Plastics recycling: insights into life cycle
impact assessment methods

S. Rajendran*, A. Hodzic, L. Scelsi, S. Hayes, C. Soutis, M. AlMa’adeed and
R. Kahraman

The increased consumption of plastics in day to day life has a significant impact on the
environment. Life cycle assessment (LCA) is widely used to select a sustainable alternative in
plastic waste management. The LCA studies on mechanical recycling and energy recovery
scenarios showed that recycling resulted in lower emissions and provided benefits to the
environment. These results are valid only if the performance of the recycled plastic is equivalent to
those of the virgin materials. Many LCA studies have been focused on individual impact
categories rather than aggregated single score. The decision making process becomes complex
if individual impact categories are used. This research is focused on the comparison of LCA
results between individual and aggregated impacts and integration of performance of recycled
plastics in LCA. The results indicated that recycling was the preferred option if it could replace a
minimum of 70–80% of virgin plastics.

Keywords: Mechanical recycling, Life cycle assessment, Plastic wastes, Polymer recycling, Environmental concerns, Global warming

Introduction

At present, research on ‘green programmes’ is increasing
in both academic and industrial sectors. Many compa-
nies are adopting ‘sustainable product development’ as a
key strategy to maintain long term business perfor-
mance. This has led to a steady increase in commercia-
lisation of many recycled products on the market.
Recycled plastics are widely used as dustbins, bags,
road posts, fences and in paving applications.

1

A great

majority of such applications are of low value. The
upcycling of waste plastics started from early 1990s.
Many upcycled recycled plastics were developed

2–5

such

as self-reinforced recycled polyolefin–polystyrene com-
posites, glass reinforced thermoplastic polyolefin waste
along with thermoset materials for structural and load
bearing applications and railway sleepers. The increased
environmental awareness, strict legislations and mar-
ket competition are pushing the plastic recyclers and
product developers to focus on high value recycled
products. Product developers use life cycle assessment
(LCA) as a technique to evaluate the sustainability of
the products. The product developers struggle to in-
corporate the quality, performance of recycled plastics
and greenness in their product development processes
because of the inconsistency of plastic wastes and the
low performance of secondary materials.

6,7

This requires integration of LCA in the product

development processes to help in identifying the resource
consumption and environmental impacts associated

directly or indirectly throughout the life cycle of the
product.

8

The LCA is defined as ‘a technique to compile

and analyse the environmental impacts involved in all
stages of the product’s life cycle (cradle to grave) i.e. from
raw material extraction stage to the disposal stage’. This
integration of LCA in the product development process
will help to establish the relationship between the
products (recycled) and its performance with the envir-
onmental impacts (e.g. climate change, ozone depletion
and photochemical oxygen formation). This research is
focused on recycled plastics so as to motivate the
development of upcycled, high value products rather
than low value products and to provide an initiative to
integrate the performance of recycled plastics in the LCA.

The aim of this research is to compile life cycle

inventory from peer reviewed literature on mechanical
recycling and energy recovery, to compare the scenarios
in various impact assessment methods and to incorpo-
rate technical performance in the LCA results.

From the early 1990s, a number of LCA studies have

been conducted on waste management strategies such as
mechanical recycling, incineration and land filling.
Craighill and Powell

9

conducted LCA on a variety of

materials and evaluated individual environmental impact
categories, such as global warming, acidification and
eutrophication. This study illustrated the problem of
comparing the different impact categories and insisted on
the implementation of a weighting procedure on plastic
recycling.

The study conducted by Molgaard

10

compared differ-

ent recycling scenarios such as sorted plastic wastes,
unsorted plastic wastes, pyrolysis and incineration with
energy recovery. The study involved all impact categories,
and it concluded that the energy recovery was the

University of Sheffield, Sheffield, UK

*

Corresponding author, email [e-mail]

ß

Institute of Materials, Minerals and Mining 2013

Published by Maney on behalf of the Institute
Received 28 June 2011; accepted 9 January 2012
DOI 10.1179/1743289812Y.0000000002

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preferred option in mixed plastic wastes and that
mechanical recycling was more advantageous in sorted
plastic wastes. However, reduced material properties due
to the degradation of sorted recycled plastics were not
taken into account, and the LCA was focused on
individual impact categories rather than the aggregated
environmental impact score.

