To characterize the system's structure, we defined three indices of the embodied Methimazole that is consumed per unit of carbon emission. First, RE represents the relative emission efficiency, which equals the ratio of embodied energy consumption to the associated carbon footprint. We also defined similar indices for the relative efficiency of direct (RD) and indirect (RI) consumption of embodied energy. For all three indices, a high ratio means a lower carbon emission per unit of energy consumption, which means that the sector for which the index was calculated has high emission efficiency. Conversely, a low ratio indicates high carbon emission per unit of energy consumption, which indicates low emission efficiency. The equations for these indices are as follows:equation(5)RE=EEECwhere RE represents the overall embodied energy emission efficiency, EE represents the embodied energy consumption, and EC represents the embodied carbon footprint. This term can be divided into two additional terms:equation(6)RD=DEDCwhere RD represents the direct embodied energy emission efficiency, DE represents the direct energy consumption, and DC represents the direct carbon footprint.equation(7)RI=IEICwhere RI represents the indirect embodied energy emission efficiency, IE represents the indirect energy consumption, and IC represents the indirect carbon footprint.