Life Cycle Assessment of Milk Packaging in Canada: Evaluating Reusable Packaging under Prospective Energy Grid Scenarios

Abstract

Plastic pollution remains a persistent environmental challenge in Canada, prompting growing policy attention toward single-use plastics. Yet, the life cycle implications of shifting materials or adopting reuse systems for food products, specifically milk packaging, are not well understood. This thesis conducts an ISO 14040/14044 aligned attributional life cycle assessment (LCA) comparing the environmental impacts of refrigerated milk packaging in Canada, including high-density polyethylene (HDPE) jugs, polyethylene terephthalate (PET) bottles, plastic milk pouches, liquid packaging board cartons, and glass bottles in both single-use and reusable systems. The functional unit is 12-L of pasteurized, refrigerated dairy milk contained in milk packaging. System boundaries are from cradle-to-grave for single-use formats and cradle-to-cradle for reuse scenarios, modeled in openLCA using the ecoinvent database and ImpactWorld+ impact methodology. Baseline packaging impacts are examined under current grid and recycling rates, and a scenario analysis is conducted under a prospective 2050 net-zero grid in Canada. Results show the packaging production stage dominates overall life cycle impacts, with lightweight flexible plastic milk bags performing best across most impact categories. Single-use glass exhibits the highest environmental impacts, while reusable glass shows improvement with increased reuse, though sanitization and transportation remain critical contributing stages as reuse increases. Under a decarbonized grid, reusable systems glass systems outperform select single-use packaging types but rarely surpass reusable plastic systems. Grid decarbonization improves electricity-intensive processes and strengthens relative performance of glass reuse, but does not outperform the advantages of lightweight, plastic-based systems. However, results are limited by data quality, availability, and quantification of microplastic impacts. Findings indicate that achieving circular packaging outcomes depends less on material substitution and more on system design. This study contributes novel, Canada-specific insight in how grid decarbonization and reuse interact in determining sustainable packaging strategy.