Is graphene a ”wonder material” also from an environmental life cycle perspective?
Konferensbidrag (offentliggjort, men ej förlagsutgivet), 2014
The nanomaterial graphene has attracted great interest for its many potential applications, including composites and electronic devises, and has been referred to by some as a "wonder material" from a technical point of view. However, the question remains whether graphene is also a "wonder material" from an environmental life cycle perspective. In order to investigate this, we applied life cycle assessment (LCA) to assess the cradle-to-gate environmental impacts of graphene production. The focus of the assessment was on the foreground system and on more inherent impact categories, namely energy use, water use, human toxicity, and ecotoxicity. Two different production routes were investigated. In the first, called chemical reduction, graphite is first oxidized to graphite oxide, and then reduced by hydrazine to form graphene sheets in solution that could be used in e.g. composites. The second is ultrasonication, where graphite is exposed to ultrasound, and thereby breaks up into graphene sheets in solution, also possible to use in composites. These two routes were compared on a kg of graphene basis. The results indicate that ultrasonication has a considerably lower cradle-to-gate impact than chemical reduction for all included impact categories. For example, the energy use of chemical reduction-made graphene appears to be more than 100 times higher than that of ultrasonication-made graphene. Comparing to the energy use of other nanomaterials, chemical reduction-based graphene appears to have an energy use close to the median. Ultrasonication-made graphene, however, appears to have a lower energy use than any previously assessed nano material. This implicates that the chemical industry should focus their efforts on developing the ultrasonication production route rather than chemical reduction.