Eriksson et al.

11

and Perugini et al.

12–14

conducted

LCA of municipal solid wastes, in which plastic wastes
were also considered. The study of Eriksson et al.

11

was

based on the assumption that recycled materials replace
a virgin material, which may not be valid in all
applications, since the level of degradation in recycled
polymers depends on the number of thermal cycles, their
previous applications and processing conditions.

Perugini et al.

13

conducted LCA on Italian recycling

systems in which scenarios such as mechanical recycling,
feedstock recycling, energy recovery and land filling
were compared. This is mandatory to include the type of
energy recovery method rather than projecting value
from the gross calorific value. The energy recovery and
emissions are dependent on the type of energy recovery
method.

14

Astrup et al.

15

conducted LCA on plastics recycling

and compared the scenarios of recycled plastics repla-
cing plastics, wood and energy on the basis of green-
house gas emission. The study suggested that replacing
virgin materials would save between 700 and 1500 kg
CO

2

-eq. tonne

–1

plastic waste. However, if the quality of

plastic waste is insufficient to replace virgin plastics, then
the second best option would be to utilise the plastic
wastes as fuel in an industrial process, such as in cement
kilns.

A recent review was conducted by Bjorklund and

Finnveden

17

on LCA of plastics and solid waste

management, mainly focusing on energy consumption
and global warming. It was suggested that the advan-
tages of avoiding the production of a primary material
had to be significant enough to motivate recycling and
that replacement of wood renders mechanical recycling
less favourable.

The Waste and Resources Action Programme

17

published a review of 16 waste management options.
The impact assessment was focused on individual impact
categories rather than aggregated single scores, and the
scenarios were assessed through a ranking procedure
based on parameters such as global warming, eutrophi-
cation, acidification, ozone layer depletion, ozone
formation and human toxicity.

The present research is focused on comparing

mechanical recycling and energy recovery by various
impact assessment methods, including single score
techniques, and to incorporate the performance of
recycled plastics in the impact assessment step.

Life cycle assessment study

In this paper, the SimaPro Version 7.1.5

18

LCA package

is used. The two scenarios considered are mechanical
recycling and energy recovery. The impacts are evalu-
ated through Eco-Indicator 99 (EI99)-egalitarian (EI-E),
hierarchists (EI-H) and individualists (EI-I) methodol-
ogies and to compare with Environmental Development
of Industrial Products (EDIP) 2003 and Centrum voor
Milieukunde Leiden (CML) 2001 methods. The two
scenarios are the following:

(i) mechanical

recycling:

waste

collection

and

further processing to make recycled plastics

(ii) energy recovery: the energy recovery process to

substitute conventional fuel (coal, oil and gas).

Goal and scope definition

The ISO standard LCA Principles and Framework

19

states that the goal and scope definition is mandatory in
all LCA studies. The goals of this study are to quantify
and compare the environmental burdens associated with
the recycling operations such as mechanical recycling
and energy recovery by different impact assessment
methods and to develop an environmental single score
containing both environmental impacts and material
performance characteristics. The functional unit defined
in this study is 1 tonne of polyolefin plastic wastes for
mechanical

recycling and

energy

recovery option,

excluding sorting residue. Sorting residue mainly con-
tains non-plastic and non-polyolefinic wastes. The scope
of the study and the system boundaries include the
following: collection of plastic wastes, transportation
during recycling operations, waste treatment of all
process residues, emissions from the energy recovery
process. The target audiences of this study are product
developers, polymer researchers, engineers, waste man-
agement professionals and policy makers.

Life cycle inventory

The process flow diagrams and system boundaries of
both scenarios are shown in Figs. 1 and 2. The life cycle
inventory data are adopted from Kremer et al.

20

This

study contains unit process data of all recycling
operations such as mechanical recycling (films, bottles)
and energy recovery (fluidised bed combustion and co-
combustion with municipal solid waste). The bottle
recycling scenario and fluidised bed combustion are
adopted for this study. The transport scenarios, elec-
tricity, natural gas and other inventories are adopted
from the Ecoinvent database.

