The Compostable Confusion
Walk into any store selling "compostable" products and you will see a bewildering array of labels: OK Compost HOME, OK Compost INDUSTRIAL, BPI Certified, EN 13432, ASTM D6400, AS 5810. Most consumers — and even many procurement managers — cannot tell the difference. This confusion leads to contamination in composting streams, greenwashing accusations, and missed opportunities for genuine circular packaging.
The fundamental distinction is simple: industrial compostable materials require controlled high-temperature facilities (55-60°C) to break down, while home compostable materials must degrade in your backyard compost bin at ambient temperatures (20-30°C). Home compostable is the stricter standard — anything that passes home composting will also pass industrial composting, but not vice versa.
PHA (Polyhydroxyalkanoates) is unique among bioplastics because it passes BOTH standards. PLA, by contrast, only passes industrial composting. This single fact makes PHA the superior choice for consumer-facing products where disposal infrastructure is uncertain.
Degradation Conditions: Side by Side
| Parameter | Home Compost | Industrial Compost |
|---|---|---|
| Temperature | 20-30°C (ambient) | 55-60°C (thermophilic) |
| Humidity | 40-60% moisture | 50-65% moisture (controlled) |
| Microbial Activity | Natural soil/compost microbes | Optimized thermophilic bacteria |
| Oxygen | Passive aeration (turning) | Forced aeration systems |
| Degradation Time (PHA) | 180-365 days | 90-180 days |
| Degradation Time (PLA) | Does NOT degrade | 90-180 days |
| Certification Standard | TUV OK Compost HOME / AS 5810 | EN 13432 / ASTM D6400 |
| Testing Body | TUV Austria / ABA | DIN CERTCO / BPI / TUV |
| Residue Limit | <10% after 12 months | <10% after 12 weeks |
| Ecotoxicity Test | Required (plant growth) | Required (plant growth) |
PHA Degradation Data by Environment
PHA degradation speed depends on temperature, moisture, and microbial population density. Here is measured data from PHApack laboratory trials (ASTM D6691 / ISO 22403 methods):
| Environment | Degradation Time | Notes |
|---|---|---|
| Home compost (25°C) | 180-365 days | Depends on pile management, moisture, and turning frequency |
| Industrial compost (58°C) | 90-180 days | Consistent results due to controlled thermophilic conditions |
| Soil burial (15-20°C) | 240-480 days | Slower due to lower microbial density |
| Marine (10-15°C) | 365-730 days | Cold water slows enzymatic hydrolysis significantly |
| Landfill (anaerobic) | 3-7 years | Limited oxygen reduces microbial activity |
Why PLA Fails at Home
PLA (Polylactic Acid) requires temperatures above 55°C to initiate the hydrolysis chain reaction that breaks its polymer backbone. In a home compost bin at 20-30°C, this reaction simply does not begin. Independent studies show PLA retains over 95% of its mass after 12 months in home compost conditions. It fragments into smaller pieces but does not mineralize — creating the same microplastic problem it was supposed to solve.
PHA, by contrast, is degraded by extracellular PHA depolymerase enzymes produced by common soil bacteria (Pseudomonas, Bacillus, Streptomyces). These organisms thrive at ambient temperatures. The enzymatic hydrolysis of PHA's ester bonds proceeds efficiently at 20-30°C, which is why PHA passes the TUV OK Compost HOME standard while PLA does not.
Certification Standards Explained
Home Compostable
- TUV OK Compost HOME (Europe)
- AS 5810 / ABA (Australia)
- NF T51-800 (France)
- Test: 20-30°C, 12 months, <10% residue
- Ecotoxicity: plant growth test required
Industrial Compostable
- EN 13432 (Europe)
- ASTM D6400 (USA)
- BPI Certified (USA)
- Test: 58°C, 12 weeks, <10% residue
- Requires industrial facility access
Consumer Choice Guide: Which Certification for Which Product?
The right certification depends on how the product will actually be disposed of. Here is our recommendation matrix:
Backyard disposal, no industrial facility access needed
Can go directly into home compost bin with food scraps
Collected via commercial composting programs
Plowed directly into field soil after harvest
Dual certification covers both disposal routes
The PHA Advantage: One Material, Every Disposal Route
The ultimate advantage of PHA over PLA and PBAT is disposal flexibility. A PHA product certified to TUV OK Compost HOME automatically satisfies industrial composting requirements as well. It also degrades in soil and marine environments. This means:
- No dependency on industrial composting infrastructure (which is scarce in most countries)
- Consumers can compost at home without special equipment
- If accidentally littered, the product still biodegrades in soil or water
- No microplastic residue at any stage of degradation
- Brands can market "compostable anywhere" without greenwashing risk
Key Takeaways
- Home compost: 20-30°C, 12 months. Industrial compost: 55-60°C, 12 weeks.
- Home compostable is the stricter standard — it implies industrial compostable too.
- PHA degrades via PHA depolymerase enzymes at ambient temperature. PLA does not.
- PHA home compost degradation: 180-365 days. PLA: does not degrade at home.
- For consumer products with uncertain disposal: always choose home compostable PHA.
Get Home Compostable PHA Samples
Request free samples of our TUV OK Compost HOME certified products. Test degradation in your own compost bin. Technical datasheets and certification documents included.
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