Polylactic acid (PLA) is one of the most widely used bioplastics today, found in everything from food packaging to 3D printing filaments. Marketed as an eco-friendly alternative to traditional petroleum-based plastics, PLA is often labeled “biodegradable” and “compostable.” But what does that really mean? Does PLA break down naturally in the environment, or does it require specific conditions to decompose?
While many consumers assume that PLA will simply disappear like organic waste, the reality is more complex. Industries relying on sustainable materials need to understand PLA’s true biodegradability to make informed decisions.
Let’s examine how PLA degrades, the conditions required for breakdown, and whether it lives up to its green reputation.
What Is PLA?
PLA is a thermoplastic derived from renewable resources like corn starch, sugarcane, or cassava. Unlike conventional plastics made from fossil fuels, PLA is synthesized by fermenting plant sugars into lactic acid, which is then polymerized.
Key Properties of PLA:
- Renewable sourcing – Made from annually replenished crops.
- Low toxicity – Generally considered food-safe.
- Moderate strength & rigidity – Used in packaging, disposable cutlery, and medical implants.
- Thermoplastic behavior – Can be melted and reshaped multiple times.
However, the critical question remains: Is PLA truly biodegradable?
Understanding PLA Biodegradation: Conditions Matter
PLA is technically biodegradable—but only under specific industrial composting conditions. Unlike materials like paper or certain bioplastics that degrade in home compost or natural environments, PLA requires:
1. High Temperatures (Above 140°F/60°C)
- PLA breakdown is accelerated in industrial composting facilities, where temperatures reach 58–70°C (136–158°F).
- At these temperatures, microbes and enzymes efficiently break PLA into lactic acid, which further decomposes into CO₂, water, and biomass.
2. Controlled Humidity & Microbial Activity
- Unlike PHA (polyhydroxyalkanoates) or starch-based plastics, PLA does not degrade well in soil or marine environments.
- In a landfill (where oxygen is limited), PLA behaves more like conventional plastic, taking decades or longer to break down**.
3. Timeframe for Decomposition
- Under ideal composting conditions, PLA can degrade in 3–6 months.
- Studies show minimal degradation over several years in natural environments (ocean, soil).
PLA vs. Other “Biodegradable” Plastics
Not all biodegradable plastics behave the same way. Here’s how PLA compares:
| Material | Degrades in Soil? | Degrades in Water? | Industrial Compost Needed? | Typical Decomposition Time |
|---|---|---|---|---|
| PLA | ❌ No | ❌ No | ✅ Yes | 3–6 months (industrial) |
| PHA | ✅ Yes | ✅ Yes | ✅ Yes | 3–12 months (natural) |
| Starch-based | ✅ Yes | ✅ Partial | ❌ No | 1–6 months (natural) |
| PET (conventional plastic) | ❌ No | ❌ No | ❌ No | 100+ years |
Key Takeaway:
PLA is compostable but not naturally biodegradable. Without industrial composting, it persists in the environment much longer than advertised.
Challenges with PLA Disposal
Despite its green image, PLA faces several real-world issues:
1. Limited Industrial Composting Infrastructure
- Most cities lack facilities capable of processing PLA, leading to contamination in recycling streams.
- When PLA mixes with PET or HDPE, it can ruin entire batches of recycled plastic.
2. Misleading Consumer Perception
- Many assume PLA can be tossed in home compost or will break down in landfills—this is false.
- Without proper education, PLA products may end up causing more harm than good.
3. Performance Limitations
- PLA has a lower heat resistance than petroleum plastics, limiting its use in hot food packaging.
- It is also more brittle, making it less durable for specific applications.
Frequently Asked Questions
Q: What is polylactic acid (PLA)?
A: Polylactic acid (PLA) is a biodegradable bioplastic derived from renewable resources such as starch, which is fermented into lactic acid and then polymerized to form the PLA polymer.
Q: Is PLA biodegradable?
A: Yes, PLA is biodegradable, but its biodegradability primarily occurs under specific conditions, such as in industrial composting facilities, where it can break down efficiently.
Q: How does the biodegradation of PLA compare to traditional plastics?
A: Unlike traditional plastics that can take hundreds of years to degrade, PLA degrades quickly in the right conditions, typically within a few months in industrial composting environments.
Q: What are the conditions required for PLA to biodegrade?
A: For PLA to degrade effectively, high temperatures, moisture, and the presence of microorganisms, which are typically found in industrial composting facilities rather than in a backyard compost, are required.
Q: Can PLA be recycled?
A: Yes, PLA can be recycled, but specific recycling processes are required. It is essential to check if local recycling facilities accept PLA plastics, as they are not universally recyclable like other polymers.
Q: What are the environmental benefits of using PLA as an alternative to conventional plastics?
A: PLA is considered environmentally friendly because it is made from renewable resources, reduces reliance on fossil fuels, and can help mitigate plastic waste through its biodegradable and compostable properties.
Q: What is the difference between compostable plastic and biodegradable plastic?
A: Compostable plastic, such as PLA, breaks down into organic matter in a composting environment, while biodegradable plastic may not necessarily decompose completely or safely in natural settings. PLA is both biodegradable and compostable under the right conditions.
Q: How does the molecular weight of PLA affect its properties?
A: The molecular weight of PLA influences its mechanical properties and degradation rate; higher molecular weight PLA generally exhibits better strength and slower degradation, while lower molecular weights may degrade faster.
Q: What happens to PLA if it ends up in a landfill?
A: If PLA is disposed of in a landfill, its biodegradation process is significantly slowed due to the lack of optimal conditions such as heat and moisture, resulting in a longer lifespan similar to conventional plastics.
The Bottom Line
PLA is a step toward sustainability but is not a perfect solution. While it can biodegrade under strict industrial composting conditions, it behaves like conventional plastic in landfills or natural environments. Understanding PLA’s limitations is crucial for businesses and consumers looking to reduce plastic waste.
If you’re using PLA:
✔ Verify local composting facilities that accept it.
✔ Avoid mixing with regular recycling to prevent contamination.
✔ Consider alternative bioplastics (like PHA) for applications requiring natural degradation.
PLA is valuable in shifting toward greener packaging, but true sustainability requires proper disposal systems and consumer awareness. PLA can be part of the solution when handled correctly—but only if we acknowledge its real-world limitations.
Choose wisely, and ensure your eco-friendly efforts bring real environmental benefits, not just greenwashed promises.
