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AIR2-CT93-1099
Biodegradability of Bioplastics: Prenormative Research, Biorecycling and Ecological Impacts |
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Contract No | AIR2-CT93-1099 |
| Total Cost | 2 524 656 | |
| EC Contribution | 1 793 723 | |
| Start Date | 01/12/1993 | |
| Duration | 36 months |
Summary
There is increasing consumer and legal pressures for an increase in the use of biodegradable (bioplastic)
packaging materials in the European Union. These have the advantage that they can be composted without
contaminating the final product with inert residues, while discarded material will decay rather than leaving
unsightly semi-permanent litter on the beach or on horticultural holdings, for example. However, the solution
to problems of disposal, litter and persistence is not simple. The term biodegradable has been applied to
many plastics, of varying chemical composition and biological stability. Where plastics do degrade, they
will provide substrates for microbial growth and require oxygen, which can affect local ecology. Hence, the
objectives of this project were to address these aspects, as well as evaluate methods for the biorecycling
of bioplastic waste. In particular methods suitable for assessing the biodegradability of plastics derived from
biological raw materials were developed and used to devise standard test systems.
Introduction
The ecological impacts of production, biodegradation and biorecycling of
bioplastics has been investigated. Extensive results were obtained and new methods and standards
developed, some of which are detailed below.
Objectives
The major objectives of the proposed project are
Microbiology
The identity of ten Pseudomonas lemoignei isolates was
confirmed by DNA hybridisations and the abilities of 171 streptomycetes to degrade four bioplastics
[including poly(3 hydroxyalkanoates), poly(e caprolactone) PCL and Bionolle (BION)] were studied and
12 PCL degrading streptomycetes were tested for in vitro degradation of MaterBi (MB) film.
The degradation of PHBV [poly(3 hydroxybutyrate co 3 hydroxyvalerate)] film by various bacteria was
studied. It was found that Gamma irradiation had a negative effect on the biodegradation rate of PHBV.
The degradation of different PHBV granules was investigated. An in vitro test for the degradation of PCL,
BION and MB was successfully designed, using Acidovorax avenae subsp. avenae PHA 1183. The effects
of inoculum density, aeration, sample shape (films, granules) were studied and a protocol for testing of
PHBV, PCL, BION and MB products proposed. Compost used in a controlled composting test with MB
film was analysed microbiologically and metabolically and the microflora was found to remain stable.
Chemical characterisation
Degraded samples were analysed by GPC, NMR. No correlation
between molecular weight changes and biodegradation measurements were found. Gamma irradiation resulted
in a decrease of molecular weight.
Synthesis of novel plastics
Some new poly(esterurethanes) (PEU) were synthesized, characterised
and tested for their biodegradability in several systems. All were poorly biodegradable.
Test for biodegradation in an aerobic aqueous environment
Results were obtained using an
upgraded manostatic respirometer device (BSB digi) with four cells for the simultaneous measurement of O2
consumption and CO2, from which result were obtained with PHBV and PCL, extended to thermophilic conditions
showing that PCL is degraded at 50°C.
Analysis of bioplastic degradation products
Bioplastic degradation products were analysed by
HPLC and GC.
Denitrifying ability
Anoxic degradation with eudiometers gave promising results with an 'ideal'
composition of polymer granules, showing an increased velocity.
Product characterisation
New PEUs, differing in length of the PCL block and in total molecular
weight, were characterised by thermogravimetric, calorimetric, dynamic mechanical and X ray diffraction measurements.
Molecular weight and PCL block length affected crystallinity of PEUs, which was promoted by an increase of PCL
block length and by a decrease of PEU molecular weight.
Characterisation after biodegradation
PHBV samples, incubated in aqueous environments, showed
no changes in their thermal properties. After aerobic composting, PHBV showed the effects of annealing during
composting (that disappeared upon melting) but no other property changes. During biodegradation, the thermal
properties of BION did not change, while PCL showed a slight increase of crystallinity, and MB showed loss of
glycerin plasticiser and constant starch/PCL ratio. Most cellulose acetate (CA) samples showed total loss of
plasticizer (triacetin) and increased affinity for water, but test bars retained some plasticizer in the core.
Life Cycle Analysis
LCA analysis was performed for two model products (composting bag and
shampoo bottle) made of PCL, BION and MB using the calculated amount of biomaterial to achieve the same
functionality with the reference materials. Four different waste management scenarios were considered (landfill,
incineration, aerobic and anaerobic degradation). It was concluded that anaerobic degradation offers the most
promising way while landfilling should be avoided. The biodegradable products showed higher values in at least
eight out of the eleven categories, including the leading category 'total energy consumption'. To achieve the
same level of performance the amount of material required was much higher for the biodegradable materials
than for the reference products.
Characterisation of degraded materials
Changes in tensile properties of BION, MB and PCL
films, degraded in vitro by strain PHA 1183, was correlated with weight loss. However, the AFM and CLSM
methods used needed some refinements, even so CLSM scans could not be adapted for reliable surface area
measurements. AFM could be applied to quantify the surface area of PHBV, BION and PCL films and gave
reliable results at the very beginning of the degradation process.
Toxicity
Test materials were examined for potential toxicity in cell culture tests. PCL and BION
appeared non-cytotoxic, as did CA and PHBV powder, which contained no additives. It was found that additives
used in the final products could cause problems. Water extracts were used for chemical analysis of the leachable
substances and culture of fibroblasts. In general, water extracts were less cytotoxic then medium extracts.
Concentration dependent cytotoxic effects of MB extracts on cells could be demonstrated. To test the degradation
products of bioplastics in alkaline or acidic solutions, a special concentrated NaCI free cell culture medium was
prepared, and a preliminary test protocol was developed with CA degradation products.
Animal feeding
Ten castrated male Large White pigs were fed a control diet, then experimental
diets using either 10 or 20 % PHBV, in some cases pre treated (hydrolysis) using NaOH. It was found that the
digestibility of the energy rich PHBV could be improved by the NaOH pre treatment. The growth performances
of the pre treated treatment were not significantly lower than the control. A similar digestibility experiment was
performed with six adult sheep fed at approximately maintenance level on hay, supplemented with corn meal,
or pre treated or untreated PHBV. The pre treated PHBV was significantly better digested than the untreated.
Composting and anaerobic digestion
Standard methods were finalised for controlled composting,
high solids anaerobic digestion and soil contact resulting in the proposal and /or acceptance of (draft) methods in
CEN, DIN and ASTM working groups. A composting bin test, to determine the biodegradation and disintegration
of test substances under aerobic conditions, was further developed using PHBV and CA and operational parameters
were discussed in DIN and CEN working groups to ensure that the methods developed would be representative for
real life composting. Available (standard) methods for ecotoxicity testing were adapted for tests with compost. In
most cases the compost dominated any effects of the biopolymer residues, which were not detected.
Invertebrate tests
A new aquatic toxicity test using Daphnia and a new method for evaluating breeding
earthworms was developed.
Participants
These included Microbiology and Organic Chemistry groups at the University of Gent
(Belgium), applied biologists from the Universitat Stuttgart (Germany), the Department of Chemistry of the Universita
degli Studi di Bologna (Italy), the Fraunhofer Institut, Munich (Germany), various groups from Eidgenossische
Technische Hochschule Zurich (Switzerland) and a company, Organic Waste Systems n.v., of Gent (Belgium).
Contacts
Coordinator
EC Scientific Officer
Participant
© Copyright 2006 Policy Statements
Updated
by CPL Press:
03/07/2007
- biomatnet@biomatnet.org
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