Advice

Ask Lumi: Is Compostable Plastic Better for the Planet?

By Katelan Cunningham · November 12, 2019

A few months ago we launched Compostable Poly Mailers on Lumi and many of you sent us insightful questions. The answers aren't simple, but worth understanding, especially for ecommerce companies.

The big picture. Compostable plastic is primarily derived from renewable resources instead of petroleum, so if you’re already shipping in standard poly mailers made from LDPE, compostable poly mailers are a step in the right direction. But if recovery is your highest priority, paper mailers are the best choice because access to recycling and composting is much more readily available. 

The nitty gritty. Read on to get a better understanding of the complexities of compostable plastics so you can make better informed decisions. 

  1. What’s the difference between biodegradable and compostable packaging?
  2. What are the pros and cons of compostable poly when it comes to sustainability?
  3. I've read about flaws in the waste management system of the United States. Are compostable plastics actually helping?
  4. Why don’t all industrial composting facilities accept compostable plastic?
  5. How are compostable plastics certified?
  6. How do I explain to customers how to compost packaging?
  7. Is it better to compost plastic at home or at an industrial facility?
  8. If my customers don't want to compost it, how should they dispose of compostable plastic packaging?
  9. How is composting the plastic better than letting it end up in a landfill?
  10. What are compostable poly mailers made of?
  11. How long do compostable poly mailers take to compost?
  12. How do compostable poly mailers compare to standard LDPE poly mailers?
  13. What is the shelf life of compostable poly mailers?
  14. What should I consider before making the switch to compostable poly mailers?

1. What’s the difference between biodegradable and compostable packaging?

Everything that is compostable is biodegradable, but not everything that is biodegradable is compostable.

If something is compostable, it will break down into nutrient-rich material for soil using the right combination of heat, moisture, and oxygen. If something is biodegradable, it will break down in nature over an undetermined amount of time, and it will not necessarily create nutrient-rich soil.

Our dictionary of sustainability properties goes into more detail about compostable versus biodegradable.

2. What are the pros and cons of compostable poly when it comes to sustainability?

In manufacturing, compostable plastics can be made from bioplastics which are a renewable resource. This is a big plus. But in recovery (after they're disposed), compostable poly mailers are only beneficial if they bypass the landfill and end up in a compost pile. In a landfill, they'll be buried under a mix of organic and nonorganic waste where they won't have the oxygen they need to biodegrade.

Alternatively, typical poly mailers are made from LDPE (low density polyethylene) which is derived from petroleum. This plastic #4 is recyclable, but the thin film gets caught in processing machines at the plants causing major production delays. That's why, in many cities, the only recycling option for traditional poly mailers mailers is a dedicated drop-off.

With both options, recovery is an issue. Even though bioplastic poly mailers have the potential to break down into compost and LDPE mailers have the potential to be recycled into new plastic, the U.S. waste stream isn't yet optimized for these materials. In most cities, the end consumer has limited access to the ideal disposal process and any poly mailer can much more easily end up in a landfill. That's why its key — especially with plastics — to educate customers about all of their disposal options.

3. I've read about flaws in the US waste management system. Are compostable plastics actually helping?

With a strain on US recycling and landfills overflowing, there are more compost-friendly packaging materials than ever. This influx of compostable plastics has put a strain on industrial composting facilities, leaving some folks wondering if manufacturing compostable plastics is putting the chicken before the egg.

The truth is that recovery for poly mailers — whether they're compostable or recyclable — is tricky due to limited infrastructure, but it can be done. The better news is that ecommerce companies have the power to drive demand for this kind of change. 

By the numbers, Germany is the best example of successful waste management — they recycled or composted 68% of their waste in 2018, compared to just 34% here in the U.S. Of all the biodegradable waste that Germany collects, they compost over half of it. How does Germany enforce proper disposal? Public education and color coded bins in public spaces and neighborhoods, in addition to penalties for noncompliance.

4. Why don’t all industrial composting facilities accept compostable plastic?

For industrial facilities, composting is a business. The entire composting process is carefully monitored and optimized for breakdown within a few months, resulting in a top notch mixture to feed farmers’ soil. There are two challenges to compostable plastics that get in the way of their business: slow degradation time and lack of regulation.

While industrial facilities can decompose materials more quickly than someone at home, compostable plastics still decompose slower than other organic matter.

The other issue for industrial facilities is that because they're fairly new, compostable plastics are lacking regulation. Some industrial facilities don’t want to risk mislabeled or missorted plastics contaminating their compost. With bioplastic production accelerating quickly, we’re hoping to see more regulations for manufacturers and more clarity for consumers so that industrial composting facilities can build an infrastructure to accept more bioplastics in the future.

5. How are compostable plastics certified?

It's important to break down the difference between standards, certifications, certification bodies, and certificates. Increasingly, certifications are required by countries and states for any items that claim to be compostable. Here's an example of a certification label you might see on a compostable bag in Europe: 

 Ask Lumi: Is Compostable Plastic Better for the Planet?

