Monday, 11 February 2013

The real cost of using neodymium in wind turbines


Following a directive from the EU on how to tackle climate change, where, by 2020, 15% of all the energy the UK uses must come from renewable sources, there has been a profusion of wind-farms around the country, and wind-swept Cornwall is now beginning to look like a giant pin-cushion.

There is much debate on the effectiveness of wind turbines but I have been particularly interested in their construction, and life-cycle analysis, which quantifies to what extent they are a totally clean form of energy. In this sense we have to consider not only the emissions produced while they are in operation, but also the contamination and environmental impact resulting from their manufacture and the future dismantling of the turbines when they come to the end of their working life.

In this respect, a paper by Martinez et al, in the Elsevier peer-reviewed journal Renewable Energy (2009) analyses the real impact that this technology has if we consider the life cycle, quantifying the overall impact of a wind turbine and each of its components. The wind turbine is analysed during all the phases of its life cycle, from cradle to grave, with regard to the manufacture of its key components, transport to the wind farm, subsequent installation, start-up, maintenance and final dismantling and stripping down into waste materials and their treatment.

They conclude that there is an environmental benefit in starting up and running wind farms, and that the biggest environmental impact comes from the foundation, due mainly to the cement. The nacelle is the heart of the turbine and inside it carries the technology required for converting kinetic energy into electricity. Hence it is the most complex component, made up of a series of elements which are widely differing in nature. Each of these elements has its own associated technology and manufacturing processes, which certainly makes the study of the nacelle as a whole more complicated. The main environmental impact shown by the study is that of the cost in copper. This metal has an enormous value and environmental impact, although it has the advantage of being recyclable.

Although this is a very comprehensive report, they omit the life cycle analysis of a crucial component within the nacelle- the powerful direct-drive permanent magnet generator, which contains a critical rare earth element, neodymium. Neodymium is commonly used as part of a Neodymium-Iron-Boron alloy (Nd2Fe14B) which, thanks to its tetragonal crystal structure, is used to make the most powerful magnets in the world. It has been used in small quantities in common technologies for quite a long time – hi-fi speakers, hard drives and lasers, for example. But only with the rise of alternative energy solutions has it really come to prominence, for use in hybrid cars and wind turbines. A direct-drive permanent-magnet generator for a top capacity wind turbine would use around 2 tonnes of neodymium-based permanent magnet material.

Neodymium is found most often in monazite and bastnasite. Due to the fact that these minerals also contain lanthanides and other rare earth elements, it is difficult to isolate neodymium. The first isolation process involves extracting the lanthanides and metals out of the ores in their salt form. This step is carried out using sulphuric acid, hydrochloric acid, and sodium hydroxide. To further isolate the neodymium from other lanthanides and metals, procedures such as solvent extraction and ion exchange are used. Once neodymium has been reduced to its fluoride form using these processes, it can be reacted with pure calcium metal in a heated chamber to form pure neodymium and calcium fluoride. Some calcium contaminants remain in the neodymium, and vacuum processes are used to remove any of these contaminants. It is an expensive and potentially environmentally harmful process.

In a recent posting (February 1st), it was noted that China produces over 90% of the world’s rare earths, and that Beijing’s export reductions in recent years have forced high-tech firms to relocate to China. An article in a UK newspaper claims to have uncovered the distinctly dirty truth about the process used to extract neodymium: it has an appalling environmental impact that raises serious questions over the credibility of so-called green technology.

According to the report, hidden out of sight behind smoke-shrouded factory complexes lie vast, hissing cauldrons of chemicals in tailing lakes that are often very poorly constructed and maintained; throughout the extraction process large amounts of highly toxic acids, heavy metals and other chemicals are emitted into the air that people breathe, and leak into surface and ground water.

The report concludes that whenever we purchase products that contain rare earth metals, we are unknowingly taking part in massive environmental degradation and the destruction of communities. It is a real dilemma for environmentalists who want to see the growth of the renewables industry but we should recognise the environmental destruction that is being caused while making these wind turbines.

So, what are your opinions, on wind-turbines and the economic and human costs of extraction of neodymium?

8 comments:

  1. That is why recycling and reuse of rare earths is so important, because while on the surface they may look "cheap" (and therefore disposable), they do have impacts other than financial.

    For this reason, the KU Leuven's RARE³ Knowledge Platform is developing breakthrough REE's recycling processes for Europe, find more information here:

    http://www.kuleuven.rare3.eu/

    Partners and collaborators are always welcome.

