a life cycle framework to support materials selection for ecodesign a

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A life cycle framework to support materials selection for Ecodesign: Acase study on biodegradable polymers

I. Ribeiro 1, P. Peças ⇑, E. Henriques 2

IDMEC, Instituto Superior Técnico, Technical University of Lisbon, Portugal

a r t i c l e i n f o

Article history:

Received 18 February 2013

Accepted 12 April 2013

Available online 22 April 2013

Keywords:

Ecodesign

Materials selection

Process-based cost models

Life cycle cost

Life cycle assessment

Biodegradable polymers

a b s t r a c t

Nowadays society compels designers to develop more sustainable products. Ecodesign directs product

design towards the goal of reducing environmental impacts. Within Ecodesign, materials selection plays

a major role on product cost and environmental performance throughout its life cycle. This paper pro-

poses a comprehensive life cycle framework to support Ecodesign in material selection. Dealing with

new materials and technologies in early design stages, process-based models are used to represent the

whole life cycle and supply integrated data to assess material alternatives, considering cost and environ-

mental dimensions. An integrated analysis is then proposed to support decision making by mapping the

best alternative materials according to the importance given to upstream and downstream life phases

and to the environmental impacts. The proposed framework is applied to compare the life cycle perfor-

mance of injection moulded samples made of four commercial biodegradable polymers with different

contents of Thermo Plasticized Starch and PolyLactic Acid and a common fossil based polymer, Polypro-

pylene. Instead of labelling materials just as ‘‘green’’, the need to fully capture all impacts in the whole life

cycle was shown. The fossil based polymer is the best economic alternative, but polymers with higher

content of Thermo Plasticized Starch have a better environmental performance. However, parts geometry

and EoL scenarios play a major role on the life cycle performance of candidate materials. The selection

decision is then supported by mapping the alternatives.

2013 Elsevier Ltd. All rights reserved.

1. Introduction

Climate change and other environmental threats brought up in

the 90’s have led to a society increasingly aware to the need of a

more sustainable path towards environmental preservation [1].

In fact, in the beginning of the 1990’s an EPA report on life cycle de-

sign [2] claimed that often environmental criteria were not consid-

ered at the beginning of design when it is easiest to avoid adverse

impacts. That decade was the turning point for a definitive para-

digm changing regarding product design. Nowadays, product envi-

ronmental improvement plays an important role towardssustainability [3], putting designers in a unique position to influ-

ence environmental strategy [1]. Furthermore, several authors sta-

ted the importance of design decisions in product’s future impacts,

being indicated that between 80% and 90% of a product’s economic

and environmental costs are fixed at the design stage [4].

Ecodesign, also known as Design for the Environment, Green De-

sign, Sustainable Design, Environmental Conscious Design, Life Cy-

cle Design, Life Cycle Engineering and even Clean Design [5], plays a

crucial role in modern industry and is also becomingthe main focus

of the future market [6]. Ecodesign is a concept within product De-

sign, in which environmental aspects contribute to delineating the

direction of product design decisions. Considering also other tradi-

tional dimensions of analysis, namely the ones more economically

or technically oriented, Ecodesign strives for developing productscausing the lowest possible environmental impacts throughout

the product life cycle [7]. Being a life cycle approach applied to de-

sign decisions, a limitation rises regarding knowledge in early de-

sign stages. The potential for product performance improvement

is inversely proportional to knowledge about the product through-

out its life cycle [3,4]. Given the high uncertainty in the design

phase regardingdata in upcoming product life cycle phases, estima-

tions [8] and sensitivity analysis are usually necessary. Several tools

integrating environmental regulations and data user-friendly plat-

forms have been developed in order to overcome this limitation.

Some are focused on product life cycle assessment (e.g. GaBi [9],

SimaPro [10], Umberto [11]), others on material and process

0261-3069/$ - see front matter 2013 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.matdes.2013.04.043

⇑ Corresponding author. Address: IDMEC, Instituto Superior Técnico, Technical

University of Lisbon, Av Rovisco Pais, 1049-001 Lisbon, Portugal. Tel.: +351 21

8419573; fax: +351 21 8419058.

E-mail addresses: [email protected] (I. Ribeiro), [email protected] (P. Peças),

[email protected] (E. Henriques).1 Tel.: +351 21 8417316.2 Tel.: +351 21 8417556.

