Friday 24 August 2012

Organic Waste Systems for Biodegradation and Composting Tests

Bruno De Wilde, Laboratory Manager, Organic Waste Systems (Belgium) described OWS as a completely independent  one-stop laboratory for biodegradability and compostability testing with 20 years experience and a track record of 2000+ tests for over 500 clients.  It is active with CEN, ASTM and ISO in developing standards and is recognised by all certification bureaus. 

With regard to compostable packs, these are not allowed in Germany, have very limited applications in most of Spain and France but are well established in the UK, Holland, Italy and Catalonia.  Blends of polymers, multi-layered structures, inks, additives, and families of products with differing compostablility all present challenges to anyone trying to get a pack certified. Differences between testing standards doesn’t help,
a comparison of ISO 16929 with ASTM D 5338 using newspaper showed complete disappearance in 3 weeks with ISO and a residue of recognisable test pieces after 12 weeks with ASTM.  Results with straw were similar to those with paper.

Oxodegradables (e.g. PE + the pro-oxydantia additive) disintegrate and give satisfactory compost appearance on ISO 16929 but fail on biodegradation testing and cannot be certified compostable.  They should be classified as “photo- or thermo-fragmentables”, not “degradables”.

Anaerobic digestion is preferable to composting because it works at lower temperature and generates methane - which is usable as biogas - as well as compost.  Digestion is preferred for kitchen, catering and industrial waste treatment where energy production can be a valuable by-product.  Composting consumes energy but is best for garden waste because it encourages the fungal activity which is needed to breakdown lignin.

Asked why some countries do not allow compostable packaging, Mr de Wilde said they worry about compostable plastics being hard to distinguish from non-compostable and hence more non-biodegradables getting into the composting stream.  Why do Bioplastics degrade more slowly in sea-water than river-water;  because the former supports fewer microorganisms and contains less nutrients.

(from a paper given at the Biopolymer World Conference, Venice, April 2012)

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