Technical ReportPDF Available

Biodegradable plastics and marine litter: misconceptions,concerns and impacts on marine environments

Authors:

Abstract and Figures

The development and use of synthetic polymers, and plastics has conferred widespread benefits on society. One of the most notable properties of these materials is their durability which, combined with their accidental loss, deliberate release and poor waste management has resulted in the ubiquitous presence of plastic in oceans. As most plastics in common use are very resistant to biodegradation, the quantity of plastic in the ocean is increasing, together with the risk of significant physical or chemical impacts on the marine environment. The nature of the risk will depend on: the size and physical characteristics of the objects; the chemical composition of the polymer; and, the time taken for complete biodegradation to occur (GESAMP 2015). Synthetic polymers can be manufactured from fossil fuels or recently-grown biomass. Both sources can be used to produce either non-biodegradable or biodegradable plastics. Many plastics will weather and fragment in response to UV radiation – a process that can be slowed down by the inclusion of specific additives. Complete biodegradation of plastic occurs when none of the original polymer remains, a process involving microbial action; i.e. it has been broken down to carbon dioxide, methane and water. The process is temperature dependent and some plastics labelled as ‘biodegradable’ require the conditions that typically occur in industrial compositing units, with prolonged temperatures of above 50°C, to be completely broken down. Such conditions are rarely if ever met in the marine environment. Some common non-biodegradable polymers, such as polyethylene, are manufactured with a metal-based additive that results in more rapid fragmentation (oxo-degradable). This will increase the rate of microplastic formation but there is a lack of independent scientific evidence that biodegradation will occur any more rapidly than unmodified polyethylene. Other more specialised polymers will break down more readily in seawater, and they may have useful applications, for example, to reduce the impact of lost or discarded fishing gear. However, there is the potential that such polymers may compromise the operational requirement of the product. In addition, they are much more expensive to produce and financial incentives may be required to encourage uptake. A further disadvantage of the more widespread adoption of ‘biodegradable’ plastics is the need to separate them from the non-biodegradable waste streams for plastic recycling to avoid compromising the quality of the final product. In addition, there is limited evidence to suggest that labelling a product as ‘biodegradable’ will result in a greater inclination to litter on the part of the public (GESAMP 2015). In conclusion, the adoption of products labelled as ‘biodegradable’ will not bring about a significant decrease either in the quantity of plastic entering the ocean or the risk of physical and chemical impacts on the marine environment, on the balance of current scientific evidence.
Content may be subject to copyright.
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
United Nations Environment Programme
P.O. Box 30552 Nairobi, 00100 Kenya
Tel: (254 20) 7621234
Fax: (254 20) 7623927
E-mail: publications@unep.org
web: www.unep.org
www.unep.org
MISCONCEPTIONS, CONCERNS AND IMPACTS
ON MARINE ENVIRONMENTS
BiodegradaBle
Plastics
& MARINE LITTER
Copyright © United Nations Environment Programme (UNEP), 2015
is publication may be reproduced in whole or part and in any form for educational or
non-profit purposes whatsoever without special permission from the copyright holder,
provided that acknowledgement of the source is made.
is publication is a contribution to the Global Partnership on Marine Litter (GPML).
UNEP acknowledges the financial contribution of the Norwegian government toward
the GPML and this publication.
ank you to the editorial reviewers (Heidi Savelli (DEPI, UNEP), Vincent Sweeney (DEPI UNEP),
Mette L. Wilkie (DEPI UNEP), Kaisa Uusimaa (DEPI, UNEP), Mick Wilson (DEWA, UNEP)
Elisa Tonda (DTIE, UNEP) Ainhoa Carpintero (DTIE/IETC, UNEP) Maria Westerbos,
Jeroen Dawos, (Plastic Soup Foundation) Christian Bonten (Universität Stuttgart)
Anthony Andrady (North Carolina State University, USA)
Author: Dr. Peter John Kershaw
Designer: Agnes Rube
Cover photo: © Ben Applegarth / Broken Wave Nebula (Creative Commons)
© Forest and Kim Starr / Habitat with plastic debris, Hawaii (Creative Commons)
ISBN: 978-92-807-3494-2
Job Number: DEP/1908/NA
Division of Environmental Policy Implementation
Citation: UNEP (2015) Biodegradable Plastics and Marine Litter. Misconceptions, concerns and impacts
on marine environments. United Nations Environment Programme (UNEP), Nairobi.
Disclaimer
e designations employed and the presentation of the material in this publication do not imply
the expression of any opinion whatsoever on the part of the United Nations Environment Programme
concerning the legal status of any country, territory, city or area or of its authorities, or concerning
delimitation of its frontiers or boundaries. Moreover, the views expressed do not necessarily represent
the decision or the stated policy of the United Nations Environment Programme, nor does citing
of trade names or commercial processes constitute endorsement. e mention of any products,
manufacturers, processes or material properties (i.e. physical and chemical characteristics of a polymer)
should not be taken either as an endorsement or criticism by either the author or UNEP,
of the product, manufacturer, process or material properties.
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
BiodegradaBle
Plastics
& MARINE LITTER
Misconceptions, concerns and iMpacts
on Marine environMents
is report was commissioned by:
e Global Programme of Action for the Protection of
the Marine Environment from Land-based Activities (GPA)
UNEP GPA
Global Programme of Action for the Protection
of the Marine Environment from Land-based
Activities, Marine Ecosystems Branch, Division of
Environmental Policy Implementation
P. O. Box 30552 (00100), Nairobi, Kenya
E gpml@unep.org
W unep.org/gpa/gpml
GPML
Global Partnership
on Marine Litter
PHOTO ©LAURA BILLINGS  CREATIVE COMMONS
Contents
Abbreviations list 2
Executive Summary 3
1. Background 5
2. Polymers and plastics - terminology and definitions 9
2.1 e need for precise definitions 9
2.2 Natural (bio)polymers 10
2.3 Synthetic polymers and plastics 12
2.4 Bio-derived plastic 16
2.5 Bio-based plastics 16
3. Fragmentation, degradation and biodegradation 19
3.1 e degradation process 19
3.2 Non-biodegradable plastics 21
3.3 ‘Biodegradable’ plastics 21
3.4 Oxo-biodegradable plastics 22
4. The behaviour of ‘biodegradable’ plastics in the marine environment 25
4.1 e composition of plastic litter in the ocean 25
4.2 e fate of biodegradable plastic in the ocean 25
5. Public perceptions, attitudes and behaviours 29
6. Conclusions 31
References 32
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
ABBREVIATIONS LIST
ABS Acrylonitrile butadiene styrene
AC Acrylic
AcC (CTA, TAC) Acetyl cellulose, cellulose triacetate
AKD Alkyd
ASA Acrylonitrile styrene acrylate
DECP Degradable and electrically conductive polymers
EP Epoxy resin (thermoset)
PA Polyamide 4, 6, 11, 66
PAN Polyacrylonitrile
PBAT Poly(butylene adipate-co-teraphthalate
PBS Poly(butylene succinate)
PCL Polycaprolactone
PE Polyethylene
PE-LD Polyethylene low density
PE-LLD Polyethylene linear low density
PE-HD Polyethylene high density
PES Poly(ethylene succinate)
PET Polyethylene terephthalate
PGA Poly(glycolic acid)
PHB Poly(hyroxybutyrate)
PLA Poly(lactide)
PMA Poly methylacrylate
PMMA Poly(methyl) methacrylate
POM Polyoxymethylene
PP Polypropylene
PS Polystyrene
EPS (PSE) Expanded polystyrene
PU (PUR) Polyurethane
PVA Polyvinyl alcohol
PVC Polyvinyl chloride
SAN Styrene acrylonitrile
SBR Styrene-butadiene rubber
Starch Starch
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
2
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
Executive Summary
e development and use of synthetic polymers, and plastics has conferred widespread benefits on
society. One of the most notable properties of these materials is their durability which, combined with
their accidental loss, deliberate release and poor waste management has resulted in the ubiquitous presence
of plastic in oceans. As most plastics in common use are very resistant to biodegradation, the quantity
of plastic in the ocean is increasing, together with the risk of significant physical or chemical impacts on
the marine environment. e nature of the risk will depend on: the size and physical characteristics of
the objects; the chemical composition of the polymer; and, the time taken for complete biodegradation
to occur (GESAMP 2015).
Synthetic polymers can be manufactured from fossil fuels or recently-grown biomass. Both sources can
be used to produce either non-biodegradable or biodegradable plastics. Many plastics will weather and
fragment in response to UV radiation – a process that can be slowed down by the inclusion of specific
additives. Complete biodegradation of plastic occurs when none of the original polymer remains, a process
involving microbial action; i.e. it has been broken down to carbon dioxide, methane and water. e process
is temperature dependent and some plastics labelled as ‘biodegradable’ require the conditions that typically
occur in industrial compositing units, with prolonged temperatures of above 50°C, to be completely broken
down. Such conditions are rarely if ever met in the marine environment.
Some common non-biodegradable polymers, such as polyethylene, are manufactured with a metal-based
additive that results in more rapid fragmentation (oxo-degradable). is will increase the rate of microplastic
formation but there is a lack of independent scientific evidence that biodegradation will occur any more
rapidly than unmodified polyethylene. Other more specialised polymers will break down more readily in
seawater, and they may have useful applications, for example, to reduce the impact of lost or discarded fishing
gear. However, there is the potential that such polymers may compromise the operational requirement of
the product. In addition, they are much more expensive to produce and financial incentives may be required
to encourage uptake.
A further disadvantage of the more widespread adoption of ‘biodegradable’ plastics is the need to separate
them from the non-biodegradable waste streams for plastic recycling to avoid compromising the quality of
the final product. In addition, there is some albeit limited evidence to suggest that labelling a product as
‘biodegradable’ will result in a greater inclination to litter on the part of the public (GESAMP 2015).
In conclusion, the adoption of plastic products labelled as ‘biodegradable’ will not bring about a significant
decrease either in the quantity of plastic entering the ocean or the risk of physical and chemical impacts on
the marine environment, on the balance of current scientific evidence.
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
3
1
BACKGROUND
PHOTO © AMANDA WYCHERLEY  CREATIVE COMMONS
Can plastiC designed
to be ‘biodegradable’
have a signifiCant
role in reduCing
oCean litter?
biodegradable
PlaSTiCS
4
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
BACKGROUND
The objective of this briefing paper is to provide a
concise summary of some of the key issues surrounding
the biodegradability of plastics in the oceans, and
whether the adoption of biodegradable plastics will
reduce the impact of marine plastics overall.
One of the principal properties sought of many
plastics is durability. This allows plastics to be used
for many applications which formerly relied on
stone, metal, concrete or timber. There are significant
advantages, for food preservation, medical product
efficacy, electrical safety, improved thermal insulation
and to lower fuel consumption in aircraft and
automotives. Unfortunately, the poor management
of post-use plastic means that the durability of plastic
becomes a significant problem in mitigating its impact
on the environment. Plastics are ubiquitous in the
oceans as a result of several decades of poor waste
management, influenced by a failure to appreciate
the potential value of ‘unwanted’ plastics, the under-
use of market-based instruments (MBIs), and a lack of
concern for the consequences (GESAMP 2015).
