Sustainable Additive Manufacturing: An Overview on Life Cycle Impacts and Cost Efficiency of Laser Powder Bed Fusion

Abstract

This overview study investigates integrating advanced manufacturing technologies, specifically metal additive manufacturing (AM) and laser powder bed fusion (LPBF) processes, within Industry 4.0 and Industry 5.0 frameworks, to enhance sustainability and efficiency in industrial production and prototyping. The manufacturing sector, a significant contributor to global greenhouse gas emissions and resource consumption, is increasingly adopting technologies that reduce environmental impact while maintaining economic growth. Selective laser melting (SLM), as the subsection LPBF technologies, is highlighted for its capability to produce high-performance, lightweight, and complex components with minimal material waste, thus aligning with circular economy goals for metal alloys. Life cycle assessment (LCA) and life cycle costing (LCC) analyses are essential methods for evaluating the sustainability of any new technology. Sustainable technologies could support the concepts of the factory of the future (FoF), fulfilling the requirements of digital transformation and digital twins. This overview study reveals that implementing AM—specifically SLM—has the potential to reduce the environmental impact of manufacturing. It underscores the ability of these technologies to promote sustainable and efficient manufacturing practices, thereby accelerating the shift from Industry 4.0 to Industry 5.0.

1. Introduction

Sustainability in industrial production is important as it directly impacts environmental emissions and global climate change [1,2]. The manufacturing sector, being resource- and energy-intensive, is a significant contributor to greenhouse gas emissions, accounting for approximately 25% of global anthropogenic emissions [1], 15% of global energy consumption [3], and 35–40% of global material consumption [3,4]. The rising atmospheric temperatures and increased toxic emissions emphasize the urgent need for more sustainable manufacturing practices to mitigate these environmental impacts [5]. To address these challenges, advanced technological solutions are being integrated into manufacturing processes developing a new generation of industry called Industry 4.0 [6]. Industry 4.0 focuses on adopting specific technologies to enhance manufacturing efficiency [6,7]. These technologies include artificial intelligence (AI) for improving maintenance practices, sensors and advanced communication technologies for real-time production monitoring, and other advanced technological enablers like augmented reality, virtual reality, robotics, and the Internet of Things (IoT) [8]. Industry 4.0 is followed by the next generation of industry, named Industry 5.0. In contrast to Industry 4.0, Industry 5.0 takes a more holistic approach by integrating these advanced technologies into complex systems that prioritize human involvement and sustainability. These systems must include humans in developing advanced digital capabilities and measuring the impact of decisions on the organization and its environment to improve sustainability and be future-oriented [6,8]. Sustainability is a crucial component in Industry 5.0 [9], emphasizing circular processes, prioritizing resource reuse, reducing waste, and minimizing environmental impact. Therefore, novel technologies are crucial in achieving the sustainability goals in Industry 5.0.

Additive manufacturing (AM) is a layer-by-layer production process based on digital models, revolutionizing manufacturing by enabling complex geometries unattainable with traditional methods, a key driver of sustainable manufacturing, for the future industrial landscape [10,11]. Among AM techniques, laser powder bed fusion (LPBF) stands out for its precision and strength in metal and alloy applications. LPBF employs a laser to selectively melt and fuse powdered material, building components layer by layer. Key LPBF methods include selective laser melting (SLM) and direct metal laser sintering (DMLS). SLM fully melts metal powder to create parts with a homogeneous, near-fully dense structure, whereas DMLS relies on sintering, resulting in slightly different material properties such as increased porosity and reduced density [12,13]. LPBF contributes to sustainability by minimizing material waste, enabling the reuse of recycled powders, and producing lightweight components that reduce energy use across their lifecycle. Advances in LPBF align with Industry 5.0 goals, prioritizing efficiency and environmental responsibility.

Measuring the environmental performance of any technology is crucial to ensure that industrial practices align with sustainability goals [14]. By focusing on the environmental impacts and efficiencies of new technologies, the manufacturing sector can achieve significant reductions in emissions while maintaining economic growth. Life cycle assessment (LCA) is a very popular tool for the investigation of sustainability in various technologies [15,16]. As manufacturing technologies develop, there is a growing recognition of the need to conduct LCA studies to gain a more comprehensive understanding of its environmental impacts. It is widely believed that as the number of stages in production increases, the environmental impacts also increase accordingly. Also, it is important to note that novel technologies are not essentially more sustainable. Novel technologies may bring more technological advancements at the cost of sustainability deterioration. Also, sometimes new technologies reduce the environmental impacts in one sector but shift it to another sector. Therefore, there is always a need for assessing the environmental performance of any technology throughout its life cycle. This work provides an overview of LPBF as a human-centric technology (HCT), examining its benefits and limitations compared to conventional manufacturing methods. It explores the LCA and LCC of LPBF to show its alignment with Industry 5.0 principles. This overview aims to support the integration of LPBF into Industry 5.0 frameworks and contribute to the standardization and analysis of its procedures.

2. Additive Manufacturing (AM)

2.1. Metal Additive Manufacturing

Traditional widely used manufacturing method relies on formative or subtractive manufacturing (SM), where materials are shaped through casting, deformation, or gradual removal to achieve the desired geometry. These methods, however, are limited by topology constraints based on part geometry or mold complexity, especially for prototyping. As opposed to SM, Additive Manufacturing (AM) is a modern process of creating objects. The distinctions between AM and SM are substantial. AM builds objects by “adding” layers of material incrementally. In contrast, SM shapes an object by “removing” material from solid blocks. This contrast is particularly evident in metallic compound fabrication, especially when dealing with complex porous structures and time-intensive processes, requiring extensive post-processing. Figure 1 illustrates the main categories of material fabrication methods, providing an overview of the SM and AM and their subsets.

