Event Carbon Footprint: How to Calculate and Reduce It

Why measure before reducing?

An event’s carbon footprint covers much more than the venue’s electricity use or waste left after the reception. Guests’ travel, catering, equipment, purchases and accommodation can generate significant emissions. Without figures, organizers risk multiplying visible initiatives without addressing the main impacts. A useful carbon assessment is primarily a decision-making tool: it helps compare formats, set priorities with suppliers and measure progress between editions.

1. Define exactly what the calculation covers

Start by specifying the format, duration, number of guests and stages covered: preparation, setup, reception, dismantling and waste treatment. Then determine who supplies the data and who consolidates the result. Emissions can be direct or indirect. The GHG Protocol distinguishes three scopes: direct emissions (scope 1), purchased energy (scope 2) and other indirect value-chain emissions (scope 3). Attendee travel and many outsourced services often fall into the third category for the organizer.

Record exclusions and assumptions from the outset. A total without a clearly stated boundary is hard to interpret, however many decimal places it displays.

2. Collect activity data

Prepare a travel survey and a supplier data request before the event. Physical quantities are preferable to expenditure figures alone. If information is unavailable, use a documented estimate and disclose its uncertainty.

• Travel: departure locations, return distances, transport modes, car occupancy and supplier journeys.
• Energy: electricity or heating kWh attributable to the event, occupancy duration and audiovisual needs.
• Catering: meals served, menu composition, drinks, packaging and surplus food.
• Equipment: hired or purchased furniture, signage, staging and equipment, including transport.
• Other sources: overnight stays where relevant, consumables and quantities of waste treated.

3. Calculate emissions in CO₂e

The operational formula is activity data × emission factor = emissions in kg CO₂e. Apply a suitable factor to each source: per passenger-kilometre, per kWh or per product quantity. Factors should match the location, year, technology and actual composition as closely as possible. The GHG Protocol recommends activity-specific data when available.

Worked example: attendee travel

Take 120 guests each travelling 40 km return, or 4,800 passenger-kilometres. Using a purely illustrative factor of 0.10 kg CO₂e per passenger-kilometre, the result is 480 kg CO₂e. The final figure depends on actual travel modes: this hypothetical factor must not be used in a published inventory. Transport records should also avoid double counting guests, teams and suppliers.

Then add the sources together and present the total in tonnes of CO₂e and, as an additional metric, kilograms per attendee. Retain the assumptions and source of every factor so the calculation can be reproduced.

4. Reduce the main sources of emissions

Travel and location

Choose a venue accessible by public transport, adapt the schedule to connections and provide practical directions in the invitation. Encourage carpooling and assess remote participation for international speakers. Choosing an accessible venue can be more effective than last-minute messaging about good habits.

Catering and food waste

Request attendance confirmations, match quantities to actual guests, offer attractive plant-based options and plan how surplus food will be handled. Make these decisions with the caterer before approving the menu, not after delivery. The aim is to reduce both food-related emissions and meals prepared unnecessarily.

Equipment and purchasing

Prefer rental, shared use and reuse of staging and signage. Avoid automatic giveaways, unnecessary printing and oversized installations. Explore BluePoint Liège’s event layout options to design a setup suited to your format without unnecessary equipment.

5. Make monitoring a shared responsibility

Include environmental tracking in the supplier brief: request available consumption data from the venue, quantities served from the caterer and equipment details from technical suppliers. Appoint one person to consolidate the results. ISO 20121:2024, whose second edition was released in 2024, provides a responsible management framework applicable to events of different sizes. It does not, by itself, constitute an emissions calculation.

6. Report results without greenwashing

Your report should show the total, breakdown by source, boundary, missing data, factors used and actions selected. Compare only events with compatible formats and methods. Distinguish actual emission reductions from voluntary contributions to climate projects: an advertised offset does not erase emissions generated. Finally, set two or three targets for the next edition, each with an indicator, owner and deadline.

From measurement to a genuinely better-designed event

The value of a carbon assessment lies less in the apparent precision of a number than in its ability to improve the next event. Even an imperfect first inventory, if transparent, can identify the largest sources and inform decisions about budget, travel, catering and equipment. A consistent method then makes progress measurable without turning environmental communication into an unverifiable promise.

From the initial planning of your next seminar, conference or corporate event, bring your team and suppliers together around one clear objective: measure what matters and reduce what can genuinely be reduced. Contact BluePoint Liège to discuss a configuration suited to your needs and plan your event on a practical basis.