Compostable bags are gaining popularity as a sustainable alternative to traditional plastic, but are they waterproof? This article explores how compostable materials handle moisture and what that means for storage, usage, and product performance.
Are Compostable Bags Waterproof?
In short: Compostable bags are water-resistant, but not fully waterproof.
Compostable bags are typically made from plant-based materials such as PLA (polylactic acid), PBAT (polybutylene adipate terephthalate), or cornstarch blends. These materials are designed to break down naturally in composting conditions — which include moisture, heat, and microbes.
As a result, compostable bags can repel water to a certain extent, especially for short-term use. However, extended exposure to water or high humidity will eventually weaken the bag’s structure.
Why Compostable Bags Aren’t Fully Waterproof
The key reason lies in their environmental function. Compostable bags are designed to:
- Break down under moisture in composting environments
- Avoid long-term persistence like traditional plastics
- Be safe for the soil after degradation
Making them fully waterproof would go against their intended biodegradation process.
Use Cases: When Are They Water-Resistant Enough?
Here are common scenarios where compostable bags offer sufficient moisture resistance:
- Carrying dry groceries
- Lining indoor bins for organic waste
- Short-term shipping in dry environments
- Packaging lightweight products
However, for wet or oily waste, or for products needing long exposure to moisture (e.g., frozen goods), you may need additional protection such as:
- A double layer
- Moisture barrier lining (still compostable options exist)
- Switching to a home compostable film with improved resistance
Can Compostable Bags Be Made More Water-Resistant?
Yes, to a certain degree. Some manufacturers offer custom compostable films with increased thickness or barrier coatings (still within compostable certification limits). These options may help improve performance for specific use cases.
At Hemcbags, we offer tailored solutions including:
- Custom thickness (up to 80 microns)
- Multi-layer compostable materials
- Sealable water-resistant finishes
Conclusion
Compostable bags are not 100% waterproof — and that’s by design. They provide adequate water resistance for most short-term and dry-use applications but should be used with caution in prolonged wet environments.
If you’re sourcing compostable bags for your business and need advice on moisture performance, feel free to contact us or request a quote.
FAQs
Q1: Can compostable bags hold liquids?
A: Only for a short time. They are not designed for liquid storage and may begin breaking down if exposed too long.
Q2: Can compostable mailers survive rain during delivery?
A: Most can resist light rain if delivered quickly, but we recommend additional protection if shipping in wet climates.
Q3: Are there waterproof compostable materials available?
A: Some materials offer better resistance, but complete waterproofing isn’t compatible with compostability standards.
Q4: How can I improve water resistance for my packaging needs?
A: Choose thicker film, double-bagging, or inquire about coated compostable options.