It is widely believed that AM technology has revolutionized manufacturing by enabling the production of complex geometries that are difficult or impossible to achieve with traditional methods, and it is believed that AM is expected to become a key manufacturing technology in the sustainable society of the future [17]. Adding layer-by-layer makes AM ideal for high-tech fields like aerospace [18] and biomedical engineering [19], enabling the production of customized, complex parts in bulk or porous forms. AM also supports topology optimization [20,21], which removes unnecessary material, resulting in lightweight yet strong structures without compromising functionality. This Feature of AM has made it an interesting technology in the food industry as well. It is believed that AM could support the customized fabrication of food products and personalized nutrition [22,23,24,25]. AM leads the way for the factory of the future (FoF), where unprecedented efficiency, sustainability, and advanced remote collaboration become standard practices [26]. Central to this transformation are the interconnected concepts of digital transformation (DTR) and digital twins (DTW), which play critical roles in shaping FoF [27]. These technologies can be seamlessly integrated into AM processes, offering capabilities that are not feasible with traditional SM methods.

As shown in Figure 1, AM encompasses a variety of techniques, with each having its applications and advantages. One key category within AM is LPBF [6,28]. LPBF uses a laser to selectively melt and fuse powdered material layer by layer to build a part [29]. This process is known for its ability to produce high-precision and high-strength components. LPBF includes several specific methods, among which selective laser melting (SLM, for near-fully dense structures) and direct metal laser sintering (DMLS, for slightly lower densities) are particularly prominent [6,30]. SLM is a well-known type of LPBF where a high-power laser is used to completely melt the powdered material, resulting in fully dense parts [29]. SLM allows us to produce parts with excellent mechanical properties and complex geometries widely used in industries that require high-performance components, such as aerospace, automotive, and medical implants [31].

2.2. Selective Laser Melting of Metal Alloys

In the SLM process, common alloys of titanium, iron, aluminum, and copper are frequently used due to their unique properties and compatibility with AM [32]. Ti-6Al-4V, the most widely used titanium alloy in SLM, is known for its excellent strength-to-weight ratio, corrosion resistance, and biocompatibility, making it suitable for aerospace, medical, and automotive applications [32,33]. Ti-6Al-7Nb is an alternative to Ti-6Al-4V, particularly in biomedical applications due to its enhanced biocompatibility [34]. Stainless Steel 316L (1.4404) is popular in SLM for its corrosion resistance and ductility, commonly used in medical and industrial applications, and 17-4 PH (1.4542) offers higher strength and hardness, suitable for tooling and aerospace applications. Maraging Steel 18Ni-300 (1.2709) is known for its high strength and toughness, often used in tooling applications.

In addition to titanium and iron alloys, which have been popular since the early days of 3D metal printing, aluminum and copper are emerging as the next frontier but come with greater challenges [35]. Al and Cu are highly reflective to laser wavelengths used in SLM, causing poor energy absorption, which limits melting efficiency and process stability. Also, both metals have high thermal conductivity, leading to rapid heat dissipation. This can cause uneven melting, residual stresses, and warping in parts. AlSi10Mg is a widely used Al alloy in SLM due to its lightweight nature, good mechanical properties, and excellent processability. It is common in aerospace, automotive, and lightweight structures. On the other hand, the pre-alloying of pure copper is so common for the easy control of factors and is used for a wide range of applications like antiviral and antibacterial compositions [36,37]. CuCrZr (copper-chromium-zirconium) alloy offers better processability than pure copper in SLM while maintaining good conductivity, often used in electrical and heat-exchange applications. Alloyed and gas-atomized CuSn10, CuAl10, CuCrZr, and CuNiSiCr are the main copper-based powders and candidates for evaluating advancements in both SLM devices and production processes. Figure 2 showcases CuSn10 samples, including lattice structures designed for thermo-electrical applications and solid, non-post-processed parts used as fracture-tensile test specimens, developed in the IPVC-CiTin additive manufacturing laboratory.

Regarding Figure 2, the entire 3D metal printing process—from powder alloying to object fabrication—should be considered for both assessment and improvement. This can be referred to as “raw material to final product” monitoring. The current focus on a limited set of elements such as Ti, Fe, Al, and Cu should be expanded to include a broader range of metals and their alloys. Metal AM research already emphasizes areas like porous structures, multi-materials, complex configurations, functionally graded materials, triply periodic minimal surfaces (TPMS), 4D printing, shape memory alloys, etc. [38,39]. These applications extend far beyond bulk objects, highlighting the advantages of AM over traditional SM methods. However, addressing technical challenges is equally critical for advancing AM technology to better align with industrial requirements. These challenges include optimizing build directions, controlling platform and chamber parameters, ensuring the quality of reusable powders, and integrating post-processing operations directly into LPBF systems as unified devices.

2.3. Development of SLM Devices over Time

Over the past two decades, the development of SLM devices has undergone significant advancements, driven by the growing demand for enhanced precision, speed, material versatility, sustainability, and customizable manufacturing solutions. These advancements not only address technical and operational requirements but also contribute significantly to environmental sustainability in manufacturing. Early SLM systems relied on low-power lasers, which restricted the range of processable materials and limited layer resolution, hindering their utility with high-reflectivity or high-melting-point metals. Modern SLM systems employ high-power fiber lasers, often exceeding 500 watts and, in some cases, reaching 1 kilowatt. These advancements improve the processing speed and resolution, allowing for the effective use of challenging materials like copper [40,41]. The increased laser power also enhances fusion depth, resulting in denser, structurally robust parts. Such improvements reduce material waste during failed builds and expand the applicability of technology, aligning with sustainability goals by minimizing resource inefficiencies.

