Scholarly article on topic 'Analysis of key environmental areas in the design and labelling of furniture products: Application of a screening approach based on a literature review of LCA studies'

Analysis of key environmental areas in the design and labelling of furniture products: Application of a screening approach based on a literature review of LCA studies Academic research paper on "Agriculture, forestry, and fisheries"

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Abstract of research paper on Agriculture, forestry, and fisheries, author of scientific article — Mauro Cordella, Carme Hidalgo

Abstract Environmental impacts of production and consumption can be controlled and reduced through instruments such as ecodesign and environmental labelling, which typically involve the analysis of complex product systems. The definition of more sustainable product options is not a trivial task and it can be complicated by factors such as the technical complexity and heterogeneity of products, available literature and impact assessment metrics used. The principles of systematic review and meta-analyses have been used to tailor an approach that can be used, to support eco-design and environmental labelling, for screening the environmental literature of products and the preliminary analysis of key environmental areas and improvement options. The approach has been applied to the furniture product group, for which 82 documents related to environmental aspects for different furniture products were collected. The screening and analysis consisted of three steps: 1. selection of reference impact categories; 2. screening of studies according to a qualitative–quantitative framework; 3. analysis of selected studies and extraction of relevant information. Five impact categories have been analysed: Acidification, Climate Change, Eutrophication, Ozone Depletion, Photochemical Ozone Formation. Analysis of documents covering a broad group of furniture products has allowed the understanding of critical areas, improvement options and technical aspects on which to concentrate investigation efforts in order to reduce the life cycle impacts. The approach can, in general, be adapted to any products for addressing the further development and implementation of measures with which to promote more sustainable options (e.g., ecodesign, environmental labelling, green public procurement criteria).

Academic research paper on topic "Analysis of key environmental areas in the design and labelling of furniture products: Application of a screening approach based on a literature review of LCA studies"

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Sustainable Production and Consumption IChoiTlE

journal homepage: www.elsevier.com/locate/spc

Analysis of key environmental areas in the design and labelling of furniture products: Application of a screening approach based on a literature review of LCA studies

Mauro Cordelia"'*, Carme Hidalgo

a Joint Research Centre - Circular Economy and Industrial Leadership Unit, C/ Inca Garcilaso, 3, Edificio Expo, 41092 Seville, Spain b LEITAT Technological Center, c. Innovacio 2, 08225 Terrassa (Barcelona), Spain

ABSTRACT

Environmental impacts of production and consumption can be controlled and reduced through instruments such as ecodesign and environmental labelling, which typically involve the analysis of complex product systems. The definition of more sustainable product options is not a trivial task and it can be complicated by factors such as the technical complexity and heterogeneity of products, available literature and impact assessment metrics used. The principles of systematic review and meta-analyses have been used to tailor an approach that can be used, to support eco-design and environmental labelling, for screening the environmental literature of products and the preliminary analysis of key environmental areas and improvement options. The approach has been applied to the furniture product group, for which 82 documents related to environmental aspects for different furniture products were collected.

The screening and analysis consisted of three steps:

1. selection of reference impact categories;

2. screening of studies according to a qualitative-quantitative framework;

3. analysis of selected studies and extraction of relevant information.

Five impact categories have been analysed: Acidification, Climate Change, Eutrophication, Ozone Depletion, Photochemical Ozone Formation. Analysis of documents covering a broad group of furniture products has allowed the understanding of critical areas, improvement options and technical aspects on which to concentrate investigation efforts in order to reduce the life cycle impacts.

The approach can, in general, be adapted to any products for addressing the further development and implementation of measures with which to promote more sustainable options (e.g., ecodesign, environmental labelling, green public procurement criteria).

Keyurords:Environmental design and labelling; Furniture products; Key environmental areas; Life Cycle Assessment; Screening approach; Systematic review

© 2016 The Author(s). Published by Elsevier B.V. on behalf of Institution of Chemical Engineers. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

* Corresponding author.

E-mail addresses: Mauro.CORDELLA@ec.europa.eu (M. Cordella), chidalgo@leitat.org (C. Hidalgo).

Received 9 February 2016; Received in revised form 5 July 2016; Accepted 5 July 2016; Published online 24 August 2016.

http://dx.doi.org/10.1016Zj.spc.2016.07.002

2352-5509/© 2016 The Author(s). Published by Elsevier B.V. on behalf of Institution of Chemical Engineers. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

1. Introduction

Environmental impacts of products can be controlled by improving the eco-efficiency of the product life cycle, which could be pursued for instance through the implementation of instruments such as eco-design and Type I environmental labels (Hauschild et al., 2005). Eco-design activities can support the reduction of the life cycle impacts of products through the consideration of environmental aspects during their conceptual stage (Anastas and Zimmerman, 2003). Type I environmental labels (International Organization for Standardization, 1999) are instead voluntary programmes aimed at identifying and marking environmentally superior products according to criteria developed on the basis of life cycle considerations. This type of label can thus serve as a pull mechanism for driving the market towards more sustainable product options.

Without considering behavioural aspects related to the interaction between products and consumers, the effectiveness of eco-design activities and product labelling depends on the early and coherent definition of key environmental areas on which to concentrate further investigation efforts for achieving relevant and tangible gains. In this sense, a core role is played by the Life Cycle Assessment (LCA) methodology (International Organization for Standardization, 2006a,b), which is the standard approach to follow for assessing the environmental impacts of products and identifying life cycle hotspots and improvement options. Moreover, a complementary product-oriented analysis may be necessary to handle legislative, techno-economic and environmental aspects of concern that are not conventionally covered, or fully integrated into the LCA (as can be the case for issues related to product quality, inherent safety of materials, indoor air pollution and, for some products, noise emissions).

LCA studies and other material available in the literature can represent important sources of information for addressing the assessment and improvement of the sustainability of products. However, the definition of more sustainable product options is not a trivial task and it can be complicated by factors such as: technical complexity and heterogeneity of products, availability of studies, and impact assessment metrics used. A preliminary and tailored screening of the literature is thus needed to focus on documents with which to build coherent outcomes and understand whether there are information gaps to be filled. This can be achieved through systematic reviews and meta-analyses (Brandao et al., 2012; Lifset, 2012; Zamagni et al., 2012; Zumsteg et al., 2012) and can be particularly useful when the scope of the analysis is broad and/or the technical and scientific production is significant, as is the case for the furniture product group (see as an example the list of documents available in Online Resource 1, Appendix A).

