The environmental assessment of innovative bio-based technologies at an early stage is necessary. A promising solution is to couple a process simulation tool with life cycle assessment. However, the impact of the modeling of the reaction and of separation steps on the environmental impacts has to be studied. This article deals with the impact of the degree of complexity of the modeling of a reaction route on the environmental performance. The corresponding case study is the production of dimethyl carbonate (DMC) via methanolysis of urea. Three scenarios were designed to model the three reactions composing the reaction pathway, which correspond to different degrees of knowledge of these reactions at the laboratory scale. Scenarios were evaluated from an environmental point of view. Hot spots analysis highlighted the low contribution of the reaction (R1) for the production of the methyl carbamate, of the separation by distillation of the mixture resulting from this reaction, of the infrastructure. Raw materials appear as the major contributor. The reaction (R2) for the production of DMC and the separation for purification of the DMC present significant impacts due to energy requirements. For the three scenarios, heating has a preponderant impact on a large number of categories. The three studied scenarios conduct to a coherent material balance quite similar, but the results of the energy balance diverge. As a result, it is necessary to increase the precision of the modeling to consider the energy aspect.