21

The power supplied

during the recycling and energy recovery options are
selected according to UK electricity mix obtained from
Ecoinvent database:

22

coal, 32?6%; oil, 1?1%; natural

gas, 39?9%; industrial gas, 1%; hydro power, 2%;
nuclear, 19?1%; wind, 0?5%; biomass, 1%; and energy
import from France, 2?5%. More details regarding life
cycle inventory can be found elsewhere.

20

Life cycle impact assessment

In this impact assessment stage, environmental loads are
converted into environmental impacts. The purpose of
this translational process is to understand the environ-
mental effects of inventory data. In this phase, the
numerous parameters of the LC inventory phase are
grouped according to different models. This leads to a
reduction of the number of parameters; hence, it helps
to reduce mathematical complexity and to improve
comparability.

There are wide ranges of impact assessment methods

available for practitioners. Every impact assessment has
its own advantages and disadvantages. Some of them
focus mainly on resource consumption. Some of the
resource based indicators are cumulative energy demand
(CED), cumulative exergy demand and ecological
footprint. The CED accounts the direct and indirect
energy demands of a product or a process from raw
material extraction to its disposal.

24

The ecological

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footprint predicts the requirement of productive land
and water to support human life.

22

Some of the me-

thods are impact related categories. For instance, the
Intergovernmental Panel on Climate Change is the
impact indicator focusing on climate change. There are
some methodologies like CML, EDIP, Eco-Indicator
and Environmental Priority Strategies, which focus
on a wide range of impact categories and resource
consumptions.

25

Some of the impact assessment methodologies (EDIP,

Eco-Indicator, Environmental Priority Strategies and
CED

23

) allow aggregating the results into a single score.

In this study, the mechanical recycling and energy
recovery are evaluated with the CML 2001 baseline
method, EDIP 2003 and EI99. The basic difference
between these methods is that CML 2001 and EDIP

2003 follow a problem oriented approach, while Eco-
Indicator 99 follows a damage oriented approach. In
order to locate the basic difference between methodol-
ogies, the scenarios are compared without including
avoided burdens and equivalent processes (see Fig. 3).
The impact assessments were carried out according to
the background literature,

26–32

and a brief description of

these methodologies is presented below.

Eco-Indicator 99

The Eco-Indicator 99 is a life cycle impact assessment
methodology based on end point models. The main
impact categories are ecosystem quality, resource use
and human health. These are subdivided into acidifica-
tion, eutrophication, ecotoxicity, ozone layer depletion,
radiation effect, respiratory effect, climate change, land

2

Energy recovery scenario

1

Mechanical recycling scenario

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use and land conversion. All the impact categories are
aggregated to get a single score. The aggregation of impact
categories was accomplished by giving a relative importance
according to cultural perspectives, such as individualists,
egalitarian and hierarchists (this step is called weighting).
The more details can be obtained elsewhere.

30,31

CML 2001

CML is a life cycle impact assessment methodology based
on midpoint models. The output of CML methods is
expressed as individual impact categories such as abiotic
depletion, acidification, eutrophication, global warming,
ozone layer depletion, human toxicity, fresh water
ecotoxicity, marine aquatic ecotoxicity, terrestrial eco-
toxicity and photochemical oxidation. The CML method
does not allow aggregation of impact categories into
single score; hence, the results are reported as individual
impact scores. More details can be found elsewhere.

32

EDIP

the EDIP methodology is based on midpoint models.
The impact categories included are global warming,
ozone depletion, ozone formation, acidification, terres-
trial eutrophication, aquatic eutrophication, human
toxicity, ecotoxicity, hazardous waste, radioactive waste,
slags/ashes, bulk waste and resources. The method
allows the aggregation of impact categories to a single
score using distance to target methodology. More details
can be found elsewhere.

27–29

Comparison methodology

Comparisons between the two scenarios are not straight-
forward since the final products are not equivalent.

Hence, the ‘basket of products’ method is adopted
(Fig. 3).

32,33

In the mechanical recycling scenario, the

virgin material to be replaced is assumed to be high
density polyethylene. In the energy recovery scenario, the
electricity and heat recovered from incineration are
assumed to substitute the average UK electricity mix
and natural gas. The life cycle inventory of avoided
burdens or substituted materials is adopted from the
Ecoinvent database. The EDIP 2003 and CML 2001
are compared at characterisation and normalisation
level, whereas EDIP 2003 and EI99 are compared at
single score level. The life cycle inventory data are ob-
tained from peer reviewed publications and Ecoinvent
database.

