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.

13 responses to “Does it make sense to use biodegradable, compostable plastics?

  1. The whole concept of sustainability in packaging is all overdone—wasted time and money–doen’t affect the earth one bit—better off to concentrate on good package development and increased shelf-life instead of this nonsense.

  2. Excellent article!
    It is indeed extremely difficult to navigate in a sustainable way these days when we are still in a very early learning phase.
    We, as packaging manufacturer, are under quite heavy pressure from our customers to take in these new materials. I completely share your frustration as we also have all these questions and no real answers.
    So what are we to do? Say no?
    I think the best approach must be to start out with the knowledge we have now. It is far from complete, so we will just be taking some small steps, and some of them will turn out to be wrong. This will slowly lead us into a new development and higher level of understanding.
    The critical part is to avoid the green washing. I dislike the marketing as shown in your Sun Chips example a lot! This can only lead to great misunderstandings and it is very likely to cause a set back of the whole development due to lack of trust and bad examples. I fear the headlines that will appear from various NGOs…
    So, I kindly ask you marketers to modify the language and be a little humble to the development process. We are in a learning phase and every little step counts. It is a common project and we have not seen the winners yet!

  3. I do not understand where you are getting your data that all additives are harmful. Please go to the Sierra website and look it up. They have documentation showing the additive does work.It does enable plastics to enteract with biota in the landfills and break down. It will not affect reycling.
    PLA is the worst producxt on the market!! It and ethanol is responsible for 75% of the food shortages in the world according to the World Bank. I question that there are even 267 composting facilities in the US that take PLA and the like. So it is being thrown away in landfills where they will degrade like normal plastics- hundreds of years. Add to that the fact that a lot of the PLA on the market use GMO’s and people should run from them.
    The Sierra resin enables plastics to break down into methane which in turn is a cheaper source of renewable energy than wind or solar power per kilowatt hour. 75% of all landfills in the US harvest their methane.

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  5. Impressive article, very excellent work! It’s a fact that the factor “landfill and waste” expecially in the third world is a growing aspect. Unfortunately here in germany nearly all waste that’s not collected via green dot recycling system is burned (and 80% of the collected plastics of green dot system too) so the enormous high prices of pla do not give any importance to use it in the european market except of the marketing aspect.

      • Eco-Pure is a spin off of ECM. They used to sell it and then came up up with Eco-Pure. Have you seen independent testing done a la ASTM 5526? They do their testing ASTM 5511 with bio reactors and sewage sludge that contain tons of biota.My socks could probably biodegrade with that test. The real test is ASTM 5526 which is done with landfill biota under landfill conditions. Sierra has done that testing. I have not heard of any testing done by Bio-tec under ASTM 5526.
        I have heard of 2 compsnies that did independent testing with Eco-Pure and the results were not very satisfactory.

      • What do you mean with spin off of ECM?


        Eco-Pure is a spin off of ECM. They used to sell it and then came up up with Eco-Pure. Have you seen independent testing done a la ASTM 5526? They do their testing ASTM 5511 with bio reactors and sewage sludge that contain tons of biota.My socks could probably biodegrade with that test. The real test is ASTM 5526 which is done with landfill biota under landfill conditions. Sierra has done that testing. I have not heard of any testing done by Bio-tec under ASTM 5526.
        I have heard of 2 compsnies that did independent testing with Eco-Pure and the results were not very satisfactory.

  6. Lots of words. Requires UV to break down. Not good for the compost. Not a secret. Works great on the streets of your local city. Takes about 100 days to melt down with sunlight. Not a bad idea. Also when working in this product segment be ye aware of some look-a-like products that contain heavy metals. If sustainable does not equal cheaper and safe it will be short lived.

  7. The Sunchip bag is made from PLA. PLA requires 3 things to break down (look up ASTM 6400): heat, aeration, and moisture. It will not break down in sunlight. That is an oxydegradable spec. (It is the one that has heavy metals in it.) It will not break down in a backyard compost- not enough heat and moisture. It will only break down completely in commercial and municipal composts. There are about 100 in the US. So the idea of using PLA for any sort of package is ridiculous unless they plan to attach little envelopes on the bag to ship them out in to these compost centers.Do not be fooled.

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