Environmental Life Cycle Analysis of Applications of Nano-Particles
Nano jungle, by Dr. Qin Hu
Life Cycle Analysis is a way to look at all environmental impacts of a certain product or application over its entire life-span. You take into account all the environmental impacts of mining for metals, drilling for oil, transporting ores, and you can even discern between scarce and abundant materials. Then you measure the impact of making half products and the final products in factories (including the energy used for all that), and calculate all the environmental impacts during the use of the product. Finally you take into account the environmental impact of discarding the products.
With this method, abbreviated to LCA, you can compare two products that deliver the same service, such as two different cars. You compare them on total toxic materials emitted into the environment, greenhouse gas emissions, total energy use per driven km, etc. You can correct for number of km’s driven or lifetime of the car. You can also calculate the effect of recycling (e.g. if recycled aluminium is used in producing your car, the environmental impact of the car is lowered; and for other products it may even be so that if you could use it twice, you already half the environmental impact). You can thus calculate where you can change the materials used or production method used to lower the impact.
Since the use of nano particles may have advantages, such as higher quality of a product, reduced energy use, etc, it would be interesting to see how the use of nano-particles compares to alternatives, e.g. through an LCA. Since learning how to perform an LCA is one of the competences for students in environmental studies, we think that questions like these should be suitable for student-research.
The fact that not all environmental impacts of nano-particles are known yet, complicates matters and puts a challenge on methodological refinement of the LCA method. In general, nano-particles behave different from larger particles. This gives them the special properties that makes them well suited for certain applications. However, it also makes them behave differently in the environment and body. Nano-particles have a relatively large surface per weight unit. Since reactions occur on the surface, they are much more reactive than larger particles. Thus, environmental standards that are based on weight units are not suitable to control nano-sized particles of a certain substance. However, nano-particles can be firmly attached to a matrix and when they do not become free, they can not enter the environment as nanoparticles. All these aspects need to be taken into account when studying environmental impacts of nano-particles.
We would gladly open the floor to discuss the use of LCA for nano-particle applications. Which other issues do you have where an LCA study could be of help to clarify the pros and cons, and alternatives?
debate ended – 4 comments:
Current debate
Nano-sized materials have new, useful properties. However, whether their use is better for the environment than their alternatives, can only be assessed in an Environmental Life Cycle Analysis. We welcome any (requests for) case studies on this!
Henk Mulder
Science Shop, University of Groningen 
Henk wrote:
Nano-scale cerium-oxide is a fuel-enhancer for diesel. By adding nano-cerium oxide, cars/trucks are said to use 5-8% less diesel per km, and the engine remains cleaner. Thus, on the positive side, less CO2, soot-particles and other exhaust gasses enter the environment, and there are economic benefits as well. However, the nano-particles themselves leave the exhaust pipe and enter the environment. The additive is used in Germany, Russia and England already; marketed e.g. in the UK as Envirox. In The Netherlands, there are talks with a Transport Firm to do tests. The Environmental NGO Leefmilieu asked in 2008: What will be the environment and health effects of this?
Students in the Course “The Scientist as an Advisor” at Utrecht University (2009) surveyed the literature:
Link: http://www.leefmilieu.nl/pdf_s/2009-02-04_Rapport%20nano-ceriumoxide%20als%20brandstofverbeteraar.pdf (in Dutch)
“Scientific studies on the effects of these particles remain contradictionary/unclear. Lung cells could be sensitive on the longer term, though it also seems that nano-cerium particles quickly stick together to form larger particles. Then they are no longer considered nano-particles, and don’t have the potentially penetrating effects anymore. Furthermore, the soot particles in diesel are also considered dangerous for the lungs, and the emission of those is reduced. Even though most studies are not negative on the health impact, the more recent scientific studies are more negative about nano-cerium oxide’s health impact than the older ones. Studies show that cerium oxide has little effect on organisms living in water; for organisms in soil or air there have been fewer studies.”
