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Mon May 7, 2018, 11:56 PM

Yet another paper on the external cost of neodymium iron boride magnets.

I recently posted in this space some graphics on the process of isolating neodymium from lanthanide ores (aka "rare earth ores" or REO)


Some life cycle graphics on so called "rare earth elements," i.e. the lanthanides.

The paper I cited was this one: Behind the Scenes of Clean Energy: The Environmental Footprint of Rare Earth Products (Zhao et alACS Sustainable Chem. Eng., 2018, 6 (3), pp 3311–3320)

The word "clean" in this paper's title, given what it discusses, strikes me as a kind of joke, but no matter.

Let's be clear on something, OK? The conversion of mechanical energy to electricity and back again depends on the existence of permanent magnets. This is true for relatively dirty forms of energy, battery driven motors, wind turbines, gas turbines, coal turbines, diesel powered turbines as well as relatively or comparitively clean devices such as nuclear power plants and the slightly less clean hydroelectric plants.

There seems to be good prospects for highly efficient devices to directly convert heat into electricity (as opposed to inefficient devices like those that powered the Voyager, New Horizons, Pioneer, Cassini...etc...space crafts as well some historical cardiac pace makers and similar devices. (There's some exciting stuff going on in thermoelectric materials, I should find time to write about it some day.)

But right now, more than 95% - probably more like 98% - of the electricity generated on the face of this planet is produced by the use of permanent magnetism.

Historically - and I'm sure in many older power plants - many of these magnets were or are "Alnico" or "AlNiCo" magnets, but political instability in the Congo region where cobalt is mined under horrific labor conditions - sometimes actual child slavery - produced a worldwide shortage of cobalt which motivated a search for new materials, and the new material discovered was the "NIB" or neodymium iron boride magnet, which not only replaced AlNiCo but proved to be superior to AlNiCo.

Actually the neodymium iron boride magnet contains a few other elements, often, like neodymium, lanthanides, especially dysprosium and praseodymium.

Europium is used in many phosphors, including energy saving fluorescent bulbs, although these may be replaced ultimately be even more efficient lighting in the form of LED's, which contain not only europium, but also the remarkable and difficult compound gallium nitride, the synthesis of which actually resulted in a Nobel Prize.

Now another paper has come along evaluating the external costs of lanthanides, which goes under the general rubric of "clean" energy although in my opinion it is neither clean, nor sustainable nor actually "renewable." The paper was just published in a journal article that came out this morning: Comparative Life Cycle Assessment of NdFeB Permanent Magnet Production from Different Rare Earth Deposits (Schreiber et al ACS Sustainable Chem. Eng., 2018, 6 (5), pp 5858–5867)

The authors come from Germany, a country with a big demand for lanthanides which is also the country with the second highest cost of electricity in Europe, after Denmark.

European Electricity Prices

We don't need no stinking data!

From the introduction to the paper which is all about "decarbonized" electricity, in spite of the fact that electricity is less decarbonized than it's been at any time in human history; the fraction relying on carbon is rising, not falling.

(If that bothers you, I suggest you call Kelly Conway to have her explain "alternate facts" to you.)

The opening paragraph speaks of this illusive "decarbonized" electricity, to wit:

In 2016, world rare earth mine production was 126 000 t of rare earth oxide (REO) equivalents predominately in China (105 000 t).1 Several rare earth elements (REEs) are used for the transformation of the fossil era into a decarbonized energy sector. REEs are essential for wind and solar energy, electric and hybrid vehicles, and low-energy lighting. Approximately 20% of the REEs are used for magnets in motors and generators.2 Rare earth iron boron magnets (NdFeB) are among the strongest permanent magnets. The basis for the technical properties of magnets is the use of the specific REEs neodymium (Nd), praseodymium (Pr), and dysprosium (Dy). A typical NdFeB magnet used in wind turbines consists of approximately 65% iron, 32% RE metals, 2% cobalt, and 1% boron.


Then the paper gets serious. Looking at the graphics from the earlier post I had on this subject, I kind of felt that as dire as they were, they pulled some punches. This is less true in the second paper cited herein because the process details and the chemistry involved is a little more graphically detailed.

It compares the external costs associated with the processing of ores from three different sources, China (Baotou) which is the world's largest producer of lanthanides, Australia, and the US Mountain Pass facility in California.

First the overview from this paper, which is similar to the earlier paper/post:



The caption:
Figure 1. Production sites of the three supply chains.




