In recent years, a number of innovative bio-based plastics sourced from renewable feedstocks have emerged as alternatives to traditional, fossil fuel-based plastic packaging materials. According to the Institute for Local Self-Reliance’s “About Bioplastics,” whether made from corn, potatoes, palm fiber, wood cellulose, or bagasse, the North American market alone accounted for around 37.5 percent of global bioplastic usage in 2010 and is projected to increase from 0.3 million metric tons in 2011 to 1.2 million by 2016, according to Douglas Smock’s “Bioplastics: Technologies and Global Martkets," September 2010 report.
The increased production and application of new bioplastic materials can be attributed to a number of environmental advantages over their petroleum-based counterparts, including the reduction of finite fossil fuel consumption in an energy dependent society, climate change mitigation due to CO2 savings from carbon sequestration of the bio-based sources, and use of the materials in conjunction with corporate social responsibility (CSR) programs to improve a company’s environmental image and meet the preferences of today’s more sustainable-minded consumer.
In addition, unique end-of-life opportunities are open to certain bio-based polymers, such as Polylactic Acid (PLA) and Polyhydroxy fatty acids (Polyhydroxyalkanoates or PHA), which are designed to be compostable in industrial composting conditions.
However, according to the California Organics Recycling Council, not all bio-based polymers are designed to be biodegradable, and not all those intended to biodegrade will necessarily compost.
Biodegradable or Compostable?“Biodegradable” plastic is a plastic that will degrade from the action of naturally occurring microorganisms (e.g. fungi or bacteria) over a period of time, while a “compostable” plastic is defined by the ASTM as a plastic, “that undergoes degradation by biological processes during composting to yield CO2, water, inorganic compounds, and biomass at a rate consistent with other known compostable materials and that leaves no visible, distinguishable or toxic residue.” The main differences between the two are the stipulated requirements for remaining toxic residues and time for the biodegradation of the compostable plastic.
Currently in the U.S., the primary method of packaging waste disposal is landfilling, where 54.2 percent of municipal solid waste (MSW) was discarded in 2010, according to the EPA.
While many plastic materials are compatible with current mechanical recycling processes, certain applications of plastics for food and pharmaceutical use can cause contamination issues that impair their physical recyclability. However, designing single-use disposable plastic packaging to be compostable, and therefore recoverable within the organic recycling (also known as composting) stream, may potentially ease the end-of-life burden of these materials that would have otherwise been destined for the landfill or incineration. Compostable packaging can also increase diversion of food waste from the landfill, which rapidly releases methane (a potent greenhouse gas) during its decomposition.
Despite the benefits of certain applications of bio-based plastics packaging, they face a multitude of challenges to proper sorting and recovery that can create a barrier to a positive end-of life within the composting stream in the U.S.
Key Issues Facing Compostable Plastics in the U.S.Over the past few years, the number of industrial composting facilities in the U.S. that more readily accept items such as packaging has declined. The limited ability of the country’s composting infrastructure to treat packaging is due in part to insufficient source-separation of organics at the municipal level, as well as a lack of industrial composting facilities treating food waste due to high cost and strict regulations. In addition, a disconnect between packaging designers and the composting facilities expected to handle these materials at their end-of-life have resulted in barriers to focused, closed-loop organic recovery processes.
In 2010, the Sustainable Packaging Coalition released a study titled “Compostable Packaging: The Reality on the Ground,” which provided insight into a focused sample of 40 U.S. composting facilities that readily accept food waste. The results revealed that a majority of the facilities surveyed actively accept compostable packaging, though most of it is fiber-based.
However, when it comes to compostable plastic packaging, many facilities don’t want it due to the following issues:
• contamination of the organics stream with non-compostable plastics, resulting in costly sorting processes or a lower grade compost product
• the length of time required for compostable packaging to break down (compostability certifications allow a longer timeframe to degrade – 180 days or 25-26 weeks – than other kitchen and food waste organics targeted for treatment in commercial composting facilities, according to a presentation by Bhalala Heeral at the USCC Compostable Plastics Symposium)
• lack of clear, standardized labeling and design of certified compostable packaging
Beyond facility rejection, these degradable materials have faced broader criticism for their potentially negative environmental impacts when not disposed of properly. For example, flexible or rigid plastics designed to be degradable or compostable are viewed as contaminants to the existing plastic recycling streams due to the challenges in separating materials like PLA from the existing PET plastic stream, and the weakening effect PLA has on the recycled PET.
Moreover, since the economics of recycling processes work best with large volumes of like plastics, newer polymers with low volumes on the market are not targeted for mechanical recycling. Attempts to keep compostable plastics out of the recycling stream and their lack of current acceptance into the organic stream means they are increasingly landfilled in the U.S., where their eventual decomposition can emit methane into the atmosphere at a faster rate than other materials.
Best Practices: Proper Standards and CertificationsTo improve the prospects for acceptance and treatment, standards for biodegradability of compostable plastics have been developed or are under further development by national standards bodies across the world, including ASTM (U.S.), BNQ (Canada-Quebec), CEN (European Union), DIN (Germany), JIS (Japan) and the International Standards Organization (ISO).
For compostable packaging to achieve its intended end-of-life potential within an industrial composting facility, those placing the item on the market within the U.S. need to ensure that it is designed to meet the appropriate defined standards to be certified as “compostable”:
• ASTM D6400 - Standard Specification for Compostable Plastics (or European equivalent EN 13432)
• ASTM D6868 - Specification for Biodegradable Plastic Used as Coatings on Paper and Other Compostable Substrates
• ISO 16929 - Plastics--Determination of the Degree of Disintegration of Plastic Materials under Defined Composting Conditions in a Pilot-Scale Test
These standards all specify the plastics materials’ requirements for biodegradation, disintegration, heavy metals limits, and requirements to prevent any negative effect on the composting process or compost quality. ASTM 6400-certified compostable plastic materials need to be properly labeled to communicate the intended diversion of them into the organics waste streams and for industrial composters to properly recognize that the certified materials have been tested and are suitable for aerobic composting conditions.
The U.S. Composting Council, jointly with the Biodegradable Products Institute (BPI), established a certification scheme for compostable plastics meeting the ASTM D6400 specification standard. Companies whose finished products are certified as meeting ASTM D6400 and/or ASTM D6868 can use the “Compostable” logo to provide assurance of compostability or biodegradability. If BPI certified, the material manufacturer must be listed on the BPI website.
This logo is the recommended labeling for all certified compostable plastics to ensure they can be properly recognized, sorted and recovered within an organic recycling facility.
Increasing Organic Recycling PracticesAccording to the California Organics Recycling Council, proper management of compostable plastics entails addressing a number of challenges to ensure the targeted end-of-life potential is achieved, including:
Standardization of environmental claims language for bio-based and compostable packaging and proper labeling of compostable plastics.
This practice is essential for the proper sorting and diversion of compostable plastics, and brand owners must be held accountable for greenwashing practices such as incorrectly labeling their products as compostable, biodegradable, or bio-based. The Federal Trade Commission’s Green Guides specify guidelines for the use of environmental marketing, but are not often enforced.
Compostable plastics may not be a solution for all non-recyclable plastic waste. But if used in focused, closed-loop scenarios, which avoid contamination of existing plastic and organic recycling streams, their benefits are persuasive.
Environmental Packaging International (EPI)
Institute for Local Self-Reliance
California Organics Recycling Council
Sustainable Packaging Coalition
US Composting Council
Biodegrdable Products Institute
U.S. Department of
Agriculture BioPreferred Program