18,20–22

The weighting is carried out by multi-

plying each impact category with a weighting factor
(numerical factor) and aggregated. The weighting factors
for EI99 and EDIP 2003 are obtained from SimaPro
database.

Results and discussions

Comparison of mechanical recycling and energy
recovery

The characterised impact assessment results evaluated
by CML 2001 baseline and EDIP 2003 methodology are
shown in Figs. 4 and 5 respectively. The single score
obtained by EI99 and EDIP 2003 methodology is shown
in Figs. 6 and 7. Apart from aquatic toxicity, ozone
layer depletion and human toxicity, the impacts of
mechanical recycling are much lower than those related
to energy recovery in both mechanical recycling and
energy recovery scenario. The single score obtained by
egalitarian (EI99-E) and hierarchist (EI99-H) views is

3

Basis of comparison, basket of products method

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quite similar to each other and favour mechanical
recycling. The results from the EDIP method indicate
that energy recovery is the preferred scenario compared
to that of mechanical recycling. The single scores
obtained by individualists (EI99-I) favour mechanical
recycling. However, it is not similar to that of EI99-H
and EI99-E. The single score index of EI99-I corre-
sponding to mechanical recycling is positive, whereas
EI99-H/E contains negative values.

Comparison of CML 2001, EDIP 2003 and EI99
methodology

In order to compare methodologies among CML, EDIP
and Eco-Indicator, the avoided burdens and equivalent
process from primary resources are omitted (see Fig. 4).
The characterised results (CML and EDIP) of the
mechanical recycling and energy recovery scenarios are
shown in the Appendix (supporting information). Some
of the impact indicators are common between EDIP and
CML, whereas some of the indicators are represented
in different units. Hence, the method of modifying
characterisation factor and comparison methodology of
Dreyer et al.

33

is adopted. The ecotoxicity category is

not taken into account for discussion, owing to the
length of the manuscript, but is reported in the results
presented in Figs. 4 and 5.

Resource consumption or abiotic depletion

In the EDIP method, the resource consumption is
represented as a total of all primary resources, whereas
in CML, the method is based on stock availability and

extraction rate. Even though the methods are different,
in both of these methods, mechanical recycling was
found to consume more primary resources than energy
recovery. The mechanical recycling operations consume
0?78 kW h kg

2

1

,

and

energy

recoveries

consume

0?36 kW h kg

2

1

, which could be one of the primary

reasons. It should be remembered that the resource
consumption also includes other materials or chemicals
that are used during recycling or energy recovery
operations.

Global warming

Using both methods, energy recovery was found to emit
higher levels of greenhouse gasses than mechanical recycling.
The energy consumption is one of the indirect contributors
of greenhouse gas emission, but apart from energy
consumption, the incineration process is found to emit high
levels of carbon dioxide. The CO

2

emissions during the

incineration process are found to be 2?39 kg kg

2

1

of waste

plastics. This increases the global warming impact of
incineration compared to mechanical recycling. The sub-
stance contribution analysis indicates that 94% of global
warming impact is due to CO

2

. It is also observed that non-

methane volatile organic compound is found only in the
EDIP method and not in the CML method.

Photochemical oxidants formation

In the CML method, the photo-oxidative formation is a
single indicator and expressed as ethylene equivalents,
whereas in the EDIP method, the ozone formation
is represented as two indicators: ozone formation

4

Characterised impact assessment results: mechanical recycling versus energy recovery, CML 2001 baseline method

5

Characterised impact assessment results: mechanical recycling versus energy recovery, EDIP 2003 method

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(vegetation)

and

ozone

formation

(human)

and

expressed as m

2

ppm h and person ppm h respectively.

