with Singapore at 11% — both long-haul routes with high per-trip emissions.

The problem isn't that travel came back. The problem is that most companies dismantled whatever rudimentary tracking they had during COVID (if they had any at all) and are now scrambling to rebuild it under a mandatory reporting regime. You can't just estimate this one. Your auditor will want to see actual data — routes, distances, cabin classes, hotel nights — not a rough percentage of your travel spend.

How to Calculate Flight Emissions (and Where Companies Get It Wrong)

There are three methods for calculating flight emissions under the GHG Protocol's Scope 3 guidance. They sit on a spectrum from least accurate to most accurate, and the method you choose determines both the quality of your number and the effort required to produce it.

Spend-based method. Take total dollars spent on flights, multiply by an industry-average emission factor per dollar. The Australian spend-based emission factors derived from input-output tables give you kilotonne CO2-e per million AUD for the air transport sector. This is the fastest approach, and it's the worst. You'll get a number, but that number won't tell you anything useful about which routes, which travellers, or which policies are driving emissions. And the emission factor per dollar doesn't differentiate between a $600 economy domestic fare and a $600 premium economy fare on a discounted route — even though the emissions are completely different.

Distance-based method. This is what most companies should be using. You take the actual route (Sydney to Melbourne, 713 km one way), apply a per-passenger-km emission factor adjusted for cabin class, and sum across all flights. The UK DESNZ/DEFRA 2025 conversion factors — which are the most commonly used international reference — give you factors that look roughly like this:

Category	Economy (kg CO2-e/km)	Business (kg CO2-e/km)	First (kg CO2-e/km)
Short-haul (< 3,700 km)	~0.15	~0.23	~0.31
Long-haul (> 3,700 km)	~0.12	~0.34	~0.60

Those numbers already include the well-to-tank emissions from fuel production. But they don't include radiative forcing — the non-CO2 warming effects of burning jet fuel at altitude. If you want to include those (and DESNZ recommends you should), you apply a multiplier of 1.9. That nearly doubles the number. A Sydney-Melbourne return in economy goes from about 165 kg CO2-e to around 310 kg CO2-e once you include radiative forcing.

Whether to include radiative forcing is genuinely debated. The science is real — contrails, NOx, water vapour at altitude all create warming effects beyond just the CO2 — but the 1.9 multiplier is an estimate with significant uncertainty. DESNZ itself notes the multiplier could reasonably be anywhere between 1 and 4. We include it when our clients' frameworks require it (CDP asks for it, for instance), and we flag it transparently when they don't. There's no consensus yet, and we won't pretend there is.

Flight-specific method. If you can get actual fuel burn data from the airline or your travel management company, you multiply fuel consumed by the jet fuel emission factor (roughly 3.16 kg CO2 per kg of jet fuel). This is the most accurate method but almost nobody outside the aviation industry has access to this data at scale. CTM and FCM — two of Australia's biggest corporate travel management companies — both partner with providers like RDC Aviation that calculate fuel burn by specific aircraft type, route, and load factor. If your TMC provides this data, use it.

The Cabin Class Multiplier Is Bigger Than You Think

This is where business travel emissions get politically uncomfortable inside a company.

A return flight from Sydney to London — 16,989 km each way — in economy class generates roughly 1.8 to 2.0 tonnes of CO2-e per passenger (without radiative forcing). The same flight in business class: approximately 5 to 6 tonnes. With radiative forcing applied, you're looking at 3.4 to 3.8 tonnes for economy and 9.5 to 11 tonnes for business. One return long-haul business class flight can exceed some employees' entire annual carbon footprint for everything else they do.

The reason is simple geometry. A business class seat takes up roughly 2.5 to 3 times the floor space of an economy seat. The aircraft burns the same fuel regardless of how the cabin is configured, so each business class passenger is allocated a proportionally larger share of the total fuel burn.

For a professional services firm with 200 staff, where 40 partners and directors fly business class internationally 4 times per year and the remaining 160 staff fly economy domestically 8 times per year, the maths works out roughly like this: 40 people x 4 return long-haul business class trips x 5.5 tonnes each = 880 tonnes. 160 people x 8 domestic economy returns x 0.17 tonnes each = 218 tonnes. Your 40 business class travellers generate four times the emissions of your 160 economy travellers combined.

That's not a judgement call — it's just the maths. But it means travel policy changes targeting cabin class on long-haul routes have an outsized impact on your total emissions number. We're not naive enough to think partners at a law firm are going to fly economy to New York. But the data at least makes the trade-off visible.

Don't Forget Hotel Nights and Ground Transport

Flights dominate business travel emissions, but hotels and rental cars aren't zero.

Hotel emissions are calculated per room-night and vary wildly by location. The Greenview Hotel Footprinting Tool (which DEFRA uses as its source) puts a 4-star hotel in Sydney at approximately 34.8 kg CO2-e per room-night. That includes electricity, gas, water, and waste from the hotel's operations, allocated per occupied room. Budget hotels tend to be lower (less air conditioning, smaller rooms). Luxury resorts in energy-import-dependent locations like the Maldives can be 150+ kg CO2-e per night.

