AIR2-CT93-1099 Biodegradability of Bioplastics: Prenormative Research, Biorecycling and Ecological Impacts

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AIR Cluster VI - Bioplastics : Biological Conversion : Biopolymers/Gums : Composts/Fertilisers : Paints/Coatings/Plastics

	Proposal No:	AIR2-CT93-1099
	Date Prepared:	September 1999
	Source:	Final technical report 1997

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Final technical report 1997t

Summary

Introduction In the European Union (EU) 5 to 10 million tons of plastic waste ends up in landfills or is incinerated. The application of biodegradable plastics and their disposal through composting and anaerobic digestion is now under discussion. For the labelling of materials as biodegradable or compostable, reliable test methods are needed. Biological disposal methods enable the biorecycling of natural resources used for the production of these bioplastics. In the project, standard test systems and methods for the assessment of the biodegradability of bioplastics were developed. Methods for the biorecycling of bioplastic waste, and to define ecological impacts of production, biodegradation and biorecycling of bioplastics were evaluated.

Activities A set of bioplastics (Biopol, Bionolle, MaterBi, polycaprolactone, cellulose acetate) that are described as biodegradable was used. Several hundred microbial strains that degrade bioplastics in vitro were isolated and identified, revealing the biodiversity and biodegrading abilities of microorganisms that are able to degrade these materials in the environment. A range of standardised biodegradation tests were developed and optimised. A battery of in vitro tests with defined cultures of biodegrading microorganisms allows rapid and reproducible preliminary assessment of biodegradability of bioplastics, and yields excellent material for further documentation of biodegradation. This approach can be followed by highly standardised bench scale simulation tests in aqueous and solid environments.

For aerobic testing in aqueous conditions a respirometer test was developed and retrofitted with conductivity equipment to measure C0₂ production and establish carbon balances. For anaerobic testing in aqueous conditions the use of automated Methanomat equipment was shown to be promising. Two solid biodegradation tests were used: the controlled composting test for the determination of biodegradation under aerobic conditions, followed by a soil contact test; and the high-solids anaerobic digestion test for the determination of biodegradation under anaerobic conditions, followed by a compost stabilisation test. Compostability was determined using a new composting bin test coupled with several ecotoxicity tests that were adapted for application in compost. A compostability testing scheme was proposed.

Several analytical tools were evaluated for assessing the biodegradation bioplastics, and methods were optimised. These included chemical analysis, bulk morphological characterisation, tensile characterisation, surface characterisation and analysis of intermediate degradation products. The test systems were also used to identify biorecycling methods, to upgrade biodegradable bioplastic waste to, e.g. fertiliser and biogas, animal feed, or as novel carbon sources in waste water denitrification systems. Several bioplastics proved to be appropriate for denitrification purposes. Experiments with polymer granules spiced with salts led to promising results for use in water treatment. Native bioplastics showed low digestibility in swine and sheep, but digestibility could be enhanced by More than 30% by pre-treatment, and seems to be a viable way of recycling the energy-rich bioplastic to food for animals.

A protocol for screening biopolymers for potential toxicity using cell culture tests was developed on the basis of ISO, EN, and ASTM standards for testing the in vitro cytotoxicity of medical devices and materials. Cell proliferation and cellular activities responded very sensitively to toxic agents, allowing a screening for acute toxicity of test samples under well defined conditions in a relatively short time.

A number of new polymers were synthesized and tested. These included polyesters, i.e. poly (8-valerolactone), poly (F- caprolactone-co-5-valerolactone), and poly (e-caprolactone-co-ethylene oxide-co-E-caprolactone), and poly (ester- urethanes) based on poly (F-caprolactone) as a soft segment and methylene-bis-cyclohexyldiisocyanate and butanediol as a hard segment. These polymers were characterised and their biodegradability tested in some of the test systems.

Biodegradation and biorecycling data were entered into a life cycle analysis, following a "cradle to grave" approach, for a more rational comparison of the environmental impacts of different scenarios, such as "biodegradable plastics from renewable resources and biodegradation" versus "petrochemical plastics and incineration/landfilling".

Life cycle analysis was performed for the model products "waste bag", "composting bag" and "shampoo bottle". These three model products were chosen because in such applications biodegradable materials have already proven suitable. On the basis of the required material functionality for such applications, a comparison with standard polymeric materials was carried out. It was concluded that the biodegradable materials might be an ecologically better choice in the future only if developments can increase functionality of the material.

Discussion On the basis of the functionality obtained with those materials investigated, it was concluded that at present they are not able to really compete with their classical counterparts. Despite various objections and uncertainties concerning life cycle analysis, LCA's performed here gave an idea of the environmental ranking of the biodegradable materials with respect to their "classical" counterparts. This analysis indicated the ongoing needs of research and development for this kind of materials to make them competitive on a much larger scale. However, it was quite obvious that the material improvement required is a long-term development for the probability of success is difficult to forecast. With such improvements, biodegradable materials based on renewable resources are the better choice in comparison to those produced synthetically.

Finally, it has to be pointed out that the investigations described above were performed on generally selected model products. The materials were used according to the specifications, compositions and process data supplied by the manufacturers, meaning that no special material or process adaptations were performed. Therefore the obtained results show overall tendencies, but would have to be verified again for any specific application or material composition.