August 17, 2010 | General

Understanding Variables In Compostable Product Testing

BioCycle August 2010, Vol. 51, No. 8, p. 31
Which compostable food service items are right for your facility?
Steve Mojo

FOR 10 years, the Biodegradable Products Institute (BPI), which promotes use of biodegradable polymeric materials, has supported diversion of food scraps from landfills to composting facilities. Over the past decade, the benefits of going in this direction are becoming more apparent and now include the potential reduction of greenhouse gas emissions from landfills. As composting facilities search for more food scraps (and receive requests to process these materials), they will increasingly encounter food service items that comply with the ASTM D6400 or ASTM D6868 standards to disintegrate and biodegrade satisfactorily under composting parameters outlined in the specifications.
For this reason, actually testing products in a given composting process may be the best way for a facility to determine which items are right for them to receive. However, it is important to keep in mind that “testing” of compostable items is subject to many factors. This is illustrated in the article, “Compostables Trial At Municipal Yard Trimmings Operation,” on page 28 of this issue.
Biodegradation testing is inherently variable. How items are placed in the piles, along with the moisture, oxygen and feedstocks surrounding them, all influence how well an item biodegrades. For example in a test run a few years ago, a composter placed five identical cups in their piles. At the end of the test, three cups passed and two failed. The composter went on to take a few loads that contained these cups and found that they fully biodegraded during processing. This highlights that even items that are known to fully biodegrade during composting may not do so in a given situation.
In some cases, composting facilities conduct the product trials using mesh bags. This will increase the variability of a given test. While it is easier to find the tested items, the mesh bags can limit the amount of moisture or oxygen that gets to the test items. These factors can reduce the overall rate of disintegration and biodegradation.


Many products that claim to be “biodegradable” or “compostable” are made with traditional, nondegradable plastics. Despite the manufacturer’s claims, these items will never biodegrade. Testing on a number of cutlery items last year showed that they consisted of 30 to 70 percent polypropylene, to which starch has been added. Non-ASTM compliant items are typically marketed as “biodegradable” and able to stand temperatures up to 245°F or higher. Often they are cheaper than compostable items that meet the ASTM specifications. Composters should be wary of products that only claim to be “biodegradable” and do not meet ASTM D6400 or ASTM D6868. There are no specifications for making a “biodegradable” claim and hence, you do not know what you are getting.
Vendors selling compostable food service products need to do a better job of distinguishing compostable items from noncompostable ones. In some cases, it is hard to tell which items in a distributor’s catalogue meet the ASTM Specifications and may be BPI-approved from the items that do not. Purchasers should be sure to specify compostable foodservice items (i.e. meeting ASTM D6400 or D6868), if they are involved in a food scrap diversion program. At the same time, distributors and vendors should make sure that they understand the real needs of the customer.
As composters expand the array of feedstocks accepted, they will need to decide what items will work within their system and what will not. Products that meet ASTM Specifications D6400 and D6868 are composting successfully in sites throughout the U.S., Canada and Europe. In order to determine if products that meet these specifications will work satisfactorily for them, composters can conduct qualification tests and move forward at a measured pace.
A good place to find products that meet the ASTM Specifications is the BPI website: If you do use a BPI approved product, please let me know how they are working in your system by emailing

Steve Mojo is Executive Director of the Biodegradable Products Institute.

Sign up