Abstract:Weighting model is the only valuation model of life cycle impact assessment (LCIA) profile now. It simplifies evaluation function into linear function, and makes the determination of weighting factor complicated. Therefore the valuation of LCIA profile is the most critical and controversial step in life cycle assessment (LCA). Development on valuation models, which are understood easily and accepted widely, is urgently needed in the field of LCA. The modeling approaches for the linear evaluation function were summed up. The modeling approaches for the nonlinear evaluation function were set up by function approximation theory, which include choosing preference products, forming preference data, establishing artificial neural network (ANN) and training ANN by preference data. By selecting 7 material products as preference product, experience was done with modeling approaches of the nonlinear evaluation function. The results show that the modeling approaches and valuation model of the nonlinear evaluation function are more practical than the weighting model.

Key words: material life cycle assessment; life cycle impact assessment; valuation model; weight model; function approximation; artificial neural network; preference product