The principal reasons plastic ends up in the ocean are:
• Inadequate waste management by the public
and private sector;
• Illegal practices;
Littering by individuals and groups;
• Accidental input from land-based activities and
the maritime sector, including geological and
meteorological events;
A lack of awareness on the part of consumers,
for example of the use of microplastics in
personal care products and the loss of fibres
from clothes when washed.
Efforts to improve waste management and
influence changes in behaviour, on the part of
individuals and groups, face many challenges, and
the results of mitigation measures may take many years
to demonstrate a benefit (GESAMP 2015).
Plastics are ubiquitous in the oceans as a result
of several decades of poor waste management,
influenced by a failure to appreciate the
potential value of ‘unwanted’ plastics
PHOTO © CHESAPEAKE BAY PROGRAM  CREATIVE COMMONS
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
5
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
It has been suggested that plastics considered to
be ‘biodegradable’ may play an important role in
reducing the impact of ocean plastics. Environmental
biodegradation is the partial or complete breakdown
of a polymer as a result of microbial activity, into CO2,
H2O and biomasses, as a result of a combination of
hydrolysis, photodegradation and microbial action
(enzyme secretion and within-cell processes). It is
described in more detail in section 3. Although this
property may be appealing, it is critical to evaluate
the potential of ‘biodegradable’ plastics in terms of
their impact on the marine environment, before
encouraging wider use.
A material may be labelled ‘biodegradable’ if it
conforms to certain national or regional standards that
apply to industrial composters (section 3.1), not to
domestic compost heaps or discarded litter in the ocean.
Equally important is the time taken for biodegradation
to take place. Clearly the process is time-dependent
and this is controlled by environmental factors as well
as the properties of the polymer. The environmental
impact of discarded plastics is correlated with the time
taken for complete breakdown of the polymer. At every
stage there will be the potential for an impact to occur,
whether as a large object or a nano-sized particle.
There is considerable debate as to the extent to
which plastics intended to be biodegradable do
actually biodegrade in the natural environment. This
extends to the peer-reviewed scientific literature but
is most intense between those organisations that can
be thought to have a vested interest in the outcome,
such as the producers of different types of plastics,
the producers of additive chemicals intended to
promote degradation and those involved in the waste
management and recycling sectors.
Deciding what constitutes best environmental
practice through the choice of different plastics and non-
plastics is not straightforward. Life Cycle Assessments
(LCA) can be used to provide a basis for decisions about
optimal use of resources and the impact of different
processes, materials or products on the environment.
For example, LCA could be employed to assess the use
of plastic-based or natural fibre-based bags and textiles,
and conventional and biodegradable plastics. In one LCA
–based study of consumer shopping bags, conventional
PE (HDPE) shopping carrier bags were considered to
be a good environmental option compared with bags
made from paper, LDPE, non-woven PP and cotton, but
strictly in terms of carbon footprints (paper to cotton in
order of increasing global warming potential; Thomas et
al. 2010). This analysis did not take account of the social
and ecological impact that plastic litter may have.
In contrast, an analysis of textiles - that included
factors for human health, environmental impact
and sustainability - placed cotton as having a much
smaller footprint than acrylic fibres (Mutha et al. 2012).
However, it is important to examine what is included
under such broad terms as ‘environmental impact’. For
example, a third study which also performed an LCA-
based assessment of textiles concluded that cotton
had a greater impact than fabrics made with PP or PET,
and a much greater impact than man-made cellulose-
based fibres (Shen et al. 2010). This was on the basis
of ecotoxicity, eutrophication, water use and land use.
Neither textile-based LCAs considered the potential
ecological impact due to littering by the textile products
or fibres. Clearly, the scope of an environmental LCA
can determine the outcome. Ecological and social
The degree to which ‘biodegradable’ plastics
actually biodegrade in the natural environment
is subject to intense debate.
PHOTO © PETERCHARAF  RACEFORWATER
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
6
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
perspectives should be included in a comprehensive
LCA approach, as well as the time-scales involved.
Without such evaluation, decisions made in good
faith may result in ineffective mitigation measures,
unnecessary or disproportionate costs, or unforeseen
negative consequences.
As with all such assessment studies, it is very
important to consider the scope, assumptions,
limitations, motivations, data quality and uncertainties
before drawing conclusions about the study’s validity
and wider applicability.
PHOTO LUDWIG TRÖLLER  CREATIVE COMMONS
The environmental impact of discarded plastics
is correlated with the time taken for complete
breakdown of the polymer.
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
7
2
POLYMERS AND PLASTICS
TERMINOLOGY AND DEFINITIONS
PHOTOGERAINT ROWLAND  CREATIVE COMMONS
Can plastiC designed
to be ‘biodegradable’
have a signifiCant
role in reduCing
oCean litter?
biodegradable
PlaSTiCS
8
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
POLYMERS
AND PLASTICS
- TERMINOLOGY
AND DEFINITIONS
2.1 The need for precise
definitions
There is great scope for confusion in the
terminology surrounding ‘plastic’ and its behaviour in
the environment. Section 2 provides some definitions
to terms used in this report.
The term ‘plastic’, as commonly applied, refers to a
group of synthetic polymers (section 2.3).
Polymers are large organic molecules composed
of repeating carbon-based units or chains that occur
naturally and can be synthesised. Different types
of polymers have a wide range of properties, and
this influences their behaviour in the environment.
Assessing the impact of plastics in the environment,
and communicating the conclusions to a disparate
audience is challenging. The science itself is complex
and multidisciplinary. Some synthetic polymers are
made from biomass and some from fossil fuels, and
some can be made from either (Figure 2.1). Some
polymers derived from fossil fuels can be biodegradable.
Some biodegradable plastics are made
from fossil fuels, and some non-biodegradable
plastics are made from biomass
Fig. 2.1 Schematic illustrating the relationship between primary materials source, synthetic and natural polymers, thermoplastic
and thermoset plastics and their applications: from GESAMP, 2015
Fossil fuel derived
Synthetic polymer
Thermoplastic Thermoset
Biomass derived
Biopolymer
cellulose, lignin,
chitin, wool, starch,
protein, DNA, etc.
insulation, coating, adhesive,
composite, tire, balloon,
micro-abrasive, etc.
bottle, food container, pipe,
textile, shing gear, oat,
milk jug, lm, bag, cigarette
butt, insulation, micro-bead,
micro-abrasive, etc.
Plastic debris
PU, SBR, epoxy, alkydPE, PP, PS, PVC, PET
Microplastics
Manufactured
(primary)
Manufactured
(primary) Fragmentation
(secondary)
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
9
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
Conversely, some polymers made from biomass
sources, such as maize, may be non-biodegradable.
Apart from the polymer composition, material
behaviour is linked to the environmental setting, which
can be very variable in the ocean. Terms are sometimes
not defined sufficiently, which can lead to confusion or
misunderstanding (Table 2.1)
The conditions under which ‘biodegradable´
polymers will actually biodegrade vary widely. For
example, a single-use plastic shopping bag marked
‘biodegradable’ may require the conditions that
commonly occur only in an industrial composter (e.g.
50 °C) to breakdown completely into its constituent
components of water, carbon dioxide, methane, on
a reasonable or practical timescale. It is important, if
users are to make informed decisions, for society to
have access to reliable, authoritative and clear guidance
on what terms such as ‘degradable’ or ‘biodegradable’
actually mean, and what caveats may apply.
2.2 Natural (bio)polymers
Bio-polymers are very large molecules with a long
chain-like structure and a high molecule weight,
produced by living organisms. They are very common
in nature, and form the building blocks of plant and
animal tissue. Cellulose (C6H10O5)n is a polysaccharide
(carbohydrate chains), and is considered the most
abundant natural polymer on Earth, forming a key
constituent of the cell walls of terrestrial plants.
Chitin (C8H13O5N)n is a polymer of a derivative
of glucose (N-acetylglucosamine) and is found
in the exoskeleton of insects and crustaceans.
Lignin (C31H34O11)n is a complex polymer of aromatic
alcohols, and forms another important component of
cell walls in plants, providing strength and restricting
the entry of water. Cutin is formed of a waxy polymer
that covers the surface of plants.
Table 2.1 Some common definitions regarding the
biodegradation of polymers
Term DefiniTion
Degradation The partial or complete breakdown
of a polymer as a result of e.g.
UV radiation, oxygen attack, biological
attack. This implies alteration of
the properties, such as discolouration,
surface cracking, and fragmentation
Biodegradation Biological process of organic matter,
which is completely or partially
converted to water, CO2/methane,
energy and new biomass by
microorganisms (bacteria and fungi).
Mineralisation Defined here, in the context of
polymer degradation, as the complete
breakdown of a polymer as a result of
the combined abiotic and microbial
activity, into CO2, water, methane,
hydrogen, ammonia and other simple
inorganic compounds
Biodegradable Capable of being biodegraded
Compostable Capable of being biodegraded
at elevated temperatures in soil
under specified conditions and
time scales, usually only encountered
in an industrial composter
(standards apply)
Oxo-degradable Containing a pro-oxidant that
induces degradation under favourable
conditions. Complete breakdown of
the polymers and biodegradation
still have to be proven.
Other types of natural polymers are poly amides
such as occur in proteins and form materials such as
wool and silk. Examples of common natural polymers
and their potential uses by society are provided
in Table 2.2.
The conditions under which ‘biodegradable´
polymers will actually biodegrade vary widely.
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
10
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
Table 2.2 Examples of common natural polymers and uses by society.
Polymer naTural occurrence Human uses
Chitin Exoskeleton of crustaceans:
e.g. crabs, lobsters and shrimp
Exoskeleton of insects
Cell walls of fungi
Medical, biomedical (lattices for growing tissues)
Agriculture
Lignin Cell walls of plants (Ligno-cellulose)
Construction timber
Fuel as timber
Newsprint
Industrial – as a dispersant, additive and
raw material
Cellulose Cell walls of plants, many algae
and the secretions of some bacteria
Paper
Cellophane and rayon
Fuel - Conversion into cellulosic ethanol
Polyester Cutin in plant cuticles
Protein fibre
(e.g. fibroin, keratin)
Wool, silk Clothing
Single-use plastic shopping bag marked
‘biodegradable’ may require the conditions that
commonly occur only in an industrial composter
PHOTO © VWASTE BUSTERS  CREATIVE COMMONS
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
11
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
2.3 Synthetic polymers and plastics
There are two main classes of synthetic polymers:
thermoplastic and thermoset (Figure 2.1). Thermoplastic
has been shortened to ‘plastic’ and, in lay terms, has
come to be the most common use of the term. In
engineering, soil mechanics, materials science and
geology plasticity refers to the property of a material able
to deform without fracturing. Thermoplastic is capable
of being repeatedly moulded, or deformed plastically,
when heated. Thermoset plastic material, once formed,
cannot be remoulded by melting; common examples
are epoxy resins or coatings. Many plastics often contain
a variety of additional compounds that are added
to alter the properties, such as plasticisers, colouring
agents, UV protection, anti oxidants, and fire retardants.
Epoxy (EP) resins or coatings are common examples of
thermoset plastics. Synthetic polymers are commonly
manufactured from fossil fuels, but biomass (e.g. maize,
plant oils) are increasingly being used. Once the polymer
is synthesised, the material properties will be the same,
whatever the type of raw material used.