For a firm where 200 staff average 30 hotel nights per year across Australian capital cities, that's 200 x 30 x ~35 kg = 210 tonnes. Not nothing, but it's a fraction of the flights number.

Rental cars and taxis are typically the smallest component. The average Australian light vehicle emits about 191 g/km (NGA Factors 2025 and National Transport Commission data). A rental car driven 200 km in a day produces roughly 38 kg CO2-e. Most companies have limited visibility into rental car usage — it's buried in expense claims, not in a structured data feed. We've found that for professional services firms, ground transport usually accounts for less than 5% of total business travel emissions. Worth tracking for completeness, but don't lose sleep over it until your flight data is solid.

The Data Collection Problem (This Is Where It Actually Gets Hard)

Knowing the formulas is the easy part. Getting the data into a format where you can apply them — that's where most companies stall.

There are four main data sources for business travel emissions, and most companies need a combination.

Travel management company (TMC) reports. If you use a TMC like FCM, CTM, or Corporate Traveller, they already have structured booking data — routes, dates, cabin classes, sometimes even aircraft types. CTM's Data Hub breaks out CO2 by traveller, trip, service type, and fare class. FCM splits emissions across air, hotel, and car. This is your best starting point. The data is already structured and usually available via API or quarterly export. But it only covers travel booked through the TMC — and we've seen firms where 30 to 40% of travel is booked directly by employees outside the managed channel.

Corporate card data. Your finance team has every travel transaction that hit a corporate card. The problem is it's financial data, not travel data. A $487.32 charge from Qantas doesn't tell you the route, the cabin class, or the distance. You can apply a spend-based factor to it, but you'll lose all the granularity that makes the distance-based method useful. Corporate card data is a backstop for unmanaged travel — it fills gaps but it shouldn't be your primary source.

Expense management systems. SAP Concur, Expensify, or whatever your company uses. These sit somewhere between TMC data and card data in terms of usefulness. Employees upload receipts — airline e-tickets, hotel folios, taxi receipts — that contain the actual route and property information. But the data is unstructured. It's in PDFs, screenshots, email confirmations. Extracting structured emissions data from expense receipts at scale is exactly the kind of problem we built Carbonly's AI document processing pipeline to solve — our multi-agent system uses multimodal AI vision to read travel agency invoices, airline e-tickets, and hotel receipts the same way it reads utility bills, pulling out flight routes, distances, cabin classes, and hotel nights without templates.

Manual collection. Someone in the sustainability team sends a quarterly email asking staff to fill in a travel log. This works for organisations with 20 employees. It does not work for 200. And the data quality is terrible — people round distances, forget trips, mis-remember cabin classes. If you're doing this, you already know it's broken.

The honest answer is that no single source gives you everything. A typical mid-market firm ends up combining TMC data (70% of trips), expense system extraction (20%), and corporate card spend-based estimates for the remainder. The goal isn't perfection — it's getting your primary data source above 80% coverage by the distance-based method, with spend-based filling the gaps.

ASRS Scope 3 Category 6: What Your Auditor Will Want

Under AASB S2, Scope 3 emissions reporting is deferred for year one but becomes mandatory from the second reporting period for all material categories. The safe harbour provisions under the Treasury Laws Amendment protect you from civil liability for Scope 3 disclosures in the early years — but "safe harbour" doesn't mean "report whatever you like." Your auditor still needs to assess whether your methodology is reasonable.

For Category 6 business travel, expect your auditor to ask for:

The calculation methodology used (spend-based, distance-based, or hybrid) and why
The data sources and their coverage (what percentage of trips are captured by each source)
The emission factors applied, with references (DEFRA year, NGA Factors edition, ICAO methodology)
Whether radiative forcing was included and the justification either way
Year-on-year comparisons and explanations for material changes
Evidence of internal controls over data quality (reconciliation of TMC data to expense reports, for example)

If you reported 800 tonnes of business travel emissions and your auditor can't trace that number back to actual flight records, you've got a problem. We've covered what auditors actually look for in a separate post, and the principles apply directly here — traceability, consistency, completeness.

Travel Policies That Actually Move the Number

We've seen a lot of corporate travel policies that read well in the annual report but don't actually change behaviour. "Encourage video conferencing where possible" is not a policy. It's a suggestion.

Here's what actually works, based on what we've observed across companies tracking their data over multiple years.

Hard caps on cabin class for routes under a certain distance. Economy-only for domestic flights and flights under 4 hours. This is the single highest-impact policy change, because the cabin class multiplier on short and medium-haul routes is where the easy wins are. Nobody needs a business class seat for Sydney to Melbourne.

Pre-trip approval for international travel with an emissions threshold. If a proposed trip will generate more than 2 tonnes of CO2-e (roughly a return long-haul economy flight), it needs sign-off that the trip can't be replaced by video. This doesn't eliminate international travel — but it forces the question to be asked before the ticket is booked, not after.

