FREQUENTLY ASKED QUESTIONS

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ABOUT THE PROGRAM


What is the compostable field testing program?  

The Compostable Field Testing Program (CFTP) is a non-profit, international initiative to bring field testing of compostable products to composters and to collect, anonymize and publish the resulting data. 

The program was officially founded in 2016 by the Compost Research and Education Foundation (CREF) and BSIbio Packaging Solutions (BSIbio). The program has only succeeded with considerable support and advisory from other entities across North America. 

With the publication of the CFTP's Results Dashboard, and the accompanying Field Report coming in late 2024, the founding objectives of the CFTP will have been achieved, enabling new research directions to build on this foundation.

What is the purpose of the compostable field testing program?  

The CFTP's purpose is to: 

- Provide composters with easy-to-use field test methods and starter kits to assess compostable item disintegration in real-world facilities while capturing operating data and disintegration results
- Assist compost facilities in producing quality field test results
- Gather the resulting data on disintegration and operating conditions, then anonymize and publish it 
- Track emergent research questions and share these with the wider value chain for compostable products

What kind of compostable materials have been tested?

Materials tested in the CFTP include fiber, lined fiber, and compostable polymer products. The specific materials include:
- PLA (both amorphous and crystallized)
- PLA-lined paper (from tree fiber)
- Bagasse (sugarcane fiber)
- PLA-lined Bagasse
- Paper (from trees)
- Molded fiber (from mixed sources such as wood, bagasse and bamboo)
- Cellulose film (derived from trees)

Can I field test and contribute my data?

Absolutely! If you are interested in conducting a field test, please reach out to us through our Contact Form.

How is compostability researched? 

Compostability research can be loosely categorized into: 

Laboratory studies: These studies are conducted in a controlled environment to evaluate the rate of decomposition of compostable products and microbial growth. They follow standardized methods, for example ASTM D6400, to assess the biodegradation and the disintegration of compostable materials. 

Field studies: These studies are conducted in a real-world setting to evaluate the performance of compostable products inside a composting facility. They assess the disintegration only. Field studies require that laboratory studies exist to confirm a product is actually biodegrading, that is, being converted by microbes at a molecular level. 

What field test methods are used in the CFTP?

The primary method the CFTP uses, and the most common method for field testing, uses a mesh bag to contain the test items along with feedstock during the test - called the "mesh bag method". An alternative "bulk dose" method for situations where containment is not possible or desired has been tested and remains under development. Disintegration results from both test methods are viewable in the Results Dashboard

What composting methods / Technologies Have Participated in the field testing program?

The facilities which have participated in the CFTP represent the following technologies:
- Aerated Static Pile; including both Extended and Covered Aerated Static Pile, which may deploy biological covers and/or synthetic textiles
- Turned Windrow
- Agitated In-Vessel

There have also been two trials involving High-Solids Anaerobic Digestion followed by either tunnels or static pile. The data for these trials is not included in the Results Dashboard as it is focused on results in aerobic facilities. 

What other research questions does the CFTP have?

Although the CFTP's focus has been exclusive to disintegration results and whether/how disintegration results correlate to specific operating conditions, additional research questions have emerged and been of interest, including:

- How does the microbial community vary within a mesh bag and the surrounding material? 
- How do other operating parameters vary between the mesh bag and the surrounding material, e.g. moisture, temperature, pH?
- What happens to the fragments of compostable items that end up in the 'unders', below the screens, during analysis in a field test? Do they continue biodegrading? 
- How does the presence of compostable biopolymers impact microbial communities? 

ABOUT THE DATA


Why are results shown by % Residual?

When data is gathered in a field test, the qualities of an intact test item are compared with the qualities of the residuals of that item after testing. 

The % Residual Remaining, whether by weight or surface area, is the most direct way of reporting these results. It tells what percent of the original product is left at the end of the field test. 

The % Residual Residual is the inverse of % Disintegrated - if the residual's remaining weight or surface area is 100%, that means it's 0% disintegrated. On the other hand, if the residual is 1% of the intact item, it's 99% disintegrated. 

What are the pros and cons of weight vs surface area for measuring residuals?

The CFTP's data includes three different measurements that can be taken of an item residual in a field test:

1. Wet weight - weighing residuals, with compost brushed off them, right when they get out of the test. Items are likely to still be as moist as the compost pile.
2. Dry weight - weighing residuals after they have been air-dried or oven/microwave-dried for long enough that they've reached a stable dry weight. Only items which are deformed by oven-drying are air-dried, like biopolymers. 
3. Surface area - calculating the 2D surface area based on photographs. 

