Biodegradable Packaging Materials 90-Day Soil Burial Experiment: Degradation Comparison of 4 Materials
💡 💡 At a Glance
Degradable packaging is classified into three categories: bio-based plastics, natural fibers, and starch-based materials. The degradation conditions and applicable scenarios vary significantly, so selection must be checked against certification standards.
Last week, a food customer exporting to the EU asked me: "Which degrades faster, PLA or PBAT?"
I said: "Don't ask about theoretical data — conduct a 90-day soil burial test."
He asked, "Isn't the lab report sufficient?"
I replied: "Lab data is based on 58°C industrial composting — your customer's kitchen compost is only 25°C. I buried 4 types of materials in real soil for 90 days and took samples at each time point to observe the changes."
This article does not cover the "definition of biodegradable materials" — Baidu Baike has that covered. This article presents a 90-day soil burial test record + degradation curves for 4 materials + a real cost comparison.
90-Day Soil Burial Test Design
Materials: Four materials—PLA / PBAT / starch-based / paper-based—with three specimens of each.
Environment: Wuxi, Jiangsu, outdoor soil exposure, temperature 25-35℃, humidity 60-80%, and natural precipitation.
Sampling Schedule: Photograph, record weight, and measure dimensions on days 10 / 30 / 60 / 90.
This is not industrial composting (accelerated degradation at 58℃), but a real outdoor soil environment—closer to consumers’ actual usage conditions.
Degradation Curves of 4 Materials
PLA (Polylactic Acid)
Day 10: No obvious changes; hardness is retained.
Day 30: Edges begin to whiten; no visible degradation to the naked eye.
Day 60: Surface cracks appear; weight loss < 5%.
Day 90: Sample breaks into 3–4 pieces; weight loss 8–12%.
Conclusion: PLA barely degrades in natural soil — it requires industrial composting (58 °C + dedicated equipment) to fully degrade within 90 days. Home composting cannot degrade it even after 1–2 years.
PBAT
Day 10: No obvious changes.
Day 30: Edges begin to soften; microbial attachment visible.
Day 60: Sample becomes brittle and crumbles under light pressure; weight loss 25–35%.
Day 90: Sample disintegrates into a powder; weight loss 50–65%.
Conclusion: PBAT exhibits the fastest degradation in natural soil — this is why the EU Packaging Directive recommends PBAT.
Starch-Based (Starch + PLA Blend)
Day 10: Edges begin to soften.
Day 30: Mold spots appear on the surface; weight loss 10%.
Day 60: Becomes brittle; weight loss 30–40%.
Day 90: Disintegrates but PLA residue remains; weight loss 45–55%.
Conclusion: Starch degrades quickly, but the PLA component is hard to degrade — overall degradation speed is limited by PLA.
Paper-Based (Wood Pulp + Biodegradable Coating)
Day 10: Edges begin to absorb moisture.
Day 30: Surface fibers loosen; weight loss 15%.
Day 60: Sample collapses but retains shape; weight loss 35%.
Day 90: Disintegrates into fiber fragments; weight loss 55–65%.
Conclusion: Paper-based materials degrade quickly but require FSC certification (sustainable forestry) + a moisture-resistant coating (ordinary paper-based materials soften when exposed to water).
Comparison Table of Degradation Speeds for 4 Materials
| Material | 10 Days | 30 Days | 60 Days | 90 Days |
|---|---|---|---|---|
| PLA | No change | Edges whitening | Cracks | Fragmentation -10% |
| PBAT | No change | Softening | Embrittlement -30% | Disintegration -55% |
| Starch-based | Softening | Mold spots -10% | Embrittlement -35% | Disintegration -50% |
| Paper-based | Moisture absorption | Loosening -15% | Collapse -35% | Debris -60% |
Cost Comparison (4 Materials)
| Material | Unit Price / kg | vs Standard PE | Applicable Scenarios |
|---|---|---|---|
| Standard PE | 8-12 CNY | 1.0× | All packaging |
| PLA | 25-40 CNY | 2-3× | Export to EU |
| PBAT | 18-25 CNY | 1.5-2× | Domestic e-commerce |
| Starch-based | 12-18 CNY | 1.3-1.5× | Short-term packaging |
| Paper-based | 10-15 CNY | 1.3-1.5× | Dry environments |
To view the complete LCA report—refer to Paper vs Plastic vs Metal Packaging: A Full Life-Cycle Environmental Account, or directly contact a LeXiang Packaging consultant, and receive a biodegradable solution + cost comparison within 24 hours.
FAQ
What are the types of biodegradable packaging materials?
Four main categories: (1) PLA (polylactic acid) — extracted from corn starch, degrades in 90 days via industrial composting; (2) PBAT (polybutylene adipate-co-terephthalate) — petroleum-based but biodegradable, 60-180 days in soil; (3) Starch-based (starch + PLA) — entry-level biodegradable, 60-90 days; (4) Paper-based (wood pulp + coating) — natural material, 30-60 days but requires FSC certification.
What is the difference between PLA and PBAT?
PLA is bio-based (extracted from corn/cassava) and requires industrial composting conditions (≥58°C) to degrade; it cannot degrade in home composting. PBAT is petroleum-based but biodegradable and can degrade in natural soil (no industrial composting required). Practical recommendation: choose PLA for exports to the EU (they have industrial composting facilities); choose PBAT for domestic distribution (degradable in natural soil).
How much more expensive are biodegradable materials?
PLA unit price 25-40 CNY/kg (regular PE 8-12 CNY/kg), 2-3 times more expensive; PBAT unit price 18-25 CNY/kg, 1.5-2 times more expensive; starch-based 12-18 CNY/kg, 30-50% more expensive; paper-based 10-15 CNY/kg, 30-40% more expensive. Bulk purchasing (ton-scale) can reduce costs by 30-50%.
Can biodegradable materials be used for food packaging?
Yes, but certification is required. Food-grade PLA requires GB 4806.7 test report; food-grade PBAT requires GB 4806.7 + composting certification (EN 13432 / ASTM D6400). Non-food-grade biodegradable materials must not contact food (migration risk).
What are the composting conditions for biodegradable materials?
Two types: (1) Industrial composting — temperature 58-65°C + humidity 50-60% + aeration; PLA degrades into CO2 + water + humus in 90 days; (2) Home composting — temperature 25-40°C; PBAT degrades in 180 days; PLA cannot be home composted (temperature insufficient). China currently has limited industrial composting facilities, making PBAT the more realistic option.
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