Does it make sense to use biodegradable, compostable plastics?

SunChips’ conversion from a 33% PLA structure last year to a 100% compostable PLA structure in 2010, resulted in the following claim, prominently printed on the front of the SunChips bag: “WORLD’S FIRST 100% COMPOSTABLE CHIP PACKAGE”, while the back of the bag is covered by declarations about the bag’s compostability. The Sun Chips website goes even one step further and states: “BECAUSE THE EARTH LIKES TO EAT HEALTHIER TOO” and when you wait awhile the projected chips bag disappears in the mud.

However, a Canadian municipal composting program is telling consumers not to place SunChips bags in composting bins because they take too long to break down. SunChips, from the Frito-Lay unit of PepsiCo, switched early this year in Canada to bags made from 100% polylactic acid (PLA). The Green Bin Program of Canada’s Niagara Region discovered that SunChips bags take 14 weeks to biodegrade, which is too long; single-layer compostable trash bags take only three to four weeks. The Niagara Region is advising consumers to discard SunChips bags with regular trash.

Some ten years ago the packaging industry started to attract consumer’s attention for biodegradable plastics, and, although still in its infancy, biodegradable plastics continue to enjoy a growing interest with the public at large.
Biodegradable plastics, however, do not automatically solve environmental problems simply because they can be composted. Their use only makes sense if they are more sustainable than non-biodegradable materials at a performance level that is the same or even better. The biodegradability is supposed to create added value, for instance, by disposing as organic waste to be composted rather than incinerated.

Biodegradation*) takes place when micro-organisms utilize carbon substrates to extract chemical energy that drives their life processes. The carbon substrates become ‘food’ which micro-organisms use to sustain themselves.
Under aerobic conditions (composting, soil), the carbon is biologically oxidized to CO2 inside the cell releasing energy that is harnessed by the micro-organisms for its life processes. Under anaerobic conditions (landfills), CO2+CH4 are produced. Thus, a measure of the rate and amount of CO2 or CO2+CH4 evolved as a function of total carbon input to the process is a direct measure of the amount of carbon substrate being utilized by the micro-organism (percent biodegradation). This is fundamental, basic biology and biochemistry taught in freshman classes and can be found in any biochemistry textbook. This forms the basis for various national (ASTM, EN, OECDI) and international (ISO) standards for measuring biodegradability of microbial utilization of chemicals and biodegradable plastics.

It has been claimed by a few companies for quite some time that the addition of a low percentage (about 1-5%) of proprietary additives in the form of a masterbatch to PE, PP, PVC, PET and other carbon chain polymers renders the carbon chain polymer completely biodegradable in both aerobic and anaerobic environments – that would mean that 100% of the polymeric carbon is completely utilized by micro-organisms as measured by the evolved CO2 (aerobic) or CO2+CH4 (anaerobic). However nowhere a company claiming the biodegradability has provided such data to substantiate the 100% claim.

There are two classes of additives being marketed – ‘oxo’ and ‘organic’ which are sold as masterbatch concentrates. The ‘oxo’ additive is supposed to promote chain scission, thereby making the polymer small enough to be utilized by the micro-organisms present in the disposal environment. The ‘organic’ additive initiates or promotes microbial attack, and that in some way triggers the micro-organism to begin breaking down the carbon-carbon backbone chain polymer. Unfortunately, the scientific data and the literature do not support the actual claims being made in the market place. Many reports and studies include the word ‘biodegradation’ in the title, however, the meaning and context of the term is very broadly and loosely applied.

Compostability is not synonymous with biodegradability, a distinction that regulations make clear. But who knows? For the consumer the qualification ‘biodegradable’ sounds like the plastic material can degrade in a natural environment to enrich the soil, in most of the consumer’s eyes this means: compostability. Without reliable metrics, one doesn’t know for sure whether the compostable and biodegradable bag is even worth the consumer’s interest to buy into a greener world.

The Sustainable Packaging Coalition (SPC), estimates that there exist some 3,400 industrial composting facilities in the United States. Yet, of that total, only 267 of those facilities accept food waste and the packaging that may come with it. A poor 8% of all composting facilities.
The assumption is that a facility accepting food waste, could also accept compostable packaging associated with food or beverage waste. But not all facilities are inclined to do this, as the problems with packaging are evident. The biggest issue is that compostable packaging does not break down thoroughly or quickly enough, leaving bits of unwanted plastic material in the compost stream. Mixed with food waste, any packaging can start to degrade quickly, making it difficult for a composter to identify or separate it. Even when going through a screener, it is difficult to tell whether it is compostable or conventional plastic.

It is even worse. Biodegradable packaging that is recyclable might have entered the waste stream where it is causing major problems in some long-life products using recycled plastics such as pipes, builders’ sheeting, agricultural sheeting and the like – with possible market loss to the recycling industry. The failure is essentially caused by the degradation process breaking down the molecular structure of the plastic.

While the industry is greenwashing its image in regard to the consumer, the same consumer is left with the fictional idea that he is helping to save the environment by buying products in so-called biodegradable, compostable, packages.

And here we are back to zero. While the food industry is introducing biodegradable and compostable packages, the Canadians are advising the consumer not to dispose the SunChips bag (and similar packages) in the green bin, European Bioplastics argues that the so-called “oxo-biodegradable” industry is failing to live up to international established and acknowledged standards that effectively substantiate claims on biodegradation and compostability and Napcor (National Association for PET Container Resources) claims, that, although, PLA is an eminently recyclable material by itself, it cannot be mixed with other resins. Unfortunately, it presents a low-melt problem when it gets mixed in with PET. It’s as different from PET as PVC is.

What’s the answer? Stop all biodegradable developments? What is the consumer expected to do? Disposing all plastics in the general waste bin, means it will end up in landfills or in incinerators and in some instances in the recycling system, frustrating the recycler as his system isn’t suited for the biodegradable varieties. In all these situations the consumer is unwillingly destroying the green credentials of PLA.

The SPC recommends several measures, including: a standardized, colour-coded label on fibre-based packages to identify their materials. This isn’t the answer in my opinion as it makes labelling more and more complicated. Food ingredients, nutrition values, track-and-trace information, barcode, data-matrix, land of origin, Resin Identification Code, recycling logo, green logo, expiring date, etc, etc are all too much for the consumer to swallow in his 4 seconds of decision making when in the supermarket aisle. We need a simpler solution to transmit all the necessary information to the consumer.

And in the meantime? Why use and promote biodegradable and compostable packaging material when it all ends up in landfills or incinerators. Increasing usage of biodegradable films is in conflict with ‘separation-at-source’ initiatives. Consumers are confused when it comes to separating biodegradable, compostable and recyclable plastics.
The food industry is very much aware of this and consequently promoting ‘compostability’ in such a prominent way as Frito-Lay and others are doing, has the smell of ‘monkey business’.

*) Note: Part of this article is extracted from: “Misleading Claims and Misuse of Standards Continues to Proliferate in the Nascent BioPlastics Industry Space” – written by Ramani Narayan, Professor at the Michigan State University and published in bioplasticsMagazine of Jan 2010.