What Are Compostable Bags?

Every day, I see more plastic waste piling up in our landfills. As someone who has worked in environmental product sourcing for over a decade, I know we need better solutions for our waste management problems.

I want to share what I’ve learned about compostable garbage bags through my years of experience. These bags are changing how we think about waste disposal, and I believe it’s important to understand both their benefits and limitations.

What Does “Compostable” Mean?

Compostable garbage bags are bags made from plant-based materials like cornstarch that break down completely into natural elements within 12 months in industrial composting conditions. They leave no toxic residue and produce zero pollution during decomposition.

Renewable raw materials: mainly from crops, reducing dependence on oil.
Non-toxic decomposition: the final products are water, carbon dioxide and organic fertilizer.

Features:

Certification standards: must pass strict tests (such as a decomposition rate of more than 90% within 90 days).
Applicable scenarios: It is necessary to distinguish between industrial composting (high temperature) and home composting (normal temperature).

What Are Compostable Bags Made Of

Compostable bags are made from biodegradable materials that break down into natural elements in composting conditions, leaving no toxic residue. They are typically derived from renewable plant-based sources or bio-based polymers. Here are the most common materials used:

1. Plant-Based Starches (PLA – Polylactic Acid)
   Cornstarch, sugarcane, or potato starch: These starches are fermented and processed into PLA, a common compostable plastic alternative.
   Properties: Flexible, biodegradable, but requires industrial composting to break down efficiently.
2. PBAT (Polybutyrate Adipate Terephthalate)
   A petroleum-based polymer that is biodegradable and often blended with PLA to improve flexibility (e.g., in compostable trash bags).
3. PHA (Polyhydroxyalkanoates)
   Made by bacterial fermentation of sugars or lipids (e.g., from corn or vegetable oil).
   Fully biodegradable in soil, water, and compost.
4. Cellulose-Based Materials
   Derived from wood pulp, cotton, or other plant fibers.
   Often used for lightweight compostable packaging.
5. Mushroom & Mycelium-Based Materials
   Some brands use fungal mycelium grown on agricultural waste to create durable, compostable materials.

Type of Compostable Bags

Industrial Compostable Bags

Require high-temperature composting (50–60°C) found in industrial facilities.
Decomposition timeframe: Typically 3–6 months.
Common uses: Municipal organic waste collection, restaurant composting programs.

Home Compostable Bags

Designed to break down in backyard compost heaps (lower temperatures).
Decomposition timeframe: 6–12 months.
Common uses: Household food waste disposal, garden composting.

How Do Compostable Bags Work?

1. Microbial Action

• Microorganisms (bacteria, fungi) digest the organic materials (e.g., cornstarch, PBAT).
• Enzymes break down long polymer chains into smaller molecules.

2. Heat & Moisture

• Industrial composting: High temperatures (50–60°C) speed up breakdown (3–6 months).
• Home composting: Slower decomposition (6–12 months) due to lower heat.

3. Final Breakdown into Organic Matter

• Fully composted bags turn into:
  • CO₂ (minimal emissions compared to plastic incineration).
  • Water.
  • Nutrient-rich humus (great for soil).

Benefits of Using Compostable Bags

1. Reduces Plastic Pollution

• Traditional plastics persist for centuries; compostables break down cleanly.
• No microplastics left behind.

2. Lowers Carbon Footprint

• Made from plants (e.g., corn, sugarcane), which absorb CO₂ as they grow.
• Production emits fewer greenhouse gases than petroleum-based plastics.

3. Supports Circular Economy

• Waste becomes compost → enriches soil → grows more plants → creates new bags.
• Closes the loop sustainably.

4. Safe for Food & Organic Waste

• Non-toxic decomposition (unlike biodegradable plastics, which may leave chemicals).
• Ideal for food scraps, yard waste, and compostable packaging.

5. Encourages Better Waste Habits

• Promotes composting and reduces landfill dependency.
• Helps municipalities divert organic waste from landfills (where it emits methane).

Certification Standards for Compostable Bags

International Standards:

• ASTM D6400 (US): Ensures bags compost properly in industrial settings.
• EN 13432 (EU): Tests biodegradability, disintegration, and ecotoxicity.
• AS 4736 (Australia): The leading standard for compostable packaging in Australia.

Certification Labels:

• OK Compost (TÜV Austria): One of the most trusted certifications.
• BPI Certified (US): Backed by the Biodegradable Products Institute.
• Seedling Logo (EU): Indicates compliance with EN 13432.

Compostable vs. Biodegradable Bags

• Compostable bags require specific conditions (moisture, heat, microbes) to break down completely.
• Biodegradable bags break down naturally but may leave microplastics and lack strict certifications.

What Are the Disadvantages of Compostable Bags?

When I first started working with compostable bags, I noticed some customers were frustrated by certain limitations. The bags seemed less durable than traditional plastic, and the higher cost made some buyers hesitate.

The main disadvantages of compostable bags include higher production costs (usually 20-30% more than plastic), shorter shelf life (typically 12-18 months), and lower tensile strength. They also need specific composting conditions to break down properly.

Cost Factors

The higher price of [compostable bags¹]comes from:

• More expensive raw materials
• Specialized manufacturing processes
• Smaller production scales
• Certification requirements

Storage Requirements

These bags need proper storage conditions²:

• Cool, dry environment
• Away from direct sunlight
• Used within recommended timeframe
• Protected from high humidity

What Is the Difference Between Compostable and Plastic?

Many of my clients ask about the real differences between these materials. The confusion is understandable – they look similar but have completely different environmental impacts.

Compostable bags are made from plant-based materials that decompose into natural elements, while plastic bags are made from petroleum products that never fully break down. Compostable bags leave no toxic residue, unlike plastic which creates microplastics.

Material Comparison Table

Feature	Compostable Bags3	Plastic Bags
Source	Plant-based materials	Petroleum products
Decomposition4	3-12 months	500+ years
End Product	Natural elements	Microplastics
Environmental Impact5	Biodegradable	Persistent pollution
Strength	Moderate	High
Cost	Higher	Lower

How Quickly Do Compostable Bags Break Down?

Through my experience with various composting facilities, I’ve seen firsthand how decomposition times can vary. The process depends heavily on specific environmental conditions.

Under ideal industrial composting conditions (temperature 55-60°C, proper moisture and microorganisms), compostable bags break down in 90-180 days. In home composting conditions, it may take 6-12 months for complete decomposition.

Decomposition Factors

Several key elements affect breakdown time:

1. Temperature Control

   • Industrial facilities maintain optimal heat
   • Home composting varies with weather
   • Higher temperatures speed degradation

2. Moisture Levels

   • Proper humidity aids microorganism activity
   • Too much water slows the process
   • Too little water halts decomposition

3. Oxygen Access

   • Regular turning helps decomposition
   • Proper layering ensures air flow
   • Anaerobic conditions slow breakdown

Future Trends in Compostable Bags

1. Material Innovations: Researchers are developing faster-decomposing, more durable bioplastics.
2. Cost Reduction Efforts: Scaling up production will make them more affordable.
3. Policy Changes: Governments are banning single-use plastics, driving demand for compostable alternatives.

Conclusion

Compostable garbage bags offer a real solution to plastic pollution. While they have some limitations, their ability to break down naturally makes them an important tool for sustainable waste management.