Evaluating University Scope 3 Waste Emissions Using a Process-based Life Cycle Assessment and Common Modeling Approaches

Abstract

Climate change has become one of the most pressing global challenges in modern society, as atmospheric carbon dioxide concentrations have surpassed 420 parts per million, contributing to widespread impacts on human well-being and the planet’s health. These challenges have driven governments, institutions, and organizations to pursue mitigation efforts aimed at reducing the rate and magnitude of climate change. As a result, climate change mitigation efforts increasingly rely on accurate greenhouse gas emissions accounting to inform effective reduction strategies and avoid misdirected mitigation efforts. Universities in particular, have prioritized comprehensive emissions reporting and frequently report Scope 1, Scope 2, and Scope 3 emissions to track progress, guide decision making, and enable comparisons across institutions. However, calculating Scope 3 emissions present significant challenges due to broad system boundaries, limited data availability, and rely on estimation models with varying assumptions and methodologies. This leads to emission estimates exhibiting substantial uncertainty, variability, and limited standardization across universities. To reduce the uncertainty surrounding Scope 3 and to improve standardization, examining the calculation models to generate these estimates can provide insight into how they might be improved. This work focuses on investigating the variability and accuracy of commonly used Scope 3 emissions models by focusing on a single subcategory within Scope 3: waste (Scope 3 Category 5: Waste Generated in Operations). Chapter 2 of this study evaluates multiple Scope 3 waste calculation models by applying them to an identical dataset, enabling direct comparison results. The analysis reveals large variability between model estimates that are primarily driven by differences in system boundaries, underlying assumptions, and treatment of material-specific waste.

To address this high variability and establish an independent baseline for comparison, Chapter 3 presents a process-based life cycle assessment of the same waste dataset, generating a more comprehensive and site-specific estimate of emissions. The process-based life cycle assessment is compared to the model-based estimates to assess how accurately Scope 3 models represent the environmental impacts. While some models produce total emission values that appear similar, a more in-depth comparison revealed substantial differences in material-level contributions and end-of-life pathway emissions. These findings highlight the importance of transparency in Scope 3 emissions modeling and the need for material-specific results to ensure emissions reduction efforts are targeted effectively. Ultimately, this work demonstrates the limitations of current Scope 3 emissions estimation approaches and shows the value of process-based life cycle assessment for validating model-based calculations. The results provide guidance for universities seeking more accurate and transparent Scope 3 emissions reporting and offer insights that can inform future calculations across other Scope 3 categories.