Improving Scope 3.1 Carbon Accounting: A Framework for Selecting Weight-Based Material Emission Factors

Scope 3.1 emissions from purchased goods and services often represent a substantial share of corporate greenhouse gas footprints, yet their quantification is characterized by high uncertainty and limited transparency. In practice, organizations frequently rely on weight-based secondary emission factors, which can vary substantially depending on underlying assumptions such as production technology or geographical origin. Existing standards and data quality approaches provide important guidance on representativeness, reliability, and data exchange, but offer limited operational support for selecting appropriate emission factors. This study addresses this practical challenge by examining emission-factor variability for selected material groups, identifying key influencing factors, and developing a qualitative decision-support framework for evaluating, selecting, and documenting secondary emission factors in Scope 3.1 accounting. The results demonstrate that emission factors for the same material can differ by more than an order of magnitude, leading to substantial deviations in carbon footprint results if selected inconsistently. The proposed framework, while not replacing supplier-specific primary data or formal data-quality assessment, reduces selection-related uncertainty, and supports more reliable carbon accounting, particularly in data-constrained supply chain contexts. By providing a transparent screening logic for early-stage Scope 3.1, the study enables more informed sustainability and procurement decisions.