In terms of volume, the market is dominated by a
limited number of well-established synthetic polymers
(Figure 2.2 below). However, there is a very wide range
of polymers produced for more specialised application,
with an equally wide range of physical and chemical
properties (Table 2.3). In addition, many plastics are
synthesised as co-polymers, a mixture of two or more
polymers with particular characteristics. Objects may
be produced using more than one type of polymer
or co-polymer. All these factors result in, for the non-
specialist, a bewildering array of materials. Although their
characteristics and behaviour may be well understood
with regard to the designed application (e.g. insulation
slabs, shopping bags, fishing line) their behaviour in
the marine environment may be poorly understood.
Fig. 2.2 European plastics demand (EU27 + Norway & Switzerland) by resin type and industrial sector in 2012. Polyamide (mainly
Polyamide 6 and 6.6) in fishing gear applications and polystyrene, polyurethane foams used in vessel insulation and floats,
are employed extensively in the marine environment. Figure courtesy of PlasticsEurope (PEMRG)/Consultic/ECEBD
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
12
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
Table 2.3 Common synthetic polymers – source, use and degradation properties
abbreviaTion
full name common
source
examPles of
common uses
bioDegraDaTion
ProPerTies
in TerresTrial
environmenT
INCLUDING
MEDICAL
APPLICATIONS
bioDegraDaTion
ProPerTies in
aquaTic/marine
environmenT
reference
ABS (acrylonitrile
butadiene
sytyrene)
Copolymer
Fossil fuel Pipes,
protective headgear,
consumer goods,
Lego™ bricks
AC Acrylic Fossil fuel Acrylic glass
(see PMMA)
AcC
(CTA,
TAC)
Acetyl
cellulose,
cellulose
triacetate
Biomass Fibres,
photographic
film base
Biodegradability
depends on degree
of acetylation1
1 Tokiwa
et al. 2009
AKD Alkyd Partly
biomass
Coatings,
moulds
Cellophane Biomass
(cellulose)
Film for packaging
DECP A group of
degradable
and electrically
conductive
polymers
Biomass
& fossil fuel
Biosensors and
tissue engineering
Degradable within
living tissues2
2 Guo
et al. 2013
EP Epoxy resin
(thermoset)
Fossil fuel Adhesives, coatings,
insulators
PA Polyamide e.g.
Nylon™ 4, 6, 11,
66; Kevlar™
Fossil fuel Fabrics, fishing lines
and nets,
PAN Polyacrylonitrile Fossil fuel Fibres, membranes,
sails, precursor in
carbon fibre
production
PBAT Poly(butylene
adipate-co
-teraphthalate
Fossil fuel Films Biodegradable7 7 Weng et al.,
2013
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
13
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
abbreviaTion
full name common
source
examPles of
common uses
bioDegraDaTion
ProPerTies
in TerresTrial
environmenT
INCLUDING
MEDICAL
APPLICATIONS
bioDegraDaTion
ProPerTies in
aquaTic/marine
environmenT
reference
PBS Poly
(butylene
succinate)
Fossil fuel Agricultural
mulching films,
packaging
Biodegradable1Some degradation
after 12 months
but retains 95%
tensile strength3
Some degradation
after 2 years4
1 Tokiwa
et al. 2009
3 Sekiguchi
et al. 2011
4 Kim et al.
2014a,b
PCL Polycaprolac-
tone
Fossil fuel 3D printing,
hobbyists,
biomedical
applications
Biodegradable by
hydrolysis in the
human body
Biodegradable1
Some degradation
after 12 months3
1 Tokiwa
et al. 2009
3 Sekiguchi
et al. 2011
PE Polyethylene Biomass
& fossil fuel
Packaging,
containers,
pipes
Extremely limited,
potential minor effect
in Tropics due to
higher temperature,
dissolved oxygen
and microfauna/flora
assemblages5
5Sudhakar
et al. 2007
PES Poly(ethylene
succinate)
Fossil fuel films Biodegradable1 1 Tokiwa
et al. 2009
PET Polyethylene
terephthalate
Fossil fuel,
fossil fuel
with biomass
Containers, bottles,
‘fleece’ clothing
PGA Poly
(glycolic acid)
Sutures,
food packaging
Biodegradable
by hydrolysis in
the human body
PHB Poly
(hyroxybutyrate)
Biomass Medical sutures Biodegradable1
Some degradation
after 123
1 Tokiwa
et al. 2009
3 Sekiguchi
et al. 2011
PLA Poly(lactide) Biomass Agricultural
mulching films,
packaginzg,
biomedical
applications,
personal hygiene
products,
3D printing
Biodegradable1
Compostable5
1 Tokiwa
et al. 2009
5 Pemba
et al. 2014
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
14
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
abbreviaTion
full name common
source
examPles of
common uses
bioDegraDaTion
ProPerTies
in TerresTrial
environmenT
INCLUDING
MEDICAL
APPLICATIONS
bioDegraDaTion
ProPerTies in
aquaTic/marine
environmenT
reference
PMMA Poly(methyl)
methylacrylate
Fossil fuel Acrylic glass,
biomedical
applications,
lasers
Biodegradable3 3 Cappitelli
et al. 2006
POM Poly(oxymeth-
ylene)
Also called
Acetal
Fossil fuel High performance
engineering
components
e.g. automobile
industry
PP Polypropylene Fossil fuel Packaging,
containers,
furniture, pipes
PS Polystyrene Fossil fuel Food packaging
EPS Expanded
polystyrene
Fossil fuel Insulation panels,
insulated boxes,
fishing/aquaculture
floats, packaging
PU
(PUR)
Polyurethane Fossil fuel Insulation, wheels,
gaskets, adhesives
PVA Poly(vinyl
alcohol)
Fossil fuel Paper coatings Biodegradable
PVA Poly(vinyl
acetate)
Fossil fuel Adhesives
PVC Poly
(vinyl chloride)
Fossil fuel Pipes, insulation
for electric cables,
construction
Rayon Rayon Biomass
(cellulose)
Fibres, clothing Biodegradable Biodegradable
SBR Styrene-
butadiene
rubber
Fossil fuel Pneumatic tyres,
gaskets, chewing
gum, sealant
Starch Starch Biomass Packaging, bags,
Starch blends e.g.
Mater-Bi™
Biodegradable in soil
and compost6
Minimal deterioration
in littoral marsh of
seawater6
6 Accinelli
et al. 2012
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
15
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
2.4 Bio-derived plastic
Bio-based plastics are derived from biomass such as
organic waste material or crops grown specifically for
the purpose (Table 2.4). Utilising waste material can be
seen as fitting into the model of the circular economy,
closing a loop in the resource-manufacture-use-waste
stream. The latter source could be considered to be
potentially more problematic as it may require land
to be set aside from either growing food crops, at a
time of growing food insecurity, or from protecting
sensitive habitat, at a time of diminishing biodiversity.
One current feature of biomass-based polymers is
that they tend to be more expensive to produce
than those based on fossil fuels (Sekiguchi et al. 2011,
Pemba et al. 2014).
Perhaps the two most common bio-based plastics
are bio-polyethylene and poly(lactide). While most
of the conventional polyethylenes are produced
from fossil fuel feedstock, bio-polyethylene a leading
bio-based plastic is produced entirely from biomass
feedstock. Similarly, bio-polyamide11 is derived from
vegetable oil and poly(lactide) is a polyester produced
from lactic acid derived from agricultural crops such
as maize and sugar cane.
2.5 Bio-based plastics
The term bio-plastic is a term used rather loosely.
It has been often described as comprising both
biodegradable plastics and bio-based plastics, which
may or may not be biodegradable (Figure 2.3; Tokiwa
et al, 2009). To avoid confusion it is suggested that
the description ‘bio-plastic’ is qualified to indicate
the precise source or properties on the polymer
concerned.
Utilising waste material can be seen as
fitting into the model of the circular economy,
closing a loop in the resource, manufacture, use,
waste stream.
Table 2.4 Examples of common bio-based plastics
Polymer DerivaTion aPPlicaTions
Cellophane Cellulose (e.g. wood, cotton, hemp) Sheets - packaging
Base layer for adhesive tape
Dialysis (Visking) tubing
Chitosan Chiton Tissue engineering,
wound healing,
drug delivery
Rayon Cellulose (e.g. wood pulp) Threads - clothing
§ most types of polyamide are derived from fossil fuels
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
16
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
PHOTO DOUG BECKERS  CREATIVE COMMONS
One current feature of biomass-based
polymers is that they tend to be more
expensive to produce than those based
on fossil fuels
Biodegradebale
plastics
Bio-plastics
Bio-based
plastics
PBS
PCL
PES
PEA
PHB
PE
NY11
AcC
Starch
Fig. 2.3 Bio-plastics comprised of biodegradable and
bio-based plastics (taken from Tokiwa et al. 2009; available under
the Creative Commons Attribution license).
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
17
3
FRAGMENTATION, DEGRADATION
AND BIODEGRADATION
PHOTO © RALPH AICHINGER  CREATIVE COMMONS
Can plastiC designed
to be ‘biodegradable’
have a signifiCant
role in reduCing
oCean litter?
biodegradable
PlaSTiCS
18
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
FRAGMENTATION,
DEGRADATION AND
BIODEGRADATIONTS
If a products is marketed as biodegradable
it should conform to a recognised standard
defining compostability, for example
ASTM 6400 (USA) , EN 13432 (European)
or ISO 17088 (International)
3.1 The degradation process
Fragmentation
The degree to which synthetic polymers degrade
depends on both the properties of the polymer and
the environment to which it is exposed (Mohee et al.
2008). At the point when the original polymer has been
completely broken into water, carbon dioxide, methane
and ammonia (with proportions depending on the
amount of oxygen present), it is said to have been
completely mineralised (Eubeler at al. 2009).
Fragmentation and biodegradation proceeds through
a combination of photo- (UV) and thermal-oxidation
and microbial activity. In the marine environment UV
radiation is the dominant weathering process. It causes
embrittlement, cracking and fragmentation, leading to
the production of microplastics (Andrady 2011). This
means that fragmentation is greatest when debris is
directly exposed to UV radiation on shorelines. Higher
temperatures and oxygen levels both increase the rate
of fragmentation, as does mechanical abrasion (e.g.
wave action). Once plastics become buried in sediment,
submerged in water or covered in organic and inorganic
films (which happens readily in seawater) then the rate of
fragmentation decreases rapidly. Plastic objects obs erved
on the deep ocean seabed, such as PET bottles, plastic
bags and fishing nets, show insignificant deterioration
(Pham et al 2014). In addition, the inclusion of additive
chemicals such as UV- and thermal-stabilizers inhibit
the fragmentation process.
Biodegradation
Biodegradation is the partial or complete breakdown
of a polymer as a result of microbial activity, into
carbon, hydrogen and oxygen, as a result of hydrolysis,
photodegradation and microbial action (enzyme
secretion and within-cell processes). The probability
of biodegradation taking place is highly dependent on
the type of polymer and the receiving environment.
