DEGRADATION OF PLASTICS IN THE ENVIRONMENT - Plastics and Environmental Sustainability - page 260

have been reported as well (Rojas and Greene, 2007). A study funded by
the European Commission (Feuilloley et al., 2005) found the
pre-photodegraded PE with the additive to only biodegrade approximately
15% after 1 year in soil. 20 These materials are not compostable according to
ASTM 6400 or EN 13432 (Thomas et al., 2010).
6.5.2 Degradable Plastics and Sustainable Development
It is interesting to assess the contribution of using enhanced-degradable
plastics in place of conventional varieties to sustainable development.
1. The use of enhanced photo- or biodegradable plastics has a potential
negative impact on recyclability of plastic waste. The potential of
degradable plastics contaminating a recovered plastics waste stream
intended for recycling, poses a serious problem (EUPR, 2009; Kitch,
2001). Sorting cannot remove degradable plastics effectively from the
recycling stream. This is especially true of photodegradable plastics;
most biodegradable plastics can be sorted with automated NIR systems
(but these do not work well with plastic film). The presence of even 10%
degradable material (with residual pro-oxidant) adversely affected the
quality of recycled HDPE (Samsudin et al., 2013). A recent study 21 by
European Plastic Convertors (EuPC) concluded that as little as 2 wt.% of
oxo-degradable material can affect recyclate quality adversely. Some
biodegradable plastics or additives are hydrophilic, can release sorbed
water as steam, or thermally degrade or even caramelize at polyolefin
reprocessing temperatures, discoloring or weakening the recycled
plastic product.
2. The use of photodegradable or oxo-biodegradable plastics can
effectively reduce the threat of entanglement (e.g., use in six-pack
yokes) of animals in litter such as six-pack rings, plastic strapping
bands, or netting and also help control aesthetic degradation by litter.
Several states legally require their six-pack rings to be photodegradable.
This advantage of preventing entanglement and perhaps reducing
visible litter, however, has to be weighed against the emerging concern
on microplastics in the environment (Andrady, 2011). Weathering
degradation of plastics into fragments in a very short timescale
(compared to regular plastics) presents a potential ecological hazard.
The implications of the marine organisms ingesting these microplastic
fragments (see Chapter 10 ) are not well understood at this time. But the