The shift to multi-laser systems has dramatically enhanced productivity. Whereas early SLM systems were limited to single-laser configurations, modern setups often include multiple lasers, enabling faster build times and accommodating larger-scale or batch manufacturing. This advancement is particularly relevant for industries like the aerospace and automotive industries, where the time-efficient production of lightweight, complex parts reduces material usage and lifecycle emissions, contributing to sustainability through improved fuel efficiency in end-use applications. Material handling and efficiency have also seen significant advancements. Earlier systems were prone to powder waste and contamination due to basic handling mechanisms. Today’s SLM devices incorporate advanced powder recycling, sieving, and conditioning units, enabling the reuse of unused powder and reducing the reliance on virgin material. These enhancements are critical for expensive metals like titanium alloys, where cost savings and resource conservation align with broader environmental objectives.

Another key area of development is the expansion of build volumes. Early SLM systems featured small chambers that necessitated assembling multiple components for larger structures. Modern devices now offer industrial scale build platforms exceeding 1 cubic meter, enabling the production of larger parts in a single build. This reduces the need for assembly, streamlines post-processing, and lowers material waste, making SLM a practical solution for industries with demanding sustainability requirements, such as aerospace, defense, and energy. SLM systems now integrate advanced closed-loop monitoring systems that track critical parameters like melt pool characteristics, laser power, and chamber temperature in real time [42,43]. This capability enhances part quality and consistency, minimizes defects, and reduces waste, thereby improving the technology’s alignment with sustainability principles. Furthermore, the evolution of SLM software has enabled advanced design and simulation capabilities, including generative design and topology optimization. These tools allow for the creation of lightweight, optimized structures that reduce material usage and enhance energy efficiency in both production and application, directly addressing sustainability goals.

Advancements in inert gas flow mechanisms and thermal management systems have improved process consistency and reduced resource consumption. Modern systems optimize gas usage, reducing the environmental impact of auxiliary processes while maintaining part quality. Post-processing solutions, including in situ heat treatments and automated surface finishing, have also become integral to SLM workflows. By standardizing and automating these steps, SLM reduces labor and energy requirements, further aligning with sustainable manufacturing practices. Energy efficiency remains a core focus of SLM development. Manufacturers have implemented energy-saving technologies and sustainable practices to minimize the energy-intensive nature of the process. These efforts address both economic and environmental concerns, supporting global sustainability targets by reducing the carbon footprint (CF) of advanced manufacturing processes. Furthermore, the ability to localize production with SLM reduces transportation emissions, contributing to more sustainable supply chains. The evolution of SLM technology reflects a dual commitment to technological innovation and sustainability. Enhanced precision, material efficiency, energy utilization, and waste reduction collectively position SLM as a transformative tool for sustainable manufacturing. By addressing key industry and environmental challenges, SLM aligns with global efforts to reduce resource consumption and carbon emissions, making it an integral component of future sustainable industrial practices.

3. Metal Additive Manufacturing in Industry 5.0

3.1. Environmental Impacts and Sustainability of LPBF

LPBF technology has emerged as a critical tool in advancing environmentally sustainable manufacturing, offering substantial benefits in material efficiency, energy consumption, transportation emissions, lightweight structures, customization, and waste reduction. These advantages, which address key inefficiencies in traditional manufacturing, position LPBF as a transformative approach for achieving sustainability goals during both production and product use phases. One of the most significant advantages of LPBF lies in its material efficiency. Unlike traditional subtractive manufacturing methods that result in considerable material waste, LPBF allows for the precise placement of the material, significantly reducing excess and enabling the recycling and reuse of unmelted powder. This near-net-shape characteristic minimizes waste and optimizes resource utilization. Additionally, the process facilitates the efficient use of high-value materials like titanium alloys, reducing costs and resource consumption. These benefits align with broader sustainability goals, as noted by Huang et al. [44], who emphasize LPBF’s ability to reduce process scrap and enhance material efficiency.

Although LPBF is energy-intensive, it offers distinct advantages in energy utilization compared to traditional manufacturing. The ability to produce complex geometries in a single build eliminates the need for multiple production steps, such as assembly and extensive machining, which are often energy-intensive. LPBF reduces energy consumption across the product lifecycle by streamlining processes and minimizing material waste. Moreover, optimizing machine utilization and reducing idle energy consumption are critical for improving energy efficiency in LPBF operations. The localized production capabilities of LPBF further enhance its environmental sustainability by reducing transportation-related emissions. By enabling on-demand manufacturing close to the point of use, LPBF minimizes the need for extensive supply chains and long-distance shipping, reducing the number of operators like HCT and significantly lowering its carbon footprint (CF).

LPBF also excels in producing lightweight and complex structures that are often unattainable with traditional manufacturing methods. This capability is particularly beneficial in sectors such as the aerospace and automotive sectors, where weight reduction is crucial for improving fuel efficiency and reducing emissions over a product’s lifecycle. The ability to consolidate parts into a single build also reduces assembly steps and material waste, further amplifying the environmental benefits. The design flexibility inherent in LPBF technology allows for component optimization tailored to specific applications, which reduces material usage and extends product lifecycles. Customization minimizes the need for repairs and replacements, making LPBF an environmentally responsible choice. Studies [1] highlight the role of advanced design capabilities, such as generative and topology optimization, in reducing waste and improving environmental outcomes, ensuring that parts are both efficient and durable.

In addition to these benefits, LPBF’s additive nature significantly reduces waste during production compared to traditional subtractive methods. Unlike conventional machining, which generates substantial scrap material, LPBF builds parts layer by layer, minimizing material loss [45,46]. The ability to recycle unused powder further supports waste reduction efforts, making LPBF a material-efficient and environmentally conscious technology. By avoiding the energy-intensive production of tooling, reducing process scrap, and consolidating parts, LPBF addresses critical inefficiencies in traditional manufacturing processes. Its capacity to produce optimized components also delivers environmental benefits during the use phase, such as lower emissions due to improved fuel efficiency. Combined with its potential for localized production and resource efficiency, LPBF stands out as a cornerstone of sustainable manufacturing practices. However, challenges such as energy intensity and cost efficiency remain areas for further research and development. As technology advances, LPBF is poised to play an increasingly vital role in environmentally responsible industrial practices, driving innovation and sustainability across multiple sectors.

