A03040: Investigation of the nature and extent of biodegradable polymers in direct food contact applications

Study Duration: April 2002 to May 2004

Contractor: Central Science Laboratory

Nearly three million tonnes of plastic waste are produced in the UK each year, much of which is packaging. More than half of this is food packaging. Plastic waste is almost all non-degradable and over 80 percent of plastic waste products are put in landfills. The use of biodegradable polymers to make food packaging is beginning to be a practical reality. Commercial applications are in prospect, especially where the higher cost of biodegradable materials compared to synthetic polymers derived from petroleum can be off-set by a marketing advantage. 'Sustainable' and 'non-polluting' are attributes that are traded on. Also, there is increasing governmental pressure on manufacturers via eco-taxes to reduce the amount of non-degradable plastic packaging.

It would be quite easy to assume that if polymers are derived from natural sources and/or are biodegradable then they must automatically be safe. But this may not be the case. This project addressed the identification of possible migrants and any testing requirements for biodegradable polymers intended for food contact.

The project aims were realised via a group of 6 linked objectives, which were:

• Gather information on the chemical composition of biodegradable polymers intended for food contact.
• Gather information on the conditions of use including the type of foods packaged along with the contact conditions of time and temperature.
• Make estimates of the amount of biodegradable polymers used in the UK per annum.
• Evaluate the migration potential from biodegradables given their composition and conditions of use.
• Evaluate the suitability of standard migration test protocols, for example from the sectors of paper and plastics, for use to test biodegradables.
• Produce final report on the information gathering exercise along with recommendations for further work, including experimental work, if any is required.

A large number of biodegradable polymers is available or under development. Nevertheless, the actual market for biodegradable polymers (excluding paper and board) for food contact applications is presently very limited indeed. The only biobased food-packaging materials used commercially on a major scale are based on cellulose. An estimate made in 2003 concluded that of the 2.7 million tonnes per annum polymer market in the UK, less than 0.1% of this production is from bio-based materials. It is not known what fraction of this very small percentage is used for food packaging applications. There is currently no system of coding (e.g. by logo) and no system has yet been setup in the UK to monitor sales and usage of biodegradable food packaging polymers.

A hydrolysable linkage is a feature common to most polymers that are biodegradable and most of the biodegradable polymers available are polyesters. The source materials can be synthetic (e.g. monomers derived from petroleum) or bio-based (i.e. monomers or polymers derived from crops or other living sources). The nature and the source of the material determine the possible chemical migrants. In general, biodegradable polymers built up by polymerisation of monomers (from either natural or synthetic sources) have a more defined composition than biodegradable polymers obtained as such from biopolymers. This is because the processes available to purify monomers (e.g. distillation, recrystallisation) are more efficient than the processes available to purify polymers (e.g. washing). Consequently, the composition and possible contaminants in biodegradable polymers should be limited where needed by compositional and/or migration limits, perhaps coupled with restrictions on source materials and the manufacturing processes used.

The methods of test for migration, using food simulants, are likely to be directly applicable to testing most biodegradable polymers. Since the methods of test are supposed to be directly related to the actual conditions of use in contact with food, and mimic these, then if a biodegradable polymer is suitable for a particular application in contact with food then a correctly specified test procedure should be applicable also. One caveat is that tests for overall migration may not be technically possible for humidity-sensitive materials.

The benefits of this project to the Food Standards Agency and to consumers, are two-fold:

• The project was conducted during a period in which the Commission of the European Union was consulting on, and then adopted, an amendment to the EU Directive on regenerated cellulose films (RCF). New types of RCF are available which have a plastic coating and which are compostable and biodegradable. These plastic-coated RCF films have the potential to expand the range of packaging applications for biodegradable RCF beyond the limited uses for dry foods found to date, and may be the most significant factor influencing the uptake and usage of biodegradable food packaging polymers. The activities and findings of this project should help guide discussions on this amending Directive, especially with respect to the rules provided for testing these plastic-coated RCF materials.
• The activities and findings of this project will also guide the development and application of any specific measures needed to ensure that biodegradable polymers shall neither endanger human health nor contaminate or change the properties of the food.

Final report is availabl from the FSA Library and Information centre. To obtain a copy, please contact the Enquiry Desk, Dr Elsie Widdowson Library and Information Services, Food Standards Agency tel: 020 7276 8181/8182 or email: infocentre@foodstandards.gsi.gov.uk

Contact: For any enquiries concerning this research project, please contact the relevant programme contact or email: science@foodstandards.gsi.gov.uk