Systematic literature reviews are analyses of studies selected on the basis of predefined criteria and which aim to extract relevant information with which to answer specific questions. Results can be also combined quantitatively through meta-analyses (Ressing et al., 2009). Systematic reviews and meta-analyses are widely used in disciplines such as ecology, epidemiology, medicine, psychology or software engineering, where standardised frameworks and protocols have also been proposed (Chambers and Wilson, 2012; Lifset, 2012; Ressing et al., 2009; Thompson et al., 2012; Zumsteg et al., 2012). Utilisation in the field of LCA has begun in the last few years, both at a practical and methodological level (see for instance: Price and Kendall, 2012; Wolf et al.,

2015; Zamagni et al., 2012), although no widely recognised guidelines are available (Brandao et al., 2012; Lifset, 2012; Zumsteg et al., 2012). Because of this, Zumsteg et al. (2012) proposes general guidance on how to conduct a systematic review of LCA studies. Recommendations on aspects to consider when evaluating a LCA study can also be found in European Commission (2013).

The principles of systematic review and meta-analyses have been used in this paper to tailor an approach that can be used to support the implementation of eco-design activities and environmental labelling of furniture products in Europe (although it could potentially be extended and adapted to other products and contexts) for the following:

1. The screening of the environmental literature on the products analysed.

2. The preliminary analysis of key environmental areas and improvement options.

Considering that this is an initial step for the implementation of the instruments above (further in-depth analyses and stakeholder consultations are necessary to investigate technical, economic and environmental aspects), the approach was streamlined by:

1. keeping the goals and scope of the review process and selection criteria focused on specific aspects and practical objectives of the intended application (rather than more methodological issues);

2. defining a simple and flexible qualitative-quantitative evaluation framework which can be easy to apply and allow the efficient extraction of preliminary information from the literature about environmental impacts and critical aspects of products.

On the other hand, the approach itself is not a standalone tool as it has to be coupled with further analyses and information and does not, on its own, allow a full and robust quantification of the environmental profile of products (for which a statistically representative set of data would be needed), or the exploration of more methodological issues and developments. However, these and other aspects could be taken into account in further updates of the approach.

2. The furniture product group

Furniture is a product group of great interest for eco-design activities and product labelling (see for instance: EU Ecolabel, 2014; The International EPD® System, 2014a). The definition of furniture covers a broad set of products used daily in both domestic and non-domestic spaces for functions such as storage, hanging, supporting, lying, sitting, working and eating. Typical products are chairs, desks and tables, cupboards and wardrobes, kitchens, bed structures and sofas, which can all be made of different materials (e.g. wood, metals, plastics, glass, textiles, stone) and placed on the market in a variety of designs (Postell, 2012). Apart from the heterogeneity in terms of product types, designs and materials used, furniture is also characterised by a broad and complex value chain, as depicted in Fig. 1 for a generic product. From a system perspective, the product's life cycle can be split into three main blocks: upstream activities (i.e. production, supply and processing of materials and components), core activities (i.e. product manufacturing, assembly, finishing, packing and storage); and downstream activities (i.e. product distribution, retail, use, maintenance and end of life).

MANUFACTURING OF FURNITURE

Fig. 1 - Streamlined value chain of a generic furniture product.

3. Materials and methods

The first stage of the screening approach consisted of collecting documents which could potentially allow the identification of key environmental areas and improvement options for the furniture product groups and with which to address potential activities on eco-design and environmental labelling (i.e. the research question).

The search of documents was performed in April 2013 through search engines and databases of peer-reviewed literature (Google Scholar, 2016; ScienceDirect, 2016; Scopus, 2016). The search was based on combinations of key words such as LCA, environment, sustainability and specific types and materials of furniture products (e.g. office furniture products, wooden furniture). Additional documents were gathered from webpages of EPD schemes (The International EPD® System, 2014a; The Norwegian EPD Foundation, 2016) and through a direct call for contributions from experts in LCAs and furniture products (e.g. by mailing the LCA discussion list managed by Pré).

This resulted in a sample of 82 documents dealing with environmental issues related to different types of furniture (see the list available in Online Resource 1, Appendix A), which includes scientific papers, environmental product declarations (EPDs) and other technical reports.

The second stage consisted of screening and analysing the collected documents, which was performed on three steps:

1. selection of reference impact categories;

2. screening of studies according to a qualitative-quantitative framework;

3. analysis of selected studies and extraction of relevant information.

3.1. Selection of reference impact categories

The environmental analysis of product groups can be complicated both by the broadness and heterogeneity of

the scope and also by the variety of impact assessment approaches followed in different studies, as is the case for furniture.

General recommendations on impact categories to cover in LCA studies and related assessment methods are, for instance, provided in the Product Environmental Footprint (PEF) Guide (European Commission, 2013). The document proposes 14 environmental impact categories and related indicators, building on the information produced in the ILCD Handbook (European Commission's Joint Research Centre, 2011), where existing impact assessment methods were reviewed, evaluated and classified. The ILCD Handbook indicates that, at the state of the art, "recommended and satisfactory" assessment methods exist for the Climate Change, Ozone Depletion, Particulate Matter / Respiratory Inorganics impact categories, with further research and development efforts needed for other methods.

The greater the number of impact categories analysed, the more comprehensive the description of the environmental profile of products. Nevertheless, the availability of reliable information tends to decrease and trade-offs among different impact categories tend to increase as the numbers of impact categories and indicators increase. Considering that the goals of the approach presented is to identify key environmental areas and improvement options in the life cycle of the products analysed, the screening was streamlined by selecting a sample of key impact categories which could be considered of relevance for the product group under analysis and for which satisfactory and reliable information can be found. A narrow set of impact categories can be functional for the definition of key environmental areas and improvement options, as indicated in ADEME (2010) and Cordella et al. (2015) for example.

Reference impact categories for the present application were selected based on the observation of standard methodological requirements contained in Product Category Rules (PCRs) defined for furniture products within Type III Environmental Declaration programmes (AFNOR, 2011; The

International EPD® System, 2009, 2014b; The Norwegian EPD Foundation, 2009, 2013) and on the parallel consultation of studies where LCA results have been normalised (ADEME, 2010).