The EDIP 1997 method uses ethylene equivalents as
reference substance, similar to that of the CML method.
The CML method is mainly based on volatile organic
contents, whereas the EDIP 2003 method is focused on
both volatile organic content and NO

x

emissions. The

EDIP method claims that this differentiation is neces-
sary for modelling site specific impacts. However, in
both CML and EDIP, fluidised bed incineration showed
higher impact compared to mechanical recycling. The
contribution analysis was performed on characterised
results and shown in Fig. 8. The contribution analysis
indicated that sulphur dioxide and methane were the
major contributors in the CML method, whereas
nitrogen oxide and methane were the major contributors
in the EDIP method. The main reason is that the CML
and EDIP methods do not provide characterisation
factors respectively for nitrogen oxides and sulphur
dioxide.

Acidification

The CML method is based on the proton release
capability of a compound and expressed as kg SO

2

equivalent. The EDIP method uses the area (m

2

) of the

ecosystem exposed to acidifying pollutants. Both CML
and EDIP methods estimate higher acidification values
for the incineration scenario. In both of these methods,
mechanical recycling shows reduced impacts, which could
be due to release of SO

2

during plastic incineration. The

characterisation factors used in CML methodology are
adopted from the methodology guide,

31

since the Swiss

based characterisation factors contain characterisation
factors for sulphuric acid. The effect of hydrogen chloride
release during incineration and other energy generation
process is smaller in CML compared to EDIP. The
substance contribution analysis is shown in Fig. 8.

Ozone layer depletion

In both methods used in this study, the impact of the
energy recovery option is slightly higher than that of
mechanical recycling. The substance coverage in the
EDIP and CML methods is quite similar and repre-
sented as kg-CFC-11 equivalents.

Human toxicity

The comparison of human toxicity between CML and
EDIP is quite complex, since EDIP calculates human
toxicity in three compartments, whereas CML uses a
single indicator.

In the CML method, the human toxicity values for

mechanical and energy recovery are quite close to each
other (0?0422 and 0?045 1,4-dichlorobenzene equiva-
lent), whereas in the EDIP method, mechanical recovery
shows higher toxicity values than mechanical recycling.

Normalisation

Both CML 2001 and EDIP 2003 allow normalisation of
the results. However, the selection of a normalisation
reference is critical. Adoption of common geographical
and temporal scales is mandatory to compare normal-
ised results across each impact category as well as with
other impact assessment methods. The normalisation
reference used for EDIP is global person equivalents for
global impact categories and European person equiva-
lents for local and regional impact categories. The year
1990 is used as a normalisation reference year for EDIP.
For the sake of comparison, in CML, global per capita
normalisation references are used for global impact
categories, such as resource depletion, ozone layer
depletion and global warming. For local and regional
impact categories, European per capita normalisation
factors are used. The normalisation references are

6

Single score: EDIP methodology (ER: energy recovery;
MR: mechanical recycling)

7

Single score: Eco-indicator 99 (ER: energy recovery;
MR: mechanical recycling)

a acidification; b photochemical oxidant formation

8

Contribution analysis (ER: energy recovery; MR: mechanical recycling)

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adopted from Ref. 32. The normalised results are shown
in Fig. 9.

Figure 9 shows that normalised impacts are higher for

energy recovery scenario in all impact categories except
in abiotic depletion. The EDIP scores are higher for
human toxicity and photochemical ozone formation,
which is mainly due to the difference in characterisation
and normalisation factors. The impact assessment study
without considering avoided burden and equivalent
process (or system expansion) indicates the environ-
mental intensiveness of mechanical recycling, especially
in human toxicity and resource consumption.

Comparison of single scores

According to ISO standards,

19

weighting is an optional

element in impact assessment. Weighting is a quantita-
tive procedure where the relative importance is com-
pared among other impact categories and aggregated to
get a single score; the relative importance is given as
weighting factors. However, weighted and aggregated
values cannot be used for public policy making
decisions.

The

single

score

obtained

from

Eco-

Indicator is a dimensionless figure and expressed as a
point unit. The value of 1 point is one thousandth of
yearly environmental load of one European inhabitant.
On the other hand, in EDIP, the single score is the
representation of yearly target for a European inhabi-
tant. The weighting in EI99 can be performed according
to three perspectives: hierarchist, egalitarian and indivi-
dualist. All these weighting factors are based on cultural
perspectives.

34,35

The weighting in EDIP 2003 is based

on political targets for the year for an inhabitant.

