## 4 Results and Discussion
### Role of AM in Reducing Green Wastes  
AM has made a significant contribution to minimizing environmental damage by reducing green waste. Although the issue of energy consumption needs to be addressed, most of the green waste can be eliminated through AM. Table 3 shows the relationship between AM and green waste. Despite the benefits of AM with respect to waste reduction, it is important to mention that not all materials can be manufactured via additive manufacturing and that not all AM materials can be easily recovered or recycled. For instance, polylactic acid (PLA), a biopolymer made from plant materials, finds applications as AM filament feedstock material but does not degrade under ordinary conditions, thereby constituting waste at the end of its life [89]. Furthermore, AM also produces waste in the form of failed prints, destructive prototypes, and leftover materials [90; 91; 92; 93]. The properties of recycled materials such as plastic are often affected by factors such as ultraviolet radiation, contamination during waste collection, and the degree of degradation during processing [94]. In addition, the volume of waste generated may increase for AM techniques such as wire-based direct energy deposition, where materials must be machined to produce a near-net shape [1]. When producing highly complex parts with AM, support structures are used to ensure that the desired shapes are attained. However, these support structures are discarded after the printing process [95]. This leads to material wastage. Another concerning issue is the toxicity of some of the AM materials. For example, powder bed fusion processes such as selective laser melting utilize metal powders that are toxic and highly flammable [48]. Also, photopolymers that are used in processes such as stereolithography release volatile organic compounds that are toxic in nature [96]. It should also be noted that the process of producing metal powders is energy-intensive in nature [97]. This raises environmental concerns, and there is a need for further study on the usage of sustainable materials. Most thermoplastics used in extrusion processes such as fused deposition modelling are often difficult to effectively recycle. This is because of contamination and degradation \begin{table}
\begin{tabular}{c c c} \hline \hline
**Green Waste** & **Contribution/Impact of AM** & **Reference** \\ \hline Excessive water usage & The concept of green packaging through AM & \\  & can lead to a 90\% reduction in the amount of & The report of the World Economic Forum [31]. \\  & water required for production. & \\ \hline Greenhouse gases & Reduces the CO\({}_{2}\) emissions due to the & [PERSON] et al. [1], [PERSON] et al. [71] \\  & methods used and reduced transportation. & \\ \hline Excessive power usage & Reduction in the consumption of electricity. & [PERSON] and [PERSON] [49], [PERSON] et al. [70], [PERSON] et al. [71], [PERSON] and [PERSON] [74], [PERSON] and [PERSON] [83]. \\ \hline Pollution & Pollution is reduced through the use of & [PERSON] et al. [1]. \\  & biodegradable, organic, non-toxic substances. & [PERSON] et al. [1]. \\ \hline Excessive resource usage & Less resource usage as the exact amount & [PERSON] et al. [1], [PERSON] et al. [70] \\  & is used. & \\ \hline Environmental impacts & \begin{tabular}{c} AM has the potential to reduce \\ environmental impacts such as abiotic \\ depletion, acidification, global warming, \\ eutrophication, terrestrial, marine and \\ aquatic ectoxicity \\ \end{tabular} & [PERSON] et al. [87] \\ \hline Poor health and safety & \
\begin{tabular}{c} AM increases the automation levels, making \\ the process safe and saving lives. \\ \end{tabular} & [PERSON] et al. [1]. \\ \hline Rubbish &
\begin{tabular}{c} Reduces the amount of rubbish as the \\ thermoplastic and other materials can be \\ recycled and reused. \\ \end{tabular} & [PERSON] et al. [1], [PERSON] et al. [71], [PERSON] et al. [88]. \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Role of AM in reducing green waste. that occurs during the printing process [98].