## 3 Sustainability of Additive Manufacturing
### Sustainability Assessment
#### 3.3.1 Economic Impacts of AM  
The economic features are in different forms and numerous sustainability-related evaluations can be integrated and utilized in order to reduce production cost [11]. The economic benefits mostly reflect efficiency improvement of design and manufacturing rather than avoiding the tooling costs. In addition, reduction in idle time between design and manufacturing stages and the time between different manufacturing steps will result in a cost reduction. Based on the literature, energy consumption in transportation can lead to a significant saving of $56-$219 billion by 2025, while lightweight components are fabricated [13]. AM technology makes minimum waste because only the needed materials are consumed [18]. Considering all these modifications, AM processes themselves, enjoy lower input materials, less waste, and a shorter supply chain that all together, would provide a saving of $113-$370 billion by 2025 [123]. [PERSON] et al. [133] reported that the AM market grew to $3.07 billion in 2013 and it is predicted that it will grow to around $10.8 billion in 2021. In another report by [PERSON] [134], it is estimated that cost reductions will range from $170 to $593 billion by 2025, for the markets with a great potential of AM processes, such as medical, aerospace, and tool making. [PERSON] et al. [135] investigated the markets related to AM as follows:  
(1) By 2025, the potential of the mid-term global market of AM is predicted to be $230-$550 billion;  
(2) The main markets for AM are consumer products ($100-$300 billion), the products related to medical components ($100-$200 billion), and finally tool and mold industries ($30-$50 billion).  
AM has become the subject of numerous research due to the promising industrial potential which is started from product prototyping to industrial end-user applications [136; 137; 134]. The market evolution, supply chain management, production, and machinery costs are some aspects of economic dimensions, as shown in Figure 9. There are three main aspects of the economics of AM, which are as follows [138]:  
**1. Measuring the value of the products:** The definition of added value involves all aspects related to materials, machining process, and other purchased items for production. In fact, added value can raise the value of the production output with considering all taxes, employees' salary, and gross operating as well. [PERSON] et al. [139] estimated that spare parts sales for AM products were $1.307 billion in 2014 around the world while the USA has the largest portion of this amount with $498 million. As a result, the global value-added to the AM process totaled $667 million in 2014, which is 0.01% of the global manufacturing value-added [138].  
**2. Estimating the adoption and distribution of AM technology:** A firm needs various resources (such as labor, natural resources, and other items required for production process), established processes, and adequate capabilities (such as controllability, flexibility, and integration) in order to make products and services [140]. AM technology has great influences on a firm's capabilities. Accordingly, controllability and flexibility are the principal challenges of any firm that AM can  
Figure 9: Sustainability dimensions of additive manufacturing [117].  
positively improve. AM technology has high controllability, which makes it greatly attractive for more firms as well. Regarding the literature [138], it is estimated that AM business will surpass $4.4 billion in 2020, $16.0 billion in 2025, and $196.8 billion in 2035, therefore, it is required to deviate from its present trends of adoption.