Figure 2. Exemplary process chain of the three supply chains for the production of Nd.


Now this is straight up. Flotation - the Mountain Pass and Baotou mines (and probably the Australian) mine are all in water stressed locations, leaching with dilute hydrochloric acid, "sulfiding" which is reacting sulfur to form metal sulfides, "roasting" which is heating the sulfides to give off sulfur dioxide and sulfur trioxide, digesting the resulting oxide in sulfuric acid, reprecipitating with ammonium carbonate (made from natural gas), redissolving in hydrochloric acid and four steps in solvent extraction using chelating agents manufactured from dangerous petroleum in a dangerous petroleum solvent (kerosene or similar), this to separate the 16 different elements, (including scandium and yttrium) or 17 if you count the radioactive thorium always found in lanthanide ores. Finally the extraction solutions are treated with toxic oxalic acid to precipitate the oxalates, and roasted again, to give oxides again which are then electrolytically reduced to the individual elements.

Delicious.

I cannot write a comment here, without hearing some rote and most often extremely silly objection that goes "...but nuclear..."

This sounds exactly to me like "...but her emails..." and represents a Trumpian distortion similar to "but her emails..."

But since I'm going to hear this kind of delusional bullshit, including remarks about how "dangerous" used nuclear fuel is even though in half a century of storing it, this while burning gas and coal based electricity to whine about it on line, used nuclear fuel hasn't actually killed anyone in this country, this while the de facto "acceptable" dangerous fossil fuel waste (aka air pollution) and dangerous renewable biomass waste (aka air pollution) kills 19,000 people a day, every day.

A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990–2010: a systematic analysis for the Global Burden of Disease Study 2010 (Lancet 2012, 380, 2224–60: For air pollution mortality figures see Table 3, page 2238 and the text on page 2240.)

It is true that the Purex process for the separation of nuclear materials from used nuclear fuels - the Purex process being the only commercial nuclear fuel reprocessing process ever employed - is a solvent extraction process, and is similar in many ways to solvent extraction to separate lanthanide. If I were building a modern nuclear fuel reprocessing plant it's not the process I would choose, but historically everyone has chosen Purex, and rather than talk about what could be, let's talk about what is:

It is also true that several of the elements in used nuclear fuels are lanthanides, mostly from lanthanum through europium, and including significant amounts of neodymium. However the difference between nuclear neodymium and mined neodymium is one of scale. To power a single human being operating at 5000 watts of average continuous power, about twice the world wide per capita power demand (but half the American power demand) about 1 gram of plutonium would need to be fissioned per year. Isotopes decaying to neodymium in the fast fission of plutonium (which is what would be the best case) are rather pronounced since the natural element has 5 stable and 2 quasi stable - isotopes that are slightly radioactive but have enormously long half lives and so have survived mostly intact since the formation of the earth - isotopes. None of the other radioactive isotopes besides these two naturally occurring isotopes 144 and 148 have half lives longer than a few days, and thus neodymium removed from nuclear fuel, is essentially the radiologic equivalent of natural neodymium, ready for use without any radiation "problem." Because it has so many stable or quasi stable isotopes neodymium is a prominent fission product. In fast fission of plutonium about 13% result in an isotope that will decay to stable or quasi stable neodymium.

However, the energy to mass density of nuclear fuel is so high - which is the reason for its environmental superiority to all other options - that even if all the energy on the planet generated by humanity were provided by fast nuclear fission of plutonium, the neodymium produced each year would only represent only a tiny fraction of current demand, about 550 tons per year.

Let's return to the paper though:

This figure gives the "equivalents" (note the differing units) of the impact of producing 1 kg of neodymium:



The caption:
Figure 5. Environmental impacts of 1 kg of Nd obtained from Bayan Obo, Mountain Pass, and Mount Weld.


You may wonder about the (small) risk of ionizing radiation that appears in this graphic. This is because all of the lanthanide ores contain (besides the naturally occurring radioisotopes of the lanthanides themselves, including but not limited to neodymium, thorium.

Thorium is an excellent fuel for nuclear reactors, not quite as good as uranium since uranium is significantly soluble in seawater and thorium is not, and therefore uranium is sustainable forever, and thorium only for a few thousand years.

