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Compostable Packaging: A U.S. Packaging Producer’s Guide to the New Rules — and the Science Beneath Them

In the United States, “compostable” and “biodegradable” are two words that have quietly become regulated, certifiable, and legally enforceable claims — and a growing number of producers are discovering the distance between “we said it’s compostable” and “we can prove it.”

The shift is easy to miss because it didn’t arrive as one federal law. It arrived as a patchwork: a tightening set of state laws, intensifying federal enforcement^[1], and a revision cycle at the standards bodies that is rewriting what the words are even allowed to mean. The purpose of this briefing is to connect those pieces for the people who actually have to comply with them — to lay out what the new U.S. rules require, what they mean for the packaging you design and sell, and the science the rules are built on.

Part 1
The new U.S. regulatory landscape

State law, not federal, is where “compostable” is defined and enforced today, and California sets the ceiling everyone else builds toward.

California’s AB 1201 is the most stringent. To label a product “compostable” or “home compostable” in California, it must be certified to ASTM D6400 or D6868 (or OK compost HOME for home claims), contain less than 100 ppm total organic fluorine, and — critically — qualify as an allowable agricultural organic input under the USDA National Organic Program (NOP)^[2]. That last requirement is the one catching producers off guard. Enforcement, after an extension, bites on June 30, 2027.

The organic-input gate has teeth that surprise people. The NOP’s National List allows only a narrow set of synthetic materials as compost feedstocks, and in January 2026, the USDA’s National Organic Standards Board voted unanimously against adding synthetic compostable plastics — including PLA and PHA — to that list^[3]. The practical consequence: a cup can be genuinely, testably compostable, certified to ASTM D6400, carry a BPI mark, and still fail California’s labeling test on the organic-input requirement. The Biodegradable Products Institute is pursuing California legislation to decouple AB 1201 from the NOP, but until that succeeds, this gate stands.

California doesn’t stop there. SB 343 restricts “recyclable” claims and the chasing-arrows symbol to materials genuinely accepted in the state’s systems, and SB 54, the state’s extended-producer-responsibility law, requires all single-use packaging sold in California to be recyclable or compostable by 2032^[4]. Together, they mean that both of a producer’s end-of-life claims — recyclable and compostable — now have to be earned.

The standards that actually define the claim

Underneath the regulations sit the technical specifications they point to. In the U.S., ASTM D6400 is the specification for compostable plastics — recently refreshed to its 2026 edition (D6400-26). D6868 (currently the 2021 edition) covers plastic coatings and additives on paper and fiber substrates, and the newer D8410 (2022) is a dedicated specification for predominantly cellulosic-fiber products like molded-fiber bowls. BPI is the dominant certifier that tests products against these specs and grants the “Certified Compostable” mark^[5–7, 14].

New for 2025, ASTM also published a pair of field-testing methods — D8618 and D8619 — that measure disintegration in actual operating composting facilities rather than only in the laboratory. They could support SB 54’s compostability requirements, and they signal where the whole system is heading: regulators wanting proof of real-world performance, not just lab performance^[8].

The clean way to hold the U.S. picture in your head:

• Treat “compostable” as a claim you must be able to defend. For every “compostable,” “home compostable,” or “biodegradable” claim, you should be able to produce — on demand — a current certificate with a registration number, the underlying test reports, and PFAS results.
• Certify to the destination market, because there is no global “compostable.” For the U.S. and Canada, that means ASTM D6400 or D6868 (or D8410 for fiber) plus a BPI mark; for the EU, EN 13432 plus OK compost INDUSTRIAL or the Seedling logo. If you export, you dual-certify. And never let “industrially compostable” and “home compostable” be used interchangeably — they are different certificates, built on different evidence, and most industrially compostable materials fail the home compostable test (such as PLA).
• Treat California as your binding constraint. A D6400-certified, BPI-marked PLA or PHA item can still lose its “compostable” label in California on the organic-input gate alone. If you sell PLA- or PHA-based foodservice ware into California, audit those SKUs now and build a relabeling or reformulation plan well ahead of June 30, 2027. “We’re certified” will not, by itself, protect the label there.
• Design the chemistry to keep the claim. Specify PFAS-free barriers and keep total organic fluorine under regulated limits^[14]; a contaminant present at well under one percent can still disqualify the whole claim. Avoid additives and multilayer constructions that defeat both composting and recycling. And be aware that the standards tolerate only a small fraction of unproven, non-biodegradable content — a window that ASTM’s 2026 revision is explicitly tightening on microplastics grounds.
• Match the claim to where the package actually ends up, and don’t oversell access. A certificate proves capability, not availability. Most U.S. consumers cannot reach a facility that accepts compostable packaging, and many composters reject it outright. Qualify your claims honestly — “compostable in industrial facilities where accepted; not home compostable” — which is both the truthful position and your strongest defense against state-law exposure. Compostability earns its value mainly for food-contaminated, hard-to-recycle formats: tea bags, produce stickers, foodservice ware, bin liners. For rigid bottles and recyclable mono-materials, recyclability is usually the stronger end-of-life, and relabeling them “compostable” can trade a working outcome for a missing one.

