Life Cycle Aspects of Nanoproducts, Nanostructured Materials, and Nanomanufacturing: Problem Definitions, Data Gaps, and Research Needs
Chicago, Illinois: November 5-6, 2009
Critical questions for the nanotechnology and life cycle assessment workshop
Thomas P. Seager
Rochester Institute of Technology
What are the best estimates of the quantity, functionality, and composition of nanostructured materials over the next twenty years? How are these likely to be used and into which products are they likely to be incorporated?
The degree of variability and uncertainty present in nanostructured materials is unprecedented. In some cases, characterization of the materials themselves (e.g., purity, physical dimensions) may be a formidable experimental challenge because nanomaterials may have secondary, tertiary, or quaternary structural characteristics that are functionally important (like proteins). This means that chemically similar nanostructured materials may relate to the functional unit in LCA of myriad products different ways. A ‘taxonomy’ of nanostructured materials would be extraordinarily useful if it would allow people to classify materials into broad general categories that shared similar characteristics. For example, both quantum dots and nanoscale TiO2 are nanostructured materials – but for different functional reasons. The former exhibits quantum confinement, while the latter may be merely very, very small. Both characteristics can be important, but for dissimilar reasons and with dissimilar ramifications.
Are there sufficient quantities of low availability materials (e.g. In, Te) readily available for producing nanostructured devices and products on a large scale? If so, what is the waste burden created during their procurement? Might there be political or social factors that should be addressed as deposits of rare materials are accessed?
Not all nanostructured materials involve very rare elements. Silicon or carbon nanotubes are made from abundant elements. However, it may be that for those that do use vary rare elements, the quantities required at the nanoscale are much lower than would be required in a bulk application to achieve the same functional result. From this perspective, nanoscience may be a boon with regard to the criticality of elements.
What are the trends in the consumption of energy and materials during the manufacture of nanostructured materials? Are there efficiencies or better practices that research can help advance? What is the potential for the development and application of “green” technologies and design-for-the environment principles for the manufacture of nanostructured materials? Do “top-down” manufacturing methods produce more waste than “bottom up” methods? Might the life-cycle environmental implications attributable to release of bulk chemicals (e.g., CO2, solvents, mercury) in the production and/or end-of-life management of nanomaterials exceed the potential impacts of the materials themselves?"
There is insufficient research directed at both the greening and the scaling up of nanomanufacturing processes. That is, at the lab scale, material or energy efficiency are rarely important considerations in a research program that is focused primarily on functionality. But from an environmental perspective, understanding the implications of these processes at scale is incredibly important. It is not clear that rules of thumb (regarding green engineering for bulk materials) are necessarily consistent with environmental objectives for nanoscale processes, but in many instances they are likely to be. To date, nanoscience is insufficiently informed by principles of green chemistry, waste minimization, or pollution prevention. New knowledge with regard to materials process or manufacturing (such as mechanisms of catalysis at the nanoscale) may result in meaningful life-cycle environmental benefits.
What are the barriers and knowledge gaps related to recovering wasted materials during manufacture (thereby limiting waste production), and recycling nanostructured materials at the end-of-life stage?
The nanostructured materials that engender the greatest environmental investment in manufacture are likely to be those that are used sparingly – e.g., as additives, coatings, trace constituents, or in composites. These types of materials are notoriously difficult to recycle effectively – partly because they are typically not designed for efficient recycle.
Are current LCI and LCA methodologies adequate for application to the life cycle impacts of nanotechnology/nanomaterials? What are the limitations and research needs of the various LCA methodologies for assessing these rapidly emerging technologies?
The Woodrow Wilson Institute workshop says “Yes!” But the final report explicitly excludes impact assessment stages. That is, the current LCA framework is sufficient for creating an accounting of chemicals that constitute a life cycle inventory and is ostensibly workable for the first stage of impacts assessment -- i.e., characterizing the inventory to meaningful impact midpoints. However, the data gaps (e.g., with regard to toxicology of nanostructured materials, efficiency of manufacturing processes, or even functionality of nanomaterials themselves) are extraordinary. In comparison to bulk materials, in which toxicological uncertainties are already large, nanostructured material present an insurmountable challenge. Consequently, it is essential for LCA to be informative in a context of very high uncertainty and variability – which is not (especially in practice) one of the strengths of current LCA approaches.