What Is A Compostable/Biodegradable Mailer | Eco-Mailer Guide

What it is

A compostable/biodegradable mailer is a flexible shipping envelope or pouch manufactured from materials that can be broken down by microorganisms. "Biodegradable" is a broad term meaning a material will eventually degrade in the environment under some conditions. "Compostable" is more specific: a compostable mailer is designed to convert into carbon dioxide, water, inorganic compounds and biomass within a defined timeframe, leaving no toxic residue, and commonly meets recognized standards (for example ASTM D6400 or EN 13432). Examples of compostable materials include certain bioplastics (PLA, PHA, PBAT blends), uncoated kraft paper, or paper treated with certified compostable coatings.

How compostable and biodegradable differ

It’s important to understand the distinction: biodegradable simply indicates eventual breakdown. Compostable implies that the material will biodegrade under composting conditions within a specified period and result in non-toxic residues that support plant growth. Compostable claims are meaningful only when backed by certification (for example BPI in North America, OK Compost in Europe) and when the local composting infrastructure can actually process the material.

Materials and construction

Compostable mailers are usually made from one or more of the following:

• Unbleached kraft paper: sturdy, recyclable, and often home-compostable when untreated.
• Bioplastics: PLA (polylactic acid), PHA (polyhydroxyalkanoates), or blends like PLA+PBAT used for clear compostable plastic-like mailers.
• Coated paper: kraft or paper with a certified compostable coating to improve moisture resistance.
• Compostable adhesives, tapes, and print inks: needed to keep the whole package compostable.

When and where they’re used

Compostable mailers are commonly used by e-commerce retailers, subscription box services, direct-to-consumer apparel brands, small businesses, and eco-focused merchants who want to reduce the environmental footprint of single-use shipping packaging. Typical use cases include apparel, soft goods, documents, accessories, and other low-moisture, non-fragile items.

Examples:

• A small clothing brand ships t-shirts in a kraft mailer with compostable tape and prints disposal instructions on the back.
• A subscription food sample company uses certified compostable mailer liners for dry, shelf-stable samples.

Performance considerations

Compostable mailers can match many functional properties of conventional plastic mailers—tear strength, punctuation resistance, and water tolerance—when properly engineered. However, they can differ in important ways:

• Moisture resistance: Some compostable materials are less water-resistant than polyethylene; coatings or bioplastic layers can improve this but must also be compostable.
• Durability: Heavier or sharp items may puncture compostable mailers more easily than thick plastic films.
• Heat and storage sensitivity: Certain bioplastics can warp or lose strength at high temperatures or with prolonged UV exposure—important for warehouse storage and transit in hot climates.
• Compatibility with packaging equipment: Verify automated sealing machines and labelers work with the material to avoid production delays.

End-of-life: industrial vs home composting

Many commercially available compostable mailers require industrial composting conditions: sustained high temperatures (around 55–60°C), controlled humidity, and specific microbial activity to fully break down within the certified timeframe. Home compostable items are formulated to degrade in typical backyard compost piles at lower temperatures but are less common for mailers with higher barrier requirements. Always check certification labels and instructions:

• Industrial compostable: Requires municipal or commercial organics processing.
• Home compostable: Can break down in backyard systems; look for explicit home-compostable certification.

How to use and dispose

To get the environmental benefit, correct use and disposal are crucial:

1. Choose certified products: Look for recognized certifications (ASTM D6400, EN 13432, BPI, OK Compost) and credible manufacturer documentation.
2. Prepare the package: Remove non-compostable components such as conventional plastic labels, synthetic window films, or non-certified tape. Use compostable tape and labels when possible.
3. Educate customers: Clearly label the mailer with disposal instructions—e.g., "Compostable — industrial composting required"—and include a short explanation or QR code linking to local composting resources.
4. Dispose properly: If your city has organics collection, instruct customers to place mailers in that bin. Otherwise, advise on home compostability if applicable or point customers to drop-off composting sites.

Benefits

Compostable mailers can reduce reliance on fossil-fuel plastics, potentially lower greenhouse gas emissions over life cycle if properly composted, and appeal to eco-conscious consumers. They can also keep packaging out of recycling streams, avoiding contamination of plastic recycling.

Limitations and trade-offs

Compostable mailers are not a universal solution. Key limitations include:

• Infrastructure gap: Without accessible industrial composting, many compostable items will end up in landfill where decomposition is slow and benefits are diminished.
• Cost: Compostable materials and certified components (tape, inks, labels) often cost more than conventional alternatives.
• Potential for greenwashing: Claims must be substantiated by certification and transparent end-of-life guidance.
• Contamination risk: Non-compostable closures, stickers and mixed-material construction can ruin compostability.

Best practices

To implement compostable mailers effectively:

• Verify certification for the whole package system (mailer film, adhesive, tape, inks).
• Design for single-material construction where possible or ensure all materials are compostable.
• Test packaging on your products for protection, sealing, and compatibility with automated equipment.
• Provide clear, simple disposal instructions on the mailer and on order confirmation emails.
• Work with suppliers who provide documentation and chain-of-custody information about feedstock and processing.
• Consider lifecycle trade-offs—if municipal composting isn’t available, recyclable paper mailers or recycled-content plastic may be a better local choice.

Common mistakes to avoid

Beginner-friendly warnings:

• Assuming compostable always equals "safe everywhere"—many types need industrial composters.
• Using non-certified materials and making unverified claims.
• Failing to remove or replace non-compostable tapes, labels or windows.
• Choosing compostable mailers for wet, heavy, or sharp products without adequate testing.

Final advice

Compostable and biodegradable mailers can be an effective part of a sustainable packaging strategy, especially for brands that can provide clear end-of-life routes and educate customers. Start by auditing local composting infrastructure, sourcing certified materials, trialing them with your fulfillment processes, and communicating disposal steps to customers. When done correctly, compostable mailers reduce reliance on conventional plastics and support a circular approach to packaging—but success depends on thoughtful design, certification, and accessible composting systems.