Sustainability assessment is becoming an unquestionable issue for manufacturing companies that are urged by governments and customers to provide environment-friendly products. Machining, as one of the major manufacturing operations, has high potential factors regarding the environmental impacts of production system. Nevertheless, environmental assessments are mainly done post-product design and post-machining processes design. Integrating environmental assessment in the machining processes design could lead to significant improvements in sustainable manufacturing field. Major difficulties to perform such an assessment are the availability of the machining data and the lack of calculation rules to express them in terms of environmental impacts. This article presents a new approach based on the STandard for the Exchange of Product model data—compliant Numerical Control to integrate the machining environmental assessment in the earlier design phases. It proposes to establish cognitive links between the machining data included in STandard for the Exchange of Product model data—compliant Numerical Control and environmental indicators. The approach is implemented on a demonstrator and validated by a use case.