Methodology
The summary version of the methodology PDF (event-v1.2.0).
1. Boundary
The boundary follows ISO 20121 event-management practice. We report what the organiser controls or significantly influences: attendee travel, venue energy allocated by booked-hours share, catering, materials and waste. Accommodation is counted when it is reported; none was reported for this event, so there is no accommodation line. Out of scope: attendee leisure travel after the event, third-party private hospitality, and travel between attendees' own offices.
- · Geographic: UK + inbound international attendees.
- · Temporal: 2026-03-19 (single day, plus travel days +/-1).
- · Consolidation: Operational control: Pawston is the organiser.
2. Categories included and excluded
| Category | GHG Protocol | Tier | tCO₂e |
|---|---|---|---|
| Travel (attendees, speakers, crew) | Scope 3 · Cat 6 | T2 · Survey | 26.0 |
| Catering | Scope 3 · Cat 1 | T2 · Survey | 3.6 |
| Venue energy (allocated) | Scope 2 (location-based) | T1 · Primary | 2.7 |
| Materials | Scope 3 · Cat 1 | T3 · Spend-based | 1.9 |
| Venue gas heating (allocated) | Scope 1 (direct combustion) | T1 · Primary | 1.1 |
| Staff commuting | Scope 3 · Cat 7 | T2 · Survey | 0.3 |
| Waste | Scope 3 · Cat 5 | T3 · Spend-based | 0.1 |
3. Calculation methods, per category
Eight lines: attendee rail, car, coach, Underground and short-haul air, speakers, crew, and 138 non-responders projected from respondent mode-mix banded by distance. Survey answers cover 312 of 450 tickets.
Lunch, breaks, drinks reception, food preparation and single-use service ware for 460 covers.
Sub-metered hall, allocated by booked hours / total available hours. Counted: location-based, 2,734 kg. Disclosed beside it and not added: market-based (residual mix), 3,181 kg.
Lanyards, signage, printed programmes and amortised AV hire.
Heating share for event hours, allocated by booked hours. Scope 1 here is gas burned in the venue plant, not vehicles.
Pawston event-day staff to and from the venue: commute and taxis.
Food waste, mixed recyclables, general waste and paper, from venue weighbridge records.
4. Emission factor sources (pinned at publish)
| Source | Version | Used for | Role |
|---|---|---|---|
| DEFRA UK government GHG conversion factors | 2024 v1.1 | Travel, energy, waste | Pinned calculation source |
| Cornell Hotel Sustainability Benchmarking Index (CHSB) | 2023 | Accommodation, when reported (none reported for this event) | Benchmark default for low-data estimates, carried at wide uncertainty |
| Poore & Nemecek (food) | 2018 | Catering menu lines | Benchmark default for low-data estimates, carried at wide uncertainty |
| Illustrative estimates | demo | Menu lines, materials, serviceware, residual mix | Placeholder for this demo; a real report uses supplier, spend-based or published factors |
| Exiobase | v3.8.2 | Spend-based residuals | Pinned calculation source |
5. Allocation decisions
Venue energy: allocated by a recorded allocation decision: method booked_hours here (booked hours / total available hours); headcount_share where the venue hosts a concurrent activity. The share is stored as numerator / denominator and disclosed in the methodology PDF. Where no decision is recorded, the whole meter is attributed to the event and a share of 1.0 is disclosed. Sub-metered hall + half-hourly grid factor.
Shared transport: coach and rail allocated per-pkm (passenger-kilometre), so capacity changes do not transfer between attendees.
Catering: meal-level allocation by menu line × portions served. Surplus produced but not served is allocated to waste rather than catering.
6. Uncertainty analysis
Records are correlated in the MC roll where they share a factor family (short-haul flight σ moves together across attendees, not independently), so the headline band does not understate the true uncertainty. σ values are taken from Schulte (2024), IPCC AR6 (2019), the PEF guide and Meinrenken (2022).
7. Double-count guard
Venue energyis reported under the event but flagged so it does not also appear under the venue operator's annual report. Two-way flagging handled at publish.
Staff travelby Pawston event-day staff is reported here (Cat 7 employee commuting) and excluded from Pawston's own commuting line for the same dates.
Bundled catering covered by the venue contract is allocated to the event, not the venue, to avoid splitting one meal across two reports.
8. Limitations and caveats
The 31% non-responder share is the line with the widest relative uncertainty (36.6% of its own value). Their travel is projected from respondent mode-mix banded by distance, not assumed to be local. Extrapolated buckets carry an additional log-space σ of 0.50 × (1 − response rate), composed in quadrature with the bucket's structural σ.
No accommodation was reported for this event, so the footprint has no accommodation line. Where hotel stays are reported, room emissions would be estimated from a benchmark default (Cornell Hotel Sustainability Benchmarking Index 2023, UK average), carried at wide uncertainty, not a pinned calculation source. Finer detail requires per-property disclosures that most hotels do not publish.
The footprint is illustrative of what HemeraScope can produce. Live numbers depend on the organiser's data quality at intake.
Once the headline is on the page, the next decision is the invitation list and venue catchment. That's where the lever sits, not in the calculation.
What we claim, and what we don’t
- · Every line names its factor, source, version + vintage in plain text on the page.
- · Every number is σ-banded: central value + 95% CI on the page, not buried in an appendix.
- · Every line names the person who recorded it. Override decisions traceable to a named person.
- · Inputs hash + MC seed published with the headline. A second run on the same inputs returns the same number, bit-identical.
- · Non-responder treatment documented on the page, including which cohort the imputation drew from and what σ that adds.
- · Double-count guard runs across every line, three checks (cross-event, cross-scope, cross-org-allocation). Passes shown explicitly.
- · Methodology PDF mirrors the page content: same numbers, same factor versions, generated from the same publication snapshot.
- · Replay is one command; the inputs hash anchors a deterministic recompute.
- · No third-party assurance: ISO 14064-3 assurance requires an external assuror. Hemera produces the evidence pack; the assuror signs.
- · No sector-specific add-on protocols wired in v1.
- · Factors are DEFRA 2024 where DEFRA publishes one; the menu, materials and residual-mix lines use illustrative estimates, marked Estimate.
- · Demo numbers are illustrative for a fictional Pawston event, not a real footprint.
Roadmap
The v1 surface is deliberately narrow. The following items are on the path, not in the shipped engine today:
- · Sector-specific add-on protocols, ICT-event, hospitality-event, broadcast-event modules.
- · Third-party assurance integration, evidence pack export hand-off to ISO 14064-3 assurors with stable record IDs.
- · Mixture-of-candidates σ (v2), structural σ today; v2 widens the band where one activity maps to multiple plausible factors.
- · Year-on-year longitudinal integrity, change-log + restatement protocol across publication snapshots.
Methodology PDF
The methodology PDF mirrors this page plus three appendices: full activity records, attendee survey responses (anonymised to outward postcode), and the change log against the prior publication.