Compostable Bioplastics Explained
Compostable bioplastics break down into carbon dioxide, water, and biomass under defined composting conditions - but only when they are certified to a real standard. This guide from Earth Conscious Solutions (ECS), integrator for Nant Biorenewables finished bioplastics and Calcean mineral fillers, explains what compostable actually means, how it differs from biodegradable, the difference between home and industrial composting, and how mineral fillers reduce plastic content.
In this guide
What this compostable bioplastics guide covers
Fundamentals
What is a compostable bioplastic?
A compostable bioplastic is a plastic that, under defined composting conditions, breaks down into carbon dioxide, water, and biomass within a set time and leaves no toxic residue. The word that matters is "defined": a material is only genuinely compostable if it meets a published standard - in North America that is ASTM D6400 (or ASTM D6868 for coated paper), and in Europe it is EN 13432. Certification marks such as BPI Certified Compostable and TUV OK Compost verify that a product actually passed those tests.
"Bioplastic" and "compostable" are not the same thing, which is a common source of confusion. Bioplastic refers to where the material comes from (partly or wholly bio-based rather than fossil-based). Compostable refers to how it ends of life. A plastic can be bio-based but not compostable, or fossil-based but compostable. This guide is about the compostable end-of-life claim, which is the one that has to be certified.
ECS supplies finished compostable products and resins through Nant Biorenewables, including certified compostable tableware and straws, and pairs them with mineral fillers from Calcean where a formulation calls for reduced polymer content.
Comparison
Compostable vs biodegradable - what is the difference?
This is the single most important distinction in the category. "Biodegradable" has no standardized definition, no required timeframe, and no required end conditions - almost anything will biodegrade eventually, so the word alone tells a buyer nothing. "Compostable" is specific: it requires that the material break down into carbon dioxide, water, and biomass within a defined period under defined conditions, with no toxic residue, as verified against ASTM D6400 or EN 13432.
In practice, that means you should treat an uncertified "biodegradable" claim with skepticism and look instead for a compostability certification mark. For the full breakdown - including why a bare "biodegradable" label can be a greenwashing red flag - read the dedicated article on compostable vs biodegradable.
Composting conditions
Home compostable vs commercially compostable
Not all "compostable" products break down in the same place. The certification tells you which composting environment is required.
| Attribute | Commercially (industrial) compostable | Home compostable |
|---|---|---|
| Conditions | High heat (around 55-60 C), managed facility | Ambient backyard temperatures |
| Certifying standard | ASTM D6400 / EN 13432 | TUV OK Compost HOME |
| Common marks | BPI Certified, TUV OK Compost INDUSTRIAL | TUV OK Compost HOME |
| Where it breaks down | Commercial compost facility only | Home compost pile |
Most certified compostable tableware and straws are industrially compostable - they need the heat of a commercial facility and will not fully break down in a backyard pile. A smaller set of products carry TUV OK Compost HOME, which verifies breakdown at ambient temperatures. Matching the product to the disposal infrastructure your customers actually have is the difference between real diversion and contamination.
Standards and certifications
What do BPI, TUV, ASTM D6400 and EN 13432 mean?
Every compostability claim on this page is tied to one of these third-party standards. These are the names to require from any supplier.
ASTM D6400
The US standard for plastics designed to compost in municipal and industrial aerobic composting facilities.
EN 13432
The European standard for industrial compostability; requires roughly 90 percent disintegration within 12 weeks and 90 percent biodegradation within 6 months.
BPI Certified
The Biodegradable Products Institute mark, verifying a product meets ASTM D6400 or D6868 for commercial composting.
TUV OK Compost
TUV Austria marks for INDUSTRIAL and HOME compostability - the HOME mark verifies breakdown at ambient temperatures.
Formulation
How do mineral fillers cut plastic content?
One way to reduce the polymer content of a plastic product is to replace part of it with a mineral filler. Calcean supplies oolitic aragonite - a biogenic calcium carbonate formed from renewable marine sources - that can be blended into resin as a functional filler. Because the aragonite is biogenic (formed by living systems) rather than quarried, and because it displaces petroleum-derived polymer, it lowers the fossil-plastic fraction of the finished part while contributing strength.
Nant Biorenewables uses Calcean's calcium carbonate in some of its formulations, which is exactly the kind of cross-partner integration ECS is positioned to specify: pairing a certified compostable resin with a biogenic mineral filler. For how these fillers work in a bioplastic blend, see mineral fillers for bioplastics.
Microplastics
How do you reduce microplastics in plastic products?
Conventional plastics fragment into microplastics because their polymer chains persist in the environment. The two credible routes to reducing that are, first, switching to a material certified to fully compost (ASTM D6400 / EN 13432) so it converts to carbon dioxide, water, and biomass rather than persistent fragments; and second, using additives and blends designed so the finished plastic breaks down more completely rather than shedding micro-fragments.
ECS supplies a microplastic-eliminating additive approach through its biodegradable blend program. For the mechanism, the certifications to demand, and how to evaluate additive claims critically, read the article on the additive to eliminate microplastics.
Explore the guide
Compostable bioplastics cluster articles
Compostable vs Biodegradable
Why one is a certified claim and the other is not, and how to spot greenwashing.
InnovationAdditive to Eliminate Microplastics
How certified-compostable formulations and additives reduce persistent micro-fragments.
CertificationHome vs Commercially Compostable
Why an industrial-compostable product may not break down in a backyard bin, and which mark to specify.
CertificationWhat Does BPI Certified Mean?
What the BPI Certified mark verifies, the ASTM standards behind it, and why it is not home compostable.
FAQ
Compostable bioplastics questions, answered
What does BPI certified compostable mean?
BPI (Biodegradable Products Institute) certification verifies that a product has passed testing to the ASTM D6400 or ASTM D6868 standard for industrial composting. It is a third-party mark, so it is more reliable than an uncertified "compostable" claim on the packaging.
Are compostable straws actually compostable?
Certified compostable straws do break down - but most require a commercial composting facility (ASTM D6400 conditions), not a backyard pile. Check whether the product carries an industrial mark (BPI, TUV OK Compost INDUSTRIAL) or the TUV OK Compost HOME mark, and match it to the disposal infrastructure available.
What is the difference between compostable and biodegradable?
Compostable is a certified claim: the material must convert to carbon dioxide, water, and biomass within a defined time under defined conditions with no toxic residue, per ASTM D6400 or EN 13432. Biodegradable has no standardized definition, timeframe, or end conditions, so on its own it tells a buyer very little.
What is a carbon-negative or biogenic filler?
It is a mineral filler such as Calcean's oolitic aragonite, a biogenic calcium carbonate formed from renewable marine sources. Blended into resin, it displaces petroleum-derived polymer and adds strength. Because it is biogenic rather than quarried and reduces the fossil-plastic fraction, it improves the material footprint of the finished part.
Can a plastic be bio-based but not compostable?
Yes. Bio-based describes where the raw material comes from; compostable describes how it breaks down at end of life. A plastic can be partly bio-based yet not certified compostable, or fossil-based yet certified compostable. Always look for the composting certification separately from the bio-based claim.
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