*3.1. Results of the Energy and Material Consumption Analysis*

Figure 4 shows the material flow for vehicle production elaborated in this study. Here, materials that are necessary for the production of vehicle parts, as well as energy consumed in its production processes, are represented. The mass of oil was considered to be 22.6 g/MJ, natural gas 27.5 g/MJ, and coal 34.4 g/MJ [26,27]. Moreover, the mass of the electricity was estimated as 56.2 g/MJ, when considering the Japanese grid mix, which is generated through oil (19.2%), natural gas (37.5%), coal (32.8%), and others (10.3%) [28]. The efficiency of the generation facilities was considered to be between 42% and 60%, depending on the energy resource utilized in transformation [28]. Plastics and rubbers were made by raw material that were derived from crude oil, and those feedstocks are also represented in the figure as energy resources.

The proposed flow emphasizes the necessity of a considerable amount of resources and material for the production of a vehicle. As raw material, copper ore is the most consumed, due to its low concentration of copper material, followed by iron ore and bauxite. On the other hand, energy resources are mostly consumed in the production of steel and aluminum parts. Figure 5 summarizes those values, where it can be observed that more than 7762 kg of raw material and energy resources is consumed in order to produce a vehicle of 1,481 kg. This means that 5.23 kg of resources are necessary to produce 1 kg of vehicle. Here, copper ore has the highest percentage values, with 2.29 kg of raw material per kg of vehicle (3391 kg per vehicle), followed by energy resources, with 1.46 kg of them being consumed per kg of vehicle (2165 kg per vehicle). The values presented in Figure 5 are also included in Figure 4, where the total raw material and energy resources on the left side of the figure are transformed in stages to a final vehicle on the right.

**Figure 4.** Material flow for vehicle production.

Figure 6 summarizes the results related to energy consumption. The total energy consumed to produce a vehicle was calculated as 62 GJ (41.8 MJ/kg of vehicle). Figure 6a shows that steel parts are the most representative, encompassing 35% of the total. Moreover, even copper parts consume a high quantity of raw material; due to the low concentration of copper on its ore, the energy that is required in its production processes is not as high as could be expected. It can be observed from Figure 6b that natural gas is the highest consumed energy resource in vehicle production, and Figure 6d shows that its consumption is almost equally distributed in aluminum, steel, and plastic parts production, as well as in vehicle assembly. Finally, Figure 6c shows that the energy that is consumed in the production phase of a vehicle is dominated by the mining and material production processes, which represent 68% of total consumption, followed by the part production processes, at 19%, and vehicle assembly, at 13%.

**Figure 5.** Mass of materials and resources consumed in automobile production.

Figure 7 shows the energy consumption of each productive process of vehicle production. The figure is divided into mining-material production, part production, and vehicle assembly processes. It can be seen that 82% of the total coal is consumed in the steel production processes, 28% electricity in the alumina reduction process, and 26% natural gas in the plastic fabrication processes, showing a demand concentration of determinate resources in specific facilities.

**Figure 6.** Energy consumption in vehicle production:(**a**) by material; (**b**) by energy resource; (**c**) by productive phase; (**d**) by material and energy resource.

**Figure 7.** Energy consumption in each productive process.

Finally, the first chart of Figure 8 shows the energy that is required to produce each type of vehicle part per kg of material; those constants have generally been defined in previous studies as embodied energy [5,15]. The proposed energy consumption values could vary widely by part, despite being produced by the same material. More conspicuous are the parts that are made by steel, where the energy that is required to produce forged products doubles that needed to elaborate the stamped ones. Moreover, aluminum parts are the most energy-intensive parts. Figure 8 shows the energy that is required to produce each type of part per unit of vehicle. It can be seen that the stamped steel parts consume the major volume of energy (23%) necessary for the production of vehicles, followed by cast and machined aluminum products (13%).


**Figure 8.** Energy required for the production of each type of vehicle part.
