bioplasticsMAGAZINE_0902

Politics
Fig. 4: Waste incineration plant in Vienna, Austria,
designed by Friedrich Hundertwasser
So-called ‘oxo-degradable plastics’ are not suitable
for organic recovery
So called ‘oxo-degradable plastics’ (i.e.: polyolefines
with metal-containing additives) are sometimes advertised
as being ‘biodegradable’ or even ‘compostable’. Such
claims are misleading if they are not substantiated by
showing compliance with the relevant standards EN
13432, EN 14995, ISO 17088 or ASTMD-6400. These
define the requirements for materials which can be called
‘compostable’. In the case of packaging, such claims
are bound by legal definition to the compliance with EN
13432 in several EU countries. There are no known ‘oxodegradable’
materials in the marketplace which fulfil
either of these standards. Claims of compostability for
such products are therefore wrong and untrustworthy. In
Italy and Australia for example, lawsuits resulted in fines
for using misleading claims in the marketing of such
products.
Thermal Recovery
‘Thermal recovery’ is the term for all exothermic
waste management processes which yield energy and/or
heat. Incineration is the most prominent example. The
high calorific value of bioplastics and the clean product
composition allow all bioplastics to be recovered thermally.
In case the incineration plant (Fig. 4) is equipped with an
energy recovery unit, the energy resulting from burning
renewable resource based bioplastics will be considered
‘greenhouse-gas neutral’.
Mechanical Recycling
Mechanical (or physical) recycling is understood as
the recycling back into plastics. It will only lead to high
quality products when the input material is very pure. This
is the case e.g. for the reprocessing of production waste:
Converters of plastics usually have facilities installed to
recycle the production scraps as a valuable raw material
and feed them back into the production process. Only a
small proportion of the total plastics market is currently
being recycled back into plastics.
Recycling usually becomes much more complicated
when mixed post-consumer plastics waste is used.
The typical situation is that post-consumer plastic
waste collection schemes deliver a mixture of polymer
types (fractions of PE, PP, PVC, PS, PET, etc. including
laminates, compounds, coated products etc.). These
products are often contaminated with various labels, inks,
glues, residues etc., so that the resulting recyclates are of
limited quality.
With rising environmental concerns and during times
of high raw material prices, investments in recycling and
sorting technologies increase. Sorting and pre-treatment
technologies have been improved and now allow the
selection of quite pure plastic waste.
Bioplastics are adding to the variety of plastics on
the market. However, owing to comparably low market
volume, mechanical recycling of bioplastics is currently of
no significance. With growing volumes, it will be possible
to install specific collection, separation and recycling
technologies for bioplastics as well. Solutions can be based
e.g. on the available NIR (near infra-red) technology which
can detect virtually every plastic type, including different
bioplastics. It has been shown that this technology allows
for example the automatic sorting of PLA bottles from PET
bottles [3].
Chemical Recycling
The conversion of plastics back into monomers, which
can then be polymerized to plastics again, is called
chemical recycling [2]
This recovery route can for example be applied to
convert PLA back into lactic acid. It must be noted though,
that due to the so far little amounts of post consumer PLA,
this option cannot be judged so far concerning technical
and economic feasibility.
22 bioplastics MAGAZINE [02/09] Vol. 4