Materials and Design 51 (2013) 300–308

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selection (e.g. CES [12]). Furthermore, in terms of cost estimations,

Activity Based Costing (ABC) has been proposed by Bras and

Emblemsvag [13] to address life cycle design. This approach, also

named Process Based Cost Models (PBCM), efficiently compares

alternative designs, allows analysing the generation of cost esti-

mates, cost profiles and cost contributors. Moreover, it is extremely

suitable when dealing with product designas it focus on correlating

cost with design changes [14,15].Material selection is an important part of product design. As

Ashby [16] stated, ‘‘Materials are the ‘‘stuff’’ of engineering de-

sign’’. Therefore, Ecodesign principles should also be applied when

evaluating material options. In fact, according to Field et al. [17]

‘‘the four main factors upon which the designers rely when con-

sidering materials choice are the relationship between materials

specifications and technical performance of the product, the eco-

nomic performance of the product, the environmental perfor-

mance of the product and the practice of industrial design

embedded in the product and its functionality’’. The increasing

environmental awareness of nowadays society has affected most

of industrial processes and products. Particularly plastic, one of

the most versatile materials in the modern age, is widely used

in many products throughout the world. However, the increase

of its consumption has focused public attention on a potentially

huge environmental accumulation and pollution problem that

could persist for centuries, due to their lack of degradability, to

the closing of landfill sites and to the growing water and land pol-

lution [18,19]. Furthermore, as over 99% of plastics are of fossil

fuel origin, their rapid increase will put further pressure on the al-

ready limited non-renewable resources on Earth. This new con-

text of an environmentally conscious society has fostered the

development of new solutions for plastics, with lower environ-

mental impacts [20]. In fact, biodegradable and compostable plas-

tics may serve as a promising solution to the overloaded landfills

by diverting part of the volume of plastics to other means of

waste management and, in most of the cases, by preserving

non-renewable resources [21]. Thermo Plasticized Starch (TPS)

has been seen as a possible substitute for petroleum based plas-tics as it is both renewable and degradable. However, due to its

water sensitivity and low mechanical properties, it’s not suitable

for many plastic products. One solution developed to overcome

these limitations was to combine plasticized starch with another

biodegradable polymer [22,23]. PolyLactid Acid (PLA) is currently

one of the most promising biopolymers, with good mechanical

properties, thermal plasticity and biocompatibility, being a prom-

ising polymer for various applications [24]. In fact, some studies

have found that PLA has comparable mechanical and physical

properties to that of Polytethyleneterephtalate (PET) and Polysty-

rene (PS) [25,26], therefore being able to fulfil very different com-

mercial applications [22,27].

This study proposes a comprehensive life cycle framework to

support Ecodesign in material selection. It is clear the need toevaluate in design decisions both costs and environmental im-

pacts throughout the product life cycle. Our proposal is to use

process models to feed the required data. By modelling all pro-

cesses in each stage of the product life cycle, it is possible to gen-

erate the inputs for Life Cycle Cost (LCC) and Life Cycle

Assessment (LCA) models, and so to evaluate the life cycle eco-

nomic and environmental performance of alternative materials.

These alternative materials are the options already limited by

product logic, specific requirements or other material selection

methodologies (e.g. material property charts). The comprehensive

analysis is then focused on the technically suitable and most

promising material alternatives. A case study is also presented

regarding the performance evaluation and comparison of four dif-

ferent types of commercial biodegradable polymers (BDP) withdifferent amounts of TPS and PLA content and a common fossil

based polymer, Polypropylene (PP) considering samples produced

by injection moulding.

2. Life cycle framework

The framework proposed in this paper is composed by several

consecutive and interacting blocks of information and computingtools.It begins with thedefinition of theanalysis scope foreachpart,

in whichthe alternativematerials andlifecyclestagesto analyse are

defined, as well as the processes included in each phase. The subse-

quent step is to model each process using process-based models

(PBM), derived from the process-based cost models (PBCM). Usually

used for cost modelling, the PCBM approach is proposed to model

also environmental resources consumption and emissions as most

of them are simultaneously cost and environmental drivers. The

processes involved in each life cycle stage are therefore modelled

in order to compute the resources requirements and, further on,

the costs and environmental impacts. This is a demanding task, as

a significant number of manufacturing technologies can be involved

in the process, and furthermore the relations between part design

and the technological requirements along the process need also to

be considered. For this task engineering knowledge of each technol-

ogy in the process is required, as the modelling is not simply a cost

or environmental accounting procedure.

