Issue 06/2018

From Science & Research
Compostable polymers are increasingly found in applications
such as packaging, disposable nonwovens and
hygiene products, consumer goods and agricultural
products. A wide variety of compostable polymers have been
developed, derived both from petrochemical and renewable
sources. But, what do we know about how these materials behave
in other environments or conditions outside of industrial
composting facilities?
In 2018, the European Parliament introduced the new
‘European Strategy for Plastics in a Circular Economy’, in
which the opportunities and risks associated with the growing
use of plastics with biodegradable properties, have also been
acknowledged. In the absence of clear labelling or marking
for consumers and without suitable waste collection and
treatment options, these plastics could aggravate the leakage
of plastics into the environment and cause mechanical
recycling problems. On the other hand, the European Strategy
states that biodegradable plastics can certainly have a role in
some applications, and that innovation efforts in this field are
welcome but that the behaviour and consequences of their
biodegradability must be demonstrated.
This article will present the main findings of a study on
the degree of disintegration of a compostable polymer and
a visual analysis of the material degradation in different
environmental conditions. It will present different tests
carried out under industrial composting conditions, home
compost conditions, composting conditions in a lab-scale test
(aggressive synthetic solid) and in soil (natural environment) at
two different temperatures. Furthermore, the ecotoxicological
effects of the environment after the disintegration process
was evaluated to obtain a full understanding of the behaviour
of these polymers.
The present study revealed that two main aspects determine
the degree of disintegration of a compostable biopolymer
(PLA and PBTA blend): on the one hand, the aggressiveness
of the medium (microbial activity) and on the other hand, the
temperature.
The most aggressive medium, an enriched synthetic solid,
gave rise to average disintegration degrees of 96.09 %, followed
by natural compost of vegetable origin and a normalized soil,
thus reaching disintegration degrees of 87.76 % and 72.05 %
respectively at thermophilic temperature (58 ºC).
By:
Elena Domínguez
Researcher, Sustainability and Industrial Recovery department
AIMPLAS
Paterna, Valencia, Spain
Compostable
plastics’
behaviour in
different
environmental
conditions
Figure 1. Degree of disintegration of the
material tested in different environments and
thermophilic conditions (58 ºC)
Figure 2. Degree of disintegration of the material
tested in different environments and mesophilic
conditions (25 ºC)
58ºC day 7 day 37 day 69 day 90
25ºC day 7 day 90
Synthetic Solid
Synthetic Solid
Normalized
Soil
Normalized
Soil
Compost
Compost
30 bioplastics MAGAZINE [06/18] Vol. 13