The Problem with PLA: Why the Industry's First Compostable Bioplastic Is No Longer Enough
For nearly a decade, polylactic acid (PLA) was synonymous with "compostable packaging." Born from the promise of replacing petroleum-based plastics with something derived from corn starch or sugarcane, PLA captured the imagination of sustainability-minded brands and consumers alike. The material earned certifications, landed in grocery stores, and became the default choice for anyone looking to move beyond single-use plastic.
But PLA has a problem—actually, several problems. And the industry is catching on.
Polyhydroxyalkanoates (PHA), a family of biopolymers produced by bacteria, is rapidly emerging as the next generation of compostable packaging materials. Unlike PLA, PHA biodegrades in home compost, marine environments, and soil. It performs across a broader temperature range, passes more stringent certification requirements, and is beginning to meet the regulatory demands of a world increasingly skeptical of greenwashing.
This guide covers everything you need to know about PHA vs PLA: the science behind both materials, what certifications actually mean, how regulations are shifting the landscape, and why the business case for switching is stronger than ever.
The Science: PHA vs PLA at the Molecular Level
What Is PLA?
Polylactic acid is a thermoplastic polymer derived from fermented plant sugars—typically corn starch in North America, sugarcane in other regions. The fermentation process produces lactic acid, which is then polymerized into PLA pellets that can be processed much like conventional plastics.
PLA is a linear polyester with a relatively simple molecular structure. This simplicity is both its strength and its limitation. PLA is transparent, has good tensile strength, and can be processed on standard equipment—which is why it scaled so quickly.
However, PLA's chemical bonds are stable under normal environmental conditions. That stability is the core of its biodegradation problem. PLA requires:
- Temperatures above 55–60°C (131–140°F) sustained for weeks
- High humidity
- Specific microbial populations
These conditions exist in industrial composting facilities—but almost nowhere else. In home compost bins, backyard piles, marine environments, or soil, PLA behaves more like a conventional plastic: it persists for years or decades without meaningful degradation.
What Is PHA?
Polyhydroxyalkanoates are a family of biopolymers synthesized naturally by bacteria under nutrient-limited conditions. When bacteria encounter an environment with excess carbon (like sugar or plant oils) but limited nitrogen or phosphorus, they produce PHA granules as an internal energy reserve—essentially biological fat stores.
The most commercially relevant PHA variants include:
- PHB (polyhydroxybutyrate): The most common PHA, with properties similar to polypropylene but fully biodegradable
- PHBV (poly(3-hydroxybutyrate-co-3-hydroxyvalerate)): A copolymer with improved flexibility and processing characteristics
- PHBH (poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)): Enhanced flexibility, used in flexible packaging applications
Unlike PLA, PHA biodegrades through a fundamentally different mechanism. Extracellular enzymes (depolymerases) produced by soil and aquatic microorganisms can attack PHA's ester bonds across a wide range of temperatures—from cold marine environments to warm industrial compost facilities. The end products are water and CO₂ (aerobically) or water, CO₂, and methane (anaerobically).
Key Performance Differences
PropertyPLAPHABiodegradation environmentsIndustrial compost onlyHome compost, soil, marine, industrialBiodegradation timeframeMonths (industrial only)Weeks to months (varies by environment)Heat resistanceLow (~55°C deformation)Higher (varies by formulation)FlexibilityRigid/brittleRange from rigid to flexibleMarine degradabilityNoYes (certified)Oil/grease resistanceLimitedGoodFeedstockCorn/sugarcane sugarsSugars, plant oils, or waste streams
Certifications: What the Labels Actually Mean
The compostable packaging certification landscape is complex, inconsistent, and—from a consumer standpoint—confusing. Understanding what each certification requires (and what it doesn't require) is essential for making informed sourcing decisions.
Industrial Compostable Certifications
BPI Certified Compostable (USA): The Biodegradable Products Institute certification is the primary industrial compostable standard in North America. It requires testing under ASTM D6400 (for plastics) or D6868 (for products with plastic coatings). BPI certification means the product will biodegrade in an industrial composting facility within 180 days. It says nothing about home compostability or marine degradability.