PBM starts from the description of the intended product (part(s)

material(s) and geometry(ies)). The process(es) involved in pro-

duction is(are) then modelled regarding the sequence of steps, cy-

cle time, resources (equipment and labour) requirements and

specifications, etc. This can be obtained with theoretical and

empirical relations correlating the properties of the part and the

requirements of the involved technologies. By adding inputs

regarding the operating conditions of a certain plant it is possible

to build up the operations description, which allows computing

the needed resources regarding the number of tools, equipment,

operators, etc. (or, as far as equipment and operators might not

be dedicated, the time allocated to the product being analysed).The integration of additional relations correlating consump-

tions/resources time use and design features may be relevant to

further explore critical aspects. These are for example models to

estimate tooling reliability and maintenance performance and en-

ergy as a function of part geometry and material. The need to de-

velop them depends on several aspects, namely the processes

involved and the design alternatives. For example in energy inten-

sive processes with high variations of power use over a production

cycle (e.g. plastic injection moulding) it is essential to model effi-

ciently the energy consumption.

Having defined the scope and modelled all the processes it is

possible to compute the required resources to produce the part(s)

for each alternative material option. The deep level of process

parameterization of the PBM based tool permits a myriad of sensi-tivity analysis forming a bloc of information that will be used as in-

put for the LCC and LCA analysis – the third step. Therefore the

third step is to include price factors to each cost driver to assess

the economical performance of an alternative throughout the life

cycle. In parallel, an impact assessment is also performed to the

data inventory retrieved from the PBM to assess the environmental

performance. The life cycle impact assessment (LCIA) phase con-

nects the inventory data with the environmental impacts. In this

study, the main objective in performing this step is to have a global

quantitative result of each alternative, similarly to the cost dimen-

sion. Several methods are available nowadays and two main types

exist: problem (e.g. CML 2002) and damage oriented methods (e.g.

Eco Indicator 99) [28]. The first model the impacts at a midpoint

somewhere in the environmental mechanism between emissionsand damages to minimize uncertainty. The second model the cause

I. Ribeiro et al./ Materials and Design 51 (2013) 300–308 301



effect chain up to the endpoint, or the actual environmental dam-

age within protection areas. Although the first provide more reli-

able results, the second is easier to interpret [29]. In this analysis

the Eco Indicator 99 (EI’99) was chosen, using the hierarchic/aver-

age perspective (H/A), which is a moderate perspective generally

accepted by the scientific community [30].

Finally, with the outputs regarding the environmental and eco-

nomic evaluation of the alternative materials, an integrating gra-phic-based comparison proposed by Peças et al. [15] is used to

address two aspects subject to controversy when dealing with

these dual outputs. First, the question of adding costs (although

considering an interest rate) supported by the different stakehold-

ers involved in the whole life cycle in different timeframes, namely

the upstream stakeholders (part designer and producer) and the

downstream stakeholders involved in the use and end-of-life

(EoL) phases. Second, the separation between costs and environ-

mental impacts (EI) that forces the decision maker to choose a de-

sign alternative with two dimension of analysis, often with

opposite performances evolution.

The first step of the integrated comparison is the normalization

of the costs and environmental impacts of each life cycle phase.

These normalized environmental impacts/costs are then aggre-

gated in Production related (upstream phases) and User related

(downstream phases) values. For each design alternative ( A1, ...,

Ak, . . .), the normalized production related costs (nCP ), the normal-

ized user related costs (nCU ), the normalized production related

environmental impacts (nEP ) and normalized user related environ-

mental impacts (nEU ) are computed according to equation 1 for

each alternative:

Scorek ¼ nCP k þ a nCU k þ b ðnEP k þ a nEU kÞ ð1Þ

in which a is the relative importance given to the downstream life

phases and b is the relative importance given to the environmental

impacts. Both are relative to the production related costs, which are

fully supported and paid by the producer (importance of 100%). This

approach assumes that the cost of upstream life cycle phases (pro-duction cost) is fully important for any stakeholder involved.

So in the (a, b) space the domains of the ‘‘best alternatives’’ (the

ones with the highest Score for each pair of a and b values) can be

mapped. The proposed characterization helps to understand the

influence of each candidate material on the performance dimen-

sions of the product life cycle. Some candidate materials can be vis-

ible for large ranges of a and b values meaning that their best

performance is not significantly affected by changing the relative

importance the decision maker attributes to upstream and down-

stream costs and environmental impacts. Others will not be ‘‘visi-

ble’’ in the performing mapping, meaning that its performance is

lower than at least one of the other alternative material. Further

information regarding this method can be found elsewhere [15].

