## 3 Measuring the benefits and costs of applying the technology:
#### 3.3.2 Environmental Impacts of AM
Accordingly, the definition of a product or process, and the system boundary should be determined as well. Then, the next step is input or output inventory analysis (Life Cycle Inventory: LCI). All input (material, energy) and the resulting outputs (waste, emissions) should be identified and accordingly quantified. After that, the other step (third) consists of the Life Cycle Impact Assessment (LCIA methods such as Impacts 2002+, Eco-Indicator 99, or CML) for achieving the outcome of the quantified inputs and outputs on the ecosystem and human health. In the last step, the consequences could be controlled by the interpretation of the system [157]. LCA is the most commonly used approach for measuring the environmental impact for the entire life cycle of the product [158], from the purchase of raw materials to fabrication, use, and disposal [157; 159] (see Figure 11). Figure 11: Life cycle phases [157]. Figure 10: Conceptual framework of life cycle analysis (LCA) [153]. In order to have a more accurate understanding of the material, process and energy consumption and production wastes and disposal can be taken into account to estimate the environmental performance of the production process [160]. In recent years, numerous studies have been conducted about the LCA method and its applications. Based on LCA investigations, some AM processes, e.g., Laser Engineered Net Shaping (LENS), Construction Laser Additive Direct (CLAD), and Direct Metal Deposition (DMD), are very environmentally friendly compared to traditional manufacturing processes [11]. [PERSON] et al. [161] quantified the life-cycle energy and greenhouse gas (GHG) emissions savings potential of AM production for metal-based aircraft parts in the US. Based on the results, energy savings for AM processes is estimated to reach 70-173 million GJ/year in 2050 with a reduction in cumulative GHG emission which is predicted to be around 92.1-215.0 million metric tons. Many studies have investigated the energy consumption and they only depend on the electrical consumption of AM machines during the production process. Contrary to these studies, [PERSON] et al. quantified AM processes with its accuracy of inventory data through the production phase of the life cycle of products. They proposed a generic approach for purchases and characterization of inventory of AM processes. Their methodology relied not just on electrical energy, it is also depending on material consumption. They also investigated the environmental impact of AM according to life cycle inventory data, which are related to energy, material, and fluid. Ultimately, they proposed a predictive model and provided a novel methodology for the combination of technical, environmental, and economic assessments [162]. [PERSON] et al. presented an innovative methodology to measure the environmental impact of its CAD model for having more accuracy. Their methodology focused not just on electrical consumption but on material and fluid consumption as well, and it consequently contributes to the environmental impact. Furthermore, this methodology applies a set part process, which leads to considering various production strategies and the resulting influence on the universal environmental impact. The methodology was according to both analytical and experimental models [163]. [PERSON] et al. also proposed another methodology that all consumptions including fluids, electricity, and material, were considered in the evaluation of the environmental impact. This method evaluates the consumption amount in the machine using a sustainable approach. The method was defined based on a predictive model of the consumption from the CAD model of the part and the manufacturing path [155].