DIN CERTCO / TÜV Austria OK Compost INDUSTRIAL (Europe): Europe's equivalent industrial compostable certification, based on the EN 13432 standard. Similar requirements to BPI—industrial conditions only.
PLA can and does achieve these certifications. This is precisely why "certified compostable" has become a misleading marketing claim: the certification is real, but the real-world composting pathway is functionally unavailable to most consumers. Industrial composting facilities are not ubiquitous, most don't accept residential compostable packaging, and most consumers don't have access to them.
Home Compostable Certifications
TÜV Austria OK Compost HOME: Tests biodegradation at ambient temperatures (25°C/77°F), reflecting real-world backyard composting conditions. This is a significantly more rigorous standard than industrial composting certification—and PLA cannot pass it.
ABA Home Compostable Certification (Australia): Australia's home compostable standard, recognized internationally as one of the more demanding programs.
PHA-based products can and do achieve home compostable certifications. This is a critical differentiator: a PHA product certified for home composting gives consumers a genuine end-of-life pathway without reliance on industrial infrastructure.
Marine Degradable Certifications
TÜV Austria OK Biodegradable MARINE: Tests biodegradation in marine water environments at 30°C. Given the scale of ocean plastic pollution, this certification represents an increasingly important attribute for food service packaging.
PHA passes marine biodegradability tests. PLA does not.
The Certification Gap in Practice
Here's the practical reality of certifications for brands: a product labeled "certified compostable" with only an industrial certification is, for most consumers in most markets, functionally non-compostable. Without access to industrial composting facilities—which accept certified packaging, which process it correctly, and which are located near enough to be used—those products go to landfill or contaminate recycling streams.
PHA's ability to biodegrade across multiple environments—home compost, soil, and marine water—means that even when the ideal end-of-life pathway is unavailable, the material continues to break down. This makes PHA a more defensible choice both environmentally and from a regulatory compliance standpoint.
Regulatory Landscape: Where the Law Is Heading
Regulation is reshaping the compostable packaging market faster than many brands anticipated. Several major jurisdictions have moved or are moving to restrict what products can be labeled "compostable" and under what conditions.
California SB 54 and the PPRS
California's Plastic Pollution Prevention and Packaging Producer Responsibility Act (SB 54) is among the most significant plastic packaging regulations in US history. While SB 54 focuses primarily on recyclability and recycled content, California has simultaneously been tightening the standards for what can be labeled compostable.
California AB 1201 requires that products labeled "compostable" must be certified by an approved third party and must be accepted in compost programs in the state. This effectively raises the bar for what "compostable" means commercially—and puts PLA's limitations under regulatory scrutiny.
European Union: The Green Claims Directive
The EU's Green Claims Directive, moving through the legislative process as of 2024, will require companies to substantiate environmental claims with verified evidence before making them to consumers. "Compostable" will be one of the claims under review. Under the directive's framework, a product that is only industrially compostable but marketed broadly as "compostable" could be classified as greenwashing.
The EU is also advancing the Packaging and Packaging Waste Regulation (PPWR), which includes provisions specifically addressing when compostable packaging is appropriate and what standards it must meet. Early drafts suggest that home compostability will be a preferred standard for certain packaging categories—particularly items like tea bags, coffee pods, and lightweight food-contact packaging where compostable materials offer a genuine advantage over recyclable alternatives.
FTC Green Guides
The US Federal Trade Commission's Green Guides, last updated in 2012, are under revision. The FTC has been collecting public comments specifically on environmental marketing claims including "compostable." Industry observers expect the revised guides to tighten requirements for compostable claims, potentially requiring disclosure of whether products require industrial composting facilities.
What Regulatory Trends Mean for Brands
The regulatory direction is clear: the bar for "compostable" claims is rising. Products that are only industrially compostable face increasing legal and reputational risk. Brands investing in PHA now are positioning ahead of these requirements rather than racing to comply after the fact.
For brands operating in the EU, California, and other progressive jurisdictions, the risk calculus has shifted. The question is no longer just "is this product certified compostable?" but "can we substantiate this claim in all markets where we sell?"
