There is a general perception that nanotechnologies will have a significant impact on developing 'green' and 'clean' technologies with considerable environmental benefits. The best examples are the use of nanotechnology in areas ranging from water treatment to energy breakthroughs and hydrogen applications. As a matter of fact, renewable energy applications probably are the areas where nanotechnology will make its first large-scale commercial breakthroughs (see: Nanotechnology applications could provide the required energy breakthroughs).
Conflicting with this positive message is the growing body of research that raises questions about the potentially negative effects of engineered nanoparticles on human health and the environment. This area includes the actual processes of manufacturing nanomaterials and the environmental footprint they create, in absolute terms and in comparison with existing industrial manufacturing processes (read more: "Nanotechnology - not that green?"). In order to make any conclusive observations, 'green' nanotechnology requires a full life cycle assessment like any other industrially manufactured products.
A white paper ("Green Nanotechnology Challenges And Opportunities") issued by the ACS Green Chemistry Institute in partnership with the Oregon Nanoscience and Microtechnologies Institute addresses the critical challenges to advancing greener nanotechnology.
Researchers agree that the safest possible future for advancing nanotechnology in a sustainable world can be reached by using green chemistry. Green chemistry means designing chemical products and processes in a way that reduces or eliminates hazardous substances from the beginning to end of a chemical product’s life cycle.
The practice began in the United States with the passage of the Pollution Prevention Act of 1990, which established a national policy to prevent or reduce pollution at its source whenever feasible. Reducing pollution at the source, according to the act, "is fundamentally different and more desirable" than managing waste and controlling pollution. Since then, the EPA Green Chemistry Program has built collaborations with academia, industry, other government agencies, nongovernmental organizations and international partners to promote pollution prevention through green chemistry.
As the report "Green Nanotechnology: It's easier than you think" (pdf) states: "Green nanotechnology offers the opportunity to head off adverse effects before they occur.
Green nanotechnology can proactively influence the design of nanomaterials and products by eliminating or minimizing pollution from the production of the nanomaterials, taking a life cycle approach to nanoproducts to estimate and mitigate where environmental impacts might occur in the product chain, designing toxicity out of nanomaterials and using nanomaterials to treat or remediate existing environmental problems.
Green nanotechnology does not arise de novo; rather, it builds on the principles of green chemistry and green engineering and focuses them through a new lens on the unique and often counterintuitive effects that occur in nanoscale materials."
Apart from the obvious areas of using nanomaterials in the areas of solar cells, biofuels and fuel cells, green nanotechnology applications might involve a clean production process, such as synthesizing nanoparticles with sunlight or the recycling of industrial waste products into nanomaterials, such as turning diesel soot into carbon nanotubes.
Just as an aside: there is some truly green nanotechnology: growing nanomaterials in plants – however this will never address industrial production of nanomaterials.