This approach is illustrated in Fig. 1 and allows estimating inearly design stages alternative materials and designs comprehen-

sively. By evaluating possible alternatives regarding their impacts

throughout their life cycles economically and environmentally, it

supports designers to take more informed decisions prior to the

production phase and therefore without major investments. This

is extremely useful when dealing with non-traditional materials,

where the impacts in the production, use and end-of-life stages

may still be uncertain. In particular in the area of Ecodesign, new

materials have been developed to lower the environmental im-

pacts of products. However, these materials are often evaluated

only regarding the material production phase and their technical

adequacy to the intended function. Being cost performance still a

decisive metric for design decisions, a broad life cycle analysis

regarding both dimensions and the different stakeholders will pro-vide a better support for informed decisions.

3. Case study

The motivation for this study was the increasing awareness of

today’s society to the potentially huge environmental accumula-

tion and pollution problem driven by the plastic products. This

new context of an environmentally conscious society has fostered

the development of new solutions for plastics, with allegedly lower

environmental impacts, as BDPs. The development of these mate-

rials has been driven by the increasing concern in sustainable

development, by the desire to reduce dependence upon finite re-

sources and by changing policies and attitudes in waste manage-

ment. However, it’s crucial to understand the economic and

environmental implications of the transition to these ‘‘greener’’

materials. For this the life cycle framework proposed was appliedto a case study aiming to compare the use of BDPs vs. a common

fossil based polymer. In particular, four different commercial types

of BDPs with different amounts of TPS and PLA are compared with

PP, considering a final product produced by injection moulding.

This case study does not consider a real product, but samples in-

jected in the materials to analyse (Fig. 2). Both samples are injected

in one shot in the same mould, being in the study regarded as the

product. The main focus is the material and its life cycle impacts

when used in a generic plastic product. This allows exploring the

potential of the proposed framework to support materials selection

for Ecodesign. Table 1 presents the alternative materials analysed,

regarding their composition in PLA and TPS and their main proper-

ties relevant for the manufacturing process. Significant differences

are observed between the alternative materials regarding density,melting point and Melt Flow Index (MFI). Higher density materials

Fig. 1. Comprehensive life cycle framework.

302 I. Ribeiro et al. / Materials and Design 51 (2013) 300–308



will correspond to the samples with higher weight, given that the

part geometry is the same. The melting point of the materials in

the injection moulding case reflects mainly in the amount of en-

ergy required to melt the material. MFI is a measure of the ease

of flow of melted plastic and represents a typical index for quality

control of thermoplastics. Therefore, materials with higher MFI are

typically the ones with more potential for the injection moulding

process.

3.1. Scope and data assessment

Starting with the scope definition, all the alternatives, pro-

cesses, and inputs/outputs were set in the product life cycle.

Fig. 3 represents the life cycle phases included, along with the pro-

cesses flows. Notice that use phase is here disregarded as the study

is only focused on the material economic and environmental per-

formance comparison and not in how it contributes to fulfil the

functionalities of particular products. Nevertheless, being BDPs

usually used in disposable consumable products such as tooth-

brushes or food/liquid containers, there would be no significantly

different costs or environmental impacts associated with its use.

3.1.1. Material production

The first life cycle phase is material production. The alternative

materials, described in Table 1, are associated to a specific unit cost( €/kg). In parallel, their EI’99 was computed according to the

quantities of TPS and PLA present in the different compositions

(Table 2). It is important to notice the relation between the pres-

ence of TPS and PLA and the environmental damages resulting

from their production. The larger the PLA content the more damag-

ing the BDPs are for the environment. This is mainly due to the ex-

tra processes (fermentation and condensation processes) required

to produce lactic acid from native starch, with the additional en-

ergy consumption (24 MJ/kg of PLA) [31]. The specific EI’99 value

for TPS and PLA materials was computed according to Eqs. (2)

and (3). Regarding PP, the specific EI’99 value was already defined

in SimaPro [10] databases for the weighing system chosen.

EI099TPS=PLA ¼ %TPS EI099TPS þ %PLA EI099PLA estimated ð2Þ

EI099PLA estimated ¼ EI099TPS þ 24 EI099EnergyðPortugalÞ ð3Þ

Fig. 2. Geometry of the samples to be injected with different materials ( Asurf is the sample surface area and S the thickness).

Table 1

Alternative materials specifications regarding composition and process.

Material Trade name Composition Density (kg/m3) Melting point (C) Melt flow index (g/10 m in)

10/90 Biomind C004 10%PLA + 90%TPS 1200 90 15–30

40/60 Solanyl 35F 40%PLA + 60%TPS 1280 140–145 13

80/20 Biomind R006 80%PLA + 20%TPS 1250 130 20–40

90/10 Bioplast GS2189 90%PLA + 10%TPS 1300 130 20–40

PP PPH 9020 – 905 165 25

Fig. 3. Scope of the case study analysis.