Since the CFTP's original goal was to make field testing as accessible as possible, the only measurement that was required in tests over the years is the wet weight. As the CFTP's test methods were refined over the years, surface area data has begun being collected since 2023.

Weight measurements are easier to get, but tend to be more conservative than surface area. Surface area is very labor-intensive, thus more expensive to gather, and the limitations of the analytical software can result in either over-estimations or under-estimations of disintegration. However, overall surface area will report a higher rate of disintegration than weight. 

In both measurements, the end residual can yield a higher value than the intact value (greater than 100% residuals remaining). Neither measure is perfect, and both are useful. 

What are the pros and cons of testing by mesh bag vs dose? 

The mesh bag method contains test items with feedstock throughout a field trial. This allows for tracking of individual test items, and the end results can be expressed on the individual item level. A CFTP mesh bag test will generally include between 10 and 30 individual items (or replicates) across 8 to 20 different item types. The mesh bag method poses some challenges which can generate conservative results. There is a lack of industry consensus on a positive control material. Also, the lack of agitation during the compost process and the mesh presenting a barrier to free flow of moisture and microbes  potentially limits disintegration within the bag. The mesh bag method is still the most commonly practiced method. 

The dose method involves adding loose test items into feedstock and mixing. It requires the use of 100s to 1000s of individual items across a limited number of item types which must all be easily differentiable from one another. The results are expressed for an item type as a whole, rather than on an individual-item basis.  The dose method has the benefit of working for facilities that can't use a mesh bag, such as agitated in-vessel facilities. It also more closely represents the real circumstances for these items when they enter a compost facility, as the items are in direct contact with the rest of the pile and undergo whatever agitation or turning the facility implements. This test method has increased costs compared to the mesh bag, and is in the early stages of development and refinement on gathering and interpreting the disintegration data. 

Why are some results over 100% residuals? 

When assessing item residuals at the end of a field test, there's a likelihood that the weight or surface area will actually be higher than the intact item. This doesn't always mean that the item did not break down; it can mean it was impossible to separate the residual from detritus or it absorbed non-evaporable substances. Although this represents a source of error in the data, CFTP has elected to preserve these data points in the dashboard since they tell an important story about variations in data gathering methods and analysis.

In the results dashboard, no data points are excluded based on exceeding original weight, but the data is automatically "capped" at 100% residuals (or 0% disintegrated). Data can be viewed without capping at 100% by selecting the checkbox to Show results with over 100% Residuals Remaining. This only works if you have selected in the Display Options to show results by % Residuals Remaining.

How do I read a box-and-whisker plot? 

Click over to the Results Dashboard page then scroll down to see tips on how to read and interpret a box-and-whisker plot.

Why are Fiber-based products showing low disintegration / high residuals left over?

In the mesh bag results, the fiber-based items tend to show lower disintegration / higher residuals than biopolymer products. This is consistent with other field testing results led by other organizations. 

Although more research is required to have decisive answers to this question, there are early signs in the data that moisture and agitation are crucial for fiber breakdown. Thus, since the mesh bag method exposes test items to little to no agitation, the method itself could actually inhibit fiber breakdown. 

Another factor is trial duration. Many facilities operate on increasingly shorter timeframes, as short as 30 days or less, when compost is still quite hot. However, fiber is broken down mostly by fungi, which thrive at lower temperatures that generally come after the initial phase of composting. If a facility is screening before curing, or if a field test ends before the fungal communities proliferate, the fiber products will not have been exposed to the conditions important for their breakdown, leading to high residuals left over. 

I heard compostable polymers don't really compost, so why do the results show they're breaking down? 

A report that compostable polymers aren't breaking down might be due to confusion with conventional contamination. It can be hard or impossible to distinguish between a compostable polymer and a conventional, non-compostable polymer, especially at the end of a compost process. 

As for why the results show generally high breakdown for compostable biopolymers - by and large, the field tests for this data took place in facilities that operate within the recommended initial ranges for thermophilic composting. This includes high temperatures and reasonably high moisture values, which are preferred conditions for biopolymers to undergo biodegradation. If biopolymers hit this critical stage, there's a higher likelihood that they will break down completely.
The reverse of this is a second reason for reports that compostable products don’t compost. If the high temperatures and moistures that help biopolymers break down aren't reached in the first phase of composting, they're likely to not break down completely by the end of the composting process. When this happens, it will appear that the polymers are not compostable.

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