The literature on the biodegradation of a wide range
of synthetic polymers has been extensively reviewed by
Eubeler et al. (2009, 2010). Partial biodegradation can
lead to the production of nano-sized fragments and
other synthetic breakdown products (Lambert et al.
2013).
A number of national and international standards
have been developed, or are under development,
to cover materials designed to be compostable or
biodegradable (e.g. ISO, European Norm - EN, American
Society for Testing and Materials - ASTM International).
These standards are appropriate for conditions that
occur in an industrial composter, in which temperature
are expected to reach 70 °C. The EN standard requires
that at least 90% of the organic matter is converted
into CO2 within 6 months, and that no more than
30% of the residue is retained by a 2mm mesh sieve
after 3 months composting1. A recent literature review,
commissioned by PlasticsEurope, concluded that most
1 EN 13432:2000. Packaging. Requirements for packaging
recoverable through composting and biodegradation.
Test scheme and evaluation criteria for the final acceptance
of packaging; http://www.bpiworld.org/page-190437,
accessed 10th February 2015.
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
19
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
plastic packaging marketed as biodegradable meets
the EN 13432 or equivalent standard (Deconinck and
De Wilde 2013). Test procedures include weight loss
and production of CO2. However, the plastic may still
retain important physical appearance such as overall
shape and tensile strength even with significant
weight loss.
In addition, ASTM produced a standard
for ‘Non-floating biodegradable plastics in the
marine environment’ (ASTM D7081-05). It has
been withdrawn but is currently being subjected
to ASTM’s balloting process for reinstatement2.
An additional standard (ASTM WK42833) is being
developed that will cover ‘New Test Method for
Determining Aerobic Biodegradation of Plastics
Buried in Sandy Marine Sediment under Controlled
Laboratory Conditions.
2 http://www.astm.org/Standards/D7081.htm
PHOTO © FOREST AND KIM STARR  CREATIVE COMMONS
Fig. 3.1 The relationship between melting temperature (Tm °C)
and biodegradability (TOC - Total Organic Carbon mg l-1)
by the enzyme lipase of the fungus Rhizopus delemar.
(taken from Tokiwa et al. 2009; available under the Creative
Commons Attribution license).
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
20
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
The biodegradability of polymers is influenced by
a range of intrinsic factors. A higher molecular weight
(Eubeler et al. 2010), higher melting temperature and
higher degree of crystalinity all reduce the degree to
which the polymer is likely to biodegrade (Figure 3.1,
Tokiwa et al. 2009).
3.2 Non-biodegradable plastics:
Many common polymers can be considered
as effectively non-biodegradable. This means that
complete mineralisation, requiring a process of gradual
fragmentation, facilitated by UV, higher temperature
and an oxygenated environment, will happen so
slowly as to be considered negligible in the natural
environment. Conditions of UV exposure, which
occur more frequently on land, or the coastal margins
in tropical or sub-tropical climates, may result in the
fragmentation of some material, such as non-UV-
stabilised PE sheeting (Figure 3.2). However, as soon
as plastics become buried in sediment, submerged,
or covered by organic and inorganic coatings, the rate
of fragmentation declines rapidly. Common examples
include: PE, PET, PA (Polyamide 11), PS, EP, PU, PVA,
PVC and SBR (see Table 2.3).
3.3 ‘Biodegradable’ plastics
Biodegradable plastics are polymers that are
capable of being broken down quite readily by
hydrolysis, the process by which chemical bonds are
broken by the addition of water (GESAMP 2015).
This process is influenced by the environmental setting
and is facilitated by the presence of microorganisms.
Some polymers have been designed to be
biodegradable for use in medical applications (Table
2.3). They are capable of being metabolized in the
human body through hydrolysis catalysed by enzyme
activity. Some polymers, such as poly (glygolic acid)
and its copolymers, are used as temporary sutures
while others have been designed for slow-release
drug delivery used, for example, in the treatment of
certain cancers, or the delivery of vaccines (Pillay et
al. 2013, Bhavsar and Amiji 2007). Others have been
designed to form temporary lattices for cell growth
(Woodruff and Hutmacher 2010). Despite these
engineered properties it does not mean that all such
Fig. 3.2 Fragmentation of PE with exposure to UV in a cool
temperate climate at 61.6 °North; (a) standard PE sheeting,
(b) PE sheeting with UV stabilizer added, for horticultural use.
© Peter Kershaw
A higher molecular weight, higher melting
temperature and higher degree of crystalinity
all reduce the degree to which the polymer
is likely to biodegrade
a
b
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
21
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
polymers will be rapidly biodegraded in the external
environment. Outside the human body the degree
or rate of biodegradation becomes very dependent
on the surrounding environment, which will show a
much greater variability (e.g. temperature, humidity,
oxygen levels, microbe assemblages, UV irradiation).
For example, polycaprolactone and polylactide are
both used for 3D printing and producing hard durable
components, as well as for time-limited medical
applications.
Plastics made from the same initial polymer can
show differences in material properties and rates of
biodegradation. For example, a study of cellulose-
based fabrics demonstrated that biodegradation
was greatest in rayon and decreased in the order
rayon > cotton >> acetate (Park et al 2004). The tests
used were soil burial, activated sewage sludge and
enzyme hydrolysis. Biodegradability was related to the
crystalinity of the fibres (rayon had lowest crystalinity)
and the fabric weave. The bio-plastic PLA is a polyester,
produced from lactic acid derived from agricultural
crops such as maize and sugar cane, and it can be
biodegraded by a variety of micro-organisms (Eubeler
et al. 2010). However, despite the biological origins
degradation under natural environmental conditions
is very slow and it requires industrial composting for
complete biodegradation (GESAMP 2015).
A polymer may be marketed as ‘biodegradable’ but
this may only apply to a limited range of environmental
conditions, which are probably not encountered in
the natural environment (Figure 3.3). This can lead
to misunderstandings and confusion as to what
constitutes biodegradability. For example, some items,
such as plastic shopping bags supplied for groceries,
may be labelled as ‘biodegradable’. However, it is quite
possible that the item will only degrade appreciably in
an industrial composter (section 3.1). Such polymers
will not ‘biodegrade’ in domestic compost heaps or
if left to litter the environment. This lack of clarity
may lead to behaviours that result in a greater degree
of littering (Section 5.0). The State of California has
passed legislation that covers the use of the terms
‘biodegradable’ and ‘compostable’ on consumer
packaging.
3.4 Oxo-degradable plastics
These are conventional polymers, such as
polyethylene, which have had a metal compound
(e.g. manganese) added to act as a catalyst, or
pro-oxidant, to increase the rate of initial oxidation
and fragmentation (Chiellini et al. 2006). They
are sometimes referred to as oxy-biodegradable
or oxo-degradable. Initial degradation may result
in the production of many small fragments (i.e.
microplastics), but the eventual fate of these is poorly
understood (Eubeler et al. 2010, Thomas et al. 2010).
As with all forms of degradation the rate and degree of
fragmentation and utilisation by microorganisms will
be dependent on the surrounding environment. There
appears to be no convincing published evidence that
oxo-degradable plastics do mineralise completely in
the environment, except under industrial composting
conditions. The use of a catalyst will invariably tend to
restrict the applications the plastic can be used for as
it will alter the mechanical properties.
The conclusions of the present paper are based on
evidence presented in the peer-reviewed literature.
But, it should be appreciated that the degree to
which oxo-degradable plastics really do offer a more
‘environmentally-friendly’ option over traditional
polymers is the subject of intense debate. This appears
to be influenced, at least in part, by commercial
interests, both for those supporting the use of oxo-
degradable plastics and for those opposing them.
For example, a position paper issued by European
Bioplastics (European Bioplastics 2012), an industry
association of European bioplastics producers,
strongly challenged the conclusions of an LCA of oxo-
degradable bags commissioned by a producer of pro-
oxidants (Edwards and Parker 2012). Without wishing
to be drawn into this debate, it should be pointed
out that decision-makers are unlikely to be influenced
solely by reliable, independent and peer-reviewed
scientific evidence.
A literature review (Deconinck and De Wilde 2013)
of publications on bio- and oxo-degradable plastics,
commissioned by Plastics Europe, concluded that the
rate and level of biodegradation of oxo-degradable
plastics ‘is at least questionable and reproducibility’.
Outside the human body the degree or rate
of biodegradation becomes very dependent
on the surrounding environment, which will
show a much greater variability
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
22
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
The lack of consensus on the desirability or otherwise
of oxo-degradable plastics is evident from the
disputed entry in the on-line Wikipedia dictionary3.
A useful commentary on many of the disputed claims
is available. (Narayan 2009).
Meanwhile, a review commissioned by the UK
Government, published in 2010, concluded that
oxo-degradable plastics did not provide a lower
environmental impact compared with conventional
plastics (Thomas et al. 2010). The recommended
solutions for dealing with end-of-life oxo-degradable
plastics were incineration (first choice) or landfill.
In addition, the authors observed that:
… as the [oxo-degradable] plastics will not degrade
for approximately 2-5 years, they will still remain
visible as litter before they start to degrade’.
(Thomas et al. 2010)
3 Accessed 9th February 2015
Plastics containing pro-oxidants are not
recommended for recycling as they have the
potential to compromise the utility of recycled
plastics (Hornitschek 2012). There has been debate
on the need for legislation to control the marketing
of products made with oxo-degradable polymers in
the state of California and within the European Union.
There has been debate on the need for
legislation to control the marketing of
products made with oxo-degradable polymers
Fig. 3.3 Examples of single-use plastic products marked as either ‘oxo-degradable’ or ‘100% biodegradable’.
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
23
4
THE BEHAVIOUR OF
‘BIODEGRADABLE’ PLASTICS
IN THE MARINE ENVIRONMENT
PHOTO © JENNYVIDS  CREATIVE COMMONS
Can plastiC designed
to be ‘biodegradable’
have a signifiCant
role in reduCing
oCean litter?
biodegradable
PlaSTiCS
24
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
THE BEHAVIOUR
OF ‘BIODEGRADABLE’
PLASTICS IN THE MARINE
ENVIRONMENT
4.1 The composition of
plastic litter in the ocean
Plastics are ubiquitous in the marine environment.
A number of studies have been published illustrating
the wide range of polymer compositions found in
seawater, sediments and biota (Table 4.1). There does
not appear to have been any attempt to analyse the
proportion of ‘non-biodegradable’ and ‘biodegradable’
plastics in the ocean. Much of the biodegradable
plastics market is focussed on packaging, single-use
consumer products, and horticultural applications.
This suggests that the input of biodegradable plastic
into the ocean will be broadly similar to the overall
plastic input when adjusted for regional differences
in uptake of biodegradable plastics. As the quantity
and types of plastic entering the ocean is unknown
it follows that the quantity of biodegradable plastics
entering the ocean is also unknown.
The exact quantities of different polymers observed
in the marine environment will depend on the
nature of local and regional sources, long-distance
transport pathways, material properties (size, shape,
density) and conditions experienced at each location
(e.g. UV irradiance, temperature, oxygen level, physical
disturbance, biological factors). Sampling methods
commonly under-sample material < 330 microns in
diameter, and identification is usually restricted to the
major polymer types. Sampling at mid-water depths
and at or near the seabed is much more resource
intensive than sampling the sea surface or shoreline,
and is conducted much less frequently.