Table 2

Specific costs and environmental impacts of the material production phase of the

alternative materials. EI’99 computed according to Eqs. (2) and (3).

Material Unit cost ( €/kg) EI’99 (points/kg)

10/90 2.6400 0.08721

40/60 2.3000 0.16014

80/20 3.1200 0.25738

90/10 3.5000 0.28169

PP 1.1639 0.33000


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where EI’99TPS = 0.0629 pts/kg and EI’99Energy(Portugal) = 0.0123 pts/

MJ [10,31]

3.1.2. Mould production

As far as parts are produced by injection moulding, a dedicated

mould is needed to provide the intended shape to the melted poly-

mer and cool it down until the part geometry is stable enough for

ejection. The mould production usually comprises a process that

include several technologic steps, namely milling, drilling, turning,

EDM, etc. In this case the same mould is capable of producing the

parts in the alternative material in analysis. Therefore, a deep mod-

elling of cost drivers and impacts involved in the mould production

process is not necessary for sake of comparison. So, only the mould

production global cost and the amount of steel required to produce

the mould were taken into account (see Table 3) and computed in

terms of costs and environmental impacts.

3.1.3. Part production

The part production phase comprises the injection moulding

process. In this phase the amount of needed materials is computed

(considering the scrap originated in the process that is subse-

quently shredded and reintroduced in the process as secondary

material), together with the selection of machines, estimation of

energy and time required to produce the parts.

For the case under analysis the energy consumption was con-

sidered a critical aspect. It depends on the injected material, mean-

ing that it changes among alternatives, and it is both an

environmental and cost driver. Furthermore, injection moulding

machines have a very variable consumption pattern, being inade-

quate to use only the machine nominal power and time to compute

the energy consumption. Therefore, an energy balance was pro-

posed to model the machine consumption:

E ¼ mc pðT melt T ambient Þ þ kmH F þ PV inj

emelt ; fill

þ t cooling ðP idle þ P cooling systemÞ

ð4Þ

where m is the mass of injection shot, c p is the specific heat of poly-

mer, T melt is the melting temperature of the polymer, T ambient is the

ambient temperature, k is the degree of crystallinization, H F is the

heat of fusion for 100% crystalline polymer, p is the average injec-tion pressure and V inj the volume of polymer injected, t cooling is

the cooling time, P idle is the machine power in idle mode and P cooling

system is the average power consumption of the cooling system. The

first term regards the energy required to melt the polymers and fill

the mould cavity. This energy, with an efficiency factor allocated, is

supplied by the machine barrel heaters and hydraulic motors to

drive the screw responsible for the melting and filling. The second

term regards the energy consumption during the part cooling time,

in which heat is drained off through the water/oil cooling system,

being the machine mainly in an idle status. According to Osswald

et al. [32], the cooling time usually represents 80% of the total injec-

tion cycle time, increasing exponentially with the part thickness.

The injection cycle time per part was measured experimentally

for different injection conditions, although some empirical rela-

tions exist for its estimation when in situ measurements are not

possible [32]. For an annual production volume of 200,000 parts,

produced in batches of 25,000 units, the lower cycle time for qual-

ity parts was used to compute the total production time. Produc-

tion time, considering also machine setups, was then an input for

labour, machine, building and overheads cost drivers. Material

consumption for each alternative material was also calculated con-

sidering, in the PP alternative, the shredding loop to recover the

process scraps. The computed resource requirements are presented

in Table 4. The main differences are the higher amount of energy

consumed during PP injection and in opposite, the lower cycle time

and correspondent lower production time required.

Fig. 4 illustrates the part production costs and environmental

impacts for each alternative material, along with the main injec-

tion process parameters. The trend for costs reduction with the

increasing of the PLA content is significant.

The better injection characteristics of PLA compared with TPS

ones, namely the melt flow index, allow the BDPs with higher

PLA content (90/10 and 80/20) to be injected with lower cycle

times. The reduced production time compensate the higher costs

for the BDPs with higher PLA content. The higher production costs

of BDP parts when compared to PP ones are caused by a higher cy-

cle time and a higher material cost. An opposite trend between

BDPs is observed regarding environmental impacts. The increase

of TPS content decreases the overall environmental impact of the

materials. Being the main environmental impact driver the raw

material input, the lower cycle time connected with PLA is not en-ough to balance the lower specific environmental impact of TPS. Fi-

nally, in the material production phase PP is not the material with

best environmental performance, being surpassed by BDPs with

higher TPS content (10/90 and 40/60).

