Biodegradation Testing: 3 Real Verdict Types — ISO 14855 Soil Burial / OECD 301 Aerobic / 18-Day Composting: Which Three Reports Should a Printer Request First When It Receives a “Biodegradable” Order?

In April 2026, a customer producing kitchen-waste bags contacted us to make 600 groups of ten thousand home-compostable bags. The specification clearly stated: “Biodegradable, compliant with GB/T 41010.”

Our reply was: “Please provide the test report.”

The customer sent a PDF whose cover read “XX Biodegradable Plastics Testing Report.” The title was “Product Biodegradation Performance Test,” and the “Test Basis” field listed ISO 14855.

The customer asked: “Doesn’t this already show that it is biodegradable?”

We turned to page 3 of the report and found three problems.

First, the report’s test duration was 180 days of soil burial, not 18 days for home composting. Second, the sample was “PLA pellets,” not the finished modified compound the customer would use. Third, the report stated a final mineralization rate of 62%, whereas the home-composting determination threshold corresponding to GB/T 41010 does not hinge on this metric.

This article explains three things: what each of the three “biodegradable” tests actually measures, which three reports a printer should request first when a customer asks, and why printers must be especially careful about biodegradability claims—because we print packaging, not materials, yet reports are often issued in the material manufacturer’s name.

First Verdict Type: ISO 14855 Soil Burial—Testing Whether It Will Eventually Decompose

ISO 14855 places the material under aerobic soil conditions, buries it, periodically measures the amount of carbon dioxide released, and ultimately calculates a “final mineralization rate” (mineralization rate).

The logic of this test is: the material is broken down by microorganisms → it is converted into water, carbon dioxide, and microbial biomass → the more carbon dioxide released, the more complete the decomposition.

The most common customer misunderstanding is that seeing “ISO 14855 passed” means the word “biodegradable” can be printed directly on packaging.

Our answer is: ISO 14855 is a final mineralization test for soil burial. It proves that “this material can ultimately be broken down in soil,” not that “this package can be composted in 18 days.” Whether a compostability mark may be printed on packaging depends on the corresponding standard for the target market.

There is also a pitfall we have encountered: a material manufacturer’s report covers “a certain grade,” while the customer actually uses “a certain grade + a certain additive formulation.” In March 2026, a customer provided a PLA report. After checking it, we found that the sample was pure PLA pellets, while the customer’s material contained a 15% PBAT blend. Once PBAT is added, the mineralization rate under soil burial changes significantly, so the report no longer covers the actual material.

Our rule is therefore: the report must match “the exact material grade the customer actually ordered.” If it does not, send it back.

Second Verdict Type: OECD 301 Aerobic Biodegradation—Testing When Degradation Begins

OECD 301 is a set of aerobic biodegradation test standards from the Organisation for Economic Co-operation and Development. The most common method is OECD 301 B: the material and microorganisms are placed in a sealed container, oxygen consumption and carbon dioxide release are measured at regular intervals over 28 days, and the degree of biodegradation is calculated.

It differs from ISO 14855 in three respects.

The 28-day window is key to understanding OECD 301. Many customers hold OECD 301 reports and say, “More than 90% degradation in 28 days, so it is biodegradable.” That statement is not wrong in itself, but it omits three qualifications:

• It means “reaching” a percentage, not “turning into water and carbon dioxide.” A biodegradation level of 90% means that 90% of the carbon has been converted; the remainder may be microbial biomass.
• Sufficient oxygen is required. The aerobic test applies under the turning conditions of a composting plant, but not in oxygen-deficient environments such as landfills or lake bottoms.
• It must be industrial composting conditions (approximately 58℃ constant temperature and sufficient humidity). Home composting temperatures do not reach this level.

We encountered a real failure. The customer was making horticultural degradation film and used an OECD 301 report showing 92% degradation over 28 days, which was then used in promotional materials. What the customer did not know was that OECD 301 is valid on the premise of constant 58℃ industrial composting conditions and continuous oxygen supply, whereas the customer’s horticultural application involved ambient-temperature outdoor composting with widely fluctuating temperatures and uneven oxygen.

The customer asked: “Then how should I phrase it?”

Our recommendation was: do not print a “compostable” mark on the package. Instead, use wording that matches the target market, such as “industrial compostable” or “soil biodegradable,” and print the test standard number alongside it. This is not wordplay—these are different marks under the regulations of different countries, and printing the wrong one constitutes false advertising.

Third Verdict Type: 18-Day Home Composting—The One Most Often Overstated

Home-composting standards, such as EU EN 13432 and China’s GB/T 41010, require complete degradation within 180 days in a home-composting pile at approximately 20-30℃, with a clearly specified 18-day interim assessment point.

