Investigations into the possibility to compost paraffincoated packaging materials
Utilisation of biodegradable materials is indispensable for effective economic operation (Soyez, 1998). However, the requirements to be met by the application characteristics sometimes prevent use of such materials. For example, packaging materials for foodstuffs, where protection of the contents is the predominant aim, are required to display hydrophobic properties. Paraffin-coated papers have been used for this purpose for quite some time, e.g. for meat products and baked goods. The hydrophobicity impedes the biodegradation of these packaging materials. This also restricts safe disposal after use.
It must therefore be elucidated to what extent these materials are degraded by biological processes. However, the packaging material should not only be biologically degradable but also compostable in order to be incorporated into the normal pathways of waste disposal. The compostability must be proven. It is to be demonstrated that the paper can be degraded within the treatment period envisaged for each particular method. The degradation products of paper must not be visually noticeable in compost and they must also not adversely affect the quality of the compost.
Since 1998, there is a binding DIN standard for this purpose; the V 54.900 'Test of compostability of plastics' (DIN, 1998). This standard envisages a multi-stage test of the materials used for biodegradability including composting in intensive and extensive plants. The latter involve, for instance, open stack composting as is encountered in the vast majority of composting plants. These simple plants must also ensure that the substances are degraded virtually without residues. It must be considered that it is not the material alone which is processed - in this case coated papers - but always a mixture of material including the materials which can anyway be fed to composting. These are separately collected biomass, agricultural waste products and structural material. In the case of paper and cardboard the regulations governing biological waste dated 1st October 1998 permit addition of only small amounts of them, about 10 % by weight.
In the project presented here, paraffin-coated packaging materials from the foodstuff sector were tested under the conditions mentioned. They supplement existing investigations into the compostability of coatings with palm oil, stearin and biowax emulsions (Baier, 1998). The investigations are to provide information about the compostability of the papers used under conditions relevant to practice, and in particular to test whether open stacks are suitable for co-utilisation of coated waste papers. This is related to the general suitability of such systems (Low-Tech plants) and to the expected effects of co-utilisation with regard to compost quality and possible disposal amounts.