This study conducts a Life Cycle Assessment (LCA) comparing Direct Energy Deposition (DED-Arc/M), also known as Wire Arc Additive Manufacturing (WAAM), with conventional subtractive manufacturing to determine the more sustainable method. A central goal of the research is to enhance the LCA methodology by addressing the challenge of data collection during the Life Cycle Inventory (LCI) stage. Specifically, the study aims to develop a calculation model capable of estimating resource consumption throughout the manufacturing process, thus eliminating the need for extensive data collection. This calculation model uses part geometry, material properties, machine specifications, and process parameters to estimate resource consumption during the WAAM process. To ensure the accuracy of the model’s predictions, theoretical estimates will be validated through experimental trials with WAAM, where real-world process data will be collected and compared to the model’s outputs to verify its reliability.