Why are compostable bags not allowed in California?
If you supply fresh produce, run a food-service operation, or ship physical goods through California, you have probably heard a frustrating contradiction: the state that mandates organic waste diversion also seems to forbid the one bag category that sounds like the perfect solution—compostable bags. Walk into a municipal organics program brief and you will read that only paper bags, clear plastic liners, or no bag at all are accepted. Yet the California law SB 1383 was written to keep organic material out of landfills. Why, then, are compostable bags not allowed in California? The answer sits at the intersection of material science, sorting technology, infrastructure limitations, and a history of greenwashing that has made waste operators deeply skeptical of any bag labelled “biodegradable.” For a B2B buyer selecting packaging for a multi-state supply chain, understanding this nuance is not academic—it determines whether your shipment gets processed or rejected as contamination.
The real story has less to do with a blanket ban and far more to do with what the law considers a genuinely compostable bag. California requires any plastic-like bag placed in an organics bin to meet a specific set of performance standards and—most importantly—to be accepted by the specific composting facility that receives your customer’s waste. On paper, that sounds manageable. In practice, the gap between a certified product and a facility willing to take it is wide enough that many jurisdictions instruct residents and businesses to simply leave bags out.
Where the confusion begins: SB 1383 and organics collection
California’s Short-Lived Climate Pollutant Reduction Law, SB 1383, took full effect for businesses in 2022. Its target is to reduce organic waste disposal by 75% from the 2014 baseline. The arithmetic is stark: according to CalRecycle, the state generates roughly 23 million metric tons of organic waste each year—food scraps, yard trimmings, soiled paper—and about half of it went to landfills, where it decomposes anaerobically and emits methane. Methane accounts for roughly 10% of the state’s total greenhouse gas inventory, and landfills contribute about 20% of that methane load. Diverting organics to composting facilities or anaerobic digesters cuts that emission stream directly.
The regulation itself does not say “thou shalt not use compostable bags.” Instead it sets product-labeling restrictions (Chapter 5.1 of the Public Resources Code, often called the “compostable claims” law) and places the burden on jurisdictions to design collection programs that produce clean organic feedstock. When a city, a hauler, and a compost facility sit down to agree on an acceptable materials list, the conversation almost always lands on one practical observation: bags that look like conventional polyethylene are the top cause of contamination. A 2023 survey by the US Composting Council indicated that more than four out of five composting facilities in the United States actively screen out and remove all film plastic, including certified compostable film, because operators cannot reliably distinguish one from the other at the speed of a commercial sorting line. In California, where large-scale facilities run 24-hour receiving operations and process over 500 tonnes of incoming material per day, the tolerance for hand-picking misidentified bags is near zero.
This is the core operational reason why compostable bags are not allowed in California programmes: not because the material is inherently harmful, but because the sorting infrastructure cannot validate it at scale. A bag that meets ASTM D6400 and carries a BPI certification mark is still a bag that looks and feels like LDPE until it spends 90 to 180 days in a controlled composting environment. On a picking line that handles fresh waste, that bag is indistinguishable from the conventional plastic the facility is built to reject.
The certification gap: what a bag must do to be called “compostable”
Many procurement teams are comfortable with certificate numbers on a datasheet, but few have walked through the tests behind them. For a film to carry an ASTM D6400 or EN 13432 certification, it must pass a four-part evaluation: biodegradation, disintegration, ecotoxicity, and heavy-metals analysis. Under ASTM D5338, the material is incubated at 58°C (±2°C) in a controlled compost environment for up to 180 days, and the carbon-to-CO₂ conversion must reach at least 90% relative to a positive control. Disintegration requires that after 84 days, no more than 10% of the original dry weight remains on a 2-mm sieve. Ecotoxicity—commonly tested via OECD 208 plant germination trials—ensures the finished compost supports seedling growth comparably to a reference compost.
These numbers are impressive on a technical data sheet, but they depend on a specific set of conditions: temperature maintained above 50°C for several weeks, moisture content between 50 and 60%, and a microbial population that actively turns the pile. Most open-windrow composting facilities in California operate in the lower end of that thermal range, especially during winter months. A 2021 study published in Waste Management tracked the degradation of certified compostable bags in five commercial sites across North America and found that, while the materials disintegrated almost completely in an in-vessel system running at a strict 58°C, less than 40% of the film area had disappeared after 120 days in a static pile that averaged 44°C. For a facility that sells screened compost to farms and vineyards—where visible film is a product-quality defect that can trigger a rejected load—that partial degradation is a financial risk they are unwilling to take.
