As nanotechnology applications and nanomaterials slowly move into mainstream manufacturing, there will have to be an increasing focus on the environmental footprint that the production of various nanomaterials creates. A growing research body promises to lead to green(er) nanomanufacturing technologies. However, as we discussed in a Nanowerk Spotlight last year, this emerging field of green nanoscience faces considerable research challenges to achieve the maximum performance and benefit from nanotechnology while minimizing the impact on human health and the environment. As it stands now, it remains to be seen what the environmental footprint of nanotechnologies will be. So far, the message is mixed.
The flurry of recent announcements regarding reports, international cooperations, and new research activities that deal with the potential risks of manufactured nanomaterials is a clear indication that the field of nanotoxicology is gaining momentum - and not too soon. While there still is no coherent international approach to determining if and what risks are posed by what kind of nanotechnology materials, individual research groups are picking certain areas of concern and forge ahead with - often highly specific - toxicology studies. A lack of standards and definitions makes these early investigations hard to compare and sometimes they even contradict each other, a situation that is especially confusing in risk assessments of carbon nanotubes. Some studies, though, present findings that, on the face of it, are especially worrying in their potential implications and deserve much more attention to be sorted out one way or another. A recent report on the toxicity of metal nanoparticles in soil is such an example.
Synthetic fibers are ubiquitous in modern society and their manufacture represents a huge, multi-billion dollar worldwide industry. Synthetic fibers - carbon fibers, nylon, polyester, kevlar, spandex, etc. - are manufactured from fossil fuels, usually from oil, but sometimes from coal or natural gas. Most of these materials are not biodegradable and, in addition to their significant carbon footprint during production, they pose environmental problems at the end of their life cycle. Natural fibers, on the other hand, such as wool and cotton, come from renewable animal or plant sources but they usually lack the high-performance characteristics of many synthetic fibers. This may change, as the new field of bio-based nanomaterials promises to deliver environmentally friendly, high-performance bio-fiber materials that can replace some of the synthetic materials.
Climate change is high on the global agenda. While the United Nations Climate Change Conference in Poznan, Poland, in December 2008, is an important step towards achieving an international agreement on climate change scheduled for the upcoming Conference of the Parties in Copenhagen at the end of 2009, policy makers and practitioners alike are increasingly looking for practical solutions. A new report by the United Nations University Institute of Advanced Studies (UNU-IAS) offers three innovative solutions in responding to climate change, namely nanotechnology, ocean energy and forestry. The 46-page report goes beyond the technological, biological and procedural aspects of these solutions by critically assessing the opportunities and challenges that each type of innovation presents. This report addresses the question why these innovations - despite their large potential to reduce emissions, ocean energy alone could cover the world's electricity needs - have not yet reached the stage of mass commercialization
The hydrogen that will power tomorrow's cars is not a naturally occurring resource that can be tapped by drilling a hole in the ground. Hydrogen has to be produced, and that can be done using a variety of resources. The cleanest by far of course would be renewable energy electrolysis: using electricity to split water into hydrogen and oxygen; this electricity could be generated using renewable energy technologies such as wind, solar, geo- and hydrothermal power. As it stands, most of today's hydrogen production is 'dirty' - it is produced from methane in natural gas using high-temperature steam in what is called steam methane reforming. Many research groups around the world are working hard on developing cheap, clean and efficient technologies to produce hydrogen from water, particularly using sunlight (artificial photosynthesis). This would be the ultimate clean, renewable and abundant energy source. However, to become commercially viable, fuel cells have to overcome the barrier of high catalyst cost caused by the exclusive use of expensive platinum and platinum-based catalysts in the fuel-cell electrodes - the reason is that platinum is the most efficient electrocatalyst for accelerating chemical reactions in fuel cells. Scientists have found that platinum catalysts can be replaced with bacteria-produced hydrogenase enzymes that have nickel and iron in their active sites.
As we have show before, nanotechnology applications could provide decisive technological breakthroughs in the energy sector and have a considerable impact on creating the sustainable energy supply that is required to make the transition from fossil fuels. Although we love to write about all the clean and green applications that will be nanotechnology enabled, the harsh reality is that dirty energy is still fuelling our way of life. No matter if you are a member of the "drill, baby, drill" crowd or if you are actively involved in saving energy and think that the development of renewable energies can't come fast enough, we have to live with the fact that the world's energy production will continue to depend on oil, gas and coal for quite a few more years. But even here, nanotechnology applications might offer some improvements. A new report shows that nanotechnology, in the form of carbon nanotube rubber composites, could help to significantly enhance oil production efficiency by allowing to probe and drill deeper wells.
The toxicity issues surrounding carbon nanotubes (CNTs) are highly relevant for two reasons: Firstly, as more and more products containing CNTs come to market, there is a chance that free CNTs get released during their life cycles, most likely during production or disposal, and find their way through the environment into the body. Secondly, and much more pertinent with regard to potential health risks, is the use of CNTs in biological and medical settings. CNTs interesting structural, chemical, electrical, and optical properties are explored by numerous nanomedicine research groups around the world with the goal of drastically improving performance and efficacy of biological detection, imaging, and therapy applications. In many of these envisaged applications, CNTs would be deliberately injected or implanted in the body. While it has been shown that carbon nanotubes can indeed act as a means for drug delivery, negative effects such as unusual and robust inflammatory response, oxidative stress and formation of free radicals, and the accumulation of peroxidative products have also been found as a result of carbon nanotubes and their accumulated aggregates. As a possible solution, scientists have provided compelling evidence of the biodegradation of carbon nanotubes by horseradish peroxidase and hydrogen peroxide over the period of several weeks. This marks a promising possibility for nanotubes to be degraded by horseradish peroxidase in environmentally relevant settings.
There is a general perception that nanotechnologies will have a significant impact on developing 'green' and 'clean' technologies with considerable environmental benefits - be it 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. 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. However, there is one area of nanotechnology that so far hasn't received the necessary attention: the actual processes of manufacturing nanomaterials and the environmental footprint they create, in absolute terms and in comparison with existing industrial manufacturing processes. Analogous to other industrial manufacturing processes, nanoproducts must proceed through various manufacturing stages to produce a material or device with nanoscale dimensions.