B iode gra da b l e

Plastics& MARINE LITTER
Misconceptions, concerns and impacts
on marine environments

1.002 millimeters0.0004 millimeters1.0542 millimeters1.24 millimeters0.002 millimetersCopyright © United Nations Environment Programme (UNEP), 2015
This 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.
This 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.
Thank 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
The 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 citingof trade names or commercial processes constitute endorsement. The 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.

B iode gra da b l e

Plastics& MARINE LITTER
Misconceptions, concerns and impacts
on marine environments

1.002 millimeters

This report was commissioned by:
The Global Programme of Action for the Protection of
the Marine Environment from Land-based Activities (GPA)
0.0004 millimeters

GPML

1.0542 millimeters
Global Partnershipon Marine Litter

UNEP GPA
Global Programme of Action for the Protection
1.24 millimetersof the Marine Environment from Land-based
Activities, Marine Ecosystems Branch, Division ofEnvironmental Policy Implementation
P. O. Box 30552 (00100), Nairobi, Kenya
E gpml@unep.org
W unep.org/gpa/gpml

0.002 millimetersPhoto: ©Laura Billings / creative commons

Contents
Abbreviations list

2

Executive Summary

3

1.

Background5

2.

Polymers and plastics - terminology and definitions

9

2.1 The 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

Fragmentation, degradation and biodegradation

19

3.1 The degradation process

19

3.2 Non-biodegradable plastics

21

3.3 ‘Biodegradable’ plastics

21

3.4 Oxo-biodegradable plastics

22

3.

4.	The behaviour of ‘biodegradable’ plastics in the marine environment

5.

25

4.1 The composition of plastic litter in the ocean

25

4.2 The fate of biodegradable plastic in the ocean

25

Public perceptions, attitudes and behaviours

29

6.	Conclusions

31

	References32

Abbreviations list
ABS			

Acrylonitrile butadiene styreneAC			

Acrylic

AcC (CTA, TAC)		

Acetyl cellulose, cellulose triacetate

AKD			Alkyd

ASA			

Acrylonitrile styrene acrylate

DECP			

Degradable and electrically conductive polymers

EP			 Epoxy resin (thermoset)

1.002 millimeters

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

2

PVA			

Polyvinyl alcohol

PVC			

Polyvinyl chloride

BIODEGRADABLE
PLASTICS AND
MARINE LITTERSAN			

Styrene acrylonitrile

SBR			

Styrene-butadiene rubber

Starch			StarchMisconceptions,concerns and impacts
on marine environments

sretemillim 42.1

0.002 millimeters

sretemillim 4000.0

1.0542 millimeters

Executive Summary
The development and use of synthetic polymers, and plastics has conferred widespread benefits onsociety. 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 presenceof plastic in oceans. As most plastics in common use are very resistant to biodegradation, the quantityof 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 ofthe 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 canbe used to produce either non-biodegradable or biodegradable plastics. Many plastics will weather andfragment in response to UV radiation – a process that can be slowed down by the inclusion of specificadditives. 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
1.002 millimeters
is temperature dependent and some plastics labelled as ‘biodegradable’ require the conditions that typicallyoccur 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
0.0004
millimetersseawater,and they may have useful applications, for example, to reduce the impact of lost or discarded fishinggear. 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
1.0542 millimeters
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
1.24 entering
millimeters
decrease either in the quantity of plastic
the ocean or the risk of physical and chemical impacts on
the marine environment, on the balance of current scientific evidence.

3
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
Misconceptions,concerns and impacts
on marine environments

0.002 millimeters1

4

biodegradable
PLASTICsCan plastic designed
to be ‘biodegradable’
have a significant
role in reducing
ocean litter?

Photo: © Amanda Wycherley / creative commons

BackgroundBackground

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;

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, andwhether the adoption of biodegradable plastics will
reduce the impact of marine plastics overall.

• Accidental input from land-based activities andthe maritime sector, including geological andmeteorological events;• A lack of awareness on the part of consumers,for example of the use of microplastics inpersonal care products and the loss of fibres
from clothes when washed.

One of the principal properties sought of many
plastics is durability. This allows plastics to be used
for many applications which formerly relied onstone, metal, concrete or timber. There are significant
advantages, for food preservation, medical productefficacy, electrical safety, improved thermal insulationand to lower fuel consumption in aircraft andautomotives. Unfortunately, the poor managementof post-use plastic means that the durability of plastic
becomes a significant problem in mitigating its impact
on the environment. Plastics are ubiquitous in theoceans as a result of several decades of poor waste
management, influenced by a failure to appreciate
the potential value of ‘unwanted’ plastics, the underuse of market-based instruments (MBIs), and a lack ofconcern for the consequences (GESAMP 2015).

Plastics are ubiquitous in the oceans as a resultof several decades of poor waste management,
influenced by a failure to appreciate thepotential value of ‘unwanted’ plastics
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Efforts to improve waste management andinfluence changes in behaviour, on the part ofindividuals and groups, face many challenges, andthe results of mitigation measures may take many years
to demonstrate a benefit (GESAMP 2015).

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Photo: © Chesapeake Bay Program / creative commons

1.0542 millimeters1.24 millimeters

5
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
Misconceptions,concerns and impacts
on marine environments

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The degree to which ‘biodegradable’ plastics
actually biodegrade in the natural environment
is subject to intense debate.