Five impact categories were selected for testing the screening approach on furniture:

1. Acidification;

2. Climate Change;

3. Eutrophication;

4. Ozone Depletion;

5. Photochemical Ozone Formation.

The quantification of impacts for the categories Acidification, Climate Change and Eutrophication generally appears compulsory in the PCRs consulted for furniture and supported by the indications provided in (ADEME, 2010). Potential environmental impacts in these categories are significantly proportional to the consumption of energy, as reported in Askham et al. (2012) and Huijbregts et al. (2006).

Ozone Depletion and Photochemical Ozone Formation are two impact categories to quantify within the International and the Norwegian EPD Systems. In particular, the consideration of Photochemical Ozone Formation may be relevant for furniture because of the use of solvents (ADEME, 2010).

Depletion of resources, production of waste and toxicity could be other parameters of potential interest (ADEME, 2010; AFNOR, 2011; The International EPD® System, 2009, 2014b; The Norwegian EPD Foundation, 2009, 2013) but they have not been included in this application.

Although resource scarcity is considered as an important parameter to take into account, an impact assessment category on resource depletion was not included when the screening approach was applied. Significant differences exist between methods used to assess impacts due to depletion of resources which call for further improvement and consensus (Klinglmair et al., 2014). In addition, depletion of resources and production of waste are often reported in the available literature for furniture as material and energy flows. It should however be noted that the selected impact assessment metric allows the analysis, at least partially, of the environmental importance of materials and waste over the life cycle as impacts due to consumption of resources, as well as to production of waste, are analysed with respect to five impact categories. For a product group like furniture it is expected that the consideration of an additional impact category specifically handling depletion of resources would confirm the importance of materials as a key environmental area. In contrast, a more detailed assessment of depletion of resources may be more relevant for electronic products, as may be for instance the case for computers, TVs and washing machines.

With respect to toxicity parameters, this is recognised as an important issue for protecting human health and the environment. This impact category is not covered in the PCR documents consulted for furniture, which typically ask for the collection of information on use and emission of chemicals. Moreover, no "recommended and satisfactory" methods exist for this impact category (European Commission's Joint Research Centre, 2011), with further methodological improvements and investigation at the substance level needed to build a comprehensive database. Efforts in this area are ongoing to converge towards a "scientific consensus model" (USEtox, 2014). Positive effects in this area could in the meantime be achieved through a product-oriented approach carefully investigating how to reduce the inherent hazards

of products, components and substances (Cordella et al., 2009; European Union, 2010). Some preliminary indications on hazardous substances of potential concern were reported when screening the studies.

3.2. Screening of studies according to a qualitative-quantitative framework

As is typical in systematic reviews (Price and Kendall, 2012; Zumsteg et al., 2012), criteria were set in order to establish a qualitative-quantitative framework for the identification of documents of relevance for the analysis. Criteria were adapted from the recommendations provided by European Commission (2013) on aspects to consider when evaluating a LCA study.

Criteria, presented in detail in Table 1, cover aspects related to: (1) scope of the study; (2) data quality and representativeness; (3) impact assessment metric; (4) relevance of findings; (5) robustness of the study; (6) presence of an independent review process.

A sample of 82 documents of potential relevance for different types of furniture was considered for the screening (see Online Resource 1, Appendix A). The evaluation was carried out in two steps:

(I) Verification of the fulfilment of the inclusion criteria:

• coherence of the scope and adherence to the ISO 14040/4 standards;

• at least one of the reference impact categories identified in the previous step is characterised through methods which are classified as at least "C" according to the "science-based criteria overall evaluation" carried out in (European Commission's Joint Research Centre, 2011);

• relevance of the findings of the study for identifying the key environmental areas and improvement options of the product system analysed.

(II) Qualitative-quantitative evaluation of the LCA studies that pass the first level of screening, on the basis of the six criteria reported at the beginning of this section (scope of the study; data quality and representativeness; impact assessment metric; relevance of findings; robustness of the study; presence of an independent review process).

For each parameter a score from 1 to 5 was assigned, as described in Table 1, on the basis of the qualitative evaluation of the studies. Each study obtained an overall score from 1 to 30. Studies were further analysed when the total score was 15 or above. The use of scoring in the system review for the selection/analysis of documents does not appear a common practice in LCA (see, for instance Price and Kendall, 2012). Semi-quantitative indications for data-quality assessment and rating are, for instance, provided by European Commission (2013). However, a more practical and broader scoring system was considered more suitable for this application.

Documents that did not pass the screening were tracked if they were considered useful for complementing the LCA information gathered through the review with information on other environmental issues of concern which may merit further investigation. In the case of furniture, this was the case, for instance, for the analysis of hazardous substances potentially present in products and for the sourcing of wood from sustainable forest management (FAO, 2014).

New studies should be sought, or ad-hoc investigations conducted, in the event that the basis of the information produced is not considered satisfactory within the context of the analysis.

Table 1 - Criteria considered for the screening approach.

Information Inclusion criteria Evaluation criteria and scoring

1 Scope of the study - Coherent scope definition for the analysis 5 = Coherent LCA for a broad group of

products of interest

1. Type of study - Key assumptions of the study fulfilling 3 = Coherent LCA for one product OR

(e.g. attributional/consequential LCA, ISO 14040 standards Streamlined LCA for more products of

fulfilment of ISO 14040/PAS interest

2050/PCRs/PEF/...)

2. Product system(s) analysed 1 = Streamlined LCA for one product of

interest

3, Functional unit

4. System boundaries (stages and

process cut-off)

5. Main modelling assumptions

(e.g. allocation)

2 Data quality and representativeness - (I) Average data representativeness to be

evaluated for each stage:

1. Materials (including packaging) 5 = High quality data:

2. Manufacture - Representative from a geographical and

technical point of view for average

conditions of relevance within the context

analysed

3. Distribution - Up-to-date, mainly collected on site for

foreground processes (e.g. primary data

collected less than 3-5 years ago)

4. Use phase 3 = Average quality data:

5. End of Life - Representative from a geographical and

technical point of view for average

conditions of relevance within the context

analysed

- Recent (e.g. collected less than 5 years

1 = Low quality data:

- Outdated (e.g. collected more than

5-10 years ago) or of less interest from a

geographical and technical point of view

(II) The overall score for data is the average

of the points assigned to each single stage

3 Impact assessment metric - At least one impact category of reference 5 = Complete coverage of the reference

is characterised through methods which impact categories and satisfactory quality

are classified as at least "C" according to of impact assessment methods (classified

the ILCD Handbook as "A" or "B" according to the ILCD

Handbook)

3 = At least one impact category of

reference is characterised through methods

classified as "A" or "B" according to the ILCD

Handbook

1 = At least one impact category of

reference is characterised through methods

classified as at least "C" according to the

ILCD Handbook.

