Like it or not we live in a world in which we currently consume more than the planet can sustain. There is a mindset that encourages us to dispose of what we have and move on to the next. As such it represents a powerful challenge if global society is to move forward in a sustainable way, whilst recognising that resources are limited.
The plastics industry has for some time recognised the need to minimise its impact on the environment through its products and production processes. Such thinking lays at the root of the developments of what are often loosely termed bio-plastics. For many, developments in this area represent something akin to a universal panacea for minimising the impact of plastics on the environment and who believe the industry should focus disproportionally on their development. Unfortunately life is not quite that simple.
For example even the term bio plastics is actually not very precise. Such materials should preferably be termed bio – based and or bio – degradable depending upon a number of factors. The distinctions are subtle but significant.
Bio based plastics
Concerns about the depletion of fossil fuel resources have lead to efforts to develop new technologies in order to replace conventional oil and gas based plastics by others based on raw materials derived from renewable sources, often covered by the catch all term “biomass.”
Plastics (or more generally, polymers) are long chains of molecules. Such molecules – the basic building blocks – can be derived from natural and renewable resources such as wood (cellulose), vegetable oils, sugar and starch.
In theory many polymers can be synthesised in this way from renewable feedstock. For example corn starch can be hydrolysed and used as the fermentation feedstock for bio-conversion into lactic acid, which can in turn be used to create the recently developed plastic called poly lactic acid orPLA.
Rather than produce new plastic materials, another approach is to make well established plastics such as polyethene, whereby the basic building block- ethylene- is derived from renewable feedstock by first producing ethanol from sugar cane.
Bio-degradable and Compostable Plastics
The plastics industry is often challenged by the public to make more biodegradable products. It is argued that it would be a great help if plastics could simply disappear by natural causes after their useful life has expired. Indeed there are many good reasons for such a desire and products to match, but unfortunately it wouldn’t be right for everything for equally good reasons.
To understand this point it is necessary to recognise that every polymer will eventually degrade – the only question is when? The answer depends upon many factors including the type of polymer and the environment it is exposed to. Degradability can be measured on a sliding scale where the key criterion is the level of change in its initial properties due to chemical cleavage of the chain of macromolecules that it was built from.
Plastics designed to degrade comparatively quickly include oxo-degradable and UV degradable polymers that break down when exposed to oxygen or light respectively. .
To qualify as bio-degradable, however, this degradation has to happen, at least in part, due to cell mediated phenomena or microorganisms. As a result the polymer is eventually reduced to water, carbon dioxide, biomass and possibly methane.
There is not necessarily a direct correlation between bio – based products and biodegradability. For example some bio-based products such as polyhydroxyalkanoates are often bio-degradable where as others such as polyethene are not, even, if they have been derived from sugar cane. The key is the molecular structure of the resultant polymer.
To be considered as compostable it must meet some strict criteria as defined in national and international standards:
- Biodegrade: break down into carbon dioxide, water and bio mass.
- Disintegrate; after three months composting and subsequent sifting through a 2 mm sieve no more than 10% residue may remain.
- Eco toxicity: the bio-degradation does not produce any toxic material and the compost can sustain plant growth.
These few paragraphs are intended only to present some of the arguments around bio based and bio degradable plastics. We are interested to hear what you think. Why not enter the online debate?
People should read Cradle to Cradle: Remaking the way we make things. We should be heading towards either using completely biodegradeable products, or products that are 100% recyclable (closed loop system).
Biodegradability can indeed be a very useful characteristic but it is important that degradation does not occur during the actual use phase of the application resulting in a loss of physical properties. On the other hand, at the end of its life the plastic product needs to be treated in a way that total degradation is actually achieved.
As regards recyclability the vast majority of plastics (thermoplastics) are in principle 100% recyclable. Provided the same plastic type is being recycled then good properties can be obtained. However the properties achievable from a mixture of different plastic types are much reduced and variable. Mixed plastics can be used in a limited number of applications to substitute other materials (e.g. fence posts etc.). For such mixed plastic waste streams ,where recycling is not an option, the preferred solution could be their use as solid fuels, replacing traditional fuels such as coal, while reducing the impact on the environment
No plastic coming from non-renewable resources should be degraded but recycled. This is a matter of conservation not convenience. It is a matter of responsibility all (from producers to users, retailers and consumers) that we all should accept and share.
