## 3 Feedstock  
### Powder Production  
The powder preparation stage represents the most significant environmental impact in PBF-LB/M, primarily driven by the high electricity demands associated with the process, contributing to substantial fossil fuel depletion [39,40]. The carbon footprint of metal powder production is largely influenced by the choice of feedstock, with each option exhibiting a distinct environmental impact. These variations are primarily driven by factors such as the energy required for raw material extraction, subsequent processing, and transportation-related emissions. The primary manufacturing methods for AM powders include water atomization (WA), gas atomization (GA), plasma atomization, centrifugal atomization, and various other specialized metal powder production techniques. WA represents the highest-volume production process. In this method, a stream of molten metal is fragmented by high-pressure water. Due to the rapid cooling, the resulting metal droplets do not have sufficient time to spheroidize, leading to irregular particle shapes. Under optimized processing conditions, however, non-spherical powders can be used effectively in AM to produce parts with mechanical properties comparable to those of high-strength wrought materials, significantly broadening the range of viable raw materials [41,42]. Research by [PERSON] and [PERSON] [43] indicates that WA for powder production typically consumes around 6.48 MJ/kg (1.8 kWh/kg), with energy requirements significantly influenced by the melting point of the metal being processed. Conversely, GA utilizes a high-pressure gas stream to break a molten metal stream into fine droplets. These droplets then free-fall through a chamber, solidifying before collection. Surface tension during the fall allows the droplets to assume a spherical form. The alloy composition is prepared in a melting furnace using various raw materials, providing flexibility in formulation. This process yields powders with exceptional purity and favorable flow characteristics. Additionally, particle size can be controlled by adjusting parameters such as metal flow rate, gas pressure, gas flow, and nozzle design. To prevent oxidation, inert gases such as nitrogen or argon are typically employed. Notably, approximately 95% of the carbon footprint associated with GA is attributable to gas consumption during the atomization process [21; 44]. In a study by [PERSON] et al. [45], the energy required for GA AlSi10 powder was found to be 8.1 MJ/kg (2.25 kWh/kg), underscoring the significant energy demands of this process. Other studies show that aluminum powder production by GA can consume up to 42 MJ/kg (11.5 kWh/kg), resulting in approximately 5 kg of CO\({}_{2}\) emissions per kilogram of aluminum produced [21; 44]. Yields for PBF-LB/M powders are typically 20 to 40%, depending on gas die configurations, such as free-fall or close-coupled systems. Particles that fall outside the target size range are discarded, driving energy use beyond 180 MJ/kg (50 kWh/kg) and CO\({}_{2}\) emissions over 25 kg per kilogram of usable PBF-LB/M aluminum powder. To optimize gas consumption in the gas atomization process, [PERSON] and [PERSON] [46] have developed an advanced technique employing a Venturi nozzle [47]. This method utilizes carbon dioxide to generate aluminum powder at an exceptionally low pressure of 0.5 bar. It offers a cost-effective and energy-efficient solution, while also being environmentally sustainable, thus presenting significant potential for industrial application. Plasma atomization employs plasma torches to melt metal wire, with the resulting droplets being cooled and collected in a manner similar to gas atomization. This process is inherently more energy-intensive than gas atomization due to the high temperatures required to sustain the plasma arc. In contrast, centrifugal atomization involves the rapid spinning of molten metal to generate powder particles.