4 Relevance of findings - Findings of the study are relevant for the 5 = Findings of the study are very relevant

identification of key environmental areas for the achievement of the goals of the

and improvement options for the product analysis

system analysed

3 = Findings of the study are partially

relevant for the achievement of the goals of

the analysis

1 = Findings of the study have minor

relevance for the achievement of the goals

of the analysis

(continued on next page)

Table 1 (continued)

Information Inclusion criteria Evaluation criteria and scoring

5 Robustness of the study - 5 = Main assumptions and quality of the

study are considered good and sensitivity

analysis is performed to manage primary

sources of uncertainty and variability

3 = Main assumptions and quality of the

study are considered good

1 = Quality of the study can be considered

acceptable but some potential weaknesses

are detected which require critical

interpretation

6 Presence of an independent review process - 5 = Independent third party review

(e.g. paper)

3 = Other third party review

(e.g. certification)

1 = No review

3.3. Analysis of selected studies

Selected LCAs that passed the screening were analysed to understand the range of the information available from these documents and to further identify key environmental areas for furniture and possible options for improving the environmental profile of this product group in the European context.

A simple meta-analysis was also carried out to obtain rough indications of the contributions of single life cycle stages to total impacts, both as averages and variations of such contributions. This was done by processing the information on the breakdown of total impacts reported for 72 case studies. The life cycle of the products was divided into five subsystems: production and supply of materials (P1), product manufacturing (P2), distribution (P3), use and maintenance (P4) and end of life (P5).

An element complicating this contribution analysis is that the assumptions and aggregation level with which results are calculated can vary from source to source. To overcome this obstacle, the sum of P1 and P2, which were found to be the most frequently quantified contributions, was taken as a reference basis for the comparison of different subsystems. Contributions from the five subsystems have thus been expressed in relative terms as a percentage of the sum of P1 and P2, which is to say that P1 + P2 = 100%.

4. Results and discussion

The following eight LCA studies passed the screening and were further analysed, together with relevant information from the available EPDs (see Online Resource 1, Appendix A): ADEME (2010), Distretto del Mobile di Livenza (2010), Gamage et al. (2008), González et al. (2008), González-García et al. (2012), IHOBE (2010), Mitchell and Stevens (2009), and Spitzley et al. (2006). The main findings are reported in the following sections.

These LCA studies obtained a score of 15 or above and were thus considered to be qualitatively satisfactory and focused on the achievement of the practical objectives of the research question ("identifying key environmental areas and improvement options for the furniture product groups and with which to address potential activities on eco-design and environmental labelling").

4.1. Goal and scope of selected studies and EPDs

The identification of hotspots along the product life cycle was found to be a typical element of the analysis for the selected studies. In addition, some studies also addressed the comparison of different design options (see for instance: ADEME, 2010; González-García et al., 2012; IHOBE, 2010). The following furniture types are covered:

• tables, desks and workplace furniture (7 case studies in ADEME, 2010; Distretto del Mobile di Livenza, 2010; González et al., 2008; IHOBE, 2010; Spitzley et al., 2006 and 12 EPDs from 4 documents (see Online Resource 1, Appendix A));

• chairs and benches (5 case studies in ADEME, 2010; Gamage et al., 2008; IHOBE, 2010; Spitzley et al., 2006 and 37 EPDs from 30 documents (see Online Resource 1, Appendix A));

• cupboards, bookshelves and boxes (4 case studies in ADEME, 2010; Distretto del Mobile di Livenza, 2010;

• sofas (3 case studies in ADEME, 2010);

• beds and sleeping furniture sets (2 case studies in ADEME, 2010; González-García et al., 2012)

• kitchen furniture (1 case study in Distretto del Mobile di Livenza, 2010);

• wooden panels (1 case study in Mitchell and Stevens, 2009).

Selected LCA studies and EPDs generally refer to assembled products. The scope is broad in terms of products and it can be considered representative of indoor furniture. Complementary information on specific issues of relevance for outdoor furniture, such as wood treatment, should be sought separately (see for instance: Online Resource 1, Appendix A).

The assessed products are composed of a variety of materials. Generally, wood is the main material used in furniture. Wood materials can consist of wood boards or panels. Almost all products have some components made of metals, mainly aluminium and steel. The relative weight of metals and plastics become more significant for non-domestic applications. Typical plastic components are polypropylene (PP) and polystyrene (PS). Other materials can also be important for some products, such as glass for cabinets and bookshelves or upholstering textiles for seats and sofas. Some studies analysed issues related to forestry

operations and coatings of wood and recycling of materials (Distretto del Mobile di Livenza, 2010; González-García et al., 2012; Mitchell and Stevens, 2009; Spitzley et al., 2006). In terms of system boundaries:

• A cradle-to-grave assessment was carried out in six of the selected studies (ADEME, 2010; Gamage et al., 2008; González et al., 2008; González-García et al., 2012; IHOBE, 2010; Spitzley et al., 2006) and in 28 EPDs. End-of-life scenarios were typically modelled considering average conditions of waste disposal.

• Indications of the impacts associated with different disposal strategies for wooden panels were provided in Mitchell and Stevens (2009).

• A cradle-to-use assessment was carried out in 20 EPDs.

• A cradle-to-gate assessment was carried out in Distretto del Mobile di Livenza (2010) and 1 EPD.

• Impacts from the use phase were not always taken into account. The usual approach was to model and assess impacts due to product maintenance and cleaning operations (e.g. use of water, soap, vacuum cleaner) as found, for instance, in ADEME (2010), IHOBE (2010) and EPDs registered in The Norwegian EPD Foundation scheme (The Norwegian EPD Foundation, 2014a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q). However, the contribution of these activities was found to be marginal (ADEME, 2010; IHOBE, 2010). Although the design of a product may have some influence on the use phase and end of life, the impacts of these two stages of the life cycle inherently depend on consumer behaviour and the waste management strategies deployed.

