## 4 Results and Discussion
### Role of AM in Reducing Green Wastes
& Potential for job creation. & Reduction in emissions, wastewater, hazardous material consumption and solid waste. \\ \hline \multirow{4}{*}{[PERSON] and [PERSON] [127]} & Organizations that adopt GM practices such as recycling reduced their production costs. & The reduction in negative environmental impacts increases the safety and health of workers. & Adoption of recycling, emission reduction and energy reduction practices reduce the negative environmental impacts. \\ \cline{1-1}  & Cost reduction and increase in ROI were attained through GM implementation. & The reduction in negative environmental impacts of workers. & Adoption of recycling, emission reduction and energy reduction practices reduce the negative environmental impacts. \\ \hline \multirow{4}{*}{[PERSON] et al. [128], [PERSON] et al. [44]} & Eliminating of overproduction by producing parts on demand. & Potential for job creation. & AM can process biodegradable materials which decompose without negatively impacting the environment. \\ \cl  
Figure 3 presents the lean-green-additive manufacturing overlap. The overlap shows complementary areas between LM, GM, and AM that are geared toward sustainable performance. The figure indicated that the combination of the lean-green-additive manufacturing approaches could be used to achieve a reduction in the manufacturing lead time, waste reduction, reduction in energy usage, product quality improvement, improvement in safety and health-related issues, reduction in pollution, decrease in inventory, and a reduction in the production costs. Sometimes, non-value-adding activities can result from other areas linked to manufacturing, such as poor layout, ineffective maintenance, supply chain disruption, and poor work and information flow, amongst others. However, this study assumes that no non-value-adding activities result from other areas linked to manufacturing apart from the ones from LM, GM, and AM. The environmental sustainability of AM is still an open debate in the literature [1]. However, there are several ways in which AM clearly contributes towards green manufacturing. Firstly, AM allows for the manufacture of objects to their net shape using a consolidated approach without tooling. When compared to traditional subtractive processes, this reduces the amount of material in manufacturing products [88]. Also, the environmental burden associated with making production tooling is eliminated [1]. The net shape approach helps in the development of optimized product designs with improved functionality [104]. Such designs ensure products are lighter in weight and more energy efficient, thus reducing the carbon footprint. The design freedom offered by AM enables the production of consolidated parts [71]. This reduces the environmental impact associated with producing fasteners and separate assemblies. \begin{table}
\begin{tabular}{c c c c} \hline \hline [PERSON] et al. [129], & & & Polymer materials used in AM can be recycled. This reduced the quantity of polymer waste in the environment. \\ \hline [PERSON] and [PERSON] [115] & Reduced transportation through localized manufacturing. & Potential for job creation. & AM can help to reduce E-waste by transforming it to sustainable filaments. \\ \hline \hline \end{tabular}
\end{table} 
Table 6: _Cont._  
Figure 3: Lean–green–additive manufacturing overlap.