Geographical, technological and temporal delimitation in LCA. UMIP 2003 method

Weidema B P (2004)

Publication info

København: Miljøstyrelsen. (Environmental News 74)


The subject of this guideline is the geographical, technological and temporal delimitation of the product systems included in life cycle assessments (LCAs).

The purpose of life cycle assessments is to assess the environmental impacts of a choice of one product instead of another (or the choice of a specific product instead of refraining from this product). A specific choice of product may involve changes in processes and their environmental impacts throughout the life cycle of the products. For the assessment to give meaningful results, the affected processes must be identified as precisely as possible, with respect to geography, time, and technology.

The guideline contains three complementary procedures, to be used in parallel or in iteration:
1. A procedure for identifying the processes affected by a change in demand
resulting from a choice between products.
2. A procedure for identifying the processes affected when the choice involves
multi-product systems that provide their products in different proportions. The procedure modifies the systems so that they provide the same products in the same proportions.The procedure is illustrated with examples, including situations of material recycling and complex situations with several co-products from the same process and where several of the involved processes in a system expansion have multiple products or applications.
3. A procedure for identifying future processes. The procedure includes determination of the parts of the product systems that need to be forecasted, the necessary detail of forecasting, and the choice of the relevant forecasting methods. Different forecasting methods and their relevance in different situations are described.
The aim of the three procedures is to reduce the arbitrariness in performing these crucial elements of a life cycle assessment. The procedures are equally relevant for detailed, quantitative life cycle assessments and for qualitative and simplified studies, “screenings” and “matrix-LCAs”.

The three procedures all seek to identify the consequences of a choice between products, which implies a change in demand. Therefore, the procedures include the use of market information. Thereby, the procedures provide a supplement to the traditional approach to system delimitation in life cycle assessment, which typically has been forced to disregard the actual market conditions and instead apply a number of specific (implicit or explicit) assumptions.

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