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A Primer Biodegradability Testing Methods

• Aug 01, 2020

In the past year, we have seen a growing interest and commitment to the environment at both the business and consumer levels. More businesses are focused on providing environmentally friendly products, sourcing sustainable materials and reducing the impact of their waste stream. Plus, consumers are better educating themselves about the companies that they support, the products they purchase and companies’ sustainability practices.

This mindset has also carried over to Personal Protective Equipment (PPE). In PPE, the objective has always been to protect workers and their health. But, today, customers are looking for ways to be more environmentally responsible as well. At SW, the concern about our products’ impact on the environment has been top of mind for years. As one can imagine, millions of nitrile gloves get used and discarded daily, so a proprietary EcoTek technology was developed to address this. As part of the EcoTek development process, a great deal about materials and biodegradability was learned, including that in order to develop responsible products, it was critical to learn about the biodegradability testing methods. Here is an overview, or primer, of the leading methods with the goal of providing a basis for further learning.

There are two main accepted and respected methods for testing biodegradability—referred to as ASTM D5526 and ASTM D5511. Both are established by ASTM International. In short:

• ASTM D5526 is the Standard Test Method for Determining Anaerobic Biodegradation of Plastic Materials Under Accelerated Landfill Conditions. The ASTM D5526 method is the more stringent of the tests, as it runs longer in duration and better simulates real-world landfill conditions.
• ASTM D5511 is the Standard Test Method for Determining Anaerobic Biodegradation of Plastic. ASTM D5511 is a shorter test, in a simulated laboratory condition and assumes long-term expected biodegradability timing based on short-term measures.

The ASTM D5526 testing method as it is considered the more reliable of the two. This test can be run for as long as required to establish the time it takes for a glove to break-down, providing a more accurate assessment. The ASTM D5526 test mimics the most common landfill conditions. Glove samples are placed in three different, oxygen-free simulated landfill environments with varying amounts of solid wastes, at a constant temperature—referred to as wet, moderate and dry conditions. The breakdown of these samples is measured over time until the test ends after a requested number of days, or no further decay is measured. The biodegradability of the glove is then measured as a percentage difference between the remaining solid material, and the total original material.

The ASTM D5511 test is the shorter of the two tests. It is traditionally 30 days long. This test is frequently used as a stand-in while the longer ASTM D5526 is being run to provide an initial assessment of biodegradability. The ASTM D5511 test measures biodegradation under ideal landfill conditions in the laboratory. Glove samples are placed in a system where the levels of waste within are managed to encourage maximum bacterial activity. As with the ASTM D5526, the remaining solids are subtracted from the total original sample to provide the total amount of biodegradation.

It should be noted that ASTM International discourages extrapolating the final biodegradation percentage and timeline from this test because it presents a false sense of security. ASTM recommends that this test not be cited if ASTM D5526 results exist for the same material.

There are two additional tests that are critical in this process as well: the BMP tests that provide an indication of a material’s potential for biodegradation, and the ASTM E1963 test which determines if a material is harmful to plant life.

• The BMP tests (Bio Methane Potential) are a series of short tests that measure the methane output of a sample as it is consumed by anaerobic bacteria. These tests may only be relied upon to determine if a material has the potential to biodegrade. There are no established standards for BMP tests and results may vary from lab to lab.
• ASTM E1963 is Standard Guide for Conducting Terrestrial Plant Toxicity Tests. The ASTM E1963 verifies whether or not a material is toxic to plant life. Samples of a material are introduced to a number of plants, and the development of these plants is monitored. Any material that can be shown to inhibit proper growth and development of the plants is considered toxic. There is an additional method or certification worth mentioning here: the Cradle to Cradle Certified process. This certification is provided by the Cradle to Cradle Product Innovation Institute, a global non-profit. It is a voluntary material health certification process to ensure that a product is composed of materials, and made by processes, that adhere to a specific philosophy. This philosophy treats the environment as a complete organism whose metabolic process should be nurtured by avoiding toxins, non-biodegradable materials or unduly wasteful manufacturing techniques.

While this primer is an initial overview of the main methods for testing biodegradability, it is critical that all testing must have clarity in the reporting of the results. Environmental responsibility cannot be a box to check for companies—it needs to be a top-down corporate mindset and a philosophy that permeates the organization.

This article originally appeared in the August 2020 issue of Occupational Health & Safety.