6
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
Misconceptions,concerns and impacts
on marine environments

Photo: © PeterCharaf / RaceforWater

It has been suggested that plastics considered tobe ‘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 ofhydrolysis, photodegradation and microbial action(enzyme secretion and within-cell processes). It is
described in more detail in section 3. Although thisproperty may be appealing, it is critical to evaluate
the potential of ‘biodegradable’ plastics in terms of
their impact on the marine environment, before
1.002 millimeters
encouraging wider use.

to take place. Clearly the process is time-dependentand this is controlled by environmental factors as wellas 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 towhich plastics intended to be biodegradable doactually biodegrade in the natural environment. Thisextends to the peer-reviewed scientific literature but
is most intense between those organisations that canbe thought to have a vested interest in the outcome,such as the producers of different types of plastics,
the producers of additive chemicals intended topromote degradation and those involved in the waste
management and recycling sectors.

Deciding what constitutes best environmental
practice through the choice of different plastics and nonplastics 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
A material may be labelled ‘biodegradable’ if it processes, materials or products on the environment.
conforms to certain national or regional standards that For example, LCA could be employed to assess the use
apply to industrial composters (section 3.1), not to of plastic-based or natural fibre-based bags and textiles,
domestic compost heaps or discarded litter in the ocean. and conventional and biodegradable plastics. In one LCA
Equally important is the time taken for biodegradation –based study of consumer shopping bags, conventional
PE (HDPE) shopping carrier bags were considered to
be a good environmental option
srecomparedtemillim 400with
0.0 bags
made from paper, LDPE, non-woven PP and cotton, but
strictly in terms of carbon footprints (paper to cotton inorder of increasing global warming potential; Thomas etal. 2010). This analysis did not take account of the socialand ecological impact that plastic litter may have.
In contrast, an analysis of textiles - that included
1.0542 millimetersfactors for human health, environmental impact
and sustainability - placed cotton as having a muchsmaller footprint than acrylic fibres (Mutha et al. 2012).
However, it is important to examine what is included
terms as ‘environmental impact’. For
sreundertemillisuch
m 42.broad
1
example, a third study which also performed an LCAbased 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 cellulosebased fibres (Shen et al. 2010). This was on the basisof ecotoxicity, eutrophication, water use and land use.
Neither textile-based LCAs considered the potential
ecological impact due to littering by the textile productsor fibres. Clearly, the scope of an environmental LCA
can determine the outcome. Ecological and social
0.002 millimetersPhoto: Ludwig Tröller / Creative Commons

1.002 millimeters0.0004 millimeters1.0542 millimeters

perspectives should be included in a comprehensive
LCA approach, as well as the time-scales involved.
Without such evaluation, decisions made in goodfaith may result in ineffective mitigation1.24
measures,millimeters
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.

The environmental impact of discarded plastics
is correlated with the time taken for complete
breakdown of the polymer.

7
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
Misconceptions,concerns and impacts
on marine environments

0.002 millimeters28biodegradable
PLASTICsCan plastic designed
to be ‘biodegradable’
have a significant
role in reducing
ocean litter?

Photo:Geraint Rowland / creative commons

Polymers and plastics
terminology and definitions

Polymers
and plastics- terminology
and definitions

The term ‘plastic’, as commonly applied, refers to agroup of synthetic polymers (section 2.3).
Polymers are large organic molecules composedof repeating carbon-based units or chains that occur
naturally and can be synthesised. Different typesof polymers have a wide range of properties, andthis influences their behaviour in the environment.

Some biodegradable plastics are madefrom fossil fuels, and some non-biodegradable
plastics are made from biomass

2.1	The need for precise
definitions
There is great scope for confusion in theterminology surrounding ‘plastic’ and its behaviour inthe environment. Section 2 provides some definitions
to terms used in this report.

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, andsome can be made from either (Figure 2.1).
Some
1.002
millimeters
polymers derived from fossil fuels can be biodegradable.

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

Biomass derived

Synthetic polymer

Biopolymer

0.0004 millimeters

Thermoplastic

Thermoset

1.0542 millimeters

PE, PP, PS, PVC, PET

PU, SBR, epoxy, alkyd

bottle, food container, pipe,
textile, fishing gear, float,
milk jug, film, bag, cigarettebutt, insulation, micro-bead,micro-abrasive, etc.

Manufactured(primary)

insulation, coating, adhesive,
composite, tire, balloon,
1.24
millimeters
micro-abrasive,
etc.

Plastic debris
Fragmentation(secondary)cellulose, lignin,chitin, wool, starch,
protein, DNA, etc.

Manufactured(primary)

9
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
Misconceptions,concerns and impacts
on marine environments

Microplastics
0.002 millimeters

Conversely, some polymers made from biomasssources, 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, ona reasonable or practical timescale. It is important, if
users are to make informed decisions, for society tohave access to reliable, authoritative and clear guidanceon what terms such as ‘degradable’ or ‘biodegradable’
actually mean, and what caveats may apply.