What California actually restricts on the packaging side
Beginning January 1, 2021, California’s labeling law made it unlawful to sell a plastic product in the state if it is labelled “compostable” (or “home compostable”) unless the product has earned a current certification from a recognized third-party scheme. In practice, BPI certification to ASTM D6400 (industrial compostable) and TÜV Austria’s OK Compost HOME (home compostable) are the two main marks authorities look for. The law also limits use of degradable, biodegradable, and photodegradable claims unless backed by equivalent evidence. An enforcement snapshot from CalRecycle reported that in the first full year of the regulation, warning letters were sent to more than 30 companies selling uncertified bags, and approximately 15% of those involved claims tied to compostability.
Yet even when a bag carries the proper certification mark, the California Department of Resources Recycling and Recovery stops short of requiring that every composting facility take it. Jurisdictions are allowed to draft local collection rules that reflect the actual capability of their contracted processing infrastructure. That is why a BPI-certified Bin Liners product that functions perfectly in a controlled in-vessel facility in Oregon might still be listed as an unacceptable material in San Jose’s residential organics programme. The state’s position is practical: reduce contamination now, and let the accreditation system catch up later.
How this affects purchasing decisions across product categories
For a business that ships produce, pet supplies, or retail goods into California, the regulation splits decision-making into at least three layers: what the law permits, what the collection operator actually takes, and what the end-composter can process without disrupting their quality parameters. A misstep in any layer can mean your packaging—and possibly the contents—ends up in a landfill, undermining the environmental claim you made to your customer.
Take fresh-produce packaging. A supermarket chain that rolls out Produce Bags printed with the BPI logo and expects a consistent composting outcome quickly learns that store-level back-of-house sorting determines everything. If a store’s organics hauler has a no-film policy, those bags are pulled at the loading dock, often landfilling the entire bagged load. In response, several major California retailers have reverted to unlined corrugated trays or reusable containers for some categories, and only reintroduce compostable film when they have a direct line-of-sight to a dedicated processing channel.
The story is similar for pet waste. Many municipalities will accept pet waste in organics bins only if it is double-bagged in clear polyethylene or wrapped in paper, because the organic fraction is small and the risk of pathogen transmission means the stream needs high-heat treatment. A BPI-certified Doggy Bags product may meet ASTM D6400 at lab scale, but if the receiving anaerobic digester runs a 21-day retention time instead of the 180 days required for full film disintegration, the bag survives the process and becomes a screen residual. Until facility contracts are updated to specify acceptable compostable inputs, the legal requirement and the operational reality will stay disconnected.
Material benchmarks that procurement teams should request
If you plan to specify compostable bags for any market—whether California, the EU, or Australia—requesting the right documentary evidence at the sourcing stage prevents months of downstream trouble. The minimum should include a current third-party certificate with a traceable licence number, a test report showing batch-level degradation performance, and a written statement from the manufacturer clarifying which specific disposal environment the product is designed for.
A comparison of the most commonly referenced certification standards quickly reveals why “compostable” is not a universal claim.
| Certification Standard | Scope | Require biodegradation ≥90% within | Disintegration threshold | Typical certification body | |————————|——-|————————————-|————————–|—————————-| | ASTM D6400 (US) | Industrial composting | 180 days (ASTM D5338) | ≤10% dry weight retained on 2-mm screen after 84 days | BPI | | EN 13432 (EU) | Industrial composting | 180 days (ISO 14855-1 or equivalent) | ≤10% retained on 2-mm screen after 12 weeks | TÜV Austria, DIN CERTCO | | AS 4736 (Australia) | Industrial composting | 180 days (AS ISO 14855) | ≤10% retained on 2-mm screen after 12 weeks | Australasian Bioplastics Association | | OK Compost HOME | Home composting (20–30°C range) | 12 months at ambient temperature (method varies) | ≤10% retained on 2-mm screen after 26 weeks | TÜV Austria |
Even when a product carries multiple certifications, the thermal and moisture envelope of the actual disposal site dictates performance. That is why, when buyers evaluate a supplier’s data pack, the conversation should go beyond the certificate number and into the formulation. Many compostable bags are based on a blend of polybutylene adipate terephthalate (PBAT), polylactic acid (PLA), and starch. A typical PBAT/PLA film of 15–25 microns thickness can meet ASTM D6400 when PLA content is kept below about 30% and the film is processed with an appropriate nucleating agent. Push the PLA percentage higher for stiffness, and the lag phase before enzymatic hydrolysis starts can extend beyond the facility’s active composting phase. That is a subtle material trade-off that a certificate alone does not reveal, and it is precisely the kind of detail that shapes whether a bag actually disappears or appears in a reject pile.
