Synonyms 6 LCA; Life cycle analysis; Product life cycle assessment 7 Definition 8 Life cycle assessment (LCA) is a systems-oriented methodology for addressing the environmental 9 consequences associated with a product or service. It is used for studies of the material and energy 10 flows and their environmental impacts related to a product or a service, i.e., from raw material extraction, 11 to production and use, to disposal. LCA, together with life cycle thinking, life cycle management, and

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... fe 12 cycle sustainability assessment, makes up the portfolio of life cycle approaches. 13 Methodological Framework 14 Life cycle assessment (LCA) study is defined both by the product system it models and the procedure used 15 to study it, the LCA model and the LCA procedure, respectively. The LCA model describes the flow 16 system from raw material extraction to waste disposal, including production, transportation, use, and 17 recycling loops associated with a product (or a service). The procedure consists of several steps. The 18 analysis starts with the definition of goal and scope, in which the researchers specify the product(s) to be 19 studied and the purpose of the LCA study. In the inventory analysis, they construct the life cycle model 20 consisting of the technical processes of the product system, create an inventory of emissions and resource 21 usage in each process, and then calculate the amounts of emissions produced and the resources used in the 22 product system. Results at this stage are called life cycle inventory (LCI) results and consist of amounts of 23 raw materials, energy, and emissions. Next, in the impact assessment, the LCI results are translated into 24 environmental impacts. Owing to the complexity of ecological systems and environmental impacts, 25 impacts can be evaluated in various ways. Emissions and resource use can be classified, characterized, 26 and normalized with regard to their potential or contribution to various environmental problems (e.g., 27 resource depletion, global warming, and toxicity). Some environmental problems have been easier to 28 make assessment methods for (e.g., global warming), whereas others have shown to be more difficult 29 (e.g., toxicity, biodiversity loss) and for which methodology development continues. In the weighting 30 step, the relative significance of the different environmental problems is evaluated. This leads to the 31 calculation of a sum of the total environmental impact for the studied product system. There are several 32 weighting methods, each representing different perspectives on prioritization of environmental problems, 33 e.g., cultural, economic, or political values, or ecological boundaries. Whether one presents results as LCI 34 results, characterized impacts or weighted impact depends too on the purpose of the study, determined by, 35 for example, what is appropriate for public communication and what is useful for internal use. Finally, the *36 interpretation step is the iterative process during which the researchers adjust and ensure that methodo-37 logical choices fit the purpose and the stakeholders of the study and evaluate the quality of the results. 38 Also, interpretation of results can be enhanced through techniques such as dominance analysis, contri-39 bution analysis, payback time, etc. 40 72 LCA Resources 73 Comprehensive description of the methodology and its application is found, for example, in the widely 74 used textbook Hitch Hiker's Guide to LCA by Baumann and Tillman [1]. A comprehensive handbook for 75 the ISO standards on LCA has also been published by Guinée and colleagues [2] . In addition to the 76 commercial software and databases, there are also open alternatives, for example, openLCA and among 77 databases, the CPM LCA Database, the European ELCD, and the Canadian Raw Materials Database, 78 (CRMD) to name a few.