Making reference to the scheme reported in Fig. 1, in terms of data sources process data for core activities were in most cases gathered from manufacturers while information on upstream and downstream activities were usually modelled based on information from suppliers, statistics and Life Cycle Inventory (LCI) databases. Production and supply of components was normally considered an upstream activity. Nevertheless, in some cases this was integrated with the product manufacturing stage. Similarly, downstream activities were sometimes modelled as aggregated processes. It is apparent that the non-harmonised definitions of system boundaries and subsystems are factors which complicate the comparison of results obtained in different studies.

With respect to the functional unit of studies, this should ideally relate to the function, quality, design and lifespan of products. However, because of the diversity in the type of products and applications, three main approaches were found to be generally applied:

• The assessment refers to the function provided by the product (e.g. sitting, storage) and to the expected duration of use (ADEME, 2010; Gamage et al., 2008; González et al., 2008; Spitzley et al., 2006).

• The assessment refers to one unit of product and to the average expected duration of use (IHOBE, 2010). This approach usually appeared to be followed in studies related to the assessment of one or more product design options, including EPDs.

• One unit of product (González-García et al., 2012) or mass units (Distretto del Mobile di Livenza, 2010; Mitchell and Stevens, 2009) are assessed with no explicit consideration of the duration of use.

In the last two approaches there is an overlap between the functional unit and reference flow. The existence of different approaches used to define the functional unit makes the analysis of the outcomes from different studies more critical, especially when the lifespan of products is not taken into account. Function and lifetime should be essential elements to consider in the assessment of products.

4.2. Impact assessment methods used in selected studies of EPDs

Reference impact categories presented in Section 3.1 are fully covered in the LCA studies which passed the screening and by the analysed EPDs, as shown in Table 2:

• six documents (ADEME, 2010; Distretto del Mobile di Livenza, 2010; González et al., 2008; González-García et al., 2012; IHOBE, 2010; Mitchell and Stevens, 2009) and all the consulted EPDs assess impacts for the Acidification, Climate Change, Eutrophication, Ozone Depletion, and Photochemical Ozone Formation categories;

• Spitzley et al. (2006) assess impacts for Acidification and Climate Change;

• Gamage et al. (2008) assess impacts for Climate Change.

Acidification Potential (AP) and Ozone Depletion Potential (ODP) were generally characterised according to versions of the CML method (Guinée et al., 2002), which is classified as "B" according to the "science-based criteria overall evaluation" provided in European Commission's Joint Research Centre (2011). Exceptions are represented by Spitzley et al. (2006) which used the TRACI method, Bare et al. (2006) which characterised AP (classification "E") and by Distretto del Mobile di Livenza (2010) which based the calculation of ODP on semi-empirical and timedependent characterisation factors developed by Solomon and Albritton (1992) (not classified) were assessed. Eutrophication Potential (EP) and Photochemical Ozone Formation Potential (POFP) were characterised according to versions of the CML method (classification "B" for both) (Guinée et al., 2002). Climate Change has been characterised for all studies as Global Warming Potential (GWP) according to methods classified as "A": CML (Guinée et al., 2002), IPCC 2007 (Intergovernmental Panel on Climate Change, 2007), and TRACI (Bare et al., 2006).

4.3. Analysis of key environmental areas, improvement options and additional aspects of interest for furniture

The information available was processed to estimate average contributions and indicative variation ranges for different life cycle stages: production and supply of materials (P1), manufacturing (P2), distribution (P3), use and maintenance (P4) and end of life (P5).

Indications of average contributions to the impacts from the five subsystems and on estimated variation ranges were calculated as described in Section 3.3 and reported in Table 3 as ratio to the sum of P1 and P2. Such figures allow the environmental importance of different life cycle stages of a generic furniture product to be understood. In general, it can be observed that the production and supply of materials is the stage which has the greatest influence on determining the environmental profile of furniture products (average ratio of P1 to P1 + P2 from 88% to 98%, depending on the impact category). A secondary role is played by product manufacturing (average ratio of P2 to P1 + P2 from 2% to 12%),

Table 2 - Impact categories considered in selected LCA studies and EPDs and related impact assessment methods.

Impact category The International The Norwegian IE (2010) Distretto del Gamage González González- IHOBE Mitchell Spitzley

EPD® System EPD Foundation Mobile di Livenza et al. et al. García (2010) and et al.

(2009)a (2009, 2013) (2010) (2008) (2008) et al. (2012) Stevens (2009) (2006)

Acidification CML CML CML CML CML CML CML CML TRACI

Climate Change CML CML IPCC IPCC CML CML CML CML CML TRACI

Eutrophication CML CML CML CML CML CML CML CML

Ozone Depletion CML CML CML Solomon and Albritton CML CML CML CML

Photochemical Ozone CML CML CML CML CML CML CML CML

Formation

Other indicators

Depletion of energy Flow indicators CML TRACI

resources for ren. and non-ren. energy

Depletion of material Flow indicators for Flow indicators for CML for minerals CML CML CML CML TRACI

resources water, material and energy resources water, material and energy resources Flow indicator for water

Ecotoxicity Emissions of toxic substances to water Emissions of toxic substances to water CML for freshwater aquatic, terrestrial ecotoxicity CML for freshwater aquatic, terrestrial ecotoxicity CML for freshwater aquatic, marine aquatic and terrestrial ecotoxicity CML CML

Human Toxicity Emissions of toxic substances to air Emissions of toxic substances to air CML CML CML CML CML TRACI

Solid Waste Flow indicators Flow indicators Flow indicators TRACI

aAdditional indicators included in The International EPD® System (2014b): Ecotoxicity and Human toxicity, according ; to USEtox (2014); Land use according to the Recipe method (Endpoint indicator, Hierarchic

perspective).

Table 3 - Relative magnitude of impacts for single subsystems based on the contribution analysis of selected LCA studies and EPDs.a b.

