Busted: Common myths and misconceptions around compostable plastics

Misconception 1: All bioplastics are biodegradable/compostable

It is an easy mistake to make, but not all bioplastics are biodegradable. Quite the contrary, the main feature of many bioplastics is the fact that they are made from renewable resources, biomass. Most of these biobased materials are durable commodity plastics such as bio-PE or bio-PET with the same properties as their conventional counterparts. Neither PE nor PET is biodegradable, which demonstrates that the feedstock basis of a material has nothing to do with its characteristic to biodegrade. Biodegradability is an inherent feature of a material and its chemical structure. Bioplastics are a diverse family of materials with different properties. There are three main groups: Biobased, non-biodegradable materials such as PE, PET or polyamides; biobased and biodegradable materials such as PLA, PHA, and starch blends; and fossil-based, biodegradable materials such as PBAT which are mainly used as a blend for biobased and biodegradable plastics. Biodegradability is an additional feature that adds value for specific applications, such as biowaste bags or food packaging. It is not, however, the single defining attribute of bioplastics.

Misconception 2: Biodegradability is the same as compostability

Strictly speaking, biodegradation is but a collective term for a natural chemical process in which materials are transformed into natural substances such as water, carbon and biomass with the help of microorganisms. Biodegradation can occur in many different environments (soil, marine environment, composting and fermentation facilities, etc.) and under varying conditions (absence or presence of oxygen, bacteria or fungi) and at different levels of influencing factors, such as temperature, humidity and timeframe. In order to be able to make any substantial claim on the biodegradability of a material or product, all these different factors need to be taken into consideration. Resorting to acknowledged standards, which are more than a mere testing method and provide clearly defined pass/fail criteria, is the most commonly accepted way of doing so.

The European Standard for industrial compostability, EN 13432, for instance, defines the minimum requirements that materials have to meet in order to be processed in industrial composting plants (timeframe, temperature, humidity, etc.). If these requirements are not met or can't be proven, any reference to the standard or claims about compostability of the product would be considered greenwashing.

Wherever there's a successful innovation, you will find "free riders" attempting to piggyback on the good reputation of products that adhere to accepted standards, without fulfilling the latter. This hampers the market development for environmentally responsible, standard-adhering products and potentially poses a threat to the environment. European Bioplastics, the European association of the bioplastics industry, has long been warning against the malpractice of producers of additive-mediated plastics, including oxo-degradable plastics, falsely claiming that their materials (bio)degrade. These claims have not been scientifically proven and do not comply with any of the acknowledged standards for biodegradability and industrial composting (ASTM D6400 or EN 13432). Furthermore, in a recently published peer reviewed publication, scientists at Michigan State University's School of Packaging and the MSU's Biosystems and Agricultural Engineering department concluded that "no evidence was found that these [degradable] additives promote and/or enhance biodegradation of PE or PET polymers." 

Yet, the harm has been done. In a recent post published on the PlasticsToday blog, the editor has fallen into the same trap, offering a company called ENSO, a degradable additive supplier, as an example of what she calls "reasonable alternatives" to compostable products. What she doesn't mention is that California's Attorney General filed a first-of-its-kind "greenwashing" lawsuit against ENSO, over alleged false and misleading marketing claims on their degradable additives. Products based on the ENSO additives have apparently since disappeared from the shelves. This case demonstrates that the key to the success of emerging biotechnologies are acknowledged standards and stricter guidelines on how to communicate these claims in order to allow for informed consumer choices.

On the other hand, the value proposition for compostable plastics is well recognized in the market and at the municipal level. Compostable products are a key tool in the zero waste programs successfully implemented by major municipalities such as Seattle and San Francisco. In fact "the ASTM Standard Specification for Compostable Plastics D6400" is explicitly called out in California law (SB-567). The same law also prohibits "the sale of plastic packaging and plastic products that are labelled with the terms biodegradable, degradable or decomposable," which has found bioplastics producers and the recycling industry unanimously in strong support, because it precisely eliminates the sort of false and misleading marketing claims that can otherwise occur.  

Misconception 3: Compostable plastics are the solution to landfills and littering

Biodegradable materials are often wrongly presented as a way to help minimize the amount of waste in countries that have no existing waste management infrastructure. Yet, biodegradable plastics should not and cannot be considered a solution to the problem of littering and landfilling. In fact, littering must never be promoted or accepted for any kind of waste. Instead, the issue needs to be addressed by educative and informative measures to raise awareness for proper and controlled ways of management, disposal and (organic) recycling.

Municipalities are now deeply engaged with the complexities of handling their solid waste streams. Bioplastics are suitable for a broad range of end-of-life options, including reuse, mechanical or organic recycling, and energy recovery. The use of compostable plastics makes separate biowaste collection a more valuable option and helps divert more organic waste from recycling streams or from landfills and increases the volume of valuable biomass (compost). Cities like Seattle and San Francisco in the United States and entire countries like the Netherlands recognize and capitalize on the role of certified compostable products in that endeavor. Misleading claims about "false benefits" of biodegradability only distract from what we as a society really need to be focusing on: Getting better at diverting valuable material streams away from landfills.

Hasso von Pogrell is Managing Director of European Bioplastics.