Table 2.1 Some common definitions regarding thebiodegradation of polymers

Term

Definition

Degradation

The partial or complete breakdown
of a polymer as a result of e.g.
UV radiation, oxygen attack, biologicalattack. This implies alteration of
the properties, such as discolouration,
surface cracking, and fragmentation

Biodegradation

Biological process of organic matter,
which is completely or partiallyconverted to water, CO2/methane,energy and new biomass by
microorganisms (bacteria and fungi).

Mineralisation

Defined here, in the context ofpolymer degradation, as the complete
breakdown of a polymer as a result of
the combined abiotic and microbialactivity, into CO2, water, methane,hydrogen, ammonia and other simple
inorganic compounds

Biodegradable

Capable of being biodegraded

Compostable

Capable of being biodegradedat elevated temperatures in soil
under specified conditions andsretemionly
llim 4encountered
000.0
time scales, usuallyin an industrial composter(standards apply)

Oxo-degradable

Containing a pro-oxidant that

1.002 millimeters

The conditions under which ‘biodegradable´polymers will actually biodegrade vary widely.

2.2 Natural (bio)polymers

10
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
Misconceptions,concerns and impacts
on marine environments

Bio-polymers are very large molecules with a longinduces degradation under favourable
chain-like structure and a high molecule weight,
conditions. Complete breakdown of
1.0542 millimeters
produced by living organisms. They are very common
the polymers and biodegradationin nature, and form the building blocks of plant andstill have to be proven.
animal tissue. Cellulose (C6H10O5)n is a polysaccharide(carbohydrate chains), and is considered the mostabundant natural polymer on Earth, forming a key sretem
Other
illim 4types
2.1 of natural polymers are poly amides
constituent of the cell walls of terrestrial plants. such as occur in proteins and form materials such as
Chitin (C8H13O5N)n is a polymer of a derivative wool and silk. Examples of common natural polymersof glucose (N-acetylglucosamine) and is found and their potential uses by society are provided
in the exoskeleton of insects and crustaceans. in Table 2.2.
Lignin (C31H34O11)n is a complex polymer of aromatic
alcohols, and forms another important component ofcell walls in plants, providing strength and restricting
the entry of water. Cutin is formed of a waxy polymer
that covers the surface of plants.
0.002 millimetersPhoto: © Vwaste busters / CREATIVE COMMONSSingle-use plastic shopping bag marked‘biodegradable’ may require the conditions that
commonly occur only in an industrial composter

1.002 millimeters

Table 2.20.0004
Examplesof common natural polymers and uses by society.
millimeters

Polymer

Natural occurrence

Human uses

ChitinExoskeleton of crustaceans:e.g. crabs, lobsters and shrimp
Exoskeleton of insects
Cell walls of fungi

Medical, biomedical (lattices for growing tissues)
Agriculture

Cell walls of plants(Ligno-cellulose)
Construction timber
Fuel as timber
Newsprint
Industrial – as a dispersant, additive andraw material

1.0542 millimeters
Lignin1.24 millimeters

Cellulose

Cell walls of plants, many algae
and the secretions of some bacteria

Polyester

Cutin in plant cuticles

Protein fibre(e.g. fibroin, keratin)

Wool, silk

Paper
Cellophane and rayon
Fuel - Conversion into cellulosic ethanol

11
BIODEGRADABLE
PLASTICS AND
MARINE LITTER

Clothing

0.002 millimeters

Misconceptions,concerns and impacts
on marine environments

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, hascome to be the most common use of the term. In
engineering, soil mechanics, materials science andgeology plasticity refers to the property of a material able
to deform without fracturing. Thermoplastic is capableof 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 containa 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 ofthermoset 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 alimited number of well-established synthetic polymers(Figure 2.2 below). However, there is a very wide rangeof polymers produced for more specialised application,with an equally wide range of physical and chemical
properties (Table 2.3). In addition, many plastics aresynthesised as co-polymers, a mixture of two or morepolymers with particular characteristics. Objects may
be produced using more than one type of polymer
or co-polymer. All these factors result in, for the nonspecialist, a bewildering array of materials. Although theircharacteristics and behaviour may be well understoodwith regard to the designed application (e.g. insulation
slabs, shopping bags, fishing line) their behaviour inthe marine environment may be poorly understood.

1.002 millimeters

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

sretemillim 4000.0

1.0542 millimeters

sretemillim 42.1

12BIODEGRADABLE
PLASTICS AND
MARINE LITTER
Misconceptions,concerns and impacts
on marine environments

0.002 millimetersFull nameCommonsourceExamples ofcommon uses

Biodegradation
properties
in terrestrial
environment(including
medicalapplications)ABS(acrylonitrile
butadiene
sytyrene)
Copolymer

Fossil fuelPipes,
protective headgear,
consumer goods,
Lego™ bricks

AC

Acrylic

Fossil fuelAcrylic glass(see PMMA)

AcC
(CTA,
TAC)

Acetylcellulose,
cellulose
triacetate

Biomass

Fibres,photographic
film base

Alkyd

Partlybiomass

Coatings,
mouldsCellophane

Biomass(cellulose)

Film for packaging

AKD

Biodegradability
depends on degreeof acetylation1

Tokiwaet al. 20091

1.002 millimeters

DECP

Biomass
A group of& fossil fueldegradable
0.0004
millimetersand electricallyconductive
polymers

Biosensors andtissue engineering

EP

Epoxy resin(thermoset)