4.2 The fate of biodegradable
plastic in the ocean
Degradation processes
Biodegradable plastics in the marine environment
will behave quite differently than in a terrestrial setting
(soil, landfill, composter) as the conditions required for
rapid biodegradation are unlikely to occur. Plastics lying
on the shoreline will be exposed to UV and oxidation
and fragmentation will occur, a process that will be
more rapid in regions subject to higher temperatures or
where physical abrasion takes place. Once larger items
or fragments become buried in sediment or enter the
water column then the rate of fragmentation will slow
dramatically. Experimental studies of biodegradation
of polymers in seawater are rather limited in number,
and the results have to be placed in the context of
natural conditions (UV, temperature, oxygen, presence
of suitable microbiota), as well as the characteristics of
the polymer. For example, PE degradation rates may
be a little higher in tropics due to higher temperatures,
higher dissolved oxygen and a favourable microbial
assemblage, but they remain very low (Sudhakar et al.
2007).
PHOTO © BO EIDE  CREATIVE COMMONS
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
25
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
Table 4.1 Selection of reported polymer compositions in a variety of media (GESAMP 2015).
maTrix size Polymer comPosiTion reference
sediment/ shoreline < 1 mm PES (56%), AC (23%), PP (7%), PE (6%), PA (3%). Browne
et al. (2011)
sediment/ sewage
disposal site
< 1 mm PES (78%), AC (22%) Browne
et al. (2011)
sediment/ beach < 1 mm PES (35%), PVC (26%), PA (18%), AC, PP, PE, EPS Browne
et al. (2008)
sediment /Inter-
and sub-tidal
0.03-0.5 mm PE (48.4%), PP (34.1%), PP+PE (5.2%), PES (3.6%),
PAN (2.6%), PS (3.5%), AKD (1.4%), PVC (0.5%),
PVA (0.4%), PA (0.3%)
Vianello
et al. (2013)
sediment/ beach 1-5 mm
(pellet)
PE (54, 87, 90, 78%), PP (32, 13, 10, 22%) Karapanagioti
et al. (2011)
water/ coastal
surface microlayer
< 1 mm AKD (75%), PSA (20%), PP+PE (2%), PE, PET, EPS Song et al.
(2013)
water/ sewage
effluent
< 1 mm PES (67%), AC (17%), PA (16%), Browne
et al. (2011)
fish 0.13-14.3 mm PA (35.6%), PES (5.1%), PS (0.9%), LDPE (0.3%)
AC (0.3%), rayon (57.8%)
Lusher
et al. (2012)
bird -PE (50.5%), PP (22.8%), PC and ABS (3.4%), PS (0.6%),
not-identified (22.8%)
Yamashita
et al. (2011)
Bacteria capable of degrading PCL have been
isolated from deep seawater off the coast of Japan
(Sekiguchi et al. 2011). Pitting and loss of structural
integrity was observed when PCL was exposed to
species of the genera Pseudomonas, Alcanivorax, and
Tenacibaculum. The time-dependence and extent
of biodegradation was expected to be influenced by
competition from other colonizing bacteria as well as
temperature and oxygen levels. The addition of PLA to
PUR was shown to increase the rate of degradation in
seawater (Moravek et al. 2009). However, the reaction
was very temperature dependent and the results have
limited applicability to natural conditions. Experimental
studies on carrier bags composed of the starch-based
Mater-Bi™ led to the conclusion that such bags would
not automatically reduce or provide a solution to the
environmental impacts caused by marine litter, on the
basis of the slow rate of degradation observed in marine
ecosystems (Accinelli et al. 2013). Biodegradation of
plastics that are considered recalcitrant, such as PE, can
take place in the marine environment at an extremely
slow rate. There is limited evidence suggesting that
microbial degradation of the surface of PE particles
happens in the marine environment (Zettler et al. 2013).
Interactions with species
Many species are affected by interaction with
marine plastics, either by ingestion or by entanglement.
Toothed whales, sea turtles and seagulls commonly
are found to contain large quantities of plastic within
their guts during necropsies of beached specimens. It
is thought that plastic items are mistaken for prey and,
when swallowed, block the gut and cause starvation.
The degree to which the presence of plastic causes
the death of the specimen is difficult to quantify but
it does appear to have been a significant factor in
many cases. Conditions within an organism may be
very different from the ambient environment (e.g.
gut chemistry, enzyme activity, microbial action).
Differences in the behaviour of some polymers within
an organism, compared with externally, may occur but
this has not been documented sufficiently and is likely
to be species-specific.
Perhaps the most relevant study examined the
degradation of plastic carrier bags in gastrointestinal
fluids of two species of sea turtle: the herbivore Green
turtle (Chelonia mydas) and carnivore Loggerhead
turtle (Caretta caretta) (Műller et al. 2012). Fluids
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
26
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
were collected from the stomach, the small intestine
and large intestine of freshly dead specimens. Three
types of polymer were used: conventional HDPE,
oxo-degradable, and a biodegradable PBAT/Starch
blend (Mater-Bi™).
Changes in polymer mass were measured over 49
days (standard test procedure) after which weight
losses were as follows: HDPE – negligible, oxo-
degradable – negligible, and biodegradable – 4.5 – 8.5%.
This is much slower that the degradation rates claimed
by the manufacturers for industrial composting. The
study demonstrated that degradation of plastic was
much slower than for normal dietary items. The lower
rate of degradation in the Loggerhead may be due to
differences in diet and associated enzyme activity.
Biodegradable polymers and ghost fishing
Many fisheries use pots or small fixed nets.
For example, there are estimated to be approximately
77,000 fishing vessels operating in the waters of the
Republic of Korea using this type of gear (Kim et al.
2014a). These are frequently lost due to gear conflicts
or adverse weather conditions. In the Gulf of Maine
alone, it is estimated that 175,000 lobster traps are lost
each year4.
Some studies have examined the feasibility of using
biodegradable polymers in the design of fishing gear
to reduce the impact of ‘ghost fishing’, a term used
to describe the tendency for lost or discarded fishing
gear to continue to trap marine organisms, leading to
an unnecessary depletion of populations. Kim et al.
(2014b) tested the performance of conger eel pots
by comparing commercial pots used in the Republic
of Korea with pots constructed with biodegradable
(PBS) polymers for key components, using a number
of mechanical tests as well as their effectiveness.
The fishing performance was similar, although the
biodegradable pots caught fewer smaller individuals,
which was an unexpected bonus. In the commercial
fishery the pots are usually replaced every two years,
and so the durability of the biodegradable components
would be sufficient. The main advantage would be for
pots that were not recovered, as the efficacy of the
biodegradable components, specifically designed to
have a limited life in the marine environment, would
be expected to decline and reduce the extent of
continuing ghost fishing. The main disadvantage is
that the biodegradable pots are more expensive so it is
unlikely they will be exploited by the industry without
financial incentives.
4 Gulf of Maine Lobster Foundation http://www.geargrab.org/
Table 4.2 Weight loss of three types of plastic bag in
the gastrointestinal fluids of Green turtle (Chelonia
mydas) and Loggerhead turtle (Caretta caretta) (Műller
et al. 2012)
Polymer
TyPe
Polymer
source
WeigHT loss
afTer 49 Days
HDPE Shopping
carrier bag
negligible
Oxo-degradable Shopping
carrier bag
– PE with
pro-oxidant
(d2w™
technology)
negligible
Biodegradable Shopping
carrier bag -
starch-based
Mater-Bi™
from BioBag®
Green turtle 8.5%
Loggerhead turtle 4.5 %
Experiments using PE and biodegradable (PBS)
components for pot nets in the Korean octopus
fisheries (Octopus minor) produced more mixed
results, with fishing performance significantly
lower using biodegradable polymers (Kim et al.
2014a). Octopus are very sensitive to the softness
of the twine used in the trap, which shows that
an understanding of species behaviour and the
characteristics of the fishery is essential before
making recommendations of what design is most
‘environmentally friendly’. The modified pot nets were
also more expensive than those made with standard PE.
PHOTO © CHRISTOPHER DART  CREATIVE COMMON
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
27
5
PUBLIC PERCEPTIONS, ATTITUDES AND BEHAVIOURS
PHOTO © LUCY LAMBREIX  CREATIVE COMMON
Can plastiC designed
to be ‘biodegradable’
have a signifiCant
role in reduCing
oCean litter?
biodegradable
PlaSTiCS
28
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
PUBLIC
PERCEPTIONS,
ATTITUDES AND
BEHAVIOURS
A number of studies have shown that attitudes
towards the marine environment are influenced
by age, educational level, gender and cultural
background. Very few studies have been conducted
on attitudes to marine litter and on the factors that
contribute to littering behaviour (Whyles et al. 2014).
A study of attitudes of European populations found
that Governments and policy were considered to be
most responsible for the reduction of marine litter,
whereas environmental groups were considered to be
most capable of making a difference (Bonny Hartley
pers. comm.).
Human perceptions influence personal behaviour,
legislative and commercial decisions. Some, albeit
limited evidence suggests that some people are
attracted by ‘technological solutions’ as an alternative
to changing behaviour. In the present context, labelling
a product as biodegradable may be seen as a technical
fix that removes responsibility from the individual. A
perceived lower responsibility will result in a reluctance
to take action (Klöckner 2013). A survey of littering
behaviour in young people in Los Angeles revealed
that labelling a product as ‘biodegradable’ was one
of several factors that would be more likely to result
in littering behaviour (Keep Los Angeles Beautiful,
2009). Whether similar attitudes occur in different age
and cultural groups and in different regions globally
is unknown, and more research is justified.
Labelling a product as biodegradable
may be seen as a technical fix that removes
responsibility from the individual.
PHOTO © RICHARD MASONER  CREATIVE COMMON
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
29
6
CONCLUSIONS
PHOTO © ROB WWW.BBMEXPLORER.COM  CREATIVE COMMON
Can plastiC designed
to be ‘biodegradable’
have a signifiCant
role in reduCing
oCean litter?
biodegradable
PlaSTiCS
30
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
CONCLUSIONS
Plastic debris is ubiquitous in the marine
environment, comes from a multitude of sources
and is composed of a great variety of polymers
and copolymers, which can be grouped into a
relatively limited number of major classes.
Polymers most commonly used for general
applications, with the required chemical and
mechanical properties (e.g. PE, PP, PVC) are not
readily biodegradable, especially in the marine
environment.
Polymers which will biodegrade in the terrestrial
environment, under favourable conditions (e.g.
AcC, PBS, PCL, PES, PVA), also biodegrade in the
marine environment, but much more slowly and
their widespread use is likely to lead to continuing
littering problems and undesirable impacts.
Biodegradable polymers tend to be significantly
more expensive. Their adoption, in place of
lower-cost alternatives, for well-justified purposes
(e.g. key components of a fishing trap) may
require financial inducement.
The inclusion of a pro-oxidant, such as
manganese, in oxo-degradable polymers is
claimed to promote fragmentation by UV
irradiation and oxygen. The fate of these
fragments (microplastics) is unclear, but it should
be assumed that oxo-degradable polymers
will add to the quantity of microplastics in
the oceans, until overwhelming independent
evidence suggests otherwise. The current usage of
these polymers is very limited.
