The Compostable Field Testing Program’s (CFTP) goal has been to ask and answer what is happening to compostable packaging in real-world composting conditions. Understanding how certified compostable materials break down helps everyone invested in the circular economy for compost. Composters benefit when they know more about the optimal processing conditions for material disintegration. Compostable product manufacturers benefit when they understand how their products and materials do and don't fit into different composting systems. Policymakers benefit when they understand the complexity and variability of composting systems. And we all benefit from greater clarity.
WHAT THE DATA SAYS
The Big Four Takeaways
Analyzing both quantitative and qualitative data has yielded four key takeaways.
The data confirms that certified compostable products do break down, but that effective breakdown is dependent on the right mix of composting conditions. These insights shed light on the complexities of compostable product acceptance,
the critical role of operating conditions to interpret field test results, and the evolving nature of the test methods themselves.
1. Certified compostable packaging does break down! Under the right conditions...
The data shows that all types of certified compostable packaging leave no residuals under the right composting conditions. This validates compostability claims that are based on lab-based biodegradation and disintegration tests.
The optimal composting conditions for disintegration varies by material type. Time, temperature, moisture, processing technology, and feedstock variations can influence composting conditions and thus compostable product breakdown. Managing these complex interactions is the daily job of composters.
Trends for food waste diversion are driving more composters to encounter certified compostable packaging in their feedstock. It's important to understand what combinations of operating conditions are suited for these materials, and the feasibility of composters meeting them when these conditions vary from their baselines.
2. Operating conditions are as important as disintegration data to interpret field test results.
The results emphasize that operating conditions, such as temperature, moisture, maturity and stability, and duration play a significant role in influencing disintegration outcomes, making them as critical as the disintegration data itself when interpreting results.
3. Field testing is a key tool - and the methods are still evolving.
Both the mesh bag method and the dose method have strengths and weaknesses; neither is perfect. All interpretation of field test results should take into account the quality of the tests themselves.
The mesh bag method has been in use the longest. By containing and tracking individual items, it allows ease of recovery and yields results on an individual item basis. However, items are not exposed to agitation and the mesh bag has been shown to inhibit moisture flow which impacts the composting process.
The dose method on the other hand is a new approach, practiced only a handful of times. This method does expose products to the in-situ conditions loose in a pile, but this requires a lot more products, is free-mixed which increases the risk of contamination with foreign materials. Current sampling methods yield approximate results with an unknown margin of error.
Both the mesh bag and dose methods lack a widely agreed-upon positive control material.
4. Compostable product acceptance is more complex than just disintegration.
Neither a positive or a negative disintegration result is sufficient information to determine acceptance of materials at a compost facility.
Products commonly viewed with suspicion by composters, such as biopolymers, tended to have significantly less residuals than widely accepted fiber-based products. The difference between field data and acceptance comes from how we view these different materials, their role in finished compost, and the risk of contamination from non-compostable plastics and lookalikes.
Even when a field test result shows a product is breaking down in its entirety, this doesn't translate to obligatory acceptance by a composter.
Contamination of non-compostable plastics and lookalikes confuse the issue. Variability in operating conditions at different depths and locations in a pile, from pile to pile and season to season, all impact how well a product does or doesn't break down at a compost site.
Managing contamination from non-compostable plastic lookalikes remains a challenge even if compostable items are breaking down. Deciding what is allowed in feedstock involves a comprehensive review of contamination risk.
This finding underscores the need for a more nuanced approach to evaluating compostable products, and an opportunity for technologies with more controlled operating conditions to fill a market niche.
Keep going to read takeaways for composters, policymakers, packaging manufacturers and brands.
WHAT COMPOSTERS CARE ABOUT
The composter who takes food scraps will likely encounter the question, "What compostable packaging items do you accept?" Lab-based test standards are designed to ensure a product's ultimate compostability and safety in soil, but a compost facility is not a lab. The high variability in compost operations impacts how certified compostable products break down. Field testing shows us how products disintegrate under real-world conditions.