Participants of the Seminar discussing the outcome of the students report (2010) (consisting of many NGO members, and some university scientists, and public and private researchers):
Link: http://www.leefmilieu.nl/sites/www3.leefmilieu.nl/files/imported/pdf_s/2010-10-30_Milieurisico’s%20nanodeeltjes%20onderbelicht.pdf
“Cerium oxide leaves the car-exhaust as nanoparticle. It is e.g. used by transport companies in the UK (so not available at ordinary gas stations), at 5 mg/l, to save fuel. The toxicity of the particles does not seem a problem (because one saves on diesel use, one also saves on the number of nano particles caused by combustion). However, one still uses a scarce material dissipatively (so not recyclable). With soot-filters one can catch a lot of particles, so environmental standards are being strengthened currently. Adding cerium oxide saves approx. 3.5% diesel (one could thus calculate a maximum demand). Cerium oxide is also used in catalysts.
Current research questions are:
Main Issue: Make an LCA to compare the scarcity of cerium with fuel saving (and all other environmental effects)
Additional:
-Is it technically possible to put the cerium in a solid catalyst and have the same fuel saving effect, or is there any other recyclable use possible (e.g. through the soot-filter)?
-New (non-diesel based) engines might not need cerium oxide, because they are more efficient already. Would the use of cerium oxide be a suitable transition technology, until these new engines are in general use? Or will it be an excuse to continue the use of diesel engines longer? What is the relation with the environmental standards setting policy plans?
-Would it be a better solution to tune the engine power to the current maximum speed limits, to have a more efficient use of diesel (and is this better than adding additives?) (Current engines are designed to go 180km/h)”
Marga Jacobs wrote:
At the seminar on health and environment of nanotechnology applications that we organised during our project on nano-technology, more research questions came up than the one Henk used above to trigger this dialogue. We surveyed our participants to see what follow-up research questions they thought should be addressed. I summarize a number of them below, and hope some students and researchers could do some study on these:
1. How stable are nanoparticles? Can they be measured ‘in the field’ and has this been done already?
2. Nano silver is much used, which raises some questions:
a. Is it possible to measure nano silver’s presence, and at which size?
b. What is its aquatic toxicity? Can it be filtered from water?
c. Does the use of nano silver deplete silver resources?
d. Is it really necessary to use nano silver or does ‘normal’ silver have the same effect?
e. Can nano silver be a substitute for antibiotics?
f. Can micro-organisms become resistant to nano silver?
g. Is it safe to wear cycling shorts with silver nano?
3. Can nano particles cause allergic reactions that would not be caused by larger particles of the same substance?
4. Regarding the production of nano particles:
a. Are nano particles released during production (has any research been done on this?)
b. During production, a lot of non-specified waste seems to be produced. How is/can this be dealt with?
5. On toxicology:
a. How can we take particle size into account in toxicological assessments (and avoid making a single differentiation by just using 100nm or 300nm as threshold to call something a nano particle; is it possible to differentiate in an appropriate way among different sizes?).
b. Can cumulative effects be included?
c. Is a fundamental change in toxicological assessments needed?
d. How can knowledge on eco-toxicology be increased?
e. How can we avoid that risk research into nanoparticles will frequently use animal testing?
6. If you have a spray with nano particles, is the danger of other substances in the spray higher than that of the nano particles (e.g. propellants?) (e.g. in waterproof shoe spray)
7. Does the iPod nano contain dangerous nano particles?
tonsu wrote:
Replying to Henk Mulder’s comment on Cerium oxide in Diesel engines I would like
to point out the following :
A. The element Cerium is in no short supply globally. Infact it is even more common than Copper. See also http://pubs.usgs.gov/fs/2002/fs087-02/
B. In my view one should always avoid using dispersible additives in fuel that cannot easily be recovered or renewed after combusting the fuel. We all know what happened to Lead additives. A better route would be to stimulate ithe future phasing out of Diesel engines
in heavy duty trucks and replacing them in the long run with fuel cells running on either hydrogen or reformer-based biogas.
PS The National Academy of Sciences just published “A Research Strategy for Environmental, Health, and Safety Aspects of Engineered Nanomaterials”, which you can download for free: http://www.nap.edu/catalog.php?record_id=13347.
Henk wrote:
Given the remarks from Ton, this would still call for a more systematic analysis, despite the fact that scarcity does not seem to be the main issue here.