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    Replies
    1. Many thanks. It would be good to have a paper on this for SRCR ‘14 which will be held in Falmouth next year.

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  2. I think an important point you seem to have overlooked is that although some wind turbine designs are based on permanent magnet generators containing neodymium, this element is not intrinsically linked to wind power. If you look at the model range produced by Vestas (currently the world's largest supplier of wind turbines) you'll see that permanent magnets are only used in those designs with a high power output, and/or large blade size.
    http://www.vestas.com/en/wind-power-plants/procurement/turbine-overview.aspx

    The reason for this simply comes down to the fact that although permanent magnets improve efficiency and reduce the material and energy costs in the supporting structure, the high cost of REEs makes conventional electromagnetic generators more attractive for smaller-scale designs. This dividing line will of course vary with economics, but it does mean that those purchasing wind turbines have an option like any consumer to pay a premium for an item if they feel it is more beneficial to the environment.

    Of course before going out and trying to boycott the purchase/installation of permanent magnet wind turbines or hybrid cars it would perhaps be wise to stop and consider the more than 600 million hard disk drives produced each year, each containing some 3g of neodymium (or around 1,800 tonnes from a global Nb production of around 7,000 tonnes). At least with turbines the magnets will be used for something somewhat more useful than storage of data downloaded from another drive via the internet, and should prove more viable to recycle than small quantities dispersed around the globe.

    The separate issue of pollution in China extend to more than just REE processing, and it should be remembered that it is not that dissimilar to what was seen as common practice in the Western world not that long ago. In time hopefully pressure from the Chinese people themselves will affect change, but in the meantime I don't think there's much the Western world can say or do without seeming either condescending or hypocritical.
    James Rowe, Australia, via Minerals Engineers, LinkedIn

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  3. In my opinion this discussion is very relevant. The processing of the rare earth minerals bastnasite and monazite are energy intensive processes. This is due to the leaching step which is a rather high temperature baking step as these minerals are refractory. The leaching step also involves acid or sodium hydroxide at high concentrations. Residues and wastes are thus likely to be hazardous.

    After leaching there follows the separation and concentration stages, and then recovery, all which require a good deal of energy either for the process itself or for the reagents in the process.

    In the case of bastnasite, which is a fluorocarbonate mineral, there is the problem of hydrofluoric acid generation during an acid leaching step, and the safe disposal of the fluorides that are generated.

    Both minerals are associated with radioactive actinides such as thorium and uranium. Clearly, safe disposal of these wastes is problematical.

    Both from an energy balance point of view, and from an environmental impact point of view the production of rare earth element magnets is probably not as "green" as we would like it to be, or we like to think it to be. If they are used, their production and disposal should most certainly be factored into a proper life cycle assessment.

    With so many processing steps and so many hazardous wastes, there is much potential for closing one's eyes to many of the problems, as has often been done in the past in Western countries and in Africa, leaving an enormous liability for the future.
    Dick Groot, University of Pretoria, South Africa, via LinkedIn Minerals Engineers

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  4. I would like to know the energy costs in Mwh to produce 1 ton of neodymium?
    Thanks in advance
    Harry Huisman

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  5. The specific topic of Nd in wind turbines here is interesting all of it's own. But the critical issue here is the principle of addressing the net vertical supply chain of creating ALL alternate energies. They all have eco-footprint that are generally ignored by their advocates.

    People don't seem to get it. A car powered by electricity from a grid that is energized by coal fired thermal plants is not clean. Solar panels and battery systems installed in areas with abundant hydro and marginal sunlight are misguided. A wind turbine or field that does not perform to the original expectations (and most don't) must account for the energy and resources that went into it's build, installation and dismantling amortized over it's expected lifespan.

    Alternate energy technologies all have an environmental footprint, mainly as large holes in the ground called mines, that people don't even consider while being enraptured by the "free" energy they are getting.

    The true, ugly, uncomfortable, inconvenient truth of saving the planet? It's not shiny solar panels. It's not wind turbines (bird 'n bat blenders).

    It's the new 3 R's of the new millennium...Reduce, Reduce, Reduce.

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  6. I would not be drawing any conclusions here based on a UK newspaper article. what seems to have been established is that some existing wind turbines utilise Neodymium magnets which are manufactured in a classical combustion process. Most combustion of fossil fuels produces carbon dioxide. In what amounts is the critical question. Not likely to match coal, oil or gas usage in power generation.

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