Oxo-degradable polymers do not fragment
rapidly in the marine environment (i.e. persist
> 2-5 years) and so manufactured items will
continue to cause littering problems and lead to
undesirable impacts.
Some of the claims and counter-claims about
particular types of polymer, and their propensity
to biodegrade in the environment, appear to be
influenced by commercial interests.
Some evidence albeit limited suggests that
public perceptions about whether an item is
biodegradable can influence littering behaviour;
i.e. if a bag is marked as biodegradable it is more
likely to be discarded inappropriately.
On the balance of the available evidence,
biodegradable plastics will not play a significant
role in reducing marine litter.
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
31
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
REFERENCES
Accinelli, C., M. L. Sacca, M. Mencarelli and A. Vicari
(2012). “Deterioration of bioplastic carrier bags in
the environment and assessment of a new recycling
alternative.” Chemosphere 89(2): 136-143.
Andrady, A. (2011). “Microplastics in the marine
environment.” Marine Pollution Bulletin 62(8): 1596-1605.
Browne, M. A., P. Crump, S. J. Niven, E. Teuten, A. Tonkin,
T. Galloway and R. Thompson (2011). “Accumulation of
Microplastic on Shorelines Woldwide: Sources and Sinks.”
Environmental Science & Technology 45(21): 9175-9179.
Browne, M. A., A. Dissanayake, T. S. Galloway, D. M. Lowe
and R. C. Thompson (2008). “Ingested microscopic plastic
translocates to the circulatory system of the mussel,
Mytilus edulis (L.).” Environmental Science and Technology
42(13): 5026-5031.
Cappitelli, F., P. Principi and C. Sorlini (2006).
“Biodeterioration of modern materials in contemporary
collections: can biotechnology help?” Trends in
Biotechnology 24(8): 350-354.
Chiellini, E., A. Corti, S. D’Antone and R. Baciu (2006). “Oxo-
biodegradable carbon backbone polymers - Oxidative
degradation of polyethylene under accelerated test
conditions.” Polymer Degradation and Stability 91(11):
2739-2747.
Deconinck, S. and De Wilde, B. (2013). “Benefits and
challenges of bio- and oxy-degradable plastics. A
comparative literature study.” Executive Summary. Study
DSL-1, on behalf of Plastics Europe AISBL, Begium, 8pp.
Edwards, C. and Parker, G. (2012) “A life cycle assessment of
oxy-biodegradable, compostable and conventional bags.”
Interetek Expert Services Report on behalf of Symphony
Environmental Ltd. 46pp.
Eubeler, J. P., M. Bernhard and T. P. Knepper (2010).
“Environmental biodegradation of synthetic polymers II.
Biodegradation of different polymer groups.” TrAC-Trends
in Analytical Chemistry 29(1): 84-100.
Eubeler, J. P., S. Zok, M. Bernhard and T. P. Knepper (2009).
“Environmental biodegradation of synthetic polymers
I. Test methodologies and procedures.” TrAC Trends in
Analytical Chemistry 28(9): 1057-1072.
GESAMP (2015). “Sources, fate and effects of microplastics
in the marine environment - a global assessment.”
GESAMP Reports and Studies Series. GESAMP (IMO/
FAO/UNESCO-IOC/UNIDO/WMO/IAEA/UN/UNEP/
UNDP Joint Group of Experts on the Scientific Aspects of
Marine Environmental Protection).
Guo, B., L. Glavas and A.-C. Albertsson (2013).
“Biodegradable and electrically conducting polymers for
biomedical applications.” Progress in Polymer Science
38(9): 1263-1286.
Hornitschek, B. (2012). Impact of degradable and oxy-
degradable plastics carrier bags on mechanical recycling.
Report by the Transfer Center for Polymer Technology
(TCKT) on behalf of the European Plastic Converters
(EuPC). 22pp.
Karapanagioti, H. K., S. Endo, Y. Ogata and H. Takada
(2011). “Diffuse pollution by persistent organic pollutants
as measured in plastic pellets sampled from various
beaches in Greece.” Marine Pollution Bulletin 62(2): 312-
317.
Keep Los Angeles Beautiful (2009) “Littering and
the iGeneration: City-wide intercept study of youth
litter behaviour in Los Angeles.” Session paper at XIII
Environmental Psychology Conference Granada, June
23-26, 2015 http://www.congresopsicamb2015.com
(Accessed 10 Aug 2015)
Kim, S., S. Park and K. Lee (2014a). “Fishing Performance
of an Octopus minor Net Pot Made of Biodegradable
Twines.” Turkish Journal of Fisheries and Aquatic Sciences
14(1): 21-30.
Kim, S.-G., W.-I. L. Lee and M. Yuseok (2014b). “The
estimation of derelict fishing gear in the coastal waters
of South Korea: Trap and gill-net fisheries.” Marine Policy
46(0): 119-122.
Klöckner, C.A. (2013). A comprehensive model of the
psychology of environmental behaviour—A meta-analysis.
Global Environmental Change, 23(5), 1028-1038.
Lambert, S., C. J. Sinclair, E. L. Bradley and A. B. A. Boxall
(2013). “Environmental fate of processed natural rubber
latex.” Environmental Science-Processes & Impacts 15(7):
1359-1368.
Lusher, A. L., M. McHugh and R. C. Thompson (2013).
“Occurrence of microplastics in the gastrointestinal tract
of pelagic and demersal fish from the English Channel.
Marine Pollution Bulletin 67(1-2): 94-99.
Mohee, R. and G. Unmar (2007). “Determining
biodegradability of plastic materials under controlled and
natural composting environments.” Waste Management
27(11): 1486-1493.
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
32
0.0004 millimeters
1.24 millimeters
1.002 millimeters
0.002 millimeters
1.0542 millimeters
Moravek, S. J., M. K. Hassan, D. J. Drake, T. R. Cooper, J. S.
Wiggins, K. A. Mauritz and R. F. Storey (2010). “Seawater
Degradable Thermoplastic Polyurethanes.” Journal of
Applied Polymer Science 115(3): 1873-1880.
Müller, C., K. Townsend and J. Matschullat (2012).
“Experimental degradation of polymer shopping bags
(standard and degradable plastic, and biodegradable) in
the gastrointestinal fluids of sea turtles.” Science of The
Total Environment 416(0): 464-467.
Muthu, S. S., Y. Li, J.-Y. Hu and P.-Y. Mok (2012).
“Recyclability Potential Index (RPI): The concept and
quantification of RPI for textile fibres.” Ecological Indicators
18(0): 58-62.
Narayan, R. (2009). “Biodegradability - sorting through
facts and claims.” Bioplastics Magazine 4:28-31
Park, C. H., Y. K. Kang and S. S. Im (2004). “Biodegradability
of cellulose fabrics.” Journal of Applied Polymer Science
94(1): 248-253.
Pemba, A. G., M. Rostagno, T. A. Lee and S. A. Miller (2014).
“Cyclic and spirocyclic polyacetal ethers from lignin-based
aromatics.” Polymer Chemistry 5(9): 3214-3221.
Pham, C. K., E. Ramirez-Llodra, C. H. S. Alt, T. Amaro,
M. Bergmann, M. Canals, J. B. Company, J. Davies, G.
Duineveld, F. Galgani, K. L. Howell, V. A. I. Huvenne, E.
Isidro, D. O. B. Jones, G. Lastras, T. Morato, J. N. Gomes-
Pereira, A. Purser, H. Stewart, I. Tojeira, X. Tubau, D. Van
Rooij and P. A. Tyler (2014). “Marine Litter Distribution
and Density in European Seas, from the Shelves to Deep
Basins.” PLoS ONE 9(4): e95839.
Pillay, V., T.-S. Tsai, Y. E. Choonara, L. C. du Toit, P. Kumar,
G. Modi, D. Naidoo, L. K. Tomar, C. Tyagi and V. M. K.
Ndesendo (2014). “A review of integrating electroactive
polymers as responsive systems for specialized drug
delivery applications.” Journal of Biomedical Materials
Research Part A 102(6): 2039-2054.
Sekiguchi, T., A. Saika, K. Nomura, T. Watanabe, T.
Watanabe, Y. Fujimoto, M. Enoki, T. Sato, C. Kato and H.
Kanehiro (2011). “Biodegradation of aliphatic polyesters
soaked in deep seawaters and isolation of poly(ɛ-
caprolactone)-degrading bacteria.” Polymer Degradation
and Stability 96(7): 1397-1403.
Shah, A. A., F. Hasan, A. Hameed and S. Ahmed (2008).
“Biological degradation of plastics: A comprehensive
review.” Biotechnology Advances 26(3): 246-265.
Shen, L., E. Worrell and M. K. Patel (2010). “Environmental
impact assessment of man-made cellulose fibres.”
Resources, Conservation and Recycling 55(2): 260-274.
Song, Y. K., S. H. Hong, M. Jang, J.-H. Kang, O. Y. Kwon, G.
M. Han and W. J. Shim (2014). “Large Accumulation of
Micro-sized Synthetic Polymer Particles in the Sea Surface
Microlayer.” Environmental Science & Technology 48(16):
9014-9021.
Sudhakar, M., C. Priyadarshini, M. Doble, P. Sriyutha
Murthy and R. Venkatesan (2007). “Marine bacteria
mediated degradation of nylon 66 and 6.” International
Biodeterioration & Biodegradation 60(3): 144-151.
Thomas, N., Clarke, J., Mclauchlin, A. and Patrick, S.
(2010).”Assessing the environmental impacts of oxy-
degradable plastics across their life cycle.” Research Report
for the Department of Environment, Food and Rural
Affairs, London, UK. 104pp.
Tokiwa, Y., B. Calabia, C. Ugwu and S. Aiba (2009).
“Biodegradability of Plastics.” International Journal of
Molecular Sciences 10(9): 3722-3742.
Vianello, A., A. Boldrin, P. Guerriero, V. Moschino, R. Rella,
A. Sturaro and L. Da Ros (2013). “Microplastic particles in
sediments of Lagoon of Venice, Italy: First observations on
occurrence, spatial patterns and identification.” Estuarine
Coastal and Shelf Science 130: 54-61.
Woodruff, M. A. and D. W. Hutmacher (2010). “The return
of a forgotten polymer-Polycaprolactone in the 21st
century.” Progress in Polymer Science 35(10): 1217-1256.
Wyles, K. J., Pahl, S. & Thompson, R. C. (2014) “Perceived
risks and benefits of recreational visits to the marine
environment: Integrating impacts on the environment and
impacts on the visitor.” Ocean & Coastal Management, 88
pp 53-63.
Yamashita, R., H. Takada, M.-a. Fukuwaka and Y. Watanuki
(2011). “Physical and chemical effects of ingested plastic
debris on short-tailed shearwaters, Puffinus tenuirostris, in
the North Pacific Ocean.” Marine Pollution Bulletin 62(12):
2845-2849.
Yang, J., Y. Yang, W.-M. Wu, J. Zhao and L. Jiang (2014).
“Evidence of Polyethylene Biodegradation by Bacterial
Strains from the Guts of Plastic-Eating Waxworms.
Environmental Science & Technology 48(23): 13776-13784
Zettler, E. R., T. J. Mincer and L. A. Amaral-Zettler (2013).