3.2. Literature Review on Sustainability Assessment of SLM

AM, particularly SLM, has garnered significant attention for its potential to reduce environmental impacts compared to SM methods. The increasing use of LCA in material sciences has provided a systematic approach to evaluating the sustainability of these technologies. Recent studies have investigated the environmental performance of SLM, identifying its advantages and limitations compared to traditional/subtractive methods. The relevant literature is reviewed, and key points are summarized in Table 1.

Peng et al. [47] conducted a comparative LCA study on the production of an industrial hydraulic valve using SLM and CM (casting and CNC machining). Their findings revealed that SLM reduced environmental impacts by 37.42% compared to CM, with further reductions of 10–23% achievable through optimization. However, powder preparation emerged as the most impactful life-cycle stage, driven primarily by high electricity consumption. The study recommended redesigning parts for lightweight performance and optimizing the SLM process to enhance sustainability. Electricity has been consistently identified as the dominant contributor to SLM’s environmental footprint. Faludi et al. [46] demonstrated that powder materials accounted for only 10–12% of impacts, while auxiliary systems such as chillers and electrical discharge machining (EDM) for part removal often consumed more energy than the printer itself. The study emphasized the importance of maximizing machine utilization and sourcing renewable energy to reduce impacts. Additionally, reducing idle power consumption and avoiding EDM were suggested as key strategies for improving environmental performance.

Ramadugu et al. [48] examined the environmental impacts of producing a rocker arm using SLM and CM. Without topology optimization, CM demonstrated 14.53% less environmental impact than SLM. However, when topology optimization was applied, SLM outperformed CM with 21.31% lower environmental impacts. This study underscored the energy-intensive nature of SLM as a primary contributor to its environmental footprint but highlighted the significant benefits achievable through design optimization. Kokare et al. [1] compared SLM, wire arc additive manufacturing (WAAM), and CNC milling to produce a marine propeller. WAAM is an AM technology that makes use of an electric arc as a heat source to deposit metal material layer-by-layer, which makes up the final part. WAAM demonstrated superior material efficiency and lower waste, establishing itself as a promising alternative. However, SLM’s energy intensity remained a concern despite its precision and ability to create complex geometries. CNC milling, while reliable, exhibited significant material wastage and higher environmental impacts. The study stressed the importance of balancing environmental and economic factors when selecting manufacturing technologies. The sustainability of SLM has also been evaluated through emergy-based methods. Emergy is defined as the available energy that was previously used, directly or indirectly, to produce a product or service [49]. Wang et al. [45] investigated the material and energy consumption, waste generation, and production efficiency of SLM. The study concluded that while SLM exhibits near-net-shape manufacturing characteristics with minimal material waste, it suffers from high energy consumption and resource demands. This leads to a low net emergy yield ratio and a high environmental load rate. The findings suggest that sustainability improvements require renewable resource utilization, better equipment efficiency, and reduced labor costs.

The environmental benefits of SLM extend beyond the production phase, particularly in terms of its use-phase advantages. For instance, Huang et al. [44] estimated that the adoption of lightweight additively manufactured parts in aircraft could reduce annual U.S. air fleet fuel consumption by 6.4% by 2050. Similarly, SLM enables the creation of conformal cooling channels in tooling, which can reduce injection molding cycle times and electricity requirements by up to 30%. These findings highlight the importance of considering both production and use-phase benefits when assessing SLM’s sustainability. However, the environmental costs associated with increased electricity demand, powder production, and inert gas use remain challenges for SLM. Gutowski et al. [50] emphasized that while the power requirements of SLM are within the typical range for manufacturing equipment, the slow process rate results in electricity intensity that is two orders of magnitude higher than that of traditional manufacturing methods. This underscores the need for innovations in process efficiency and material recycling to mitigate environmental impacts.

Comparative studies have provided additional insights into SLM’s sustainability. Telenko and Seepersad [51] demonstrated that while SLM has higher environmental impacts than injection molding for large production runs, it offers advantages for smaller batches due to reduced tooling requirements. Similarly, Priarone et al. [18] found that despite higher cradle-to-gate impacts, the use-phase fuel savings of lightweight SLM components often offset these initial disadvantages. Böckin and Tillman [52] extended the analysis to cradle-to-grave comparisons, demonstrating that lightweight designs enabled by SLM reduce fuel consumption and lifecycle emissions. In aerospace applications, optimizing part geometry and material usage has resulted in lower cumulative energy demand compared to traditional methods.

Despite its energy intensity, SLM consistently demonstrates potential for reducing material waste, enabling lightweight designs, and minimizing upstream environmental impacts. Electricity consumption, powder production, and auxiliary equipment remain the primary contributors to its environmental footprint. Studies by Liao and Cooper [53] highlight the challenges of powder degradation and scrapping, which require further innovation in material handling and reuse. To fully realize the sustainability benefits of SLM, future research must address the trade-offs between environmental costs during production and long-term use-phase advantages. Additionally, targeted advancements in energy efficiency, material optimization, and process scalability are essential for improving its economic and environmental viability. These efforts will provide decision-makers with the comprehensive data needed to select the most sustainable manufacturing technologies for specific applications.

Table 1. Literature review on SLM sustainability assessment.