What a composter said
“Based on the results from our test with the Compostable Field Testing Program, we decided to accept a limited number of compostable products from three trusted manufacturers that passed our field tests in our turned windrow system. We are in the process of working with commercial restaurants and community events to allow a limited quantity of these tested products. We would never have taken this step if we had not conducted the field test with the support of the CFTP.”
Certified compostable packaging will break down under the right composting conditions. Optimal conditions for disintegration —such as temperature, moisture, and feedstock—vary by material. If a site's operations differ from those conditions, compostable products may not break down completely without an adjustment.
Despite common perceptions, field tested compostable biopolymer materials generally have fewer residuals than fiber-based products. This result is consistent across test methods and facility types.
Disintegration results is only one part of a larger decision-making process around acceptance of compostable products at a compost site. Composters report that other factors such as contamination from non-compostable and look-alike products inform their acceptance.
Both field testing methods (mesh bag and dose) offer useful data, but refinement is needed. Data from each method shows consistent trends, but the variability in results points to an opportunity to improve testing. The CFTP is dedicated to research to advance the methods with a science-based and transparent approach.
PERSPECTIVES FOR POLICYMAKERS
Policymakers balance the needs of the economy and the environment, ideally with people and planet care at the center. Field testing data helps inform decisions on waste management policies and infrastructure investments to promote a circular economy.
What a regional district said
"We want to help our residents divert food scraps, and to do that, accepting some form of bin liner into our composting facility is a strategy to improve diversion. We plan to field test to help understand what different compostable biopolymer bag options could work for our operations."
Certified compostable packaging breaks down successfully under optimal composting conditions, but these conditions are not uniform across facilities. It's important for policy to consider the operational diversity of composting sites and to support composters in enhancing their operations for desired feedstocks.
Accepting compostable products requires more than positive disintegration results. Consideration must be given to education and contamination prevention. Quality data can support a clean stream of compostables for facility operators, leading to improved diversion.
Field testing methods are still evolving. Current data should be interpreted cautiously. Basing policy on field test methods, which are actively being improved and have yet to be standardized, could lead to inconsistent or ineffective regulatory outcomes.
Understanding composting site operating conditions—like temperature, moisture, and time—is critical to interpreting disintegration data. Policies should support composters with reliable scientific data.
INSIGHTS FOR PRODUCT MANUFACTURERS AND BRANDS
Lab-based biodegradation testing and associated certifications have been the norm for the past several decades of compostable packaging development. Field testing for disintegration is an important bridge between the lab and real-world operations and the lab-based conditions for disintegration testing.
In the words of a manufacturer
“The release of the CFTP's data in this detail is very exciting. I think there's a real opportunity for open-source field testing data to create a feedback loop between field testing results and the manufacturing sector."
Certified compostable packaging does break down, but only under the right composting conditions. The right conditions for complete disintegration vary by material type. Manufacturers have a responsibility to consider and understand how their products will perform in diverse composting environments with variable operating conditions, and communicate the conditions required for their specific products.
Composters’ acceptance of products is not solely based on disintegration. For example, fiber-based products, often favored, actually have higher residuals than biopolymers in field tests. Manufacturers must consider the full composting process, including contamination risks and facility-specific needs, when designing products for compostability.
Manufacturers have a responsibility to design compostable products that are easily identifiable from non-compostable look-alike items. Product design and labeling must account for both perception and performance, to help composters mitigate contamination.
Field testing is an important tool for manufacturers with useful data, but the methods still need refinement. Field tests provide useful feedback, but their limitations should be acknowledged in product development. Manufacturers have a role in helping refine and standardize these methods.
Manufacturers should understand that composting facilities have varying operating conditions. The successful breakdown of compostable products is as much about these variables as the product design itself. A facility not operating within the range of conditions required to break down a particular material will not be able to process it.