Unit Process Life Cycle Inventory Models of Hot Forming Processes

Life cycle assessment (LCA) is a widely used tool to evaluate the environmental profile of a product or process, and can serve as a starting point for product and process improvement. Using LCA to support sustainable product design and sustainable manufacturing has recently attracted increasing interest. Unfortunately, the available life cycle inventory databases have very limited coverage of manufacturing processes. To make matters worse, the available datasets are either highly aggregated or consider only selected processes and process conditions. In addition, in the case of the latter, the data provided may be based on limited measurements or even just estimates. This raises questions on applicability of these databases to manufacturing process improvement where different operating parameters and conditions are adopted. Recently a novel methodology called “unit process life cycle inventory” or “uplci” has been proposed to address these issues, and models for several machining processes (e.g., turning, milling, and drilling) and joining (e.g, submerged arc welding) have been developed. This paper follows the uplci approach and develops models for a series of hot forming processes, including billet heating, performing, and indirect extrusion. It is shown that the model predictions on energy consumption are in good agreement with data measured on a production line. For hot forming processes, the results suggest that billet heating dominates the overall energy consumption and the carbon footprint relative to the deformation steps.