3.1.4. Part EoL

Two alternative end-of-life (EoL) scenarios were set. The ideal

scenario assumes that the selective collection of Biodegradable Ur-

ban Waste (BUW) is available for BDP parts and that PP parts are

collected by the society and then mechanically recycled. This

means that the parts are shredded into pellets or granulates and

serve as secondary materials. In a flawed scenario none of the

materials are selectively collected and all the parts end at the land-fill. The real situation depends on the country and social context,

being between these two extreme scenarios. Table 5 shows the

costs and environmental impacts associated to the collection and

disposal processes used in the three different possibilities of

Table 3

Mould production cost and material consumption.

Material Steel PI20 (AISI)

Material density 7850 kg/m3

Material cost 3 €/kg

Material EI’99 0.111 pts/kg

Material quantity 168 kg

Production cost 3500 €

Table 4

Part production (injection moulding) requirements for the alternative materials.

Alternative materials Machine Energy consumption [MJ] Material input (tons) Production time (h)

PLA TPS PP

10/90 Installed power – 58 kW 445.6 0.546 4.918 – 2667

40/60 656.9 2.332 3.497 – 2555

80/20 Clamping force – 85 ton 641.4 4.554 1.139 – 2278

90/10 666.9 5.328 0.592 – 2278

PP 2948.4 – – 4.121 1611




disposal, as well as the incomes generated by the final compost

(BDPs case) and the recycled PP. Notice that the collection costs de-

pend on their type: selective collection of BUW, undifferentiated

collection of SUW (Solid Urban Waste) or selective collection of

plastics. Considering the specific costs and environmental impacts

of each EoL process it is possible to assess for the entire production

volume the total costs (Portugal case) and environmental impacts

for each extreme EoL scenario.

3.2. Life cycle analyses

The life cycle cost and environmental performance of the differ-

ent material alternatives are analysed in the following sections.

3.2.1. Cost performance

The global LCC results for each material life cycle phase are

illustrated in Fig. 5. Several conclusions can be withdrawn. Regard-

ing the BDP alternatives, there is a trend for LCC reduction with the

increase of PLA content. However, based on current data, PP is still

the best economic alternative. Also it is clear that part production

(injection moulding) represents the main cost driver, followed by

the part material. Mould production can be perceived as a fixed

cost and its relevance on costs depends on the production volume

considered. For a production volume of 200,000 parts per year, it

represents less than 9% of total life cycle costs. EoL costs or profitswere determined by the different scenarios considered, ideal or

flawed, but in both represent less than 2% of the total LCC. For this

reason, only the results for the ideal EoL scenario are presented.

Despite the current economic advantage of PP, it is expectable

that future extended use of BDPs in consumable products can pos-

sibly decrease their relative raw-material cost. This would place

BDPs in a more competitive economical level. However, costs are

only one dimension of the analysis. Following, the environmental

impacts of the material alternatives are also computed in a life cy-

cle approach.

3.2.2. Environmental performance

Within Ecodesign context, the analysis of the environmentalperformance of different alternative materials drives the design

into more sustainable decisions. It requires not only knowledge

of the impacts of production of the involved raw materials (mould

steel and alternative polymers), but also of the impacts of alterna-

tive designs throughout the life cycle, namely in the production

and EoL phases of the parts/samples. Following the same scope

and process based modelling method, the assessment of the envi-

ronmental impacts of the several candidate polymers was per-

formed, using all data previously collected for the injected parts/

samples, considering an annual average production of 200,000

parts.

With the results of the life cycle inventory, the overall impact of

the 200,000 parts made of each polymer was calculated. Starting

from the parts material production and finishing at the parts endof life, the LCA (in fact the LCIA phase) was computed for both,

ideal and flawed, EoL scenarios (Fig. 6). Unitary impacts of mate-

rial, energy, transport and waste treatment were retrieved from

Simapro7.2 software.

Results show that injection material is the main environmental

impact driver in the overall life cycle. Considering the ideal sce-

nario, if all BDP parts are composted and all PP parts recycled,

the material option with lower impact is the BDP with higher

amount of TPS (90%), being possible to notice an increase of the

environmental impacts with the PLA content in the BDPs composi-

tion. PP polymer also presents low impacts if a full recycle scenario

is considered. However, in the flawed scenario PP polymer presents

high impacts when compared with TPS based BDPs. In fact, the in-

crease of TPS in the polymers composition is again the main envi-ronmental impact driver. This shows the importance of analyzing

Fig. 4. Injection cycle time vs. Injection and Raw material costs/environmental

impacts for 200,000 parts.