Authors	Technologies Investigated	Section Focused	Main Findings
Peng et al. [47]	SLM vs. CM (Casting and CNC machining)	Hydraulic valve	SLM reduced environmental impact by 37.42% compared to CM; optimization reduced impacts further by 10–23%. Powder preparation and electricity consumption were the largest contributors to impacts.
Ramadugu et al. [48]	SLM vs. CM	Rocker arm	Without topology optimization, CM had 14.53% less environmental damage than SLM. With optimization, SLM resulted in 21.31% less environmental damage than CM.
Kokare et al. [1]	SLM, WAAM, CNC milling	Marine propeller	WAAM showed better material efficiency and lower waste; SLM was energy-intensive but enabled complex geometries. CNC milling had high material wastage. Decision-making should consider environmental and economic aspects.
Guarino et al. [54]	SLM vs. CO2 Laser Cutting	316L stainless steel washer	LC was more cost-effective and eco-friendlier (2.5 times better) than SLM due to lower electricity and gas use. Advancements in SLM could improve its suitability for higher production rates.
Wang et al. [45]	SLM	Generic AM part	SLM exhibits low material waste but high energy consumption and a low net emergy yield. Sustainability improvements require renewable resources, better equipment utilization, and labor cost reductions.
Huang et al. [44]	SLM	Aircraft parts	Using lightweight SLM parts could reduce annual U.S. air fleet fuel consumption by 6.4% by 2050. Lightweight designs deliver use-phase environmental benefits, offsetting higher manufacturing impacts.
Huang et al. [55]	SLM vs. Traditional Manufacturing	Cooling channels in tooling	SLM-enabled conformal cooling channels reduce injection molding electricity requirements by 30%, offering significant energy savings during production cycles.
Gutowski et al. [50]	SLM vs. Traditional Manufacturing	Generic parts	SLM power requirements are within typical manufacturing ranges, but slow process rates result in electricity intensity two orders of magnitude higher than that of traditional methods.
Faludi et al. [46]	SLM	Aluminum turbine blade	Direct electrical energy requirements dominate cumulative energy demand (CED). Part nesting significantly reduces per-part environmental impacts.
Priarone et al. [18]	SLM vs. Traditional Machining	Aircraft bearing bracket	A 62% weight reduction from SLM offsets higher cradle-to-gate impacts through fuel savings in the use phase, achieving lifecycle environmental benefits within one year.
Böckin & Tillman [52]	SLM vs. Traditional Manufacturing	Diesel engine for truck	SLM reduced component weight, leading to use-phase fuel savings. The cradle-to-grave analysis demonstrated overall environmental benefits for transportation applications.
Baumers et al. [56]	SLM	Generic machine components	SLM environmental impact models show electricity consumption as the main driver. Use-phase improvements depend on part nesting and machine-specific recalibration.
Telenko & Seepersad [51]	SLM vs. Injection molding	Nylon parts	While SLM has higher environmental impacts than injection molding for large production runs, it offers advantages for smaller batches due to reduced tooling requirements.

Table 1. Literature review on SLM sustainability assessment.

Authors	Technologies Investigated	Section Focused	Main Findings
Peng et al. [47]	SLM vs. CM (Casting and CNC machining)	Hydraulic valve	SLM reduced environmental impact by 37.42% compared to CM; optimization reduced impacts further by 10–23%. Powder preparation and electricity consumption were the largest contributors to impacts.
Ramadugu et al. [48]	SLM vs. CM	Rocker arm	Without topology optimization, CM had 14.53% less environmental damage than SLM. With optimization, SLM resulted in 21.31% less environmental damage than CM.
Kokare et al. [1]	SLM, WAAM, CNC milling	Marine propeller	WAAM showed better material efficiency and lower waste; SLM was energy-intensive but enabled complex geometries. CNC milling had high material wastage. Decision-making should consider environmental and economic aspects.
Guarino et al. [54]	SLM vs. CO2 Laser Cutting	316L stainless steel washer	LC was more cost-effective and eco-friendlier (2.5 times better) than SLM due to lower electricity and gas use. Advancements in SLM could improve its suitability for higher production rates.
Wang et al. [45]	SLM	Generic AM part	SLM exhibits low material waste but high energy consumption and a low net emergy yield. Sustainability improvements require renewable resources, better equipment utilization, and labor cost reductions.
Huang et al. [44]	SLM	Aircraft parts	Using lightweight SLM parts could reduce annual U.S. air fleet fuel consumption by 6.4% by 2050. Lightweight designs deliver use-phase environmental benefits, offsetting higher manufacturing impacts.
Huang et al. [55]	SLM vs. Traditional Manufacturing	Cooling channels in tooling	SLM-enabled conformal cooling channels reduce injection molding electricity requirements by 30%, offering significant energy savings during production cycles.
Gutowski et al. [50]	SLM vs. Traditional Manufacturing	Generic parts	SLM power requirements are within typical manufacturing ranges, but slow process rates result in electricity intensity two orders of magnitude higher than that of traditional methods.
Faludi et al. [46]	SLM	Aluminum turbine blade	Direct electrical energy requirements dominate cumulative energy demand (CED). Part nesting significantly reduces per-part environmental impacts.
Priarone et al. [18]	SLM vs. Traditional Machining	Aircraft bearing bracket	A 62% weight reduction from SLM offsets higher cradle-to-gate impacts through fuel savings in the use phase, achieving lifecycle environmental benefits within one year.
Böckin & Tillman [52]	SLM vs. Traditional Manufacturing	Diesel engine for truck	SLM reduced component weight, leading to use-phase fuel savings. The cradle-to-grave analysis demonstrated overall environmental benefits for transportation applications.
Baumers et al. [56]	SLM	Generic machine components	SLM environmental impact models show electricity consumption as the main driver. Use-phase improvements depend on part nesting and machine-specific recalibration.
Telenko & Seepersad [51]	SLM vs. Injection molding	Nylon parts	While SLM has higher environmental impacts than injection molding for large production runs, it offers advantages for smaller batches due to reduced tooling requirements.

