Identifying the largest environmental life cycle impacts during carbon nanotube synthesis via chemical vapour deposition

Abstract

A life cycle assessment (LCA) has been conducted on the growth of multi-walled carbon nanotubes (MWNTs) via catalytic chemical vapour deposition (cCVD). Using a directly measured process, a cradle-to-gate approach has been employed for this assessment whereby analysis of the synthetic routes of the reactants used, the process energy inputs, the equipment infrastructure and generated emissions have been assessed to determine the environmental impacts of the MWNT product. Conducting an LCA has allowed the major and, arguably just as informative, minor contributors to the environmental impact of MWNT growth via a cCVD synthesis to be quantified. The high embodied energy of MWNT synthesis is often quoted as the major embodied impact in carbon nanotube growth. However, previously unmeasured contributions of the embodied impacts of the equipment infrastructure have been shown to be in the same order of magnitude in terms of environmental damage during the growth period of the MWNTs, other life cycle stages associated with the production of the chemical reactants used have a very minimal effect on the overall environmental impact due to the relatively small quantities involved in MWNT synthesis. Unique among similar studies is the capture of the impacts attributed to all chemical reactants involved in the cCVD synthesis of MWNTs.