Table 5

Specific costs and environmental impacts of different EoL processes.

Cost

( €/ton)

EI’99 (points/kg)

PP BDPs

Collection Selective collection of BUW 100

Selective collection of plastics 110

Undifferentiated collection of SUW 45

Disposal Municipal composting 50

Plastics recycling process 300 0.120

Landfill fee 30 0.060 0.0104

Recycled

products

Compost (90) 0.0046

Recycled PP (600) (0.330)

Fig. 5. LCC results and costs distribution for a production volume of 200,000 parts.


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comprehensively the alternative materials instead of labellingthem only as ‘‘green’’ materials.

Taking advantage of the process models, a sensitivity analysis

can be performed to assess the robustness of the results. The ex-

tended analysis to other production scenarios regarding the pro-

duction volume does not change the hierarchy of environmental

performance of the several materials. However, the geometry of

the part may alter the relative performance of the alternatives.

Being material input the main environmental driver, a sensitivity

analysis was performed to assess the influence of part dimension

and subsequent material input. When increasing the part surface

area, keeping constant the overall thickness, the main effect results

from the increase of material consumption and from higher energy

required to melt the material and fill the mould cavity. The cooling

time, the main parcel of the injection cycle, does not suffer signif-icant changes [31]. The size of the injection mould also increases.

However, as the same mould is used for injecting the parts made

of the different materials, this variation reflects equally in all alter-

natives. It is therefore interesting to analyse the behaviour of the

environmental impact of the alternative materials for the ideal

(Fig. 7) and flawed (Fig. 8) scenarios when parts surface area varies.

Considering an ideal scenario, results show that for smaller

parts the best environmental alternative is PP. However, for larger

parts the best alternative is the 10/90 BDP, with the higher per-

centage of TPS due to the lower material impact. Regarding the

flawed scenario, the increase of the surface area changes the hier-

archy of environmental performance of alternatives. PP is the best

alternative for parts with a surface area bellow 18 cm2. Above this

area the best alternative is the 10/90 BDP. The injection mouldingcycle time of PP and BDPs does not significantly change with the

increase of the surface area, as the thickness remains unaltered.

However, material input raises and parts made of materials with

lower specific EI’99 (BDPs with higher TPS content) increase their

environmental performance in comparison with the others. Larger

parts made of these BDPs also take a better advantage of the lower

amount of energy required to melt the material, due to their lower

injection temperature and specific heat. Parts with larger surface

areas benefit the BDPs environmental score.

A similar analysis is not presented regarding cost impacts of

part surface area variations as no hierarchical change is observed

between the alternative materials. With no significant variation

in cycle time and given that the specific material cost of BDPs is

higher that PP, the increase of part surface area would not assigna better economic advantage to BDPs.

3.3. Integrated comparison of economic and environmental life cycle

performance

Finally, as the economic and environmental evaluations do not

point to the same design alternative, an integrated comparison is

performed, considering both dimensions. The life cycle phases

are organized into two classes: the upstream and downstream

stages. The former includes the materials production (polymers

and mould steel), mould production and parts injection, while

the later involves the EoL processes (as mentioned part use phase

is disregarded in this case study). The division is justified by the

Fig. 6. Environmental impact of each alternative for an annual production volume of 200,000 parts considering : (a) EoL ideal scenario; (b) EoL flawed scenario.

Fig. 7. Sensitivity analysis to surface area – ideal scenario. Fig. 8. Sensitivity analysis to surface area – flawed scenario.




different nature of the stakeholders affected by the design decision

(producers and users/society) and by the different time horizons of

the decision effects. Therefore, the perspective of the producer can

be modelled, giving a full importance to the materials acquisition

and mould and part production costs (the costs that it fully sup-

ports and has to pay for). The scores of each alternative, Scorek,

were computed using Eq. (1) for both scenarios, considering adi-mensional values for the cost of downstream stages and environ-

mental impact. The results are illustrated in Fig. 9.

Regarding the ideal scenario, given that PP performs economi-

cally better in all life cycle phases and also performs environmen-

tally better in the EoL phase due to the significant benefit of

recycling, it is the best alternative in a wide scope of thea (relative

importance given to downstream stage) and b (relative importance

given to environmental impacts) values. Only when the concern

with environment issues is much higher than the producer ori-

ented costs (b > 4), BDP 10/90 appears as an environment-based

material alternative. However, even in this situation it only ap-

pears for a reduced importance given to EoL (PP recycling is always

a better option when compared with any other material deposition

method).Considering the flawed scenario, both PP and BDP come out as

possible best alternatives within [0;1] interval for a and b values.