The Business Case for Switching from PLA to PHA
Cost Considerations
PHA is currently more expensive than PLA on a per-kilogram basis. This is the most common objection to switching, and it's a legitimate one. However, the cost gap is narrowing as PHA production scales, and the cost comparison is more nuanced than raw material price:
- Regulatory risk mitigation: The cost of reformulating products in response to regulatory changes—or managing a greenwashing enforcement action—can far exceed the premium for sustainable materials
- Consumer premium: Products with home compostable or marine biodegradable certification can command price premiums in premium retail channels
- Total cost of ownership: PHA's better heat resistance and oil resistance can reduce failure rates and returns in certain applications
- Transition costs: Switching from PLA to PHA on similar processing equipment is significantly simpler than switching from conventional petroleum plastics—a meaningful consideration for total transition cost
Supply Chain Readiness
PHA production is scaling rapidly. Major producers including Danimer Scientific (NodaxTM), TerraVerdae Bioworks, and Yield10 Bioscience have been expanding capacity. The supply chain is more mature than it was even three years ago, and lead times and minimum order quantities are increasingly competitive with PLA.
For brands at volume, long-term supply agreements can lock in pricing and supply security while PHA production continues to scale.
Retailer and Customer Demand
Major retailers are beginning to distinguish between industrial and home compostable certifications in their sustainability requirements. Several European retailers have made home compostability a preferred standard in private label packaging specifications. This trend is expected to extend to US retail as regulatory clarity improves.
Institutional food service customers—universities, hospitals, corporate campuses with sustainability commitments—are increasingly sophisticated in their evaluation of compostable packaging claims. For brands selling into these channels, the ability to substantiate a home compostable claim is a competitive advantage.
Brand Narrative and Differentiation
PLA's compostability story is getting harder to tell credibly. As media coverage of the limitations of industrial-only compostability has increased—and as regulators have signaled stricter standards—the PLA narrative has become a liability for some brands.
PHA offers a genuinely differentiated story: a material that biodegrades in home compost, in soil, and in marine environments, produced through fermentation rather than petroleum, from feedstocks that can include agricultural waste streams. This is a narrative that holds up to scrutiny—which is increasingly valuable in a market where environmental claims face intensified examination.
Making the Switch: Practical Considerations
Product Applications
PHA is not a drop-in replacement for PLA in every application—but it performs well across most food service packaging categories:
- Cutlery: PHA's higher heat resistance is a particular advantage for cutlery used with hot foods where PLA is prone to deformation
- Cups and lids: PHBH formulations offer the clarity and rigidity needed for cold beverage applications
- Straws: PHA straws maintain structural integrity across a wider temperature range than PLA alternatives
- Clamshells and containers: Food containers benefit from PHA's improved oil and grease resistance compared to PLA
- Films and coatings: PHA-coated paperboard is emerging as a home compostable alternative to PE-coated paper, addressing one of the most challenging waste stream categories
Certification Strategy
When transitioning to PHA, consider your certification strategy holistically:
- Identify the markets where you sell and their regulatory requirements
- Determine which certifications will be most meaningful to your customers and in your sales channels
- Work with suppliers who can provide certified materials and support your own product certification process
- Plan for certification costs and timelines—certification processes take months
Communication to Customers
The switch from PLA to PHA is an opportunity to upgrade your sustainability communications. Key messages that resonate with sophisticated buyers:
- Home compostable (not just industrially compostable)
- Marine biodegradable
- Certified to [specific certification standards]
- End-of-life pathway that works even without industrial composting infrastructure
PlantSwitch and PHA-Based Compostable Packaging
PlantSwitch's CompostZero™ product line is built on PHA-based formulations that achieve both home compostable and marine biodegradable certification. Unlike PLA-based products that require industrial composting infrastructure, CompostZero products break down in real-world conditions—backyard compost, soil, and ocean environments.
Our cutlery, straws, cups, and food containers are designed to meet the needs of food service operations that want to make genuine progress on packaging sustainability, not just check a certification box. We work with customers to match the right product to their application, understand their certification needs, and navigate the transition from conventional or PLA-based packaging.
If you're evaluating the switch from PLA to PHA, we're happy to discuss your specific needs, provide samples, and share data on performance and biodegradation in the applications most relevant to your business.
Get in touch with our team to start the conversation.