The fundamental difference between this standard and the previous two is that it requires “complete degradation,” not “final mineralization reaching a certain percentage.” It also assesses more than the material itself—

• The material must 90% or more fully biodegrade within 180 days
• It must pass a series of “ecotoxicity” tests within 90 days—plant toxicity and acute earthworm toxicity
• Heavy metals in the material must not pose a hazard to soil
• It must contain organic components and cannot consist purely of minerals
• At 18 days, at least 90% of the fragments must be smaller than 2mm, with no original fragments visible to the naked eye

The 18-day interim assessment point is the most critical threshold. Many materials pass at 90 days and 180 days but fail at the 18-day stage—because the 18-day assessment measures the degree of disintegration, specifically whether the material has truly broken down into small particles rather than remaining in an intact fragment shape.

This directly determines how the printing process affects the final result.

In 2025, we accepted an order for kitchen-waste bags whose material had passed every report. However, the customer insisted on adding printing to the bags—a large-area solid print in dark green ink. During laboratory retesting, the sample failed the 18-day disintegration test, and the fragments were visible to the naked eye.

The customer asked why. We sent two samples for comparison: one printed and one unprinted, both from the same material batch. The printed sample had visibly larger fragments after 18 days.

There were two reasons: first, the printing layer itself takes longer to degrade; second, pigments and binders in the ink alter the microbial adhesion environment on the material surface.

The final resolution was to switch to light-colored/white ink and reduce the solid-coverage area. After the customer accepted the change, the retest passed. This resolution is not free for the printer—switching to a lighter color requires the same artwork to be re-laid out, while reducing solid coverage requires changes to the customer’s design file.

This is why printers must be especially careful about biodegradability claims: the material report is the material’s report; after printing, it is a different thing. A printer must either make clear when obtaining the report that “the finished product, including printing, requires retesting,” or define the boundary of responsibility for a failed retest in the contract if the customer insists on dark, solid coverage.

The Three Reports to Request When Receiving a “Biodegradable” Order

In practice, we now always request three items for any project making a “biodegradable / compostable / environmentally degradable” claim. If one is missing, we do not start production:

• First: the original test report, which must state the test standard number, test duration, and test temperature. If it only states “compliant with XX standard” without providing a report, we reject it immediately. We especially look at the three fields of standard number + duration + temperature; they determine which type of degradation, under what conditions, and over what period the report addresses.
• Second: a reconciliation of the material covered by the report against the material grade actually ordered by the customer. The grade, blend ratio, additives, and processing method—blown film, injection molding, or sheet material—must all match. If they do not, ask the customer whether a new report can be produced using the finished formulation or whether they will accept an agreement stating “retesting required after printing.”
• Third: the basis for using the mark corresponding to the target market. Is it the EU EN 13432 home-composting mark, the US ASTM D6400 industrial composting mark, or China’s soil-biodegradability mark? These three marks cannot substitute for one another or be printed on the same package. If the customer says the product is “for export to Europe and the United States,” we must clarify whether the same package will carry both marks or whether two versions will be produced—these are two entirely different layout options.

There is also a clause we insist on including in the contract: “This quotation is based on the customer’s environmental declarations and test reports. If the customer changes the material grade or adjusts the printing process, causing the finished product to no longer comply with the above standards, responsibility shall be borne by the customer.”

Customers initially question why this clause is needed. Our explanation is: the report is issued in the material manufacturer’s name, but the consequences of mishandling an environmental claim fall on the printer—market regulators examine the mark printed on the package, and the printer printed it.

Further Reading

• Biodegradable Packaging: 4 Certification Standards: ASTM D6400 / EN 13432 / GB/T 19277 / HJ/T 209—The 3 Costs Printers Should Calculate Before Submitting for Testing—What each of the four standards covers and how to select the appropriate mark.
• 3 Certification Standards for Biodegradable Packaging Materials—Compostable/Biodegradable/Recyclable: The Real Economics Behind “Can You Pass It?”—The certification process and testing costs.
• Bagasse / PLA Food Containers: What Is the Difference Between the “Industrial Composting” and “Home Composting” Marks? 3 EU Standards Tested—The specific differences between the two marks for the same material.
• Green Printing vs Green Packaging: The Real Boundary Between 3 Standard Systems; Printers and Brands Often Confuse Them—Environmental claims made at the printing stage are not the same as those made at the material stage.
• 90-Day Soil Burial Test of Biodegradable Packaging Materials: Degradation Comparison of 4 Materials—Measured differences among the four materials, with specific figures.