Part 3
The science behind the rules

Most compliance failures begin as vocabulary failures, so it is worth being precise about the words the regulations turn on.

Biodegradable means only that living microorganisms — bacteria, fungi, and the like — can break a material down into carbon dioxide, water, and biomass, eventually. That, in essence, is the whole of what the term captures: susceptibility to microbial breakdown. It fixes neither an environment nor a timeframe. On its own it is close to meaningless, because virtually every organic material biodegrades given enough time.

Compostable is narrower and testable. The defining feature, in the ASTM framework, is that the term is tied directly to composting: the material has to break down biologically under composting conditions, at a pace comparable to materials already known to compost, ending up as the same harmless products as natural organic matter and leaving behind no toxic residue and no recognizable fragments. The decisive idea is that the composting environment is built into the definition itself. Compostability is therefore a property of a material-plus-environment system, never of the material alone.

From there, certification — whether to ASTM D6400, EN 13432, or ISO 17088^{[5, 10, 12]} — tests four things that must all be true. Reading them as a single, consistent checklist is the clearest way to understand what “certified compostable” actually guarantees.

1. Breakdown (disintegration).

The item must physically fragment — under the lab standards, at least 90% of it must pass a 2 mm sieve within about 12 weeks under industrial conditions. This is the visible part of composting, and it is also the most over-trusted: disintegration alone is not compostability.

2. Mineralization (biodegradation).

Microbes must convert at least 90% of the polymer carbon to CO₂ — measured by gas evolution — typically within 180 days under industrial conditions. This is the chemical endpoint, and the distinction from disintegration is the whole ballgame. A material that shatters into microscopic pieces without mineralizing has not composted; it has produced persistent microplastics. The standards do allow a small tolerance for unproven minor constituents — historically constituents above one percent must each be demonstrated biodegradable, while the sum of unproven sub-one-percent constituents has been capped at five percent — but that window is exactly what regulators are now narrowing.

3. No toxicity or microplastics.

The finished compost must support plant growth (a seedling-emergence and growth test) and stay within strict heavy-metal limits, and — increasingly — within fluorine limits that screen out PFAS. The constituent exemption above is only an exemption from proving biodegradability; a minor additive still counts fully toward the toxicity and metals limits. “Small fraction” never means “exempt from everything.”

4. Organic in nature.

The material must be genuinely organic matter — the standards require a minimum of about 50% volatile solids. In California, this scientific requirement now has a second, legal layer stacked on top of it: the material must also be an allowable organic input under the USDA NOP — the gate that currently excludes synthetic compostables like PLA and PHA even when they pass all four scientific tests.

Why microplastics are driving the whole revision

The thread connecting these four components is the microplastics problem, and it explains why the rules are tightening now. Under genuine industrial conditions, well-designed certified materials do fully mineralize. The complication is that many real facilities run faster and cooler cycles than the 180-day laboratory protocol — and when they do, a “compostable” item can disintegrate without fully biodegrading, leaving persistent fragments behind. This is precisely why the standards world is moving in two directions at once: tightening what is allowed into a compostable product (the D6400-26 constituent revision) and standardizing how we verify what comes out of real facilities (the 2025 field-disintegration methods, D8618 and D8619). Together they are closing the gap between laboratory performance and the compost that actually lands on farmland.

Same tests, different environments — and why a claim doesn’t transfer

The final piece of the science is the one most often muddled: industrial composting, home composting, and marine/aquatic biodegradation are not interchangeable. What stays constant across all three is the underlying logic — break down, mineralize to roughly 90%, stay non-toxic. What changes are temperature, the time allowed, and the degree of management.

Industrial composting runs hot — around 58 °C, actively managed — and is the easiest bar to clear. Home composting (now genuinely certifiable through OK compost HOME and the published European standard EN 17427, among others) runs at ambient backyard temperatures and is stricter and slower, extending the clock to as much as twelve months while holding the same 90% bar. Marine and aquatic biodegradation — tested at around 30 °C in the lab via ASTM D6691, with newer methods such as D7991 for marine sediment and D8646 for estimated aquatic biodegradation time, and a long-withdrawn pass/fail specification now in the process of being reinstated — is the hardest of all, and its warm, nutrient-rich lab conditions flatter what happens in the cold, nutrient-poor open ocean^{[9, 11, 13]}.

Temperature is the master variable. PLA, the most common compostable plastic, only hydrolyzes meaningfully above roughly 58 °C — which is exactly why it passes industrial composting and fails both home composting and the marine environment. That single fact is why “compostable,” with no environment named, is the most misleading claim in the category.