Bioplastics, PLA, and 'eco' plastics: marketing vs. reality

Just because a plastic is plant-based doesn't mean it biodegrades. Just because it's labeled 'compostable' doesn't mean it composts in your backyard. Here's the honest breakdown.

Two terms that aren't synonyms

Bioplastic means a plastic made from biological raw materials (corn, sugarcane, algae) instead of petroleum. It says nothing about how the plastic behaves at end-of-life.

Biodegradable plastic means a plastic that can be broken down by microorganisms. It can be made from petroleum or biological sources — the source is independent of the biodegradation behavior.

A plastic can be:

• Bio-based AND biodegradable (e.g., PHA — the gold standard)
• Bio-based but NOT biodegradable (e.g., bio-PET — chemically identical to fossil-fuel PET, just made from sugarcane)
• Petroleum-based but biodegradable (e.g., PBAT — used in many "compostable" bags)
• Petroleum-based and not biodegradable (conventional plastic)

PLA — the most common "compostable" plastic

Polylactic acid (PLA) is the most-common "biodegradable" or "compostable" plastic in consumer products. Made from fermented corn or sugarcane starch, PLA is widely used for "eco" cups, cutlery, takeout containers, and some compostable straws.

The catch: PLA only breaks down under industrial composting conditions — sustained 50–60°C for 60–90 days with controlled humidity. It does not biodegrade in:

• Backyard compost (too cool)
• Landfill (anaerobic, no oxygen)
• The ocean (too cold, no microbial pathway)
• Roadside litter (too dry, intermittent UV)

In any of these environments, PLA behaves essentially like conventional plastic. Read more on plastic decomposition.

The PHA exception

Polyhydroxyalkanoate (PHA) is genuinely biodegradable across most environments — including marine. It's produced by microbial fermentation and is the only commercial bioplastic that breaks down meaningfully in seawater. PHA is more expensive than PLA and currently produced at smaller scale, but it's the most-promising material for genuine marine-degradable plastic alternatives.

Why "biodegradable" labels are often misleading

"Biodegradable" without further specification has no enforceable definition. A plastic that takes 100 years to biodegrade is technically biodegradable. The FTC has issued guidance against unqualified "biodegradable" claims — but enforcement is weak.

"Compostable" is regulated, but typically means industrial-compostable rather than home-compostable. The standards:

• ASTM D6400 — industrial compost in the U.S.
• EN 13432 — industrial compost in the EU
• OK Compost HOME / TÜV Austria — much stricter; home-compostable
• BPI Certified Compostable — third-party certification of ASTM D6400

If a product is labeled "compostable" without specifying which standard, assume industrial-only.

What about "ocean degradable" claims?

Largely marketing — only PHA-based bioplastics meaningfully degrade in seawater. Most products labeled "ocean degradable" are PLA or other industrial-compostable plastics that fragment in salt water at marginally faster rates than conventional plastic but don't actually disappear.

What's actually safe to choose