4. Analysis of LCA and LCC of SLM Fabrication

To visually represent the life cycle assessment (LCA) and life cycle costing (LCC) analysis of the SLM process, two diagrams are demonstrated. As an arbitrary example, copper-based fabrication is considered. Figure 3 represents the environmental impacts of the SLM process throughout its life cycle phases, which, in general, focus on energy consumption, raw material usage, emissions, and waste generation at each stage. Figure 3 is a casual illustration based on the previous studies and literature review in Section 3.1. Raw material extraction includes the mining and refining of metals or powders—for this case, refining, mixing, and alloying to achieve 90 wt.% copper and 10 wt.% tin for CuSn10 alloy. Material production considers powder preparation, alloying, quality check, packing, and transportation. LPBF Manufacturing is another factor and encompasses consumed energy by the laser and machines, environment control (especially temperature and moisture), cooling systems, and gas consumption. This is a more important issue when you set up the device in wintertime in countries like Portugal. Obviously, the maximal environmental impact happened in this stage. Product application of the manufactured parts based on energy efficiency or durability benefits is measured in this factor. In the case of the samples shown in Figure 2, solid samples will be used for crack growth and fatigue tests, while porous samples are intended for thermal management devices (TMDs). This approach has a minimal environmental impact, as the fabrication process produces an almost finished product, without the need for post-processing or dimensional checks. End-of-Life is related to the disposal, recycling, or reuse of powder materials, sensors, filters, platforms, etc.

Figure 3 shows the percentage difference between SLM and SM in energy consumption, global warming potential (GWP), water usage, and waste generation. This figure is generated based on LCA results reported in the literature. Figure 3 shows that SLM’s GWP and waste generation impacts are ≈33% and 96% lower than those of SM, respectively. This demonstrates that the primary advantage of SLM over conventional methods is the prevention of metal material waste. The improvement of energy consumption is a key aspect of the advancement of SLM devices, with each new generation being more energy-efficient, fast, and precise than earlier versions from over a decade ago.

Figure 4 highlights the distribution of costs across various stages in the SLM production approach. The cost of machining is the dominant cost driver, accounting for 41.1% of the total production cost. This is slightly higher than the machine-related cost of 39%, which includes expenses associated with purchasing, maintaining, and tooling machine tools. The labor cost, at 29%, emerges as another significant contributor, closely aligning with the stated 29% for operator activities in tasks like setup, processing, and cleanup. The post-processing cost, which encompasses activities like finishing and machine operation for post-production, contributes 26%. Comparatively, the consumables cost, representing expenses for items like electricity and shielding gas, accounts for a modest 2.1%. Lastly, the material cost, which includes raw materials like powders, is minimal at 1.5% and can be higher for alloying and special compounds. This analysis underscores that while the SLM approach is resource-efficient in material and consumable usage, the high costs associated with machining and labor dominate the overall cost structure.

5. LPBF Integration to Industry 5.0

5.1. LPBF Role in Carbon Reduction Strategies

LPBF technology is increasingly recognized for its potential to drive carbon reduction and support net-zero emission strategies. Through its inherent material efficiency, energy utilization, design flexibility, and capability for localized production, LPBF addresses key challenges of carbon emissions in manufacturing. This transformative approach to industrial sustainability is well supported by recent literature and data. Although LPBF does not directly capture carbon dioxide (CO₂), it aligns closely with carbon reduction goals by minimizing emissions through energy-efficient processes and material optimization. Unlike traditional methods such as casting and CNC machining, LPBF’s layer-by-layer fabrication significantly reduces material waste [45,47]. In LPBF, unused powder can often be recycled, reducing the energy and resource demands associated with material reprocessing, which are common in conventional manufacturing. Furthermore, LPBF avoids CO₂ emissions from protective gases, with its main emissions linked to electricity generation.

A key strength of LPBF is its ability to achieve exceptional material efficiency and waste reduction. Its near-net-shape manufacturing approach minimizes material usage, whereas optimized designs substantially reduce environmental impacts. By contrast, subtractive manufacturing methods generate significant waste, such as metal chips, which require energy-intensive recycling processes [1]. This efficiency is particularly beneficial for expensive materials like titanium, where reduced waste translates into both environmental and economic gains. While LPBF is energy-intensive during operation, it offers distinct lifecycle benefits by reducing downstream energy demands. For instance, its ability to produce complex geometries in a single build eliminates the need for multiple processing steps, such as machining and assembly, which are prevalent in conventional manufacturing. Studies [47] demonstrate that lightweight components manufactured with LPBF can reduce fuel consumption in applications like aerospace, offsetting the higher energy costs of production through improved use-phase efficiency. LPBF also excels in producing lightweight and topology-optimized designs, which are critical for enhancing energy efficiency during product operation. This capability is especially advantageous in industries such as the automotive and aerospace industries, where reducing component weight leads to lower fuel consumption and decreased CO₂ emissions. Traditional methods, such as casting and machining, often lack this design flexibility, resulting in heavier and less efficient parts.

Another significant advantage of LPBF is its potential for localized production, which supports carbon reduction by minimizing transportation-related emissions. As noted by Wang et al. [45] and Faludi et al. [46], decentralized, on-demand manufacturing reduces reliance on centralized production facilities and long-distance shipping, lowering the CF of supply chains. In contrast, conventional manufacturing processes often require centralized operations and extensive logistics, which increase their environmental impact. Moreover, LPBF indirectly contributes to carbon capture by enabling the production of high-performance, lightweight components that reduce emissions throughout their use phase. For example, the aerospace and automotive sectors benefit from topology-optimized designs that enhance fuel efficiency, as shown by studies like that of Huang et al. [44]. Additionally, LPBF facilitates advancements in carbon capture technologies by fabricating intricate geometries, such as high-performance membranes and catalysts, that improve CO₂ capture and conversion efficiencies. These relationships are summarized in Figure 5 below. Carbon capture, a process designed to reduce CO₂ emissions, involves trapping CO₂ before it escapes into the atmosphere, transporting it to designated sites, and securely storing it underground or in ocean formations.

