Environmental impact assessment of goods and services is nowadays a major challenge for both economic and ethical reasons. Life Cycle Assessment (LCA) provides a well-accepted methodology for modelling environmental impacts of human activities. One stage of the LCA methodology is Life Cycle Inventory, which consists of decomposing economic activities as elementary processes linked together through interdependency relations. This stage is needed in order to evaluate the environmental impacts of processes. A global analysis of economic activities requires considering a huge amount of elementary processes and interdependency links, making the model difficult to understand. In this paper, we propose a semantic approach for the modelling of lice cycle inventory databases. The method has the advantage of offering a more comprehensible model. We explain our model and illustrate it with life cycle inventory data for the U.S. electricity production.