by Steven A. Mojo

The ASTM Standard Specification for Compostable Plastics has improved how U.S. producers and users determine what makes plastic compostable. It also promises to improve public awareness of these products and chances at international harmonization, all while doing its part to help the environment. Steve Mojo of Committee D20 on Plastics describes just how one standard can achieve all this.

Background

In May 1999, ASTM’s Committee D20 on Plastics issued a new standard—D 6400, Standard Specification for Compostable Plastics. This marked the culmination of eight years of research and testing by leading producers and users of biodegradable plastics. More importantly, it was a turning point in the development of the industry. The goal of this paper is to discuss the developments in biodegradable and compostable plastics over the past two years and the role of ASTM D 6400.

This paper will review how the new standard has helped to generate credibility in these new materials, how it has set the stage for certification and identification efforts in the United States and, maybe most importantly, how it enabled U.S. representatives to participate and promote the harmonization of standards in this field on a global basis. It will not review the standard itself or how it was developed in detail. If the reader is interested in these topics, Ramani Narayan and Charles A. Pettigrew wrote an excellent document, which was published in the December 1999 issue of SN, titled “ASTM Standards Define and Grow a New Degradable Plastics Industry.” (Contact the editor of SN for a copy of this article or see the Web site of the International Biodegradable Products Institute (BPI).

Why was this standard so important to this industry? Prior to May 1999, no scientifically based standard existed for determining the biodegradability and compostability of plastic products. Before this point, manufacturers were free to use the test method they felt most appropriate. To measure biodegradability, most producers used tests such as those found in ASTM D 882, Test Methods for Tensile Properties of Thin Plastic Sheeting, which had historically been used to assess the physical properties of plastic films. However, none of the these tests measured the ability of the material to be assimilated by microorganisms and used as an energy source. Even though the laboratory tests indicated a significant loss of tensile strength, products frequently did not biodegrade as expected when placed into a real-world situation, such as a compost pile. Rather, the material would fragment and leave large pieces of plastic film, contaminating the compost and reducing its value. The poor performance of these materials caused a significant amount of confusion and skepticism in the market as composters and potential users found that so-called “biodegradable plastics” did not disappear as they had been led to believe.

The advent of ASTM D 6400 has changed this situation. Now there are a series of tests specifically designed for plastic products to assess their performance in a composting facility. These tests are designed to determine if a plastic product will disintegrate and biodegrade in the same way and at the same rate as other compostable materials, such as yard trimmings, food scraps, and wood chips. In this way, composters would not be plagued with non-degraded plastics and forced to screen them out and dispose of them.

While the new standard has been in the marketplace for two years, much of the skepticism and confusion about “biodegradable plastics” still exists. However, the new standard is the foundation that producers are using to generate confidence in this new class of materials and to show how they can help to divert food scraps, yard trimmings, and other compostable materials from landfills and incinerators.

Creating Opportunities

Plastic producers, users of plastic products and composters are benefiting from this new standard in a variety of ways:

• Now there is a series of tests that will clearly delineate what is compostable and what is not.
• Recognition of new compostable plastic products can be generated with a recently created labeling program for products that meet ASTM D 6400.
• U.S. representatives can more actively participate with European and Asian counterparts in standards harmonization efforts.

As mentioned previously, the new standard outlines a series of tests that replicate what takes place in a well-run municipal or commercial composting facility. (For information on the specific test methods and the rationale for each, review Narayan and Pettigrew’s article in SN). By meeting the specifications found in the standard, manufacturers will have sound scientific support for their compostability claims and know that their products will perform as anticipated in real-world situations.

Identification and labeling are two of the most critical factors in the future growth of this market. For the most part, “compostable plastics” products look and perform like the items they replace. Consumers can eat a meal using compostable cutlery and drink a soda from a compostable plastic cup and straw, and not tell the difference from conventional plastic products. Further, many composters are still skeptical about the ability of plastics to biodegrade in their facilities. To address these issues, the BPI and the U.S. Composting Council (USCC) have joined forces to create a certification and symbol to identify compostable plastic products that meet ASTM D 6400 (see the sidebar below). This symbol will make it easy for specifiers, users and composters to select plastics that are compostable.