Impact category P1: production P2: product P3: P4: use and P5: end

and supply of manufacturing distribution maintenance of life

materials (%) (%) (%) (%) (%)

Acidification 44/100 0/56 0/56 0/2 -17/5

(89) (11) (7) (0) (-1)

Climate Change 40/280 -180/60 0/46 0/1 -8/7

98) (2) (7) (0) (1)

Eutrophication 46/100 0/54 0/51 0/2 -1/117

(90) (10) (7) (0) (22)

Ozone Depletion 35/100 0/65 0/60 0/2 -16/56

(88) (12) (14) (0) (4)

Photochemical Ozone Formation -93/100 0/193 0/39 0/1 -16/5

(88) (12) (6) (0) (-1)

aCalculation basis: P1 + P2 (i.e. the cradle-to-gate impacts) is 100%. bVariation ranges are indicated, approximate average values are reported within brackets.

distribution (average ratio of P3 to P1 + P2 from 6% to 14%) and end of life (average contributions of P5 to P1 + P2 from -1% to 22%), although contributions from these stages may be more significant for some products as suggested by the spread of the variation ranges. Meanwhile, impacts due to the use phase, typically including the maintenance and cleaning of the product, appear negligible without considering aspects related to durability.

Key environmental areas and improvement options for each subsystem are analysed and discussed in the following sections together with additional aspects of potential interest for furniture products.

4.3.1. Production and supply of materials Potential impacts of furniture for the categories considered in the screening are significantly associated to the materials used in the product. On average, production and supply of materials (P1) is the stage that shows the greatest contributions to the cumulative impacts for all the impact categories considered. With the exception of Climate Change and Photochemical Ozone Formation, variation ranges calculated within each category are similar for this stage. Deviations for Climate Change and Photochemical Ozone Formation were found in two LCA studies as a consequence of the inherent characteristics of the product system and of the related modelling assumptions (González et al., 2008; The International EPD® System, 2014c).

Optimising the use of resources could be the most effective measure for decreasing the environmental impacts of furniture production, for instance through design concepts aimed at decreasing the weight of products and/or selecting materials and components characterised by lower life cycle impacts (González-García et al., 2012; IHOBE, 2010).

Impacts appear to be generally higher for metals and plastics than for wooden materials or packaging. In furniture made of mixed materials (mainly wood-based panels, metals and plastics), the contribution from the production and supply of materials is generally higher than for wooden furniture (ADEME, 2010; Spitzley et al., 2006). As a consequence, the relative importance of other life cycle stages increases in the case of wooden furniture products.

Metals have higher impacts per weight due to the fact they are very energy-intensive materials and this is especially the case for primary aluminium (Distretto del Mobile di

Livenza, 2010). Contributions from primary aluminium to the total impacts of materials are more than proportional to the relative mass content in the product. Energy embodied in this material was found to be 15% and 60% of that of all materials for two products where the primary aluminium content was 8.5% and 25% by weight respectively (Distretto del Mobile di Livenza, 2010). From a qualitative point of view, similar variations can be observed for other impact categories where potential impacts inherently depend on energy consumption. For instance, the contribution of primary aluminium in the Climate Change category was calculated to be 23%-84% of that of all materials when the content of this material in the product was 8.5%-40% by weight (Distretto del Mobile di Livenza, 2010). Use of secondary aluminium could significantly decrease impacts in categories such as Acidification, Climate Change and Eutrophication (Spitzley et al., 2006). Energy embodied in recycled aluminium was estimated to be about 10% of that embodied in the virgin metal (Distretto del Mobile di Livenza, 2010). Similar considerations can also be extended to other metals, such as steel. Indications supporting the use of recycled/recyclable metals are given in IHOBE (2010).

Plastic materials generally offer better environmental profiles than metals. The main impacts from plastics come from the use of oil both as a feedstock and energy source. Because of the inherently lighter weight of plastic materials, their use could theoretically have some positive effects in the transportation stage. Environmental benefits of recycled plastics were also indicated (González-García et al., 2012; IHOBE, 2010).

Wood appears to be the best material from an environmental point of view (ADEME, 2010; Distretto del Mobile di Livenza, 2010; González-García et al., 2012). Wood is a renewable resource and it is less energy-intensive than metals and plastics (Spitzley et al., 2006). Because of this, wooden materials have less embodied impacts for categories such as Acidification, Climate Change and Eutrophication. Advantages in the Climate Change impact category could be greater if it is considered that wood products can act as temporary storage for biogenic carbon, delaying the net emissions of CO2 and the concentration of this greenhouse gas in the atmosphere (Brandao et al., 2013; Helin et al., 2013; Perez-Garcia et al., 2005). As forbiomass, the benefits of wood materials are generally associated with greater demands for land resources

(Cordelia, 2010), although metals and plastics generate direct impacts in terms of depletion of abiotic, and in some cases scarce, resources (Klinglmair et al., 2014). A measure for decreasing impacts related to wood materials could be to encourage the use of wood and wood fibres produced according to the principle of sustainable forest management (González-García et al., 2012; IHOBE, 2010).

Among wooden materials, panels and boards are normally used as components in finished products. The main sources of environmental burdens for these materials are their embodied energy and the chemical additives resins used for their manufacture. LCA results, however, can vary depending on parameters such as materials used, nature of the wood, density of the panel, energy efficiency of the production process and sources of energy used (González et al., 2008; González-García et al., 2012; Distretto del Mobile di Livenza, 2010; IHOBE, 2010; Mitchell and Stevens, 2009; Spitzley et al., 2006). Production of wooden boards was found to be an energy-intensive process, particularly in steps like board sawing and drying (González et al., 2008; Mitchell and Stevens, 2009). Significant environmental improvements can be achieved by recovering wood from products and waste from manufacturing, for material and energy production, and by avoiding the use of resins which could lead to emissions of formaldehyde and other volatile organic compounds (VOCs) (González et al., 2008; IHOBE, 2010; Mitchell and Stevens, 2009; Spitzley et al., 2006). For instance, it was indicated that there could be a potential saving of up to 0.52 equivalent tonnes of CO2 per tonne of recycled Medium Density Fibreboard (MDF) panel produced (Mitchell and Stevens, 2009) and that reduced use of urea-formaldehyde resins could also produce environmental benefits in impact categories not related to toxicity (Spitzley et al., 2006). Significant levels of toxicity can also be associated to the use of alkyd resins and urea-formaldehyde resins (ADEME, 2010; González-García et al., 2012; Spitzley et al., 2006).

It should be pointed out that the durability of materials made of wood can be lower than that of other materials, especially in the absence of appropriate treatment. Selection of materials should be carefully adapted to the application for which the furniture products are intended as product durability and extended lifespans could be strategic design characteristics.