Fossil fuelAdhesives, coatings,
insulators

1.0542 millimeters

Biodegradation
properties inaquatic/marine
environment

Reference

Abbreviation

Table 2.3 Common synthetic polymers – source, use and degradation properties

PA

Polyamide e.g.
Nylon™ 4, 6, 11,
66; Kevlar™

Fossil fuelFabrics, fishing lines
and nets,

PAN

Polyacrylonitrile

Fossil fuelFibres,membranes,
1.24
millimeters
sails, precursor incarbon fibre
production

PBAT

Poly(butylene
adipate-co-teraphthalate

Fossil fuelFilms

Degradable within
living tissues2

2

Biodegradable77

Guo
et al. 2013

Weng et al.,
2013

13
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
Misconceptions,concerns and impacts
on marine environments

0.002 millimetersPoly(butylene
succinate)

CommonsourceExamples ofcommon uses

Fossil fuelAgricultural
mulching films,
packaging

Biodegradable1

Biodegradation
properties inaquatic/marine
environment

Some degradation
after 12 months
but retains 95%
tensile strength3

Tokiwaet al. 20091

Sekiguchi
et al. 20113

Some degradation
after 2 years4

PCL

PE

Polycaprolactone

Fossil fuel

Biodegradable byhydrolysis in thehuman body

3D printing,hobbyists,biomedical
applications

PES

Poly(ethylene
succinate)

Fossil fuel

films

PET

Polyethylene
terephthalate

Fossil fuel,fossil fuelwith biomass

Containers, bottles,‘fleece’ clothing

PGA

Poly
(glycolic acid)

Sutures,food packaging

Biodegradable
by hydrolysis in
the human body

PHB

Poly
Biomass(hyroxybutyrate)

Medical sutures

Biodegradable1

Biodegradable1

14
BIODEGRADABLE
PLASTICS AND
MARINE LITTER

Biomass

Some degradation
after 123
Agricultural
mulching films,
packaginzg,
biomedical
applications,personal hygiene
products,
3D printing

Misconceptions,concerns and impacts
on marine environments

0.002 millimeters

Tokiwaet al. 2009

Sekiguchi
et al. 2011

3

Sudhakar
et al. 2007
5

Tokiwaet al. 20091

sretemillim 4000.0

sretemillim 42.1
Poly(lactide)1

Extremely limited,
potential minor effectin Tropics due tohigher temperature,
dissolved oxygenand microfauna/flora
assemblages5

Packaging,
containers,
pipes

PLA

Some degradation
after 12 months3

Biodegradable

Biomass& fossil fuel1.002 millimeters

Kim et al.
2014a,b4

1Polyethylene

Reference

Abbreviation

PBS

Full name

Biodegradation
properties
in terrestrial
environment(including
medicalapplications)

Biodegradable1
Compostable5

1.0542 millimeters
Tokiwaet al. 20091

Sekiguchi
et al. 20113

Tokiwaet al. 20091

Pemba
et al. 20145

CommonsourceExamples ofcommon uses

PMMA

Poly(methyl)
methylacrylate

Fossil fuelAcrylic glass,biomedical
applications,lasersPOM

Poly(oxymethylene)

Fossil fuelHigh performanceengineering
components
e.g. automobile
industry

Also called
AcetalPP

Polypropylene

Fossil fuelPackaging,
containers,
furniture, pipes

PS

Polystyrene

Fossil fuelFood packaging

Biodegradation
properties inaquatic/marine
environment

Biodegradable3

Reference

Abbreviation

Full name

Biodegradation
properties
in terrestrial
environment(including
medicalapplications)

Cappitelli
et al. 2006

3

1.002 millimeters

EPS

Expandedpolystyrene

Fossil fuelInsulation panels,
insulated boxes,
fishing/aquaculture
floats, packaging

PU
(PUR)

Polyurethane

Fossil fuelInsulation, wheels,gaskets, adhesives

0.0004 millimeters

PVA

Poly(vinyl
alcohol)

Fossil fuelPaper coatings

PVA

Poly(vinyl
acetate)Fossil fuelAdhesives

PVC

Poly
(vinyl chloride)

Fossil fuelPipes, insulationfor electric cables,
construction

Rayon

Rayon

Biomass(cellulose)

1.24clothing
millimeters Biodegradable
Fibres,SBR

Styrenebutadiene
rubberFossil fuelPneumatic tyres,gaskets, chewing
gum, sealantStarchStarchBiomass

Packaging, bags,
Starch blends e.g.
Mater-Bi™

Biodegradable

1.0542 millimeters

Biodegradable

15
Biodegradable in soil
and compost6

0.002 millimeters

Minimal deteriorationin littoral marsh ofseawater6

Accinelli
et al. 2012
6

BIODEGRADABLE
PLASTICS AND
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Misconceptions,concerns and impacts
on marine environments

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.

