Navigating Scope 3: Transport GHG Emissions Assessment in Construction Supply Chains

Abstract

The construction industry faces pressure to minimise its carbon footprint, particularly by managing Scope 3 greenhouse gas (GHG) emissions. The Corporate Sustainability Reporting Directive (CSRD) mandates rigorous environmental reporting, emphasising the need for accurate accounting. Scope 3 emissions, often the largest share, necessitate precise quantification and strategic control. This study evaluates methods for calculating upstream transportation emissions, focusing on reliability, practicality, and impact on environmental reporting. Analysing eight case studies, it models logistics from direct suppliers (tier 1) and subcontractors (tier 2) to construction sites. By employing a Life Cycle Assessment (LCA) framework, findings show a variation range of 48.8% to 146.1%, depending on the calculation method and emission factors. Current reporting mainly relies on invoice price data, but spend-based methods produce significant variances, highlighting the need for distance- and fuel-based methods. Fuel-based calculations yield reliable and accurate results but demand substantial changes in data collection practices. Distance-based calculations are a practical intermediate solution, though their reliability hinges on emission factor selection. Transitioning to primary data is challenging, especially for multi-tier suppliers. Strong data-sharing frameworks with suppliers, including contractual agreements on quality, are crucial. Documenting methodologies and validating outputs ensures accuracy and identifies improvement areas. Organisations should leverage CSRD flexibility to develop effective reporting methods that combine strengths while ensuring compliance. Better supplier data and more conscious data management can help contractors make more accurate environmental accounting and create incentives for mitigating impacts through organisational choices. The current flexibility in accounting Scope 3 methods is not contributing to fair competition because market players can choose methods based on their resulting figures, not their suitability.