Quarterly reporting to business unit leaders showing their team's travel emissions. Nothing changes behaviour faster than visibility. When a partner sees their team generated 45 tonnes last quarter and every other team averaged 20, they start asking questions. We've seen this work even without formal targets — just the transparency changes decisions.

Domestic rail alternatives for routes where it's competitive. Sydney to Canberra. Melbourne to Geelong. These routes can be faster door-to-door by train when you factor in airport time, and the emission factor for rail is roughly 0.04 kg CO2-e per passenger-km — about a third of a short-haul economy flight.

Carbonly's carbon planning module lets you model what-if scenarios for these policies before you implement them. What happens to your total emissions if you shift all domestic flights under 500 km to rail? What's the impact of an economy-only policy on routes under 3,700 km? The numbers are often surprising — and they're a lot more convincing in a board paper than vague commitments.

A Worked Example: 200-Person Professional Services Firm

Let's make this concrete. Consider a hypothetical mid-market consulting firm based in Sydney with 200 staff. They don't have mining or manufacturing emissions — their footprint is overwhelmingly office electricity (Scope 2) and business travel (Scope 3 Category 6).

Estimated annual travel profile:

40 senior staff: 4 international return trips per year (business class, average 14,000 km each way), plus 12 domestic returns (economy, average 700 km each way)
160 junior/mid staff: 8 domestic returns per year (economy, average 700 km each way), 1 international return (economy, average 10,000 km each way)
Total hotel nights: 6,000 across the firm
Rental car: 50,000 km total across the firm

Running the numbers with DEFRA 2025 distance-based factors (without radiative forcing):

Senior international business class: 40 x 4 x (28,000 km x 0.34 kg/km) / 1,000 = ~1,523 t CO2-e
Senior domestic economy: 40 x 12 x (1,400 km x 0.15 kg/km) / 1,000 = ~101 t
Junior/mid domestic economy: 160 x 8 x (1,400 km x 0.15 kg/km) / 1,000 = ~269 t
Junior/mid international economy: 160 x 1 x (20,000 km x 0.12 kg/km) / 1,000 = ~384 t
Hotels: 6,000 nights x 35 kg / 1,000 = ~210 t
Rental car: 50,000 km x 0.191 kg/km / 1,000 = ~10 t

Total: approximately 2,497 tonnes CO2-e.

With radiative forcing applied to flights (x 1.9): roughly 4,337 tonnes.

For context, the same firm's Scope 2 emissions from a typical CBD office (say, 4,000 m2 in Sydney at around 150 kWh/m2/yr) would be about 384 tonnes. Business travel is 6.5 times their office electricity footprint. And more than 60% of it comes from 40 people flying business class internationally.

We're not sure all firms are ready to have that conversation at the partner level. But the data doesn't lie, and under ASRS, you'll need to disclose it.

Where This Is Still Messy

We should be honest about what's still hard.

Radiative forcing accounting isn't settled. Different frameworks treat it differently. CDP wants it included. The GHG Protocol says it's optional. AASB S2 doesn't specifically mandate it but requires you to disclose your methodology. There's no single right answer yet.

Unmanaged travel — trips booked outside your TMC — remains a data black hole for many companies. Some firms estimate it could be 20 to 40% of total trips. That's a huge gap to fill with spend-based proxies.

International hotel emission factors are thin. The Greenview Hotel Footprinting Tool covers major cities but the factors for secondary cities and regional areas are extrapolations, not measurements. A hotel in Karratha doesn't have the same emissions profile as one in Melbourne, but the available factors won't tell you the difference.

And Scope 3 boundary questions get awkward. If a client pays for your consultant's flight and hotel, is that your emission or theirs? The GHG Protocol says it's yours if your employee is travelling for your business purposes, regardless of who pays. But practically, you might not even have visibility into client-funded travel if it's booked through the client's travel system.

These aren't reasons to delay tracking. They're reasons to start now and improve your methodology over time — which is exactly what the ASRS safe harbour provisions are designed to allow.

Start With Your TMC Data This Week

If you're a professional services firm that hasn't started tracking business travel emissions, here's the one thing to do right now: request a quarterly emissions report from your travel management company. CTM, FCM, and Corporate Traveller all provide carbon data in their standard reporting. It won't be perfect. It won't cover unmanaged travel. But it'll give you 60 to 70% of your flights data in a structured format, and you can start calculating a baseline immediately.

From there, build out to expense system extraction for the trips your TMC doesn't see. Set up a Scope 3 data collection process that includes business travel alongside supplier emissions. And start the conversation with leadership about which travel policies could actually shift the number — because the number, as we've shown, is probably bigger than anyone in the boardroom realises.

Carbonly.ai automates business travel emissions tracking across flights, hotels, and ground transport — our AI document processing reads travel invoices, e-tickets, and expense receipts alongside your TMC data to give you a complete Category 6 picture. See how it works.

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