2.4 Bio-derived plastic
Bio-based plastics are derived from biomass such asorganic waste material or crops grown specifically forthe purpose (Table 2.4). Utilising waste material can be
1.002 millimeters
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 bepotentially more problematic as it may require land
to be set aside from either growing food crops, at atime of growing food insecurity, or from protecting

sensitive habitat, at a time of diminishing biodiversity.
One current feature of biomass-based polymers isthat 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 mostof 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 fromvegetable oil and poly(lactide) is a polyester produced
from lactic acid derived from agricultural crops suchas 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 bothbiodegradable 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 thatthe description ‘bio-plastic’ is qualified to indicate
the precise source or properties on the polymer
concerned.

sretemillim 4000.0
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 1.0542 millimeters
Dialysis (Visking) tubing

ChitosanChitonTissue engineering,wound healing,
drug delivery

sretemillim 42.1
Rayon

16

§

Cellulose (e.g. wood pulp)

most types of polyamide are derived from fossil fuels

BIODEGRADABLE
PLASTICS AND
MARINE LITTER
Misconceptions,concerns and impacts
on marine environments

0.002 millimeters

Threads - clothing

Photo: Doug Beckers / Creative Commons

1.002 millimeters0.0004 millimeters1.0542 millimeters
Fig. 2.3 Bio-plastics comprised of biodegradable andbio-based plastics (taken from Tokiwa et al. 2009; available under
the Creative Commons Attribution license).

1.24 millimeters
Bio-plastics

Biodegradebale
plastics

PBS
PCL
PES

One current feature of biomass-based
polymers is that they tend to be more
expensive to produce than those basedon fossil fuels

PE

17

PHB
NY11

PEA
Starch

BIODEGRADABLE
PLASTICS AND
MARINE LITTER

AcC
Bio-based
plastics

Misconceptions,concerns and impacts
on marine environments

0.002 millimeters318

biodegradable
PLASTICsCan plastic designed
to be ‘biodegradable’
have a significant
role in reducing
ocean litter?

Photo: © Ralph Aichinger / creative Commons

Fragmentation, degradation
and biodegradation

Fragmentation,
degradation andbiodegradationts

3.1	The degradation process
Fragmentation
The degree to which synthetic polymers degrade
depends on both the properties of the polymer andthe 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 theamount of oxygen present), it is said to have been
completely mineralised (Eubeler at al. 2009).
Fragmentation and biodegradation proceeds througha combination of photo- (UV) and thermal-oxidationand microbial activity. In the marine environment UV
radiation is the dominant weathering process. It causes
embrittlement, cracking and fragmentation, leading to0.0004 millimeters
the productionof microplastics (Andrady 2011). Thismeans that fragmentation is greatest when debris isdirectly exposed to UV radiation on shorelines. Higher
temperatures and oxygen levels both increase the rateof fragmentation, as does mechanical abrasion (e.g.
wave action). Once plastics become buried in sediment,
1.0542
millimetersin water or covered in organic and inorganic
submerged
films (which happens readily in seawater) then the rate offragmentation decreases rapidly. Plastic objects observedon the deep ocean seabed, such as PET bottles, plasticbags and fishing nets, show insignificant deterioration
1.24 millimeters(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 probabilityof biodegradation taking place is highly dependent on
the type of polymer and the receiving environment.
The literature on the biodegradation of a wide rangeof synthetic polymers has been extensively reviewed byEubeler et al. (2009, 2010). Partial biodegradation canlead to the production of nano-sized fragments andother synthetic breakdown products (Lambert et al.
2013).
1.002 millimeters

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)

A number of national and international standards
have been developed, or are under development,
to cover materials designed to be compostable orbiodegradable (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 temperatureare expected to reach 70 °C. The EN standard requiresthat 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 most1

EN 13432:2000. Packaging. Requirements for packaging
recoverable through composting and biodegradation.
Test scheme and evaluation criteria for the final acceptanceof packaging; http://www.bpiworld.org/page-190437,
accessed 10th February 2015.

0.002 millimeters

19
BIODEGRADABLE
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Misconceptions,concerns and impacts
on marine environments

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 stillretain important physical appearance such as overall
shape and tensile strength even with significant
weight loss.
In addition, ASTM produced a standardfor ‘Non-floating biodegradable plastics in themarine 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.
2Fig. 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).

http://www.astm.org/Standards/D7081.htm

1.002 millimeters

sretemillim 4000.0

20
BIODEGRADABLE
PLASTICS AND
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Misconceptions,concerns and impacts
on marine environments

Photo: © Forest and Kim Starr / creative Commons

1.0542 millimeters

sretemillim 42.1

0.002 millimetersa

The biodegradability of polymers is influenced bya range of intrinsic factors. A higher molecular weight(Eubeler et al. 2010), higher melting temperature andhigher degree of crystalinity all reduce the degree towhich 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 thatcomplete mineralisation, requiring a process of gradualfragmentation, facilitated by UV, higher temperature
and an oxygenated environment, will happen soslowly as to be considered negligible in the naturalenvironment. 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-UVstabilised PE sheeting (Figure 3.2). However, as soon
as plastics become buried in sediment, submerged,
or covered by organic and inorganic coatings, the rateof fragmentation declines rapidly. Common examples
include: PE, PET, PA (Polyamide 11), PS, EP, PU, PVA,
PVC and SBR (see Table 2.3).

b1.002 millimeters

Fig. 3.2 Fragmentation of PE with exposure to UV in a cooltemperate climate at 61.6 °North; (a) standard PE sheeting,(b) PE sheeting with UV stabilizer added, for horticultural use.
© Peter Kershaw

