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Potential environmental impacts of nanotechnology
So far most of the focus has been on the potential health and environmental risks of nanoparticles and only a few studies has been made of the overall environmental impacts during the life cycle such as ecological footprint (EF) or life cycle analysis (LCA). The life cycle of nanoproducts may involve both risks to human health and environment as well as environmental impacts associated with the different stages.
The topics of understanding and assessing the environmental impacts and benefits of nanotechnology throughout the life cycle from extraction of raw materials to the final disposal have only been addressed in a couple of studies. The U.S. EPA, NCER have sponsored a few projects to investigate Life Cycle Assessment methodologies. Only one of these has yet published results on automotive catalysts  and nanocomposites in automobiles  , respectively, and one project was sponsored by the German government  .
A 2007 special issue of Journal of Cleaner Production puts focus on sustainable development of nanotechnology and includes a recent LCA study in Switzerland  .
The potential environmental impact of nanomaterials could be more far-reaching than the potential impact on personal health of free nanoparticles. Numerous international and national organizations have recommended that evaluations of nanomaterials be done in a life-cycle perspective  , ,
This is also one conclusion from a recent series of workshops in the US on “green nanotechnology” (Schmidt, 2007) .
A workshop co-organised by US EPA/Woodrow Wilson Center and EU Commission DG Research put focus on the topic of Life Cycle Assessments of Nanotechnologies (Klöpffer et al., 2007)  .
Heresome of the potential environmental impacts related to nanotechnological products in their life cycle are discussed followed by some recommendations to the further work on Life Cycle Assessment (LCA) of nanotechnological products.
However, when relating to existing experience in micro-manufacturing (which to a large extent resembles the top-down manufacturing of nanomaterials) several environmental issues emerge that should be addressed. There are indications that especially the manufacturing and the disposal stages may imply considerable environmental impacts. The toxicological risks to humans and the environment in all life cycle stages of a nanomaterials have been addressed above. Therefore, the potentially negative impacts on the environment that will be further explored in the following are:
- Increased exploitation and loss of scarce resources;
- Higher requirement to materials and chemicals;
- Increased energy demand in production lines;
- Increased waste production in top down production;
- Rebound effects (horizontal technology);
- Increased use of disposable systems;
- Disassembly and recycling problems.
Exploitation and loss of scarce resources
Exploitation and loss of scarce resources is a concern since economic consideration is a primary obstacle to use precious or rare materials in everyday products. When products get smaller and the components that include the rare materials reach the nanoscale, economy is not the most urgent issue since it will not significantly affect the price of the product. Therefore, developers will be more prone to use materials that have the exact properties they are searching. For example in the search for suitable hydrogen storage medias Dillon et al.  experimented with the use of fullerenes doped with Scandium to increase the reversible binding of Hydrogen. Other examples are the use of Gallium and other rare metals in electronics. While an increased usage of such materials may be foreseen due to the expected widespread use of nanotechnological products, the recycling will be more difficult (will be discussed more in detail later), resulting in non-recoverable dissemination of scarce resources.
Energy intensity of materials
An issue apart from the loss of resources is the fact that the extraction of most rare materials uses more energy and generates more waste than more abundant materials. Table 1 illustrates the energy intensity of a range of materials. 
|Material||Energy intensity of materials (MJ/kg)|
Life cycle assessment (LCA)
As mentioned there are not many studies on LCA of nanotechnology and much information has to be understood from extrapolation of experiences from MEMS and micro manufacturing.
In the micro world LCA has predominantly been used in the Micro-Electro-Mechanical Systems (MEMS) sector. The rapid development of technologies and limited availability of data makes full blown LCAs difficult and rather quickly outdated. An example is the manufacture of a PC for which the energy requirement in the late 1980’s were app. 2150 kWh whereas in the late 90’s efficiency were improved and only 535 kWh were necessary  .
Using old data could result in erroneous results. Looking at the overall environmental impact this fourfold increase in efficiency has been overcompensated by an increase in number of sold computers from app. 21 mio to more than 150 mio  causing an overall increase in environmental impact. This is often referred to as a rebound effect. For the development of cell phones, the same authors conclude that life cycle impacts vary significantly from one product generation to the next; hence generic product life cycle data should incorporate a “technology development factor” for main parameters.