5.2. SLM Advantages over Traditional Manufacturing

When compared to SM, including casting and machining, SLM demonstrates clear environmental and operational advantages, particularly in material efficiency, energy savings, and decentralized production capabilities. However, SM retains benefits in terms of lower upfront costs and suitability for simple geometries, making it preferable in specific scenarios. While SLM involves high initial equipment costs, these are often offset by long-term sustainability and operational savings, as discussed in the literature. SLM’s integration with Industry 5.0 principles further enhances its potential for achieving net-zero goals. Unlike SM, which aligns with Industry 4.0’s focus on automation and precision, SLM leverages digital tools such as rapid prototyping and digital twins to optimize energy and material use [45]. This emphasis on human-centric, AI-driven, and sustainable manufacturing strengthens LPBF’s role in modern industrial ecosystems.

Prajapati and Kumar [57] accentuated a versatile, sustainable manufacturing process enabling the production of complex geometries with minimal material wastage, requiring optimization for standardized and sustainable practices. It is essential to compare every new technology with conventional methods to evaluate its sustainability, climate change impact, and overall environmental footprint [58]. SLM provides a compelling alternative to traditional manufacturing technologies by reducing CF, supporting net-zero strategies, and advancing material and energy efficiency. Despite challenges like energy intensity and high initial costs, its alignment with sustainability principles and potential for continuous technological improvements make it a cornerstone of carbon reduction strategies. LPBF technology has emerged as a critical enabler in reducing carbon emissions and advancing net-zero strategies. As an advanced form of AM, SLM integrates material efficiency, energy optimization, and design flexibility to address environmental challenges inherent in traditional manufacturing. Its ability to align with principles of carbon capture and carbon neutrality underscores its transformative role in sustainable industrial practices.

While SLM does not directly capture CO₂, it minimizes emissions through energy-efficient operations and optimized material usage. Unlike traditional SM methods like casting and CNC machining, SLM builds parts layer by layer, significantly reducing material waste. Figure 6 shows the contribution of process stages in the environmental impact categories. The atomization stage is the hotspot of the environmental impacts. The atomization stage is the most resource-demanding in terms of energy consumption and water usage. The atomization stage also contributes to GWP at about 55% and to waste generation at about 64%. The SLM stage contributes to GWP at about 30%. This means that the SLM stage optimization is still required to reduce the GWP. In order to reduce the environmental impacts of the whole SLM process, it is important to reduce the impacts in the atomization stage significantly. Measure such as powder recycling would help to reduce the powder requirement and also contribute to the reduction in waste generation, therefore reducing the GWP. Previous studies [45,47] highlight the advantages of SLM in recycling unused powder and eliminating material losses common in SM, where waste such as metal chips requires energy-intensive reprocessing.

6. Discussion

The integration of advanced manufacturing technologies has revolutionized the industrial and biomedical sectors, particularly through the adoption of AM methods. Studies by Rahmani et al. [59,60] highlight AM’s unique capability to create multi-material, complex-shaped structures—such as triply periodic minimal surfaces (TPMS) and lattice architectures—designed for applications like biomedical applications, bone implants, scaffolds, and antibacterial materials. These innovations are unattainable through traditional SM methods, emphasizing AM’s role in structural optimization and sustainability. Advanced and relatively recent processes such as selective laser melting (SLM) and spark plasma sintering (SPS) can be combined to develop entirely new manufacturing methods, analogous to binder jetting (BJ)—also known as binder jet 3D printing (BJ3DP). Sustainability is reflected in the efficient use of materials, combining metals and ceramics to enhance durability, reduce resource wastage, offer the potential for permanent implanting, and extend the lifecycle of biomedical implants.

Material efficiency is a key advantage of SLM, as noted by Ramadugu et al. [48]. By employing near-net-shape manufacturing, SLM minimizes waste and enhances sustainability by using only the required material. This precision is particularly advantageous for high-value materials like titanium alloys, where waste reduction has substantial environmental and economic benefits. In contrast, SM processes generate significant waste and rely on larger material volumes, necessitating energy-intensive recycling stages that contribute to higher energy consumption and emissions. Despite SLM’s energy-intensive nature, its lifecycle benefits are profound. For example, lightweight aerospace components manufactured through SLM improve fuel efficiency, offsetting the energy costs of production and reducing greenhouse gas emissions. The design flexibility of SLM facilitates topology optimization, enabling the creation of lightweight, strong, and efficient geometries that SM cannot achieve. Faludi et al. [46] emphasize that SLM’s alignment with sustainability goals makes it particularly suitable for industries requiring high-performance components, such as the aerospace and automotive industries.

Nyamekyea et al. [61] reported that Industry 4.0 technologies, particularly additive manufacturing and simulation-assisted design, enable resource efficiency and sustainability by optimizing product designs, reducing waste, and enhancing energy and material usage, with a focus on laser powder for achieving sustainable manufacturing excellence. Gopal et al. [62] showed that AM, as a sustainable and innovative technology, offers significant material and energy savings while addressing environmental concerns and enabling efficient, flexible production, making sustainability a strategic priority for manufacturers. Wurst et al. [63] highlighted that the sustainability assessment of AM processes, particularly LPBF, relies on life cycle data and tools like LCA to evaluate ecological, economic, and social impacts, identifying gaps and opportunities for improved assessment methods across the product life cycle.