3.3 0.0004‘Biodegradable’
plastics
millimeters
Biodegradable plastics are polymers that arecapable of being broken down quite readily byhydrolysis, the process by which chemical bonds arebroken by the addition of water (GESAMP 2015).
This process is influenced by the environmental setting
1.0542
millimeters
andis facilitated by the presence of microorganisms.
Some polymers have been designed to bebiodegradable for use in medical applications (Table
2.3). They are capable of being metabolized in thehuman body through hydrolysis catalysed1.24
bymillimeters
enzymeactivity. Some polymers, such as poly (glygolic acid)and its copolymers, are used as temporary sutures
while others have been designed for slow-releasedrug delivery used, for example, in the treatment ofcertain 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 theseengineered properties it does not mean that all such

A higher molecular weight, higher melting
temperature and higher degree of crystalinity
all reduce the degree to which the polymer
is likely to biodegrade

0.002 millimeters

21
BIODEGRADABLE
PLASTICS AND
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Misconceptions,concerns and impacts
on marine environments

Outside the human body the degree or rateof biodegradation becomes very dependent
on the surrounding environment, which willshow a much greater variability
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 amuch greater variability (e.g. temperature, humidity,
oxygen levels, microbe assemblages, UV irradiation).
For example, polycaprolactone and polylactide areboth used for 3D printing and producing hard durable
components, as well as for time-limited medical
applications.
Plastics made from the same initial polymer canshow differences in material properties and rates of
1.002 millimeters
biodegradation. For example, a study of cellulosebased fabrics demonstrated that biodegradation
was greatest in rayon and decreased in the orderrayon > cotton >> acetate (Park et al 2004). The tests
used were soil burial, activated sewage sludge andenzyme 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 bebiodegraded 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 forcomplete biodegradation (GESAMP 2015).

22
BIODEGRADABLE
PLASTICS AND
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Misconceptions,concerns and impacts
on marine environments

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 aspolyethylene, which have had a metal compound(e.g. manganese) added to act as a catalyst, or
pro-oxidant, to increase the rate of initial oxidationand fragmentation (Chiellini et al. 2006). They
are sometimes referred to as oxy-biodegradableor oxo-degradable. Initial degradation may resultin 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 offragmentation and utilisation by microorganisms will
be dependent on the surrounding environment. Thereappears to be no convincing published evidence that
oxo-degradable plastics do mineralise completely inthe 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 onevidence presented in the peer-reviewed literature.
But, it should be appreciated that the degree toretemildo
lim 4offer
000.0
which oxo-degradable plastics sreallya 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 oxodegradable plastics and for those opposing them.
For example, a position paper issued by
European
1.0542
millimeters
Bioplastics(European
Bioplastics2012),
anindustry
A polymer may be marketed as ‘biodegradable’ but
this may only apply to a limited range of environmental association of European bioplastics producers,
conditions, which are probably not encountered in strongly challenged the conclusions of an LCA of oxobags commissioned by a producer of prothe natural environment (Figure 3.3). This can lead sredegradable
t
e
m
i
l
l
i
m
4
2
.
1
to misunderstandings and confusion as to what oxidants (Edwards and Parker 2012). Without wishingconstitutes biodegradability. For example, some items, to be drawn into this debate, it should be pointed
such as plastic shopping bags supplied for groceries, out that decision-makers are unlikely to be influenced
may be labelled as ‘biodegradable’. However, it is quite solely by reliable, independent and peer-reviewed
possible that the item will only degrade appreciably in scientific evidence.
an industrial composter (section 3.1). Such polymers
A literature review (Deconinck and De Wilde 2013)
will not ‘biodegrade’ in domestic compost heaps or of publications on bio- and oxo-degradable plastics,
if left to litter the environment. This lack of clarity commissioned by Plastics Europe, concluded that the
may lead to behaviours that result in a greater degree rate and level of biodegradation of oxo-degradableof littering (Section 5.0). The State of California has plastics ‘is at least questionable and reproducibility’.
0.002 millimeters1.002 millimeters

Fig. 3.3 Examples of single-use plastic products marked as either ‘oxo-degradable’ or ‘100% biodegradable’.
0.0004 millimeters
The lackof consensus on the desirability or otherwiseof oxo-degradable plastics is evident from thedisputed entry in the on-line Wikipedia dictionary3.
A useful commentary on many of the disputed claims
is available. (Narayan 2009).

There has been debate on the need forlegislation to control the marketing ofproducts made with oxo-degradable polymers

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
Plastics containing pro-oxidants are not
1.24 millimeterssolutions for dealing with end-of-life oxo-degradable
recommended
for recycling as they have theplastics were incineration (first choice) or landfill.
potential to compromise the utility of recycled
In addition, the authors observed that:plastics (Hornitschek 2012). There has been debate‘… as the [oxo-degradable] plastics will not degrade on the need for legislation to control the marketingfor approximately 2-5 years, they will still remain of products made with oxo-degradable polymers invisible as litter before they start to degrade’.
the state of California and within the European Union.

1.0542 millimeters

BIODEGRADABLE
PLASTICS AND
MARINE LITTER(Thomas et al. 2010)

323
Misconceptions,concerns and impacts
on marine environments

Accessed 9th February 2015

0.002 millimeters424biodegradable
PLASTICsCan plastic designed
to be ‘biodegradable’
have a significant
role in reducing
ocean litter?