A major trend is that shrinking product dimensions raise production environment requirements to prevent polluting the product. It involves energy intensive heating, ventilation and air conditioning systems. Clean room of class 10.000 for example requires app. 2280 kWh/m2∙a whereas a class 100 requires 8440 kWh/m2∙a. The same increase of requirements is relevant for supply materials like chemicals and gases. The demand for higher purity levels implies more technical effort for chemical purification, e.g. additional energy consumption and possibly more waste. Most purification technologies are highly energy intensive, e.g. all distillation processes, which are often used in wet chemical purification, account in total for about 7 % of energy consumption of the U.S. chemical industry  . Chemicals used in large volumes in semiconductor industry are hydrofluoric acid (HF), hydrogen peroxide (H2O2) and ammonium hydroxide (NH4OH). These materials are used in final cleaning processes and require XLSI grades (0.1 ppb). Sulphuric acid is also used in large amounts, but it is a less critical chemical and mainly requires an SLSI level purity  .
Micromanufacturing of other types of products also puts higher requirements on the quality and purity of the materials, e.g. a smaller grain size in metals because of the smaller dimensions of the final product. Additionally, a considerable amount of waste is produced. For example, up to 99% of the material used for microinjection moulding of a component may be waste since big runner are necessary for handling and assembly. However, recycling of this waste may not be possible due to requirements to and reduction of the material strength  .
Miniaturisation also cause new problems in electronics recycling. Take-back will hardly be possible. If they are integrated into other product they need to be compatible with the recycling of these products (established recycling paths)  .
The very small size and incorporation into many different types of products including product with limited longevity suggests an increased use of disposable systems is required.
Life cycle assessment of nanotechnology
As mentioned previously only few LCA studies have until now been performed for nanotechnological products. A two day workshop on LCA of nanotechnological products concluded that the current ISO-standard on LCA (14040) applies to nanotechnological products but also that some development is necessary  
The main issues are that:sometimes it cracks the nerve
- There is no generic LCA of nanomaterials, just as there is no generic LCA of chemicals.
- The ISO-framework for LCA (ISO 14040:2006) is fully suitable to nanomaterials and nanoproducts, even if data regarding the elementary flows and impacts might be uncertain and scarce. Since environmental impacts of nanoproducts can occur in any life cycle stage, all stages of the life cycle of nanoproducts should be assessed in an LCA study.
- While the ISO 14040 framework is appropriate, a number of operational issues need to be addressed in more detail in the case of nanomaterials and nanoproducts. The main problem with LCA of nanomaterials and nanoproducts is the lack of data and understanding in certain areas.
- While LCA brings major benefits and useful information, there are certain limits to its application and use, in particular with respect to the assessment of toxicity impacts and of large-scale impacts.
- Within future research, major efforts are needed to fully assess potential risks and environmental impacts of nanoproducts and materials (not just those related to LCA). There is a need for protocols and practical methodologies for toxicology studies, fate and transport studies and scaling approaches.
- International cooperation between Europe and the United States, together with other partners, is needed in order to address these concerns.
- Further research is needed to gather missing relevant data and to develop user-friendly eco-design screening tools, especially ones suitable for use by small and medium sized enterprises.
Some of the concerns regarding the assessment of toxicological impacts is closely linked to the risk assessment of nanoparticles and have to await knowledge building in this area. However, the most striking is the need for knowledge and cases where LCA are applied in order to increase understanding of nanotechnological systems – what are the potential environmental impacts? How do they differ between different types of nanotechnologies? Where should focus be put in order to prevent environmental impacts? Etc.
- Nanometer societal assessment of nanotechnological applications prior to market release.
Contributors to this page
This material is based on notes by
- Stig Irving Olsen, Department of Manufacturing Engineering and Management, Building 424, NanoDTU Environment, Technical University of Denmark
and also by
- Steffen Foss Hansen, Rikke Friis Rasmussen, Sara Nørgaard Sørensen, Anders Baun. Institute of Environment & Resources, Building 113, NanoDTU Environment, Technical University of Denmark
- Kristian Mølhave, Dept. of Micro and Nanotechnology - DTU - www.mic.dtu.dk
See also notes on editing this book Nanotechnology/About#How_to_contribute.
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