# A Knowledge Graph Framework to Support Life Cycle Assessment for Sustainable Decision-Making
## 4 Case Study: 3D Printing
### Relevance of 3 DP in Advancing Sustainability  
3 DP is anticipated to continue its rapid growth due to several key advantages over traditional manufacturing technologies. These benefits include enhanced freedom of design [47], allowing the creation of intricate and innovative structures, as well as rapid prototyping [48], which accelerates product development cycles. Furthermore, 3 DP supports mass customization and the production of complex structures tailored to highly specific requirements [49; 50], allowing manufacturers to meet diverse consumer demands with unprecedented precision. Other notable advantages include one-piece fabrication using multiple materials and the potential for decentralized production, which reduces the reliance on centralized manufacturing hubs and facilitates localized production [49]. In the construction sector, 3 DP has emerged as a sustainable and eco-friendly production technology [46; 49; 50], offering environmental benefits over traditional methods. Its adoption in construction not only supports greener practices but also addresses critical sustainability challenges. Among the most significant environmental advantages of 3 DP are the following:  
* Waste reduction: 3 DP fabricates products layer by layer, utilizing only the material required to create the final product [49]. This approach results in substantial material savings and significantly reduces waste generation [46; 51]. * Production on demand: 3 DP enables the production of only the necessary quantities of a product when needed, thus minimizing the need for large inventories and reducing the risk of overproduction [50]. * Reduction in transportation: The potential for local production allows products to be manufactured closer to their point of use, thus reducing the distances the goods need to travel. This leads to lower transportation costs and reduced emissions associated with transport [46; 51]. * Efficient use of resources: by promoting more efficient use of resources, as well as enabling recycling and remanufacturing processes, 3 DP aligns closely with the principles of a circular economy [49]. * Efficient use of energy: 3 DP reduces overall energy demands [46; 49; 52]. This efficiency contributes to the adjustment of energy structures, supports circular economy strategies, and encourages the transformation and upgrading of industrial structures [49]. * Reduction of emissions: Process-related CO\({}_{2}\) emissions per unit of GDP can be significantly reduced by adopting 3 DP, contributing to lower carbon footprints [46; 52]. Nevertheless, in evaluating these prospective advantages, it is crucial to also account for the adverse effects on the environment that may arise from the implementation of 3 DP technology. One of the primary concerns is the energy consumption of 3D printers, particularly those that work with high-temperature materials or metal powders. These printers often require significant amounts of energy to operate. If this energy is sourced from non-renewable resources, associated carbon emissions can contribute substantially to climate change [53]. Moreover, the environmental implications of emissions produced throughout the printing process constitute an additional area of concern. Specifically, the thermal melting and subsequent extrusion of plastic materials can emit volatile organic compounds (VOCs), along with ultrafine particulate matter, into the atmosphere. These emissions are identified as harmful, posing significant risks to both human health and the broader environment [53]. Additionally, there exists a considerable deficit in the comprehensive understanding and assessment of the overall environmental repercussions associated with 3 DP technologies. Although its technological and economic advantages are frequently discussed, comprehensive investigations of its environmental performance remain limited [3].