Photo: © Jennyvids / CREATIVE COMMONSThe behaviour of‘biodegradable’ plastics
in the marine environment

The behaviourof ‘biodegradable’
plastics in the marine
environment
4.1	The composition ofplastic 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 inseawater, sediments and biota (Table 4.1). There does
not appear to have been any attempt to analyse theproportion 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 typesof millimeters
plastic entering the ocean is unknown
0.0004
it follows that the quantity of biodegradable plastics
entering the ocean is also unknown.

(e.g. UV irradiance, temperature, oxygen level, physicaldisturbance, biological factors). Sampling methods
commonly under-sample material < 330 microns indiameter, and identification is usually restricted to themajor 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.
1.002 millimeters

4.2	The fate of biodegradable
plastic in the ocean
Degradation processes

Photo: © BO EIDE / creative Commons

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
The exact quantities of different polymers observed
and fragmentation will occur, a process that will bein the marine environment will depend on the
more rapid in regions subject to higher temperatures or
nature of local and regional sources, long-distance
where physical abrasion takes place. Once larger items
1.0542
millimeterstransport
pathways, material properties (size, shape,or fragments become buried in sediment or enter thedensity) and conditions experienced at each locationwater column then the rate of fragmentation will slow
dramatically. Experimental studies of biodegradationof polymers in seawater are rather limited in number,
1.24 millimeters and the results have to be placed in the context ofnatural conditions (UV, temperature, oxygen, presenceof suitable microbiota), as well as the characteristics ofthe 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).

25
BIODEGRADABLE
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Misconceptions,concerns and impacts
on marine environments

0.002 millimeters

Table 4.1 Selection of reported polymer compositions in a variety of media (GESAMP 2015).

MatrixSize

Polymer composition

Reference

sediment/ shoreline< 1 mmPES (56%), AC (23%), PP (7%), PE (6%), PA (3%).

Browneet al. (2011)sediment/ sewage
disposal site

< 1 mmPES (78%), AC (22%)

Browneet al. (2011)sediment/ beach< 1 mmPES (35%), PVC (26%), PA (18%), AC, PP, PE, EPS

Browneet al. (2008)

sediment /Interand 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 mmAKD (75%), PSA (20%), PP+PE (2%), PE, PET, EPSSong et al.
(2013)

water/ sewage
effluent< 1 mmPES (67%), AC (17%), PA (16%),

Browneet 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%)

Lusheret al. (2012)-

PE (50.5%), PP (22.8%), PC and ABS (3.4%), PS (0.6%),
not-identified (22.8%)

Yamashita
et al. (2011)

1.002 millimeters
bird

26
BIODEGRADABLE
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on marine environments

Bacteria capable of degrading PCL have been Interactions with species
isolated from deep seawater off the coast of Japan
Many species are affected by interaction with
(Sekiguchi et al. 2011). Pitting and loss of structural
marine plastics, either by ingestion or by entanglement.
sretemillim 4000.0
integrity was observed when PCL was exposed toToothed whales, sea turtles and seagulls commonly
species of the genera Pseudomonas, Alcanivorax, andare found to contain large quantities of plastic within
Tenacibaculum. The time-dependence and extent
their guts during necropsies of beached specimens. Itof biodegradation was expected to be influenced byis thought that plastic items are mistaken for prey and,competition from other colonizing bacteria as well as
when swallowed, block the gut and cause starvation.
temperature and oxygen levels. The addition of PLA to
The degree to which the presence of plastic causes
PUR was shown to increase the rate of degradation in
1.0542 millimeters
the death of the specimen is difficult to quantify
butseawater (Moravek et al. 2009). However, the reaction
it does appear to have been a significant factor in
was very temperature dependent and the results have
many cases. Conditions within an organism may belimited applicability to natural conditions. Experimental
very different from the ambient environment (e.g.
studies on carrier bags composed of the starch-based
gut chemistry, enzyme activity, microbial action).
Mater-Bi™ led to the conclusion that such bags would sretemillim 42.1
Differences in the behaviour of some polymers within
not automatically reduce or provide a solution to thean organism, compared with externally, may occur but
environmental impacts caused by marine litter, on thethis has not been documented sufficiently and is likely
basis of the slow rate of degradation observed in marine
to be species-specific.
ecosystems (Accinelli et al. 2013). Biodegradation ofPerhaps the most relevant study examined theplastics that are considered recalcitrant, such as PE, candegradationof plastic carrier bags in gastrointestinal
take place in the marine environment at an extremely
slow rate. There is limited evidence suggesting that fluids of two species of sea turtle: the herbivore Green
microbial degradation of the surface of PE particles turtle (Chelonia mydas) and carnivore Loggerhead
happens in the marine environment (Zettler et al. 2013). turtle (Caretta caretta) (Műller et al. 2012). Fluids
0.002 millimetersChanges in polymer mass were measured over 49
days (standard test procedure) after which weightlosses were as follows: HDPE – negligible, oxodegradable – negligible, and biodegradable – 4.5 – 8.5%.
This is much slower that the degradation rates claimedby the manufacturers for industrial composting. The
study demonstrated that degradation of plastic wasmuch slower than for normal dietary items. The lower
rate of degradation in the Loggerhead may be due todifferences in diet and associated enzyme activity.