I assure you if these ores were being mined for their thorium content to make nuclear fuels, we'd have shits for brains people carrying endlessly about the "danger" of thorium mining, but since the very same mining is for so called "renewable energy" and not nuclear energy, people couldn't care less. The thorium is just dumped. Since all future generations will need to poke through our waste heaps to live, the thorium left from our quite literally quixotic adventure in wind mill tilting, the REO tailings, will represent one of the best tools left for them, not that we give a shit about them.

But...but...but...but...nuclear...

A generator in a nuclear plant will require neodymium just as a wind turbine will, this is true. However the external cost for the same amount of mass used in a wind turbine has a higher external cost than that in a nuclear power plant.

How so?

The reason is that a wind turbine might, in a very windy area, have a capacity utilization of 30%-40%, less in other areas. Anyone who has had the misfortune of seeing them blight the sky on a pristine mountain range will notice that some of the time they are still, not moving. Thus a wind turbine is 1/2 of a system that requires 2 units to do what one unit can do, and thus requires twice as much neodymium as a nuclear plant requires, since nuclear plants in this country have the highest capacity utilization (approximately 90% overall) of any form of mechanical to electrical energy conversion devices, including coal, gas, oil, hydroelectricity and (worst among them all) wind power.

A breakdown of the share of each type of environmental impact per process element:



The caption:

Figure 6. Share of single processes on total impacts of 1 kg Nd production.




The caption:
Figure 7. Share of process chain parts on total impacts of 1 kg Nd production.


An excerpt of the concluding remarks:

Eight out of 12 impact categories are dominated by chemical production for all deposits. This particularly applies to roasting, leaching, and solvent extraction, in which the chemicals are added stoichiometrically. Although flotation is the most important process for the production of REO (Figure S7 and S8) due to the large flow of ore, it is not relevant when looking at the overall results. The reason for that is the very low chemical/ore ratio (<1%). The case of Mountain Pass shows the effectiveness of measures such as avoiding chemicals by recycling saline wastewater, cleaner energy production by a natural gas fired combined heat and power plant, or the lack of a roasting process with corresponding emissions. All the same, those measures do not show impact on all environmental effects. For example, the impact category particulate matters formation is clearly controlled by the deposit and cannot be reduced substantially by additional measures such as sprinkling facilities. Also, changes in processing procedures are very unlikely, as they are determined by the mineral type. However, improvement in process efficiencies will have an impact here. Even changes with small specific impacts, such as off-gas treatment of electrolyzers or modern concepts for sludge treatment at all production sites, can add up to a recognizable total improvement…

...…In the end, it has to be kept in mind that data quality in general, but especially for China, is very poor. However, differences between the pathways lay beyond deviations assumed. With all environmental measures and legal restrictions, Mountain Pass provides Nd and Pr with the best environmental performance. Whether announcements of the Chinese government to improve environmental performances have turned into action yet is not known to us. However,It still helps to show benchmarks of technical improvements, though.


The remark after the last ellipsis says something by the way, which is relevant to many other consumer items other than so called "renewable energy," but will suffice to be attached here to so called "renewable energy."

Somebody pays for "cheap" so called "renewable energy." Maybe it's not the consumer, or even the producer of the the so called "renewable energy."

Remember:

...the shutdown of Mountain Pass shows that environmental superiority is not enough to promote RE production outside of China...


Environmental superiority is not enough.

Who pays? The people living in the Baotou region now and every generation that will live thereafter.

So much for "cheap."

Have a nice day tomorrow. I hope you're enjoying your work week as much as I'm enjoying mine.






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Reply Yet another paper on the external cost of neodymium iron boride magnets. (Original post)
NNadir May 2018 OP
hunter May 2018 #1

Response to NNadir (Original post)

Tue May 8, 2018, 02:03 PM

1. The alternator in my car doesn't have permanent magnets in it.

The windshield wiper and blower motors do.

Large power plants generally don't use permanent magnets, the magnetic field is created using electromagnets. These field windings take considerable energy to run, but it's only a small fraction of the generator's normal output. At very low power these fields can consume more energy than the generator is producing.

Permanent magnets are used in motors and generators that need to be efficient in their lower power ranges, the most obvious examples being wind turbines that operate most of the time below their nameplate capacity, or electric vehicles traveling at a constant velocity on flat roads.

The Tesla 1 & 2 used induction motors with a complex cast copper rotor and heavy copper field windings.

The Tesla 3 motor uses rare earth permanent magnets to get more range with less battery capacity in normal lower energy driving conditions and to improve regenerative braking efficiencies.




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