Apart from these three main groups of materials, textiles can also be an important source of environmental impacts for upholstered furniture (ADEME, 2010). These impacts could be reduced through the use of natural or recycled materials (IHOBE, 2010). The contribution of packaging to the total environmental impacts seems limited (from 0% to 6% as calculated in ADEME, 2010), although it has been found to form up to 4%-15% of the total weight of the furniture (Distretto del Mobile di Livenza, 2010). The environmental impacts of packaging could be kept low through well-known industry practices (e.g. optimising the amount of packaging used, promoting returnable types of packaging and strategies aiming at improving its recyclability, using recycled materials (González-García et al., 2012; IHOBE, 2010). No satisfactory information on other materials, such as glass and stone, has been found. Therefore a specific investigation would be necessary to understand their environmental relevance and the possibilities to reduce the related impacts for those products where their contribution is significant (e.g. kitchen furniture).

The contribution of transport to the impacts due to the production and supply of materials has been found to vary

from 1% to 43% depending on transportation distance, means of transport and impact category analysed (ADEME, 2010). Two materials which can generate significant environmental burdens during their transportation are tropical wood and metals (IHOBE, 2010). Prioritising suppliers closer to furniture production sites could be a relevant measure to decrease environmental burdens due to transport processes (IHOBE, 2010).

4.3.2. Product manufacturing

Production of furniture (P2) basically consists of assembly of components and product finishing, which in general play a secondary role from an environmental point of view compared to production and supply of materials. As in the case of P1, deviations in P2 for Climate Change and Photochemical Ozone Formation were found in two LCA studies as a consequence of the inherent characteristics of the product system and of the related modelling assumptions (González et al., 2008; The International EPD® System, 2014c).

For all the impact categories considered in the screening, the environmental burdens of this stage are mainly due to consumption of electrical and thermal energy. The energy demand can be particularly significant for painting and coating processes. The drying step alone could in some cases account for up to 70% of the energy requested during the product manufacture (Distretto del Mobile di Livenza, 2010). Significant environmental benefits could be achieved by improving the energy efficiency of manufacturing processes and increasing the use of renewable energy (González et al., 2008; González-García et al., 2012), as well as by recovering materials and waste (IHOBE, 2010).

Adhesive, solvents and coatings used during treatment and finishing processes can also represent potential sources of emission of substances that are of concern for Photochemical Ozone Formation (Distretto del Mobile di Livenza, 2010; Gamage et al., 2008; González et al., 2008; González-García et al., 2012; Spitzley et al., 2006). For instance, for furniture products where coating is applied (Distretto del Mobile di Livenza, 2010), the contribution of the manufacturing stage to the impacts becomes greater than that of materials for the Photochemical Ozone Formation category (up to 87% of the cradle-to-gate impact).

Solvents based on xylene, naphthalene and toluene, paints, varnishes, fillers and diluents are some of the chemicals of potential concern which may be used during the manufacture of furniture products. Further discussion on chemical substances used in furniture is addressed in Section 4.3.6.

4.3.3. Product distribution

As is apparent from Table 3, the magnitude of impacts due to the distribution of the final product (P3) appears similar to that of product manufacturing (P2). The impacts of this stage could be decreased by using more efficient means of transport and optimising loading and logistical strategies (ADEME, 2010; González-García et al., 2012; IHOBE, 2010).

4.3.4. Product use and maintenance

Impacts due to cleaning and maintenance operations (P4) generally appear marginal. However, the durability and actual

duration of use of products can dramatically influence the environmental impacts of furniture products, as shown in González et al. (2008) for instance. Designing products that are easy to clean and disassemble or increasing the energy efficiency of energy-consuming furniture products are other examples of actions which could decrease the environmental impacts of this stage (IHOBE, 2010). It should also be observed that the effectiveness of any actions in this area inherently depends on consumer behaviour. In this sense, it would be of vital importance to inform and educate consumers on the correct installation, use, maintenance and disposal of the product, which could be achieved through proper labelling initiatives (e.g. environmental labelling).

4.3.5. End of Life

The end of life of furniture (P5) is a stage that can have a significant influence on the determination of the environmental profile of the product, especially for impact categories such as Eutrophication and Ozone Depletion. Variation in the contribution of this stage is basically due to the disposal scenarios considered.

Landfilling is the worst treatment option although its contribution to the life cycle impacts generally appears low. Negative contributions are registered when credits are assigned for material recycling and energy recovery. Reuse of products or parts of products could also directly avoid the environmental impacts associated to the production of new units. Studies assessing different waste treatment scenarios indicate that options for recovering value from furniture products after their use are widely deployed (ADEME, 2010; Gamage et al., 2008; González et al., 2008; Mitchell and Stevens, 2009). Promoting take-back systems could also serve as additional support for the listed options, as well as minimising the number of materials and components used in products and promoting the use of recyclable materials and reusable components which are easy to identify and separate (IHOBE, 2010).

4.3.6. Additional aspects of potential interest for furniture products: chemicals

The screening of the selected documents also revealed that the use of some chemicals can represent a source of potential concern because of their toxicity. A preliminary and non-exhaustive list of substances of potential concern for furniture products could include: flame retardants, formaldehyde and other VOCs used in adhesives and resins, heavy metals (e.g. chrome used in leather tanning and lead and copper used for the metal coating of glass mirrors), organic solvents used in paints and varnishes and lubricants, other chemical substances used in the production of materials (e.g. textiles and padding materials) (ADEME, 2010; Distretto del Mobile di Livenza, 2010; Mitchell and Stevens, 2009; Spitzley et al., 2006). Avoiding the use of hazardous additives and chemicals and limiting indoor air pollution could thus be important aspects to investigate and take into consideration for the furniture product group (González et al., 2008; IHOBE, 2010; Mitchell and Stevens, 2009; Spitzley et al., 2006).

5. Conclusions and recommendations

The literature represents a valuable source of environmental information that can be used to support the implementation of instruments, such as eco-design and environmental

labelling, aimed at improving the sustainability of products on the market. Based on the principles of systematic review and meta-analysis, a streamlined approach for the screening of the environmental literature on products and the preliminary analysis of key environmental areas and improvement options has been presented and tested on documents related to such a complex product group as furniture.