Photo: © Christopher Dart / creative common

were collected from the stomach, the small intestineand large intestine of freshly dead specimens. Threetypes of polymer were used: conventional HDPE,
oxo-degradable, and a biodegradable PBAT/Starch
blend (Mater-Bi™).

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 losteach year4.

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)
Polymertype

PolymersourceWeight loss
after 49 days
1.002 millimeters

HDPE

Shopping
carrier bag

negligible

Some studies have examined the feasibility of using
biodegradable polymers in the design of fishing gear
negligible
Oxo-degradable Shopping
to reduce the impact of ‘ghost fishing’, a term usedcarrier bag
to describe the tendency for lost or discarded fishing– PE withgear to continue to trap marine organisms, leading to
pro-oxidant
an unnecessary depletion of populations. Kim et al.
(d2w™
(2014b)0.0004
testedmillimeters
the performance of conger eel pots
technology)
by comparing commercial pots used in the RepublicGreen turtle 8.5%
Biodegradable
Shoppingof Korea with pots constructed with biodegradable
carrier bag (PBS) polymers for key components, using a number
Loggerhead turtle 4.5 %starch-basedof mechanical tests as well as their effectiveness.
Mater-Bi™
The fishing performance was similar, although thefrom BioBag®
biodegradable pots caught fewer smaller individuals,
1.0542 millimeterswhich was an unexpected bonus. In the commercial
fishery the pots are usually replaced every two years,
Experiments using PE and biodegradable (PBS)
and so the durability of the biodegradable components
would be sufficient. The main advantage would be for components for pot nets in the Korean octopus
pots that were not recovered, as the efficacyof the fisheries (Octopus minor) produced more mixed
1.24 millimeters
biodegradable components, specifically designed to results, with fishing performance significantly
have a limited life in the marine environment, would lower using biodegradable polymers (Kim et al.
be expected to decline and reduce the extent of 2014a). Octopus are very sensitive to the softness
continuing ghost fishing. The main disadvantage is of the twine used in the trap, which shows thatthat the biodegradable pots are more expensive so it is an understanding of species behaviour and theunlikely they will be exploited by the industry without characteristics of the fishery is essential before
making recommendations of what design is mostfinancial incentives.
‘environmentally friendly’. The modified pot nets werealso more expensive than those made with standard PE.
4

Gulf of Maine Lobster Foundation http://www.geargrab.org/

0.002 millimeters

27
BIODEGRADABLE
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Misconceptions,concerns and impacts
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528

biodegradable
PLASTICsCan plastic designed
to be ‘biodegradable’
have a significant
role in reducing
ocean litter?

Photo: © Lucy Lambreix / CReative common

Public perceptions, attitudes and behaviours

Public
perceptions,attitudes andbehaviours

most responsible for the reduction of marine litter,
whereas environmental groups were considered to be
most capable of making a difference (Bonny Hartleypers. 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, labellinga product as biodegradable may be seen as a technicalfix that removes responsibility from the individual. A
perceived lower responsibility will result in a reluctanceto take action (Klöckner 2013). A survey of littering
behaviour in young people in Los Angeles revealed
that labelling a product as ‘biodegradable’ was oneof several factors that would be more likely to resultin littering behaviour (Keep Los Angeles Beautiful,2009). Whether similar attitudes occur in different age
and cultural groups and in different regions globallyis unknown, and more research is justified. 1.002 millimeters

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 foundthat Governments and policy were considered to be

0.0004 millimeters

Labelling a product as biodegradable
may be seen as a technical fix that removes
responsibility from the individual.

Photo: © Richard Masoner / CREATIVE COMMON

1.0542 millimeters1.24 millimeters

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Misconceptions,concerns and impacts
on marine environments

0.002 millimeters630

biodegradable
PLASTICsCan plastic designed
to be ‘biodegradable’
have a significant
role in reducing
ocean litter?

Photo: © Rob (www.bbmexplorer.com) / CReative common

Conclusions

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 thesefragments (microplastics) is unclear, but it should
be assumed that oxo-degradable polymers
will add to the quantity of microplastics inthe oceans, until overwhelming independent
evidence suggests otherwise. The current usage ofthese polymers is very limited.

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.

Oxo-degradable polymers do not fragment
rapidly in the marine environment (i.e. persist> 2-5 years) and so manufactured items willcontinue to cause littering problems and lead toundesirable impacts.

Polymers most commonly used for generalapplications, with the required chemical andmechanical properties (e.g. PE, PP, PVC) are notreadily 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 themarine environment, but much more slowly andtheir 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 oflower-cost alternatives, for well-justified purposes(e.g.
key components of a fishing trap) may
0.0004 millimeters
require financial inducement.

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
1.002 millimeters
public perceptions about whether an item isbiodegradable 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.

1.0542 millimeters1.24 millimeters

31
BIODEGRADABLE
PLASTICS AND
MARINE LITTER
Misconceptions,concerns and impacts
on marine environments

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MARINE LITTER
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on marine environments

0.002 millimeters

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1.002 millimeters0.0004-1.24 millimeters1.0542 millimeters1.24 millimeters