The rapid increase in nano-based consumer products has spurred research for alternative methods of nanomaterial synthesis to make them 'benign by design'. In recent years, so-called 'green' synthesis methods have been explored using natural alternatives (e.g., phytochemicals) to industrial chemicals, to reduce the use of harmful chemicals in the synthesis of nanomaterials. The feasibility of nanoparticle synthesis using phytochemicals has been well established. The sustainability of the synthesis processes, however, has not been critically studied from a life cycle perspective. Research on the environmental effects of nanotechnology has mostly been focused on the fate and transport and toxicity of nanomaterials. While the potential toxicity of some engineered nanomaterials in the use and the end-of-life phases is a direct impact, the synthesis phase of nanoparticles has indirect environmental costs, which may be overlooked unless we incorporate life cycle thinking into nanotechnology. The synthesis of nanomaterials can indeed be made more sustainable by applying green chemistry and green engineering principles. However, doing so without thoroughly evaluating the life cycle environmental impacts of a process would be myopic; merely replacing a conventional chemical with a plant-derived alternative does not assure improved sustainability. To address this issue, we conducted a screening-level, cradle-to-gate life cycle assessment (LCA) of several laboratory-scale syntheses of metallic nanoparticles and nanotechnologies based on renewable materials.We found that �green� synthesis methods can have major environmental impacts which can vary significantly vary from process-to-process. We also discuss the challenges in choosing appropriate functional units and identify the major gaps in the green nano-synthesis literature that limit the comparability of the reported green synthesis protocols. Our results show that despite the lack of nano-specific LCA data, screening-level LCAs of nanoparticle synthesis methods can help to choose the most environmentally benign process with the lowest life cycle footprint.

Sustainable nanotechnology: Incorporating life cycle thinking into green synthesis of nanomaterials

247th National Meeting (2014)

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