The increasing awareness of environmental impacts associated with the production, consumption, and disposal of commodities has led to the development of life-cycle assessment (LCA), which is a widely accepted and internationally standardized method to analyze and quantify environmental impacts of products and services.
A typical life-cycle assessment (LCA) analysis consists of four independent elements :
Definition of goal and scope Life-cycle inventory analysis Life-cycle impact assessment Life-cycle interpretation
The four phases of LCA are illustrated in Figure 7.1.
The starting point of each LCA is to define the goal and scope of the analysis. This includes a decision about the functional unit to which the analysis should refer, the definition of the product system and system boundaries, as well as a choice of allocation procedures, types of impact categories to be studied, and the methodology of impact assessment. The functional unit can either be a certain service or a product, with the latter being the choice of the studies reviewed in this chapter (e.g., 1 kg of polylactic acid [PLA], 1 m3 of loose-fill packaging material, or 1 Ha of agricultural land required for the production of biomass). Critical issues for a comparative environmental analysis of biobased versus fossil-based products are typically (a) the cultivation of biomass in agriculture and forestry (intensive vs. extensive practices), (b) the choice of the conventional product serving as a reference, and (c) the waste-
management option assumed for biobased and petrochemical materials (e.g., land-filling, incineration, recycling) .
The second step of LCA consists of life-cycle inventory analysis. This involves data collection and calculation procedures to quantify all environmentally relevant inputs and outputs of the system, with the most prominent ones being resource use; gaseous, liquid, and particulate emissions; solid waste; and land use.
The third step involves life-cycle impact assessment to (a) evaluate the relevance of system inputs and outputs for the environment and to (b) aggregate parameters belonging to the same environmental impact category into a single value by use of so-called characterization or equivalence factors. For example, to determine the greenhouse potential of substances emitted along a product's life cycle, all relevant emissions determined during the inventory analysis are multiplied with their specific greenhouse gas potential (characterization factor) and summed up to one single value. This value represents the specific impact (expressed in CO2 equivalents) in a particular environmental impact category (greenhouse gas potential). As an optional step, the results per impact category can be divided by a reference value (e.g., total greenhouse gas emissions of a country or total greenhouse gas emissions per capita and year) to better understand and illustrate the relative importance of the various environmental impacts. This step is generally referred to as normalization.
Life-cycle interpretation is the last step of the LCA. Here, final conclusions are drawn from both life-cycle inventory analysis and life-cycle impact assessment. This includes a check for completeness and consistency of inventory data, a sensitivity analysis, as well as a report of all results. As an outcome of this step, recommendations for producers, consumers, policy makers, or environmental stakeholders can be formulated according to the original goal of the LCA.
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