As compostable packaging becomes more common, understanding the science behind how these materials break down and under what conditions is key to protecting compost quality and building public trust.
At BPI, compostability isn’t just a label—it’s a scientifically defined process, verified through rigorous testing and third-party review. Whether designed for industrial or backyard systems, certified compostable products must meet clear, measurable performance benchmarks that prove they truly return to the earth safely.
The term “biodegradable” is often misunderstood. It simply means a material can be broken down by microbes, without specifying how long it takes, what remains behind, or whether the result is safe for soil.
“Compostable,” by contrast, means the material:
BPI Certification ensures that products meet these criteria based on the internationally recognized ASTM D6400 (for plastics) and ASTM D6868 (for coatings on paper and fiber). Certified products must pass all three scientific benchmarks:
These standards ensure that certified products perform like organic waste—not conventional plastic—within composting environments. You can learn more about the lab tests used to verify compostability here.
Certified compostables are designed for aerobic (oxygen-rich), thermophilic (heat-loving) environments typical of commercial composting facilities, where heat and microbial activity drive efficient degradation.
These controlled conditions allow materials such as PLA, PBAT, PHA, PCL, and PBS to fully decompose—transforming into CO₂, water, and biomass with no persistent plastic fragments.
Not all composting happens on an industrial scale. Backyard systems operate at lower temperatures and less consistent conditions than commercial facilities.
To address this difference, BPI developed the Home Compostability Certification.
In home composting, breakdown relies primarily on mesophilic microbes and ambient heat, rather than the sustained thermophilic conditions of industrial systems. That means only select materials—engineered with faster hydrolysis and biodegradation—perfomance can be certified for home composting.
By clearly labeling which products are suitable for which systems, BPI helps consumers make informed choices and prevents confusion or contamination between home and commercial composting streams.
Whether in a large-scale facility or a backyard bin, the same biological principles drive composting.
Step 1: Hydrolysis & Enzymatic Action
Moisture and microbial enzymes break down polymer chains into smaller molecules (oligomers and monomers). Certified materialsare designed to biodegradeefficiently under heat and moisture.
Step 2: Microbial Metabolism
Microbes consume these smaller molecules, converting carbon into CO₂, water, and new biomass. This marks complete biodegradation, leaving no persistent microplastics or harmful residues beind.
Step 3: Compost Maturity & Safety Testing
After the active composting phase, the finished compost is screened and tested to ensure it meets safety standards for:
The ASTM D6400 and ASTM D6868 specifications are harmonized with ISO guidelines and validated through reproducible laboratory testing.
BPI Certification adds multiple layers of accountability by requiring:
The addition of home compost certification extends this same rigor to lower-temperature systems, ensuring that certified materials perform predictably and safely wherever they’re used.
Certified compostable products are engineered to perform their intended function during use—for example, a compostable coffee cup keeps beverages hot and maintains its structure while holding liquid. After use, these products are designed to:
This is not true of uncertified “biodegradable” or “plant-based” materials, which often fragment into persistent microplastics.
By combining robust data, transparent labeling, and third-party verification, BPI Certification—both Commercial Only and Commercial and Home—ensures that compostable products truly work as intended. That’s how we protect composters, maintain soil health, and build a more trustworthy, circular organics system. Certified compostable products are designed to perform during use and then break down efficiently alongside food scraps into natural components—supporting soil health and circular systems.
Dive even deeper into how compostables break down at a molecular level in this blog: Why Some Plastics Compost and Others Don't, co-authored by Dr. Anthony Keyes of Natur-Tek.