27

The

weighted and aggregated single score obtained via these
four methods for mechanical recycling are shown in
Table 1. Even though single score indicators represent a
similar meaning, the values are entirely different.
Egalitarian and hierarchists approach found to have

similar values, whereas EDIP 2003 and EI99-I are found
to give very low values. The substance contribution
analysis is performed and shown in Fig. 10.

The use of energy resources (fuel, crude oil and

natural gas), consumed during polymer recycling opera-
tions such as sorting, shredding and final pelletisation, is
the major contributor to subcategory ‘fossil fuels’ in
the Eco-Indicator methodologies. This highlights that
energy consumption is directly related to environmental
impact. The energy consumption also indirectly con-
tributes to global warming, acidification, eutrophication
and human health by releasing carbon dioxide, sulphur
dioxide, nitrogen oxide, particulates and thereby enlar-
ging the total environmental impact. The magnitudes of
EI99-H and EI99-E values are high because the fossil
fuels (70%) are included in the classification and
characterisation phase and further magnified in the
weighting phase. Owing to the non-availability of
normalisation factors and weighting factors in metho-
dology guide and SimaPro,

29

fossil fuels are omitted

in EDIP 2003. This creates the significant difference
between the EDIP and Eco-Indicator approaches. The
single score value from individualist perspectives does
not give high weighting to fossil fuels, which resulted in
a reduced single score in EI99-I.

Benzene, a pollutant emitted during power genera-

tion, is classified under human toxicity and found to
contribute ,45% of the EDIP value. Furthermore,
benzene is classified under ‘carcinogens’ and ‘respiratory
organics’ category in the EI methodology, but the
magnitude is suppressed. Even in EI99-I, where the
human health is given much importance, benzene is not
found to contribute on a significant level.

Nitrogen oxide, also a pollutant emitted during power

generation, contributing to all four methodologies, is a
dominant contributor in EI99-I single score along with
particulates. These particulates are considered seriously
in all three Eco-Indicator methodologies, and their
magnitude is raised in the characterisation or damage
modelling steps. However, in EDIP, wide ranges of
inventories are covered in the human toxicity category;
however, the particulates are considered on a limited
scale. In Eco-Indicator methodology, particulates are
characterised according to different particle sizes.

Along with nitrogen oxide, carbon dioxide is found to

contribute in all four methodologies, and it is the top

9

Normalised results of mechanical recycling and energy recovery in EDIP and CML 2001 (person equivalent

10

5

environ-

mental impact/human population)

Table 1

Comparison

of

single

scores

for

mechanical

recycling

Method

Single score/milli-Pt

EDIP2003

0.544546

EI 99 hierarchist

26.487239

EI 99 egalitarian

24.01832

EI 99 individualist

13.027545

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contributor in EI99-I value and found to give a
reasonable contribution in other three methodologies.

Breakeven point

The single score index (EI99-H) was calculated for both
mechanical recycling and energy recovery scenario
according to basket of products method (see Fig. 6).
In order to include the performance of recycled plastics,
the avoided burden of 100% virgin plastic substitution is
decreased, and the breakeven point is calculated. When
recycled plastics are considered to be equivalent to that
of virgin plastics, in a particular application, the amount
of material required will be the same. However, recycled
plastics undergo severe degradation and have contam-
ination, which restricts to declare that recycled plastics
are equivalent to virgin plastics in some of the cases. As
the degradation level of recycled plastics increases, the
component made of recycled plastic has to be made
thicker so as to meet same performance (mechanical/

thermal) requirements. Hence, 1 kg of recycled plastic is
not sufficient enough to replace 1 kg of virgin plastic,
and 1 kg of recycled plastic can replace 0?5–1 kg of
virgin plastic, depending on the level of degradation and
performance of the material. The impacts are evaluated
at equivalent substitution (1 : 1) and increased as the
performance of the material decreased. This is shown in
Fig. 10. The breakeven point is evaluated through other
single score methods and shown in Figs. 11 and 12. The
breakeven points obtained by other methods are quite
similar to each other. This indicates that mechanical
recycling scenario is preferable only if the virgin plastic
substitution is above the breakeven point. The mechanical
recycling scenario is a sustainable choice only if it can
substitute more than 70% virgin plastics (high density
polyethylene). The sensitivity analysis indicates that this

a Eco-Indicator 99 H; b Eco-Indicator 99 E; c Eco-Indicator 99 I; d EDIP 2003

10

Substance contribution analysis of weighted and aggregated single scores obtained by different methods