Standards are specifications and criteria set by non-profit organizations such as ISO and ASTM. The following standards provide industrial composting specifications:

  • ASTM D6400: US standard for plastics designed to be aerobically composted in municipal or industrial facilities
  • ASTM D6868: US standard specification for end items that use plastics and polymers that are designed to be aerobically composted in municipal or industrial facilities
  • EN 13432: European standard for plastic packaging recoverable through composting and biodegradation.
  • EN 14995: European standard for any plastics recoverable through composting and biodegradation.
  • ISO 17088: Currently under development and has not been as widely used in the US and Europe

Certification labels are logos that represent a product or manufacturer's adherence to standards. Certification bodies are the organizations that approve the use of a certification label. When a manufacturer is certified, they receive a certificate number that you may see printed next to the certification label. The following certification labels were designed to represent some of the standards listed above:

  • BPI: The Biodegradable Products Institute is a nonprofit that created the BPI certification and the US certification for industrial composting based on the ASTM test methods and specifications.
  • OK Compost: TÜV AUSTRIA is a for-profit company that purchased the certification from Vinçotte. The certification was created this European certification for industrial composting based on the harmonized EN 13432 standard.
  • OK Compost Home: This European certification for home composting is also licensed by TÜV AUSTRIA with the understanding that home composting is slower.

Where does Lumi fit in in all of this? Lumi is not certifying manufacturers, however members can access certified manufacturers through the Lumi network and choose to print certified logos on their packaging.

Percentage of US Curbside Programs that Require BPI Certification on Plastics

6. How do I explain to customers how to compost packaging?

There are three ways to compost, depending on local availability:

  • Curbside: If a city picks up curbside compost, they'll have specific rules for what they accept. 
  • Dropoff: If there’s no curbside composting option, people can check the Biocycle directory to find industrial facilities in their area. 
  • At home: Compostable plastics need very high heat to break down in under a year. They should break down in home bins within 12-18 months with the right combination of heat, moisture, air, and volume. Cal Recycle has a great guide to home composting.

7. Is it better to compost plastic at home or at an industrial facility?

We don't have enough data to answer that question yet. At home you can ensure that the plastic has composted fully. If your local industrial facilities accept plastic, they can likely break it down faster due to the higher heat method.

8. If my customers don't want to compost it, how should they dispose of compostable plastic packaging?

If someone can’t compost it, then compostable plastic should go in the trash. It may seem like recycling would be better, but that’s not the case. Compostable plastics are not made to be reused.

In a recycling facility, compostable plastics will slow down the flow as they need to be removed from streams of recyclable plastics like #4 (LDPE) and #2 (HDPE). If it's thrown in a recycling bin, compostable plastic will ultimately end up in a landfill where it may not get enough oxygen or moisture to degrade.

9. How is composting the plastic better than letting it end up in a landfill?

It all comes down to gas. In a landfill, compostable and non-compostable waste is piled multiple stories high. Anything buried under the top few layers relies on anaerobic (without oxygen) decomposition. This anaerobic environment produces a combination of methane gas and carbon dioxide. Methane has over 25 times the greenhouse gas potential of carbon dioxide and contributes more rapidly to global warming. 

Compost piles are aerobic as they're turned to provide oxygen throughout. Adding oxygen drastically cut down on the amount of methane gas produced. 

Pura Vida ships in compostable poly mailers produced through the Lumi Network.

10. What are compostable poly mailers made of?

The compostable poly mailers currently available from factories in the Lumi Network are made from a blend of PLA (Polylactic Acid) and PBAT (Adipate Polybutylene Terephthalate). This combo is the most accessible bioplastic for poly mailers right now. 

PLA is derived from renewable biomass, typically fermented plant starch from corn. On its own, PLA is somewhat brittle, but when it's combined with PBAT — a petroleum derivative — it becomes stronger and more flexible.

11. How long do compostable poly mailers take to compost?

Typically, they will compost in 12-18 months in ideal conditions. Compostable plastics can take longer to break down than other organic matter because only microbes bred at high temperatures (over 140° F) can break down the long PLA molecule.

12. How do compostable poly mailers compare to standard LDPE poly mailers?

Compostable poly mailers from factories in the Lumi Network are comparable to standard poly mailers in strength, weight, and print capabilities. They can cost 5-20% more than standard LDPE poly mailers.

13. What is the shelf life of compostable poly mailers?

Compostable poly mailers have a shelf life of 9-18 months, depending on moisture and temperature. For the longest shelf life, store them in a dry, cool environment.

14. What should I consider before making the switch to compostable poly mailers?

If you're looking to make your packaging more sustainable, the first step that we recommend is to find ways to use less of it. Whatever packaging you use should have instructions for its next life, whether it should be reused, recycled, or composted.

If recovery is your sustainability priority, paper mailers may be a better because they're easy to recycle and compost. Keep in mind that paper is heavier to ship than poly, so your overall transit emissions will go up.


This Q&A just scratches the surface of all the intricacies involved in composting plastics. Do you have more questions? Tweet @Lumi with the hashtag #asklumi

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