The development of worldwide standards in this field is of critical importance to resin suppliers and processors. Creation of this new standard has enabled the United States to help move closer to this goal. For example, members of ASTM Subcommittee D20.96 on Environmentally Degradable Plastics participated along with Japanese and European representatives, in a one day conference in Wolfsburg, Germany in September, 2000, sponsored by DIN (Deutsches Institut fur Normung). The program covered existing standards and certification efforts for biodegradable plastics in Europe, Asia, and North America. There was consensus as to the three critical factors required to measure and demonstrate compostability. These are found in ASTM D 6400 and European standards and are:

• Inherent biodegradability, measured by carbon dioxide evolution after microbial assimilation;
• Ability to disintegrate, so as not to be visible or recognizable after composting;
• No impact on the ability of the compost to support plant growth.

While technical differences still do exist between the major standards, the group was confident that these could be resolved as part of harmonization efforts at ISO. Shortly after this meeting, DIN and the BPI signed a memorandum of understanding to work towards harmonization and mutual recognition of each other’s certification programs. The end result of efforts such as these is that manufacturers will be able to bring products to market more rapidly and cost effectively.

What’s Next?

The creation of ASTM D 6400 is among the first of many steps that must be undertaken to foster the growth of compostable plastics in the United States and other parts of the world. The future challenges for the industry include:

• Generating recognition and confidence in products that meet ASTM D 6400;
• Demonstrating the value of compostable plastics in the collection and recovery of potentially compostable feedstocks, such as food scraps and yard trimmings; and
• Proving that diversion of food scraps and yard trimmings from landfills is cost effective and environmentally beneficial.

Marketing of the BPI/USCC symbol and products that carry it will be an important part of recognition efforts. As specifiers, consumers, and composters see that there are products that perform as anticipated, credibility in compostable plastics will grow. As this happens, government officials and agencies will feel more comfortable in specifying products that meet ASTM D 6400 by adopting it into regulation and law.

However, for the market in compostable plastics to really grow, people must understand the role that these products play in today’s society. The expanded use of these products will make possible the cost effective collection and recovery (via composting and anaerobic digestion) of the millions of tons of food scraps and yard trimmings that still go to landfills and incinerators. These materials represent a tremendous resource for rebuilding the soil. Also, in landfills, their degradation has many unwanted effects, such as contributing to global warming. The U.S. Environmental Protection Agency estimates that if the United States collected and composted the 21 million tons of food scraps generated annually instead of sending them to a landfill, it would have the same global warming benefits as taking 2 million cars off the road.

The largest and most successful effort to date to collect and recycle food scraps took place at the 2000 Olympic Games held in Sydney Australia. By using biodegradable cutlery and food serviceware as part of an intensive recycling and composting effort, it was possible to collect and compost the wastes generated by the nine million visitors to the Games, resulting in the successful recovery of 76 percent of the solid wastes generated at the venues. This achievement would not have been possible without the use of compostable plastic products, eliminating the need for separation of plastics from the food scraps.

The landscape for “biodegradable/compostable” plastics has changed dramatically over the past decade. When first introduced, many thought that they would be the solution to the solid waste issues in the United States. However, their performance did not meet user expectations and significant confusion existed as to their appropriate uses and characteristics. But over time, the picture has become much clearer. Now manufacturers and others understand their role in helping to recover food scraps and yard trimmings. They understand the need for their applications to perform as expected during use as well as within disposal systems that utilize biologically active environments. And with the advent of ASTM D 6400 and the “Compostable Logo,” the industry has scientifically based tools by which to judge the performance and to communicate the benefits of their product. //

Copyright 2001, ASTM