The application of the approach provided useful insights of relevance for the European context into a broad group of furniture products. A comprehensive LCA of products should follow the cradle-to-grave evolution of products and take into account elements related to durability, quality, design and interactions with users and other systems. The analysis of LCA studies has pointed out that heterogeneous approaches have been applied when defining the functional unit, system boundaries and impact assessment metrics. This has complicated the interpretation of studies, a difficulty that could be overcome through the development of harmonised methods and rules, as pursued for instance by European Commission (2013).

Impact categories frequently considered in LCA studies for furniture products appeared to be: Acidification, Climate Change, Eutrophication, Ozone Depletion and Photochemical Ozone Formation. These were taken as references for the screening and resulted useful for the achievement of the goals of this application. However, the spectrum of environmental aspects to analyse could be broader. Information about the hazardous substances that can be potentially used in furniture was also gathered. The selection of the impact assessment metrics is a delicate task that depends, among others, on factors such as the relative importance of environmental issues within a certain sector and the availability of mature and widely accepted methods. Based on this, it cannot be ruled out that other impact categories may be of potential interest in the future and/or for specific applications (e.g. Abiotic Depletion for products made of metals).

The outcomes of the review show that the environmental profile of furniture is mainly defined by materials. Impacts could thus be reduced effectively through a careful selection of materials and by increasing the efficiency of use of resources. The durability of products can also have a significant influence on the life cycle impacts, as well as disposal scenarios. The toxicity of substances used in furniture is another aspect of potential concern while other aspects appear of secondary importance from a life cycle point of view. This information can be a starting point for understanding environmental issues of products and for prioritising areas and technical aspects on which to concentrate investigation efforts for reducing impacts. However, further investigation and discussion of technical, economic and environmental aspects is needed. Indeed, the definition of effective and feasible measures for improving the environmental performance of products relies on the assessment of the functionality, availability and sustainability of different materials, technology and product options.

The approach, focused on specific aspects and practical objectives, has the advantage of being relatively easy to apply, thus allowing the efficient extraction of preliminary information from the literature. On the other hand it is not a stand-alone tool as it has to be coupled with further analyses and information and does not, on its own, allow a full and robust quantification of the environmental profile of products (for which a statistically representative set of data would be

needed), or the exploration of more methodological issues and developments. However, these and other aspects could be taken into account in further updates of the approach. Given its flexibility, the approach, applied to the analysis of furniture in Europe, could potentially be extended and adapted to other products and contexts to support the conceptual stage of product design or the development of environmental criteria to use for product labelling.

Acknowledgements and disclaimer

The authors would like to thank the European Commission and the stakeholders involved in the revision of the EU Ecolabel criteria set for the furniture product group in Commission Decision 2009/894/EC. The support provided allowed the preparation of the respective background study, on which this manuscript is based. The authors are also grateful to Oliver Wolf for reviewing the paper and to Anna Atkinson for proofreading the paper.

The opinions expressed in this manuscript are purely those of the authors and may not in any circumstances be regarded as stating an official position of the European Commission.

Appendix A. Supplementary data

Supplementary material related to this article can be found

online at http://dx.doi.Org/10.1016/j.spc.2016.07.002.

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The Norwegian EPD Foundation, NEPD nr: 038E for the HAG's chair "Capisco 8106". Valid until 14 May 2013. Available online at: http://www.epd-norge.no/ (accessed 21.11.2014).

The Norwegian EPD Foundation, NEPD nr: 039E for the HAG's chair "H09 Inspiration 9230". Valid until 14 May 2013. Available online at: http://www.epd-norge.no/ (accessed 21.11.2014).

The Norwegian EPD Foundation, NEPD nr: 040E for the HAG's chair "H04 Communication 4470". Valid until 14 May 2013. Available online at: http://www.epd-norge.no/ (accessed 21.11.2014).

The Norwegian EPD Foundation, NEPD nr: 042E for the HAG's chair "Conventio 9510". Valid until 1 February 2013. Available online at: http://www.epd-norge.no/ (accessed 21.11.2014).

The Norwegian EPD Foundation, NEPD nr: 075E for the HAG's chair "Futu". Valid until 14 May 2014. Available online at: http://www.epd-norge.no/ (accessed 21.11.2014).

The Norwegian EPD Foundation, NEPD nr: 121E for the HAG's chair 'S'ideways 9732". Valid until 25 January 2014. Available online at: http://www.epd-norge.no/ (accessed 21.11.2014).

The Norwegian EPD Foundation, NEPD nr: 122E for the HAG's chair "Convention Wing 9811". Valid until 25 January 2014. Available online at: http://www.epd-norge.no/ (accessed 21.11.2014).

The Norwegian EPD Foundation, NEPD nr: 138E for the EFG's chair "Splice 10". Valid until 16 February 2015. Available online at: http://www.epd-norge.no/ (accessed 21.11.2014).

The Norwegian EPD Foundation, NEPD nr: 139E for the EFG's chair "Teamspirit 2". Valid until 16 February 2015. Available online at: http://www.epd-norge.no/ (accessed 21.11.2014).

The Norwegian EPD Foundation, NEPD nr: 140E for the EFG's chair "Savo Stool". Valid until 16 February 2015. Available online at: http://www.epd-norge.no/ (accessed 21.11.2014).

The Norwegian EPD Foundation, NEPD nr: 141E for the EFG's chair "Savo Studio 32". Valid until 16 February 2015. Available online at: http://www.epd-norge.no/ (accessed 21.11.2014).

The Norwegian EPD Foundation, NEPD nr: 142E for the EFG's chair "Savo EOS HL". Valid until 16 February 2015. Available online at: http://www.epd-norge.no/ (accessed 21.11.2014).

The Norwegian EPD Foundation, NEPD nr: 143E for the EFG's chair "SavoIkon 3 LN". Valid until 16 February 2015. Available online at: http://www.epd-norge.no/ (accessed 21.11.2014).

The Norwegian EPD Foundation, NEPD nr: 144E for the EFG's chair "Savo XO ML". Valid until 16 February 2015. Available online at: http://www.epd-norge.no/ (accessed 21.11.2014).

The Norwegian EPD Foundation, NEPD nr: 145E for the EFG's chair "Savo S3 LN". Valid until 16 February 2015. Available online at: http://www.epd-norge.no/ (accessed 21.11.2014).

The Norwegian EPD Foundation, NEPD nr: 146E for the EFG's chair "Savo Studio 22". Valid until 22 February 2015. Available online at: http://www.epd-norge.no/ (accessed 21.11.2014).

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