“Life in the “Plastisphere”: Microbial Communities
on Plastic Marine Debris.” Environmental Science &
Technology 47(13): 7137-7146..
delivery systems: an application update. International
Journal of Cosmetic Science 30: 19–33.
Misconceptions,
concerns and iMpacts
on Marine environMents
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
33
United Nations Environment Programme
P.O. Box 30552 Nairobi, 00100 Kenya
Tel: (254 20) 7621234
Fax: (254 20) 7623927
E-mail: publications@unep.org
web: www.unep.org
www.unep.org
0.0004-1.24 millimeters
1.24 millimeters
1.002 millimeters
1.0542 millimeters
... In general, plastics have a lower density when compared to seawater (1.27 kg/m 3 ). Plastic density has a range of 0.9 -1.39 kg/m 3 (Kershaw, 2015;Meier, 2009). Plastic density and examples of plastic objects found in the marine environment can be seen in Table 1. ...
... With the value of plastic density on seawater density and ignoring buoyancy, it can conclude that polyethylene, polypropylene and some types of polystyrene plastic will float in seawater. In freshwater, polyethylene and polypropylene will float in the water column by ignoring buoyancy in all types of plastic (Kershaw, 2015). Litter from land which eventually accumulates on the seafloor comes from the river, mostly in the rainy season (Jang et al., 2014). ...
Chapter
Marine pollution due to littering from anthropogenic activities is a serious global environmental problem-the main reason accumulation of debris in the environment, including in the ocean. There is a significant hazard coming from plastic debris. Besides entanglement and ingestion, marine plastics debris has more complex problems and can release additional and by-product chemical substances. If we keep producing and not doing anything, a recent study said by 2050 there would be three times more plastic than fish in the ocean. We only have a limited understanding of marine plastic debris distribution, implication, fate, and behavior. Science is the key to getting the right alternative for processing debris. To prevent marine pollution successfully requires education and outreach programs, strong laws and policies, and law enforcement for government and private institutions. This chapter explores marine plastic debris.
... The existence of heteroatoms such as oxygen and nitrogen in thermosets' backbone makes them hydrophile and hydrolytically cleavable. Therefore, thermoset plastics have biodegradability potentials [52,81,205]. In Table 1, some examples of thermoplastics and thermoset plastics are provided. ...
Chapter
Plastics’ unique physical and chemical properties made them indispensable parts of our everyday life and technology. Due to the mismanagement of plastic wastes, 10% of global plastic production annually entering the ocean accounts for 60–80% of marine debris.With the current plastic production rate, more plastics will exist in the oceans than fish by 2050. Plastic waste does not decompose in nature, or its decomposition takes a long time. Among plastic contaminants, microplastics, which are plastic pieces less than 5 mm in size, have attracted much attention because of their potential risks to organisms’ lives. This chapter discusses plastic polymers, their types, and their features that affect plastics’ degradation. Here, we present the interaction between organisms and microplastics and their hazardous effects on living organisms. Bioremediation and biodegradation are explained. Also, new approaches in biodegradation, such as enzyme engineering, are introduced. Plastic polymers’ chemical and physical features such as molecular weight, molecular backbone’s atoms, chemical bonds, crystallinity, hydrophobicity, and additives presence are important factors in vulnerability to decomposing agents. Aging and weathering by abiotic factors including sunlight, heat,moisture, and oxygen decrease the microplastics’ surface hydrophobicity and facilitate microorganism attachments and biofilm formation. Microplastics, because of releasing toxic additives, metallic and organic toxic compounds’ adsorption on their surfaces, threaten organisms’lives. Microplastics’ harmful effects on marine organisms, especially the primary producers’ food chains such as microalgae, can directly or indirectly influence food web consumers such as fish, aquatic birds, and even humans. Antibiotic adsorption on microplastics and, therefore, enrichment of potentially pathogenic and antibiotic resistant bacteria and antibiotic-resistance genes through horizontal gene transfer are other microplastics-related concerns. Following the biofilm formation, microorganisms’ activity and their secreted enzymes and agents deteriorate the microplastics and lead to molecular fragmentation and depolymerization. Assimilation and mineralization of the fragmented molecules are the last biodegradation steps that give rise to CO2, H2O, CH4, and biomass production. Some genus and species of fungi and bacteria and their powerful enzymes such as oxidoreductases and hydrolases are key players in bioremediation by microorganisms. Electron microscopy, spectroscopy techniques, weight loss measurements, mechanical properties, molar mass changes, CO2 evolution/O2 consumption, radiolabeling, clear-zone formation, enzymatic degradation, and controlled composting test are employed for biodegradation evaluation. Since more than 99% of prokaryotes and some eukaryotic microbes are unculturable, hence, to select plastic-decomposing microorganisms, culture independent methods, i.e., metagenomic analysis, are utilized. The metagenome analysis and in silico mining lead to a deeper investigation of the explored and unexplored nature to find efficient enzymes and microorganisms for microplastics’ bioremediation. Using microbial consortia and engineered microorganisms and their enzymes are other promising approaches for plastics bioremediation. Keywords : Microplastics · Bioremediation · Biodegradation · Biodegradable plastics · Aquatic environment · Bacteria · Fungi · Antibiotic resistance · Enzyme engineering · In silico and metagenomics analysis
... The existence of heteroatoms such as oxygen and nitrogen in thermosets' backbone makes them hydrophile and hydrolytically cleavable. Therefore, thermoset plastics have biodegradability potentials [52,81,205]. In Table 1, some examples of thermoplastics and thermoset plastics are provided. ...
Article
Separation and removal of microplastic pollution from aquatic environments as a global environmental issue is classified as one of the major concerns in both water and wastewater treatment plants. Microplastics as polymeric particles less than 5 mm in at least one dimension are found with different shapes, chemical compositions, and sizes in soil, water, and sediments. Conventional treatment methods for organic separation have shown high removal efficiency for microplastics, while the separation of small microplastic particles, mainly less than 100 µm, in wastewater treatment plants is particularly challenging. This review aims to review the principle and application of different physical and chemical methods for the separation and removal of microplastic particles from aquatic environments, especially in water treatments process, with emphasis on some alternative and emerging separation methods. Advantages and disadvantages of conventional separation techniques such as clarification, sedimentation, floatation, activated sludge, sieving, filtration, and density separation are discussed. The advanced separation methods can be integrated with conventional techniques or utilize as a separate step for separating small microplastic particles. These advanced microplastic separation methods include membrane bioreactor, magnetic separation, micromachines, and degradation-based methods such as electrocatalysis, photocatalysis, biodegradation, and thermal degradation.
... Empirical studies show that each year about 8 mt of plastics is deposited into the Pacific Ocean through watersheds from different parts of the world (Virsek et al. 2017;Rios-Mendoza et al. 2018). In a prediction, the UNEP (Kershaw 2015) expecting that weight of plastics in the ocean will be more than the weight of fish by 2050. ...
Chapter
The story of human civilization will remain incomplete without addressing the contribution of rivers in our life. The riverine system is the largest source of the freshwater aquatic body. River confluences and its tributaries play a significant role in human life. Today, the riverine systems from all over the world especially the South-Asian rivers are moving towards an alarming situation due to anthropogenic pollution. South Asia, the cultural and economically developing part of the Asian continent, is now combating successive increases in high population rate, urbanization and industrialization. All these factors are cumulatively leading towards riverine pollution. Plastics, especially microplastics pollution, are one of the major threats to the degradation of riverine health due to high dependence on plastics to meet expectations of daily life. Studies from different sources reveal that most of the rivers of the world are getting polluted by microplastics (<5 mm in diameter). Natural weathering processes transform the plastics into microplastics which pose a serious threat to the aquatic biota and food chains. Remediation strategies are still less understood for this new-age pollutant. This article is an initiative to gather data on plastics and microplastics pollution in the riverine system and a scientific overview of the present situation.
... Plastic waste exposed to environmental conditions begins to degrade slowly under the impact of temperature and UV radiation [9], generating a large number of macro-, micro-, and nanoparticles. These particles are freely transported by water flows and have adverse effects on the environment [10,11]. One of the key factors which determines the fate of microplastics in the environment is the density of polymers. ...
Article
Full-text available
Geosynthetic materials are applied in measures for coastal protection. Weathering or any damage of constructions, as shown by a field study in Kaliningrad Oblast (Russia), could lead to the littering of the beach or the sea (marine littering) and the discharge of possibly harmful additives into the marine environment. The ageing behavior of a widely used geotextile made of polypropylene was studied by artificial accelerated ageing in water-filled autoclaves at temperatures of 30 to 80 °C and pressures of 10 to 50 bar. Tensile strength tests were used to evaluate the progress of ageing, concluding that temperature rather than pressure was the main factor influencing the ageing of geotextiles. Using a modified Arrhenius equation, it was possible to calculate the half-life for the loss of 50% of the strain, which corresponds to approximately 330 years. Dynamic surface leaching and ecotoxicological tests were performed to determine the possible release of contaminants. No harmful effects on the test organisms were observed.
... For example "single-use plastic shopping bags marked 'biodegradable' may require the conditions that commonly occur only in an industrial composter." (Kershaw, 2015). European Bioplastics (2017) divides the family of bioplastics into three main groups: Bio-based or partly bio-based, non-biodegradable plastics such as PE, PP, or PET and bio-based technical performance polymers such as PTT or TPC-ET; both bio-based and biodegradable plastics such as PLA and PHA or PBS; and Biodegradable fossil-based plastics such as PBAT. ...
Article
Full-text available
In 2018, European Union adopted a European strategy for plastics in a circular economy as a part of their action plan for a circular economy. Sustainability is the underlying motivation behind the plastics strategy with a goal of addressing how plastics are designed, used and recycled in the EU. One of the strategies outlined is that by 2030, all plastic packaging placed on the EU market is either reusable or can be recycled in a cost-effective manner. A large portion of food packaging is multi-layer plastic that is not recyclable in a cost-effective manner. Given the difficulties associated with recycling today’s complex food packaging, what impacts will the European Union’s strategies for plastics in a circular economy have on food safety? This article explores what is being done and what can be done to mitigate the risks to food safety while adhering to the EU’s plastic strategy. It has been observed that the plastic plays a vital role in maintaining food safety, extending shelf-life and minimising food waste. However, it is currently not possible to recycle multi-layer plastic packaging which is widely used throughout the food industry, and there are currently no viable alternatives offering the same level of protection. Unless possible substitutes to multi-layer plastics offering the same level of food protection can be developed then there will be detrimental effects on food quality, safety and shelf-life, which will lead to increased food waste, additional food costs and a reduction in the variety and availability of certain foods.
Chapter
Sustainability has increasingly become an important driver for new packaging design and innovation. Concerns around climate change, pollution and depletion of natural resources have propelled plastics and flexible packaging into the spotlight. Consumer goods companies are responding with new goals around reducing packaging, increasing the use of recycled materials, reducing the amount of virgin materials and increasing the circularity of packaging. Designing for sustainability begins with understanding what the goal is—reduce, reuse, recycle, etc. This chapter introduces the primary methodology used to quantify the environmental impact of products and their packaging, the life cycle analysis. End-of-life technologies for flexible packaging are reviewed—mechanical recycling, chemical or feedstock recycling and energy recovery—in the framework of the circular economy. Finally, concepts for designing packaging for sustainability are discussed, including incorporation of postindustrial and consumer recycle into flexible packaging, and incorporating materials and features into the package structure that allow for mechanical recycling or composting.