PP appears as a cost-based alternative for the part producer: the

best option if a reduced importance is given to downstream stages

and to environment issues. BDP 10/90 option appears as an envi-

ronmental based alternative: it performs environmentally better

throughout the whole life cycle. In this case BDP performs better

in the EoL phase in both economic and environmental dimensions.

Finally, it is important to mention that recycling methods for BDPs

are currently in an early development phase. Even if their recycling

is not still a real option, in the future it might place them in a more

competitive position in sustainable EoL scenarios.

Given the best environmental performance of BDPs for parts

with higher material input, the integrated analysis was also plotted

for parts witha total surface areaof 80 cm2 (higher thanthe injected

samples). As expected, although with the same pattern, in this case

the 10/90 BDP appears in a wider range of a and b values (Fig. 10).

Given that PP use in parts produced by injection moulding is

nowadays the lower cost option, only in an environmental dimen-sion BDPs perform better. In the analyses only one BDP alternative

appears – the TPS higher content based biopolymer. Between BDPs,

TPS higher content BDPs have lower environmental impacts while

PLA higher content ones lead to lower part production costs. There-

fore, when integrating both analysis with all materials, only the

material with lower environmental impacts is best than PP in envi-

ronmental-based design decisions. However, in a decision scenario

where only BDP materials are analysed (Fig. 11), three best alterna-

tives emerge. 80/20 BDP is the best alternative when very low

importance is given to environmental impacts and 10/90 BDP for

environmental-based decisions. In between, an intermediate mate-

rial 40/60 appears as the best alternative – environmentally better

than the 80/20 BDP and economically better than the 10/90 BDP.

Results observed are similar for both EoL scenarios.

4. Conclusions

This paper addresses material selection in Ecodesign, providing

a framework to evaluate new materials in a life cycle perspective.

Frequently with few available data, designers are pushed to in-

clude ‘‘green’’ materials in new products. The specific cost and

environmental impact of the material are clearly insufficient to

make informed decisions. Our proposal is to use process models,

traditionally directed to compute process costs, to compute both

cost and environmental impact drivers of all processes in the prod-

uct life cycle phases. That is, by modelling the processes involved

Fig. 9. Best performing mapping of the alternatives – ideal and flawed scenarios.

Fig. 10. Best performing mapping of the alternatives considering a part with 80 cm2 surface area – ideal and flawed scenarios.


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in the life cycle it is possible to retrieve the required data to feed

LCC and LCA models. This strategy allows without major invest-

ments and prior to part production to assess, in economic and envi-

ronmental dimensions, the life cycle of products made of the

alternative materials. The two dimensions of analysis are then

integrated into a single measure. This allows mapping the best

materials according to the importance given to the upstream life

cycle cost (modelling the perspective of the producer and the full

importance it attributes to its costs), to the environmental evalua-

tion and to the downstream phases (modelling the importance

attributed by the user or the society as a whole). Finally, this

framework is applied in a case study regarding the comparison be-

tween Biodegradable Polymers (BDPs) vs. a common fossil based

polymer, Polypropylene (PP). Results have shown the need to de-

velop comprehensive analyses that fully capture all impacts

throughout the life cycle. Although BDPs represent a lower envi-

ronmental burden in the material production phase, the EoL phase

is crucial to determine the environmental performance of this

polymers. Given the fact that BDPs recycling is nowadays still in

an early development stage, it does not represent a real option

for these polymers. Therefore, if one considers an ideal scenario

of recycling, the fossil-based polymer PP is a competitive environ-

mental choice. Moreover, it is important to understand what vari-

ations exist within a material type. In this case, the percentage of

PLA in the biopolymers composition was also decisive in their envi-

ronmental performance.

The approach followed allows several sensitivity analyses to

different design features. BDPs perform environmentally better

for injected moulding parts with larger surface areas, in which it

is possible to take full advantage of the trade-off between the

material low impact and higher part production cycle times in

comparison to PP.

Finally, in terms of costs, PP remains the better option. How-

ever, it is important to mention the potential for future improve-

ments in BDPs performance, both in terms of costs and

environmental impacts, namely the possibility to recycle, thereduction of their specific costs and even a better industrial do-

main of BDPs injection moulding.

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Fig. 11. Best performing mapping of the alternatives considering BDP materials – ideal and flawed scenarios.


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a life cycle framework to support materials selection for ecodesign a

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