Rebuilding trust through verified supply chains
The narrative that “compostable bags do not work” is an overcorrection, driven by a decade of uncertified oxo-degradable and starch-blend films that fractured and left persistent microplastic residues. Agencies like the Federal Trade Commission in the US and the Australian Competition and Consumer Commission have fined multiple companies for unsubstantiated biodegradability claims over the past five years. California’s labeling law was drafted, in part, as a direct response to that history. The expectation now is that any organisation making a compostability claim will hold a tightly audited chain of custody, from resin through to finished product.
What does that look like at the purchasing level? When you source a bag film, ask for the resin grade certificates for each lot. PBAT polymers, for instance, are primarily produced in a few vertically integrated facilities in Europe and Asia. A reliable supplier will be able to show you the technical data sheet for the exact grade being used—not just a generic marketing sheet. For bags made from a blend of PBAT and corn starch, the starch plasticisation process matters: whether the starch is destructurised with water and glycerol in a twin-screw extruder or simply blended as a filler changes both the mechanical properties and the biodegradation curve. In-house test data on dart-drop impact and elongation at break should be available and typically fall in the range of 7–12 grams (dart) and 200–400% elongation for a 20-micron bio-flexible film, depending on PLA content. If a supplier cannot provide batch-specific physical-property data alongside the compostability certificate, consider that a risk flag.
Frequently Asked Questions
Are compostable bags completely banned in California?
No. The state does not ban them outright. It requires that compostable claims be certified by BPI or an equivalent approved third party. Local jurisdictions, however, can—and frequently do—restrict their use when their contracted composters cannot process film reliably. The effective result is that many Californians are told not to place any bag, even a certified one, in the green bin.
What certification should a business look for if it wants to supply the California market?
At a minimum, BPI certification to ASTM D6400 for industrial compostable products. If your product is intended for home composting, TÜV Austria’s OK Compost HOME or a comparable standard is needed. Note that certification alone does not guarantee acceptance by a particular facility; you still need to check with the local hauler.
Does the same restriction apply to produce bags, bin liners, and doggy bags?
The labelling and certification requirement applies equally to all organised waste bags. The operational restrictions—whether a facility actually takes them—tend to be uniform across product types because the sorting challenge is identical: the bag looks like plastic regardless of its printed purpose.
How long does a certified compostable bag actually take to degrade in a real compost pile?
Under ideal industrial conditions (≥58 °C, active aeration), 90% biodegradation can occur within 45 to 90 days. In cooler, static piles, partial degradation can still be observed after 180 days. The finished compost can contain visible film fragments if the pile never reaches target temperature, which is what makes facility operators cautious.
If a bag is EN 13432 certified, is it automatically accepted in California?
Not automatically. The California law references the applicable ASTM standard and a BPI label for practical enforcement, though enforcement agencies do recognise EN 13432 as a comparable standard. The final decision, however, rests with the organics processing facility that receives the material through its service contract.
What the situation demands from industrial buyers today
The question “Why are compostable bags not allowed in California?” leads to a more useful version: “What must my packaging do to function as a genuine sustainability tool in the markets I serve?” The answer demands that you look beyond the bag itself and into the end-of-life pathway. If your route-to-market passes through a facility that runs an active in-vessel phase—perhaps one that handles large volumes of food waste from grocery distribution centres—a bag certified to ASTM D6400, made from a well-balanced PBAT/PLA/starch formulation and supported by a detailed technical data pack, has a good chance of fulfilling its promise. If, instead, the waste stream runs through a short-cycle anaerobic digester, or a rural windrow operation where temperatures hover around 40°C, that same bag may become a persistent residual that erodes confidence in the entire compostable category.
For business buyers, the immediate steps are concrete. Audit your waste‑service contracts in California and ask the hauler for the written acceptable‑materials list, not a verbal interpretation. Cross‑check that against your packaging specification and the certification portfolio from your supplier. When you evaluate new bag films, request the full test report package—biodegradation, disintegration, ecotoxicity, heavy metals—not just a logo on a spec sheet. And use the hard‑earned data from the US market to inform purchases in other regions. A bag that works in Australia under AS 4736 may share much of the same chemistry, but the disposal environment will differ. The value of a supplier with deep material knowledge and full batch traceability is not that they promise a bag works everywhere; it is that they can show you exactly where and why it will.
CalRecycle’s ongoing rulemaking on packaging producer responsibility (SB 54) will layer more requirements onto the system in the next three years. Companies that embed full‑documentation discipline into their packaging procurement now will navigate those changes faster than those still hoping for a single‑logo shortcut. The market has moved past simple claims. Your California customer’s green bin is the final judge—and it only accepts what the facility behind it can actually process.