Chapter
Many polymer resins and film substrates are used in flexible packaging. This Chapter provides an overview, starting with the basic functions these components must provide: structural integrity, barrier, sealing, adhesion, and esthetics. A brief introduction to polymer chemistry as it relates to package performance is provided followed by short descriptions of commonly used polymers and substrates in flexible packaging. The polymer resins include polyolefins, polyamides, barrier resins, polyesters, and bio-based polymers. Additives that enhance the performance of these resins are reviewed. Substrates include polypropylene, polyethylene terephthalate, aluminum foil, metallized films, cellophane, and paper/paperboard. A final section describes regulatory considerations such as compliance with food contact regulations.
Article
Low-density polyethylene (LDPE) and polypropylene (PP) are the two main polymers with extensive applications. It might lead to plastic pollution and degradation in the aquatic environment. Former laboratory simulation studies of plastic degradation have been presented. However, most of the studies were only applied a single degradation agent without specific environmental conditions, which indicated a research gap. This research aimed to investigate LDPE and PP degradation under the influence of UV radiation and water velocity with specific environmental conditions. Five reactors of simulated aquatic environments were adjusted to desire calculated UV B dose of 158.98–438.91 W.S/cm² and water velocity variations of the Surabaya River, one of Indonesia’s urban rivers that has been polluted by microplastics. The water velocity was set in high (0.3–0.6 m/s) and low ones (0.1–0.3 m/s) to represent the fluctuated river discharge at rain and dry seasons. Total simulation time of 480 h (8 h/day for 60 days simulation) has initiated LDPE and PP degradation. LDPE experienced more weight loss (3.07%) under the combined exposure of UV and high water velocity, than PP (2.37%) under high water velocity. Synergetic effects of photodegradation, physical-mechanical, and hydrolysis degradation mechanisms could affect more severe crack tip formation of LDPE and PP rather than in single agent simulation. Major surface morphology deterioration of LDPE and PP, changes in transmittance intensities, carbonyl index in this study have revealed the importance of combined exposure of UV radiation and water velocity to plastic degradation in the aquatic environment.
Chapter
Globally, the problem of microplastics (MPs) pose to water resources is current concern to scientists. Sources of MPs to water resources include wastewater, atmospheric deposition, surface runoff and leaching. Many marine animals suffer from ingesting high amounts of MPs accumulating in the gut and cause obstruction and inflammation in their organs. Humans are equally exposed from the use of surface water and drinking water or ground water. In view of these problems and in a bid to mitigate potential risks from the release of MPs to receiving waters, stringent water quality requirements for effluents are required and scientists are now developing methods or techniques to remove MPs from water resources. We reviewed techniques developed or modified for MPs removal in water and wastewater such as Dynamic Membranes Technology (DM), membrane bioreactors (MBR), reverse osmosis (RO), dissolved air flotation (DAF), rapid sand filtration (RSF), disc filter (DF), inorganic–organic hybrid silica gels, metal based-coagulation and electrocoagulation. The principles of these techniques were discussed as well as the advantages and disadvantages. Conclusions were drawn and future areas of research were recommended.
Article
Full-text available
Polyethylene (PE) has been considered non-biodegradable for decades. Although the biodegradation of PE by bacterial cultures has been occasionally described, valid evidence of PE biodegradation has remained limited in the literature. We found that waxworms, or Indian mealmoths (the larvae of Plodia interpunctella), were capable of chewing and eating PE films. Two bacterial strains capable of degrading PE were isolated from this worm's gut, Enterobacter asburiae YT1 and Bacillus sp. YP1. Over a 28-day incubation period of the two strains on PE films, viable biofilms formed, and the PE films' hydrophobicity decreased. Obvious damage, including pits and cavities (0.3-0.4 µm in depth), was observed on the surfaces of the PE films using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The formation of carbonyl groups was verified using X-ray photoelectron spectroscopy (XPS) and micro-attenuated total reflectance/Fourier transform infrared (micro-ATR/FTIR) imaging microscope. Suspension cultures of YT1 and YP1 (108 cells/ml) were able to degrade approximately 6.1  0.3% and 10.7  0.2% of the PE films (100 mg), respectively, over a 60-day incubation period. The molecular weights of the residual PE films were lower, and the release of 12 water-soluble daughter products was also detected. The results demonstrated the presence of PE-degrading bacteria in the guts of waxworms and provided promising evidence for the biodegradation of PE in the environment.
Article
Full-text available
Gillnets and net pots are made of synthetic fiber as polyester (PE) and polyamide (PA). These are often lost by heavy weather or trawling of the active fishing gears. Lost gears result in the ghost fishing because these are non-degradable in seawater and damage to spawning grounds or habitats. To address these problems, biodegradable nets composed of aliphatic polyester were developed. This study describes four types of biodegradable net pots for capturing Octopus minor in southern Korea, which is an area associated with high rates of net pot loss. The fishing performance of the biodegradable pots was compared to that of commercial net pots. The net pot with a synthetic body and biodegradable funnel (PE/Bio) produced approximately 50% of the catch collected using a commercial net pot (PE/PA). Conversely, net pots with a biodegradable body and a synthetic funnel (Bio/PA) produced the same amount of catch as the commercial net pot. The completely biodegradable net pot (Bio/Bio) caught 60% of that using the commercial net pot. These findings suggest that net pots consisting of a biodegradable body and PA funnel may be effective in capturing Octopus minor. Partially biodegradable net pots (Bio/PA) are as effective as commercial net pots, yet uniquely allows a method of capturing Octopus minor without affecting the marine environment.
Article
Full-text available
Marine environments provide a range of important ecosystem goods and services. To ensure the sustainability of this environment, we require an integrated understanding of the activities taking place in coastal environments that takes into account the benefits to human visitors but also the risks to the environment. This paper presents two studies on the perceived risks and benefits associated with recreational visits to rocky shores in the UK and internationally. Marine experts and recreational users of the coast responded to questionnaires that explored the marine awareness and wellbeing effects of different activities on the visitor and, in turn, the perceived harmfulness of these activities to the environment. Two studies found that a visit to a rocky shore was seen to improve visitors' awareness regarding the marine environment as well as their wellbeing (with some activities being calming such as sunbathing and relaxing, and others exciting such as rock pooling). However, this was perceived to be at a cost to the environment, as some activities were noted to have detrimental effects on the habitat. Marine experts and coastal users gave very similar answers, as did British (Study 1) and international respondents (Study 2). Using an integrative approach, the perceived impacts on both the environment and visitor were then explored together. Walking and rock pooling were seen to provide considerable wellbeing benefits but had high negative impacts on the environment. In contrast, resource focussed activities such as fishing, bait collecting and crabbing were perceived as less important for visitor wellbeing yet also had negative environmental impacts. Using this integrative approach, this analysis begins to suggest priorities for management that benefits both the environment and the recreational users.
Article
Full-text available
To address global environmental challenges it is crucial to understand how humans make decisions about environmentally relevant behaviour, since a shift to alternative behaviours can make a relevant difference. This paper proposes a comprehensive model of determinants of individual environmentally relevant behaviour based on a combination of the most common theories in environmental psychology. The model is tested using a meta-analytical structural equation modelling approach based on a pool of 56 different data sets with a variety of target behaviours. The model is supported by the data. Intentions to act, perceived behavioural control and habits were identified as direct predictors of behaviour. Intentions are predicted by attitudes, personal and social norms, and perceived behavioural control. Personal norms are predicted by social norms, perceived behavioural control, awareness of consequences, ascription of responsibility, an ecological world view and self-transcendence values. Self-enhancement values have a negative impact on personal norms. Based on the model, interventions to change behaviour need not only to include attitude campaigns but also a focus on de-habitualizing behaviour, strengthening the social support and increasing self-efficacy by concrete information about how to act. Value based interventions have only an indirect effect.
Article
Monomers structurally resembling lignin were prepared by reacting 4-hydroxybenzaldehyde, vanillin, syringaldehyde, (each bio-available) or ethylvanillin (synthetic) with dibromoethane, yielding dialdehydes CHO–Ar–OCH2CH2O–Ar–CHO. Condensation copolymerization with tetraols catalyzed by para-toluene sulfonic acid yielded polyacetal ethers with cyclic acetals in the case of di-trimethylolpropane (di-TMP) and spirocyclic acetals in the case of pentaerythritol (PTOL). Number average molecular weights (Mn) were in the range of 10600 to 22200, although the insolubility of those polymers based on 4-hydroxybenzaldehyde precluded this measurement. The polymers are thermally robust and exhibit 5% mass loss via thermogravimetric analysis in the range of 307–349 °C. Those copolymers based on PTOL displayed glass transition (Tg) temperatures (108–152 °C) at least 40 °C higher than their di-TMP analogues (68–98 °C), highlighting the added rigidity conferred by spirocyclic acetals versus cyclic acetals. Preliminary degradation studies were conducted in dimethyl sulfoxide with 0.5% added aqueous HCl (concentrated or 2 M). Dynamic light scattering confirmed the facile hydrolysis of the polymers. Generally, polymer degradation was faster with a higher acid concentration and copolymers from the PTOL tetraol were more resistant to hydrolysis than those from the di-TMP tetraol.
Article
Determining the exact abundance of microplastics on the sea surface can be susceptible to the sampling method used. The sea surface microlayer (SML) can accumulate light plastic particles, but this has not yet been sampled. The abundance of microplastics in the SML was evaluated off the southern coast of Korea. The SML sampling method was then compared with bulk surface water filtering, a hand-net (50 μm mesh), and a Manta trawl net (330 μm). The mean abundances were in the order of SML water > hand-net > bulk water > Manta trawl net. Fourier transform infrared spectroscopy (FT-IR) identified that alkyds and poly(acrylate:styrene) accounted for 81% and 11%, respectively, of the total polymer content of the SML samples. These polymers originated from paints and the fiber-reinforced plastic (FRP) matrix used on ships. Synthetic polymers from ship coatings should be considered to be a source of microplastics. Selecting a suitable sampling method is crucial for evaluating microplastic pollution.
Article
Conducting polymers have been widely used in biomedical applications such as biosen-sors and tissue engineering but their non-degradability still poses a limitation. Therefore, great attention has been directed toward the recently developed degradable and electrically conductive polymers (DECPs). The different strategies for synthesis of degradable and conducting polymers containing conducting oligomers are summarized and discussed here as well as the influence of different macromolecular architectures such as linear, star-shaped, hyperbranched and cross-linked DECPs. Blends and composites of biodegradable and conductive polymers are also discussed. The developing trends and challenges with the design of DECPs are also presented.
Article
This study estimates the gross quantity of discarded fishing traps and gill-nets in the coastal waters of South Korea. Using regression analysis it is estimated that 11,436 t of traps and 38,535 t of gill-nets are abandoned annually. Experts on marine debris recommend replacement of traditional fishing gears with eco-friendly designs and establishment of incentive programmes for the fishermen in order to promote eco-friendly gear designs.