MPFREE
Packaging & Materials

Why Glass and Aluminum Score Differently Than Plastic-Alternative Packaging

Not all plastic-free packaging claims are evaluated the same way under Pillar 2.

3 min read · Updated 2026-09

Pillar 2 (Downstream Waste) draws a real distinction between two different strategies for avoiding persistent synthetic plastic: using genuinely inert materials (glass, aluminum) versus using a plastic that's engineered to break down under specific conditions.

Inert materials pass on a materials-composition basis — there's no persistent synthetic polymer to test for, so verification is a straightforward audit of what the packaging is actually made from. A "marine-degradable" or "compostable" plastic alternative is a fundamentally different claim, and it requires fundamentally different evidence: real degradation-rate data from a recognized test method, such as ASTM D6691, which requires at least 60% of a material's carbon content to convert to CO₂ within 180 days at 30°C in a marine microbial environment [1] — not a marketing claim about the material's design intent.

That's a meaningfully higher evidentiary bar than "contains no plastic," and it's why a degradability claim on packaging triggers a separate, specific certification requirement rather than riding along on the base Pillar 2 material audit.

Sources

  1. [1] ASTM D6691. "Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials in the Marine Environment by a Defined Microbial Consortium or Natural Sea Water Inoculum." View source →