Basics Bioplastics in
Basics Bioplastics in Packaging By Harald Kaeb Founder narocon Berlin, Germany Fig. 1:First Coca-Cola, then Volvic – soon a megatrend? PET bottles with bio-based content and rPET (Photo Coca- Cola) Fig. 2: Multilayer-film for demanding products are only avaliable since a short time (here combination of starchblend and cellulose films (Photo Innovia Films) Fig. 3: Compostable Deep Freeze (Material FKUR) (Photo: McCain) Fig. 4: Globally controversely discussed … albeit not so much when made of bioplastics (Photo: Novamont) Plastics in Packaging As a general rule, in western industrial nations about 50% of all goods are packaged in plastic. More than one third of the world’s plastic is used for this purpose – which represents almost 100 million tonnes of plastic packaging. The constantly increasing market is dominated by the polyolefins (PE, PP) and PET. Plastic packaging is lightweight, and can offer tailor-made solutions for almost any product. It is also relatively cheap: in the food business the packaging often makes up less than 10% of the product price. Super, successful products – and not just at first glance. Packaging is basically just as important as the stuff it holds. Food that is senstive to rough handling, such as pears or strawberries, would hardly be able to withstand long transport routes, and an iPad would find it difficult to withstand the way in which it may be treated by the customer when he is on the move. Buying easily perishable foodstuffs with no packaging could be a health risk – and not only in summer. Without the protection provided by packaging a lot of products would not even reach us. They would either be unsafe from a health point of view, or they would be many times more expensive. Despite these contributions made to our standard of living the consumer’s view of plastic packaging is surprisingly negative. Is this a lack of gratitude? No! At least not only that! With the increasing use of packaging the associated problems are also increasing. Because it is so difficult to close the loop the waste disposal sites worldwide are full of packaging plastics. Being lightweight also means easy to throw away: in the environment, in the oceans, we find packaging everywhere. And even though the litter problem lies in people‘s unacceptable behaviour it is aggravated by the fact that plastic is very slow to degrade. In many countries there is also no collection and recovery system, or what they do have is inadequate. The extravagant way that we treat finite resources is highlighted to us every day by the household rubbish bin, which is often half full of plastic packaging. Only about 10% of the EU’s 50 million tonnes of plastic is mechanically recycled or reclaimed after use. 15% is reclaimed as an energy source (incineration). Only bottles and industrial foil have a high recycling rate (40%) and most packaging plastics fail to reach a 10% recycling rate. Europe is nevertheless well placed when global comparisons are made. But it also shows that making new plastic products from waste or used material is difficult and expensive because of the mix of materials and the contamination – if it can be done at all! Today plastic packaging is still made predominantly from petroleum. A good 4% of the world’s petroleum is used in the production of about 240 million tonnes of plastic, of which packaging accounts for some 40%. The drawbacks of conventional plastics were a significant factor in driving the general development of bioplastics. Bioplastics are expected to at least offer some improvement, 46 bioplastics MAGAZINE [02/11] Vol. 6
Basics if not a total solution to the well-known problems. This means that bio-packaging should conserve fossil resources and be capable of being recycled. On top of which it should be capable of fulfilling the tasks that conventional plastic packaging does so well. Production processes Bioplastics can be processed using practically all of the current technologies for plastics processing. Packaging plastics are, as a rule, always thermoplastics which are supplied as granules that can be plasticised during processing. Thin film or sleeving from 10 to 60 microns can be blown, thicker film can be calendered or extrusion moulded. Deep drawing (or thermoforming) is used to produce containers, such as plastic cups or trays. If the film is welded pouches can be produced. Nets, as often used for fruit or vegetables, are made by fibre extrusion or are woven. Injection moulding is the process used for thick walled or complex components such as buckets or caps and closures. Bottles are produced by blow-moulding a plastic preform or parison. Causing the material to foam and produce a soft or hard foam is usually achieved by expelling a previously introduced low boiling point liquid. This allows the production of soft trays for particularly sensitive small products or protective housing for larger heavier products. When processing mono-materials, products are made that generally