Life Cycle Environmental Impacts of Synthetic Diamond Production

Conference poster, 2019

Synthetic diamond is a superhard material found in applications such as cutting and grinding of rocks, minerals, metals and plastics, but also in windows and lenses in analytical equipment. Since the 1950s, when the synthesis of diamond via the high-pressure high-temperature (HPHT) synthesis was introduced, the use of synthetic diamond has gained increasing importance within industry, for example in cutting processes. Today, synthetic diamond dominates the industrial diamond use over its natural counterpart and the production is mainly via HPHT synthesis. Chemical vapor deposition (CVD) synthesis is also applied but to a lesser extent due to various technological issues, including the tendency of CVD diamond coatings to wear and tear in tooling applications. Nevertheless, a lot of research exist in the area of synthetic diamond film production via CVD synthesis addressing technological issues and CVD diamond has been described as the potential facilitator of a new diamond age. In the strive for sustainable production, it is important to investigate the environmental impacts associated with various products and life cycle assessment (LCA) is commonly applied for this purpose. Until now, however, no study has conducted LCA of conventional synthetic diamond production via HPHT synthesis and so far, only laboratory-scale LCA results have been presented for one CVD synthesis alternative. The aim of this study is to conduct a cradle-to-gate LCA for synthetic diamond production both via the conventional HPHT synthesis and the potentially emerging CVD synthesis. For the latter route of synthesis, prospective (or ex ante) LCA was conducted and a predictive scenario was constructed focusing on microwave CVD. Future scenarios were constructed, e.g. by modelling the background energy system both using a fossil-based mix, representing the currently dominating Chinese production, and a renewable energy mix in an explorative scenario. A comprehensive uncertainty analysis was furthermore conducted for the included parameters. Environmental impacts were compared between the two routes of synthesis and hotspots in synthetic diamond production identified. The results from this research can be applied as a foundation for further LCA studies of synthetic diamond products.