People Report Do
People Report Do bioplastics disturb recycling streams? Just as a reminder: Bioplastics are A) biobased plastics made from renewable resources (which can be biodegradable or not) or B) biodegradable plastics (which can be made from renewable resources or not), thus some bioplastics are both (see also definition on page 38). Summary Biobased (non-compostable) plastics films, e.g. made from Braskem’s Green PE, are chemically identical to conventional plastics and are no more difficult to manage in plastic recycling streams. Compostable plastics are designed for organic recycling. They are clearly marked for this purpose with logos such as the Seedling logo (cf. p 14). In the event that compostable plastics do end up in conventional plastic recycling streams, the prevalent sorting technologies are able to sort them with little residual waste. When residual amounts remain, they are similar to, or easier to handle than current residual wastes in the PE stream (e.g. PS, PP, PET). They should not then add significantly to the cost or complexity of recycling processes, or the valuable recovery of recycled PE. This remains true up to a share of 10% compostable plastics in the waste stream. At this level or below, studies show negligible impact on the technical performance of recycled PE. As the market share of compostable plastics increases it will be economically rewarding to sort them out positively. This is technically possible today and should create new and valuable markets for the Waste Management Industry. The authors believe then, aside from the social and environmental benefits of bioplastics, the best evidence clearly shows that these materials are an economic opportunity, not a threat to the waste management industry. Bioplastics in mixed waste streams Modern waste recovery systems cope with intermingled materials, including a variety of different polymer types. Automated plants sort out the profitable parts of the waste stream (for example PE, or PET). The promising polymers are separated. The rest ends up in another container, usually marked and resold as ‘mixed plastics’. To achieve this advanced sorting systems use a variety of analytical methods including near infrared, ultraviolet, x-ray, laser, polarized light, fluorescent light, electrostatic, melting point and other techniques. These methods are effective in keeping contamination of the main recycling streams with unwanted material low. Biodegradable plastics should end up in biowaste bins. If such bins are not available they can still be clearly identified from their labels and sorted out for delivery to a biowaste processer. However, even in well working systems an intermingling of waste streams cannot be completely avoided. Nonbiodegradable plastics can end up in the organic waste stream (e.g. misthrows) and biodegradable, compostable plastics might be found in mechanical recycling (e.g. misidentification ). It is already the case that conventional plastics find their way, in low volumes, to the wrong stream. 12 bioplastics MAGAZINE [01/14] Vol. 9
Report photo: Fotolia/azthesmudger It can then be stated that in well run waste management facilities most residual bioplastic will end up as ‘mixed plastic’ until such a time as recovery is profitable. It can also be said, even when incorrectly sorted, that bioplastics today do not enter the waste stream in sufficient volume to cause concern more than any other type of plastic. The case against bioplastics is not evidence-based Voices in some parts of the waste management industry claim that bioplastics are a serious disturbance to the established recycling streams of for example, PE or PET. The following research and evidence refutes these assertions. It suggests the influence on the collection and processing of profitable materials is negligible. Biobased Polyethylene (PE, not biodegradable or compostable) Biobased PE is obtained by polymerisation of ethylene monomers. Depending on the polymerisation process biobased LDPE or biobased HDPE can be produced. The only difference to fossil-based PE is the source, which is plant based (bioethanol made from sugar cane, sugar beet, wheat etc.). As a result fossil and plant based PE are chemically identical. They share the exact same physical properties. Therefore biobased PE can be mechanically recycled with the fossil based PE in the corresponding recycling streams. There is no new issue. PLA/PBAT blends (compostable according to EN 13432, ASTM D6400, etc) Studies by the University of Hanover/Germany [1], [2] examined the influence of different compostable plastics on low-density polyethylene (LDPE). The tested mixtures contained between 0.5 % to 10 % foreign material. The LDPE contaminants were a PLA/PBAT blend (Ecovio® by BASF), pure PBAT and a starch blend. They found: • Mixtures of LDPE with PLA/PBAT showed the same viscosity behaviour, elasticity, and tensile strength as pure LDPE. • No optical (i.e. transparency or appearance) changes could be observed. • There was a slight decrease in the melt-flow rate at 10% foreign material. The biodegradable polyester PBAT was also tested as a possible contaminant for LDPE. The blending of pure PBAT with LDPE had no influence on the viscosity behaviour compared with pure LDPE and was affirmed to have no influence on the processing properties. The values for melt flow rate were close to the ones of pure LDPE and were also described to result in no distinctive disturbances during processing of the material. Optical changes could also not be observed. Below 10% contamination there is no issue bioplastics MAGAZINE [01/14] Vol. 9 13