11

Performance adjusted single score: breakeven point
between mechanical recycling and energy recovery
(ER: energy recovery; MR: mechanical recycling)

12

Breakeven point: comparison of impact assessment
methods in calculating minimum percentage of virgin
polymer that should be replaced by recycled polymers

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breakeven point remains same for replacing polypropy-
lene and low density polyethylene and reduces to 65% for
replacing general purpose polystyrene material.

Conclusions

Limitations from earlier reported studies on recycling
plastics consisted mainly of product development and
decision analysis.

8–16

The LCAs of recycled plastics were

mainly focused on individual impact categories rather
than using a single indicator, which still remains an
obstacle for many product developers.

Three different impact assessment methods were

compared for plastics recycling, and the advantage of
aggregation of impact categories to single score is
discussed, particularly for product developers. The
CML method can be used to assess the environmental
impacts; however, due to the non-availability of a
weighting option, it is unlikely to be chosen as a tool
for product development. The EDIP method has the
option of weighting and aggregation, but the EDIP
single score does not account resource use. The EI99 can
be chosen as a tool for product development with the
caution that damage models suffer from high uncer-
tainty and some damage models are not available.

36

The concept of breakeven point is elaborated in the

context of recycled plastics. This breakeven point is
dependent on the ecoprofile of mechanical recycling, energy
recovery and substituted material. The breakeven point
varies according to the chosen impact assessment method.
The incorporation of performance of recycled plastics in the
impact assessment method will indicate the actual ‘green-
ness’ of the product.

Appendix

Characterised results: comparison of mechanical recy-
cling and fluidised bed incineration without avoided
burden and equivalent process (MR: mechanical recy-
cling; ER: energy recovery)

Acknowledgement

The authors would like to acknowledge the Qatar

Science and Technology Park (QSTP) for funding the
project.

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Impact indicators

Unit

CML baseline 2000

EDIP 2003

MR

ER

MR

ER

Global Warming

kg CO

2

eq

5.082610

2

1

2.653

5.234610

2

1

2.661

Abiotic depletion

kg Sb eq

3.878610

2

3

1.970610

2

3

Resources

kg

5.739610

2

6

3.162610

2

6

Acidification

kg SO

2

eq

1.758610

2

3

2.607610

2

3

…

…

Acidification

m

2

2.898610

2

2

5.043610

2

2

Eutrophication

kg NO

{
3

eq

1.512610

2

4

3.022610

2

4

Aquatic eutrophication

kg N

1.052610

2

4

2.192610

2

4

Aquatic eutrophication

kg P

5.499610

2

7

4.945610

2

7

Terrestrial eutrophication

m

2

2.783610

2

2

5.780610

2

2

Ozone depletion

kg CFC-11 eq

1.549610

2

8

3.028610

2

8

1.675610

2

8

2.261610

2

8

Human toxicity

kg 1,4-DB eq

4.566610

2

2

4.217610

2

2

Human toxicity air

m

3

2.136610

3

1.740610

3

Human toxicity water

m

3

1.779

4.106

Human toxicity soil

m

3

3.315610

2

2

2.039610

2

2

Fresh water aquatic ecotox.

kg 1,4-DB eq

7.597610

2

3

4.902610

2

3

Marine aquatic ecotoxicity

kg 1,4-DB eq

1.961610

1

1.429610

1

Terrestrial ecotoxicity

kg 1,4-DB eq

4.763610

2

4

1.156610

2

3

Ecotoxicity water chronic

m3

1.772610

1

1.372610

1

Ecotoxicity water acute

m

3

6.755

4.546

Ecotoxicity soil chronic

m

3

7.262610

2

2

4.631610

2

2

Photochemical oxidation

kg C

2

H

4

6.739610

2

5

7.766610

2

5

Ozone formation (vegetation)

m

2

ppm h

2.337

4.298

Ozone formation (human)

person ppm h

1.616610

2

4

2.898610

2

4

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Life cycle impact assessment methods on plastics recycling

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