AM processes, including SLM, also support decentralized manufacturing, reducing transportation-related emissions. By enabling localized, on-demand production, LPBF minimizes logistical requirements, fostering more sustainable supply chains. Traditional SM, reliant on centralized facilities and large-scale production, exacerbates transportation-related carbon footprints. Furthermore, LPBF contributes to carbon capture through the development of lightweight, energy-efficient components and specialized geometries showcasing its broader sustainability impact. Standardized frameworks like ISO/ASTM 52910:2018 and ISO 14040:2006 [64,65] further facilitate the integration of AM and sustainability practices. ISO/ASTM 52910:2018 provides guidelines for incorporating AM into product design, ensuring efficient workflows and high-quality outputs. ISO 14040:2006 outlines principles for LCA, offering tools to evaluate environmental impacts comprehensively. These standards support the shift toward sustainable manufacturing practices and enhance the adoption of AM technologies.

It is worth noting that Selective laser melting (SLM), selective laser sintering (SLS), and direct metal laser sintering (DMLS) are metal 3D printing technologies that use lasers to build parts layer by layer, but they differ in their mechanisms and materials. SLM fully melts metal powders to create dense, solid parts, while SLS typically sinters powders, fusing them at a molecular level without fully melting. DMLS is often used synonymously with SLM but differs slightly, as it is optimized for alloys and typically involves sintering-like processes rather than full melting. Despite their differences, all three processes rely on similar core technologies, such as a laser system and a powder bed. Modern 3D printers from certain manufacturers, like EOS or TRUMPF [66,67,68,69], can support multiple processes, enabling a single device to handle both SLM and DMLS, though SLS is less common for metals and is usually reserved for polymers. Mid-sized and compact 3D metal printing devices designed for laboratory use, featuring a build volume of approximately 100–200 cubic centimeters and laser power ranging from 200 to 400 W, are increasingly preferred for modern industrial applications. These devices support multiple processes, are compatible with various metal alloys, and offer advanced features such as monitoring and remote-control capabilities, user-friendly software or applications, and precise control over part porosity and density.

A comparison between AM and SM, as summarized in

Table 2. Qualitative comparison of AM and SM across key performance metrics.

Item	Additive Manufacturing (AM)	Subtractive Manufacturing (SM)
Digitalization	Highly digitalized; requires 3D models, CAD/CAM integration, and digital workflow management.	Moderately digitalized; CNC machines rely on CAD/CAM, but manual intervention is often required for setup and operation.
Industry Integration	Emerging integration in aerospace, healthcare, and custom manufacturing sectors due to flexibility and customization.	Widely integrated in traditional manufacturing sectors, including automotive, machinery, and large-scale production.
Energy Consumption	Often higher energy consumption due to intensive electricity use.	Often lower energy consumption due to the low-energy-demanding machines.
Global Warming Potential (GWP)	Lower GWP due to reduced material waste and optimized production processes.	Higher GWP is due to material wastage and energy-intensive operations.
Production Cost	High for low-volume production due to material costs and machine expenses; decreases significantly with design complexity.	Economical for large-scale production; high initial tooling costs but lower costs per unit for large quantities.
Process Performance	Excellent for producing complex geometries, lightweight structures, and custom parts.	Superior for high-precision, high-strength, and large-scale components.

, underscores their respective strengths and limitations. AM excels in digitalization and customization, with technologies like LPBF leveraging tools such as digital twins and rapid prototyping to optimize material and energy utilization. This advanced digital integration aligns with Industry 5.0 principles, emphasizing human-centric design and resource efficiency. In contrast, SM, while dominant in traditional manufacturing due to cost advantages in large-scale production, is limited by its reliance on higher material volumes and centralized production chains, leading to greater emissions and resource consumption. From a sustainability perspective, AM, particularly SLM, demonstrates superior performance by reducing material waste, enabling lightweight designs, and consolidating production steps into energy-efficient processes. The enhanced digitalization and localized production capabilities of AM contribute to its reduced carbon footprint. SM, on the other hand, remains constrained by tooling limitations and higher lifecycle emissions.

7. Conclusions

Life cycle assessment (LCA) and life cycle costing (LCC) are crucial for advancing sustainable manufacturing in laser powder bed fusion (LPBF) and selective laser melting (SLM), key subsets of metal additive manufacturing (AM). These analyses provide a foundation for achieving sustainability goals by emphasizing renewable energy use, enhanced equipment efficiency, and reduced labour costs. The literature review of LCA studies of LPBF technologies shows that electricity consumption, powder production, and auxiliary equipment remain major contributors to the environmental footprint, though ongoing advancements in LPBF technology are reducing these impacts. While LPBF does not directly capture carbon, it reduces emissions and improves energy efficiency across a product’s lifecycle, supporting climate change mitigation and net-zero emission goals. Its application in small industries facilitates a shift from global transportation to localized, on-demand production. However, some studies show that LPBF may have higher impacts compared to traditional manufacturing, and lightweight LPBF components often offset these costs during use through fuel savings (e.g., electric vehicles and aerospace industry). The broader adoption of AM requires advancements in metal powder production, 3D printing devices, and process and post-processing standardization, alongside the integration of renewable energy sources to reduce environmental impacts, so-called “raw material to final product monitoring”.

Findings from recent literature revealed that SLM reduced environmental impacts by ≈38% compared to CM, with further reductions of 10–23% achievable through optimization. For LCA/LCC analysis, it is essential to evaluate the entire production process. For example, when comparing SLM with casting and CNC machining (CM) without topology optimization, CM exhibited ≈ 15% lower environmental impacts than SLM. However, when the optimization was applied, SLM outperformed CM, achieving roughly 21% lower environmental impacts. As AM/LPBF manufacturing technologies are relatively new, conducting comprehensive assessments like LCA/LCC and evaluating aspects such as sustainability, environmental impact, and large-scale metal fabrication capabilities remains challenging. However, preliminary estimates highlight the advantages of AM, particularly for prototyping, and its promising potential for the future of medium-sized industries. While LPBF involves high initial equipment costs, these are often offset by long-term sustainability and operational savings, as discussed in the literature.