meet simple requirements, e.g. pouches. Multiple materials are used and brought together during the process to usefully combine their properties. Depending on the demands of the application the mechanical properties, resistance to oxygen and water vapour, and gas barrier, as well as gloss, printability or feel can be modified and optimised. Combinations of paper board and plastics are widely used in the packaging business. The board gives then pack shape and rigidity and plastic gives it its barrier properties making it, for example, waterproof or greaseproof. Applications include compostable tubs and cups for ice-cream and drinks. The plastic film is either laminated (glued) or melted directly onto the board in an extrusion process. Multilayer films are produced by laminating single thin sheets of film or by co-extrusion. Double or treble thickness films are still the exception. Plastic processing offers huge opportunities for product optimisation – both technical and economic. The polymer materials have been made much easier to process and use by the introduction of processing aids, additives and colorants. Packaging is often designed and made for a specific product. They are made economically viable by minimising material usage at the same time as maximising the level of protection that they offer, and maximising the speed of their manufacture. Before a PLA yoghurt cup reaches the supermarket shelf it has to go through complex, technically difficult stages in the production chain. The manufacture of the pot, and food safety standards, are part of this. Filling the pot with yoghurt under sterile conditions and making an airtight seal when applying the lid, which has to be easy to peel off at a later date, are stages that must be able to be carried out at high speed, and which cause us to think of the demands placed on the material and other components (glue, additives, colorants, labels), and on the product designer. A plastic shopping bag which itself weighs almost nothing but which can safely be used to carry home five bottles of a good wine, is a small but high-tech product. If the product also has to be biodegradable there are even more criteria to meet in order to conform to the appropriate standards. Compostability as a functional advantage It was no accident that the biological degradability and compostability of bio-packaging were important goals right from the beginning of their development. These new functionalities for plastics are still key factors today in the shape, and promotional messages, of most of the commercialised products. The message was the perceived ability to compost organic waste and bio-packaging together in a cost-effective way. If this packaging was produced from renewable resources the loop would be closed, as in nature’s model. Food residues in the packaging make the recycling of conventional plastics rather difficult, but not for ‘organic recycling’. This idea was taken up and seriously researched for almost 20 years – from the very first packaging product. The door was finally opened by the compostable bio-waste bag which was followed by the first simple foil packaging. Biodegradable polymers can be thermoplastically processed into thin-walled film. Short shelf-life foods, mainly fresh fruit and vegetables, are typical products that can be packaged in a compostable pouch. At home the food waste and packaging can all be taken together for composting. In the distribution chain it is not necessary to separate unsaleable, rotting produce from its packaging if the produce is to be composted. A further advantage is the fact that compostable bioplastics keep produce in a fresh condition for longer, so making them saleable for longer and thus more cost effective. This results from high water vapour permeability, which however also limits to a certain extent the range of applications. Serviceware made from bioplastics has followed a comparable route. Whether we are talking about drinks cups, plates, knives, forks and spoons, or plastic shopping bags – nowadays all of these products are available in a compostable form. They are used at sports venues and events, on the road, in aircraft or on the train. Everywhere in the world this type of application, using single-trip products, is taking on an increasing importance. Where the product waste can be properly sorted on the spot, e.g. in aircraft (see bM 05/10) or at open air festivals (see bM 06/10), composting is an efficient method to use. Experts however say that anaerobic fermentation is better because compost and also a source of energy - bio-gas – is obtained. There is hardly any packaging format in the world that creates more controversy than the disposable plastic bag. No other plastic product is gaining such attention from politicians and legislators. Rapidly biodegradable bags could, during household refuse collection, help towards a better separation of organic and other waste – an important prerequisite for bioplastics MAGAZINE [02/11] Vol. 6 47
