Material flows and operational carbon emissions in full- service tourist accommodation across comfort categories

Technical Summary: Material Flows and Operational Carbon Emissions in Full-Service Tourist Accommodation

Problem Statement
The hospitality sector faces a critical methodological deficit in carbon accounting. Current dominant frameworks, such as the Hotel Carbon Measurement Initiative (HCMI), restrict system boundaries to Scope 1 (direct combustion) and Scope 2 (purchased electricity), often excluding Scope 3 supply chain emissions. This truncation creates a "blind spot" regarding food procurement, which the literature suggests is the most carbon-intensive activity in full-service hotels. Consequently, existing benchmarks may produce internally inconsistent data and, more critically, generate incorrect relative performance rankings between properties. Furthermore, there is a lack of peer-reviewed, primary-data carbon footprints for the Irish accommodation sector, a market characterized by independent full-service hotels, a decarbonizing national grid, and a grass-based agri-food system that differs significantly from European averages.

Methodology
This study employs a qualitatively-informed, embedded multiple-case study design to generate the first full-scope (Scope 1–3) operational life-cycle assessment (O-LCA) of tourist accommodation in Ireland.

• Sample: Four hotels representing three comfort categories (one 3-star, two 4-stars, and one 5-star) were selected via purposive sampling to ensure analytical leverage over statistical representativeness. The sample includes independent and group-operated properties, with varying energy configurations (natural gas vs. LPG).
• Data Collection: Primary data were triangulated from three streams:
  1. Quantitative Inventory: A full review of procurement ledgers (food/beverage invoices, delivery dockets), utility records (12 months of energy billing), and waste manifests.
  2. Field Validation: On-site visits to verify energy systems, kitchen workflows, and waste segregation, resolving ledger anomalies.
  3. Qualitative Interviews: Two semi-structured interviews with senior management (one independent proprietor, one group general manager) covering measurement infrastructure, investment logic, and supply-chain barriers.
• Emission Factors: A transparent, hierarchical factor-selection approach was used:
  • Energy: Irish-specific factors from the Sustainable Energy Authority of Ireland (SEAI).
  • Waste: UK DEFRA factors used as proxies due to the absence of Irish-specific lifecycle waste factors.
  • Food: Irish-specific peer-reviewed factors for verified domestic beef and dairy; European regional averages (Agribalyse v3.2, Ecoinvent v3.9, CONCITO) for other categories.
• Functional Unit: One occupied room-night, with results also reported per guest-night and as annual totals.
• Robustness: Sensitivity analyses were conducted using ±20% perturbation of non-Irish food factors and a "national-priority" scenario applying Irish-specific factors to all bovine/dairy items.

Key Results

• Dominance of Scope 3: Food and beverage procurement constitutes the single largest emission category across all four properties, ranging from 40% to 58% of the total annual carbon footprint. This exceeds emissions from direct combustion (Scope 1) and purchased electricity (Scope 2) at every site.
• Carbon Intensity: Per-room-night intensities ranged from 15.87 kg CO₂e (3-star) to 56.14 kg CO₂e (5-star), with a sample mean of 39.87 kg CO₂e.
• The "Ranking Reversal" Effect: The study empirically demonstrates that excluding Scope 3 food procurement alters the relative environmental performance ranking of hotels. Under Scope 1 and 2 only, a 4-star property (H002) appeared more efficient than another 4-star property (H003). However, when full Scope 1–3 emissions were included, H002's ranking worsened significantly due to its high guest throughput and associated food procurement volume, causing the two properties to exchange positions. This confirms that system boundary choice does not merely rescale footprints but can invert performance hierarchies.
• Convergence and Variability: Despite differences in energy systems and room counts, the 4- and 5-star properties converged on a nearly identical food-procurement intensity (~21.7 kg CO₂e per room-night), suggesting that service-level standards drive food emissions more than facility size. Conversely, intra-category variability was driven by management practices and building age rather than star rating alone.
• Sensitivity: The finding that food procurement is the dominant emission source and the resulting ranking reversal remained stable across all sensitivity scenarios, confirming the robustness of the results against emission factor uncertainty.

Significance and Contributions
The paper makes three primary contributions to the literature and practice:

1. First Irish Benchmarks: It provides the first peer-reviewed, primary-data operational life-cycle carbon footprints for Irish tourist accommodation, establishing a baseline for a sector previously absent from international benchmarking datasets.
2. Empirical Proof of Ranking Reversal: It offers the first property-level empirical demonstration that truncating system boundaries to Scope 1 and 2 produces misleading performance rankings. This challenges the validity of current industry-standard benchmarks (like HCMI) for comparative sustainability assessments unless boundaries are harmonized.
3. Methodological Framework for CSRD: It provides a directly replicable O-LCA methodology and emission-factor hierarchy for Scope 3 disclosure, specifically tailored to the Corporate Sustainability Reporting Directive (CSRD) requirements. The study reframes hospitality carbon footprinting not merely as an energy management issue, but as a resource-productivity and material-flow problem, where the emissions perimeter must align with the actual procurement and waste material flows.

Conclusion
The study concludes that reliance on Scope 1 and 2-only benchmarking is not merely incomplete but "actively misleading" for the hospitality sector. Achieving alignment with UN Sustainable Development Goals (SDG 12 and 13) requires a structural shift toward full-scope supply chain accountability. The research identifies that while leading operators possess the measurement infrastructure for Scope 3, the sector lacks the standardized, audit-grade certification frameworks and supplier-level data architecture necessary to execute procurement-led decarbonization at scale. The paper positions its methodology as a necessary template for closing this gap.