Uncertainty and variability in environmental life-cycle assessment

Abstract

General introductionIncreased rates of resource depletion, land use, solid waste generation and emissions of pollutants became issues of broad public concern in the beginning of the seventies (Meadows et al., 1972). Unfortunately, most of these problems are still with us today, and some of them have increased substantially (World Resources Institute, 1996). One way to decrease the environmental pressure of human activities is the environmentally improvement of production processes (Reijnders, 1996). In this respect, an important question to be answered is 'how exactly can we measure the environmentally improvement of production processes?' Environmental life-cycle assessment (LCA) aims to answer that question. The first section of this chapter provides an overview of the LCA framework. Although the framework itself is well-established, the application of the framework is in many aspects problematic. A brief overview of the problems associated with the actual implementation of the framework is described in second paragraph. Finally, the aim and the structure of the present thesis is outlined in the third paragraph. § 1.1 Environmental life cycle assessment Environmental life cycle assessment (LCA) is a tool for the assessment of the environmental impact of product systems (Heijungs et al. 1992). It considers the full life cycle of a product from resource extraction to waste disposal. LCA is generally divided into four phases: goal and scope definition, inventory analysis, impact assessment, and interpretation (Figure 1.1; ISO, 1997a).In the goal and scope definition, the aim and the subject of an LCA study are determined and a 'functional unit' is defined. An example of a functional unit is 'the consumption of 100 kg apples' with, for instance, the aim to compare the environmental impacts of different agricultural production processes of apples. In the inventory analysis, for each of the product systems considered data are gathered for all the relevant processes involved in the life cycle. A product system can be considered as a combination of processes needed for the functioning of a product or service. The outcome of the inventory analysis is a list of all extractions of resources and emissions of substances caused by the functional unit for every product system considered, generally disregarding place and time of the extractions and releases. The matrix method can be used to perform the inventory analysis (Heijungs, 1996(Heijungs, , 1997 where i is the vector of environmental interventions, H is the environmental intervention matrix, representing the extractions of resources and emissions of substances per unit process, G is the technology matrix representing the inter-process flows needed for the functioning of the product system, and u is the external supply vector, related to the functional unit. Life cycle impact assessment (LCIA) aims to improve the understanding of the inventory result. Firstly, it is determined which extractions and emissions contribute to which impact categories. An impact category can...

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