Unfortunately, the notion that degradation and its most pervasive bias (biodegradation) “are good” is gaining acceptance and momentum in society, commerce and some segments of our industry. However, few really know the meaning, significance and implications of degradation when applied to non-renewable resoruces. For instance, glass comes from sands, a finite resource, and is also a packaging material discarded at will and ending its life in landfills. I have not seen anyone pledging in favor of biodegradable glass.
Worse tha that, suppliers of oxo-degradants are missinforming users and consumers when they label their products as “bio”. If they were of such nature why is it that they have not agreed to test their products as bioplastics suppliers do and have asked?
Thanks for the opportuniy.
Eduardo de la Tijera (Mexico)
at present time no any plastic who decompose completely.bio plastic may be a very good solution in future .bioplastic basically starch based plastic .so in environmentwhen they expose ,twotypes enzymetic reactions catalyze by mesophillic and thermophillic bacteria . so in bioplastic they act only on starch part and decompose remain the plastic part .in this way vol. of plastic reduse in large extent.these types enzymetic reaction have no sufficient energy of activation that degredate the plastic portion of bioplastic.bioplastic (called as organic plastic)derived from renewable source,may be starch based ,polylactic acid(PLA),poly-3 hydroxybutyrate,polyamide-11.each and every organic matter(plastic) degredate naturally .but if it degredate at much slow rate as to be considered non-biodegradable.we must produse the bio-based plastic,because there is no any defficiency of biomass being renewable and eco friendly.
The 3 “R”-Reduce-Reuse-Recycle has gone to 4 (Recover). I now want to add number 5, namely REMOVE. When plastic has gone through “Reduce” and “Remove”; if collected will go to “Recycle.” and “Recover.” But what about the plastic that never gets collected? Hundreds of Thousands of tonnes of LITTER. By making this litter oxobiodegradable, it can be gone in a couple of years, and thus save hundreds of thousands of sea mammals and other wildlife. Recyclers have their place in this-but they only recycle about 15% of plastics: WHAT ABOUT THE OTHER 85% that never sees a recycler??
Bioplastics are the future for the plastics industry. We are now in the process of developing a bioplastics process scalable for full volume manufacturing of automotive grade bioplastics – the company (http://www.biosmart.com). We need support from the consumer to support the cost disadvantage the new technology will face at introduction – will you be willing to pay a higher ~$200 for your next car to have the plastics made from biomass?
Costs are the main limitation, we have the technology, we can make it “green” and it doesn’t have to consume human food chain materials (just the farming land).
Your responses are definitely welcome.
Gareth: Did you mean to say http://www.biosmart.ca ?
Having worked in Plastics, Bio-polymers, and Oxo-Biodegradable Plastics, I think I can say with some credibility that there is not one correct solution. We cannot live without plastic, and they do make things better for us.
Examples:
Can you imagine Life Saving Plasma and Blood in a Tin Can?
In the third world 50% of Food produce spoils before it reaches the consumer. In the Western world this is less than 3%. Much of this is due to better handling and packaging, as well as the storage advantages etc.
My feeling is that each plastic has its own market niche, and more effort should be put into making sure the correct material is used for each application, and not just looking at cost or squandering the material.
On individual materials; my issue with Plastics is they come from a very Finite source. Bio-polymers, though using materials such as Sugar Beet need an awful lot of energy to convert them, and mass of raw product (over 10,000 kg of Sugar Beet are need to make 1,000kg of PLA).
I was looking for polythene packaging for the rice that I produce when I stumbled on this fascinating discussion. Apparently, bio-polythene can be made even from rice stalks but also from other wood by-products instead of fossil fuels. I’d have to research the process much more profoundly but this is great news.
Then I note the point made by James Clark that 50% of food spoils in the developing world before reaching the consumer. When many of these countries are facing severe food insecurity and a massive global industry is devoted to resolving this, more attention on reducing the wastage makes good sense. When you add in the efforts to reduce poverty in the same countries where 75% and upwards of the populations are subsistence farmers, usually it would seem prudent to devote more time to relatively simple (I hope) solutions such as improved use of by-products.
If any of you have suggestions for further research or exploration on these topics, I’d be very interested.
Thank you.