## 3 Feedstock
### Powder Obtained by Secondary Raw Material  
Given that mining and primary production are the primary sources of energy consumption in AM using PBF-LB/M technology [33; 54], the use of secondary materials as raw input for powder production has become a critical focus of both academic and industrial \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Technique** & **Process** & **Energy Source** & **Feedstock** & **Particles Shape** & **Equipment Cost** \\ \hline \multirow{8}{*}{**Category**} & Water atomization & Induction heating & Scrap or ingot & Irregular & Low to Medium \\ \cline{2-6}  & Gas atomization & Induction heating & Scrap or ingot & Spherical & Medium to High \\ \cline{2-6}  & Centrifugal atomization & Induction heating & Scrap or ingot & \begin{tabular}{c} Spherical to slightly irregular \\ (semi-spherical) \\ \end{tabular} & Medium \\ \cline{2-6}  & Ultrasonic atomization (rePowder) & \begin{tabular}{c} Induction heating/Plasma \\ \end{tabular} & Any form & Highly spherical & Medium \\ \cline{2-6}  & Plasma atomization & Plasma & Wire & Highly spherical & High \\ \hline \multirow{8}{*}{**Category**} & Plasma & Plasma & \
\begin{tabular}{c} Irregularly \\ shaped powder \\ particles \\ \end{tabular} & Highly spherical & High \\ \cline{2-6}  & \multirow{2}{*}{**Category**} & Microwave- & \multirow{2}{*}{Plasma} & Any form & Highly spherical & High \\ \cline{1-1} \cline{3-5}  & &
\begin{tabular}{c} Cold \\ mechanically \\ derived (Direct \\ powder) \\ \end{tabular} & Mechanical work & Metal rod & Irregular & Medium \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Overview of metal powder production techniques with key process details, feedstock types, particle shapes, and equipment costs. research. Conventional alloy feedstocks used for metal powder production entail substantial energy consumption and significant carbon emissions throughout the production chain. This challenge encompasses global logistics, including transportation, melting, and forming of materials into billets, bars, coils, or wire feedstock, and extends to the energy-intensive refinement of ones into elemental metals, a process that heavily depletes natural resources. Relying solely on virgin raw materials for powder production not only drives up costs but also amplifies environmental impacts, particularly as demand for metal powders continues to rise. Contrary to the common misconception that all metal powders are derived from virgin primary metal stocks, the industry has evolved significantly in recent years. It is now widely recognized that some metal powders are produced from recycled secondary feedstock. The economic advantages of utilizing qualified scrap over virgin raw materials are considerable, largely due to the reduced energy requirements. Substituting virgin raw materials with scrap feedstock can significantly lower CO2 emissions, with reductions of several kilograms of CO2 per kilogram of alloy produced. The primary challenge moving forward is ensuring that scrap materials meet the necessary size and chemical composition specifications. Aluminum alloys can be engineered for enhanced recyclability without a significant loss in properties. This increased recyclability decreases the need for raw material extraction and processing, thereby minimizing the overall environmental impact. Continuum's advanced technology leverages only secondary metal materials to produce high-quality AM-grade powder, achieving up to an 80% reduction in carbon emissions compared to conventional metal recycling methods [55]. The powder is sourced entirely from recycled metals and is manufactured using 100% renewable energy and upcycled, purified argon gases. rePowder, developed by Amazemet, is an advanced research platform that leverages patented ultrasonic technology to produce high-quality AM-grade powders from a wide range of alloy systems [56]. This system generates powders with a narrow particle size distribution, with up to 80% of the output ready for immediate processing.