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Tuesday, January 7, 2014

Limits on the Growth of Wind and Solar Power, Part II -- Rare Earth Elements

Here’s a bit of trivia for you.   There is about one ton of neodymium in every large wind turbine.
Neodymium is element number 60 on the periodic table with an atomic weight of 144, and it is one of the "rare earth" group of elements.

And there is literally a ton of neodymium in every wind turbine, from Denmark to Kodiak Island.   Published estimates vary, but between 500 pounds to 2000 pounds of neodymium are needed for every megawatt of wind power.  The USGS estimates that the United States will need 380 metric tonnes of neodymium annually to provide 20% of our electrical power by 2030.  My calculations show that we need more -- a minimum of 3100 metric tonnes of neodymium per year.   The availability of so much neodymium is in doubt, and may limit the growth of wind power in the United States.

Neodymium has unique magnetic properties which make it the most efficient material for the generators inside the turbines.  It is considered essential for the construction of new turbines.  Attempts to find adequate substitute materials have been unsuccessful.  Other essential elements in wind turbine generators include praseodymium, dysprosium, and terbium.  Without these elements, we cannot build wind turbine generators without serious deterioration in efficiency and cost. 

A study completed in 2012 by MIT concluded that meeting the climate goal of 450 ppm CO2 will require a 7-fold increase in use of Neodymium, and a 26-fold increase in use of dysprosium over the next 25 years.

Solar cells have similar requirements in exotic elements.  Tellurium, indium, gallium, germanium, and palladium are each essential to some kind of solar photovoltaic cell.   Rare elements are particularly essential in high-efficiency solar cells.

The question is whether a sufficient supply of these elements exists to allow renewable energy to significantly replace fossil fuels, or whether availability of exotic elements places a limit on the growth of renewable energy.  

Let’s take a look.

Rare-Earth Elements
Rare-earth elements (REE) are heavy elements found in low concentrations in the earth’s crust.  The elements carry improbable names, reminiscent of the name of some tropical disease, or something from bad science fiction.  But some of the most important elements in today’s technology include Dysprosium, Terbium, Praseodymium, Yttrium, Ytterbium, Lutetium, Gadolinium, and Neodymium.  Rare-earth elements, and their unique properties probably inspired the fictional element “Unobtainium” in James Cameron’s film “Avatar”.
Uses of Rare Earth Elements
Rare-earths elements were discovered fairly late in the history of chemistry, and are displayed like a footnote at the bottom of the periodic table, in the rows labeled Lanthanides and Actinides.  The rows of elements are shown disconnected and without context, like the state of Alaska on a typical map of the United States.  According to the logic of the periodic table, the table should be expanded horizontally, and the rare earths should be inserted, forming another step in the table, representing another shell of electrons in the structure of the atom.  Lanthanides should be inserted between Barium and Hafnium, and the Actinides should be placed immediately below.  The electrical properties of these elements make them uniquely valuable in various electrical applications, especially in environmentally important technologies.  Non-technical literature often incorrectly includes other scarce and strategic elements as “rare earths”, in particular, tellurium, indium, and lithium.

 Some of these technologies are as follows:
Wind Turbines (Neodymium, Praseodymium, Dysprosium, Terbium)
Solar panels (Indium, Tellurium, Gallium, Germanium, Palladium)
Hybrid cars (Lanthanum, Neodymium, Praseodymium, Dysprosium, Terbium)
Exhaust catalysts (Cerium, Lanthanum)
Compact fluorescent lights (Yttrium, Europium, Terbium)
LEDs (Yttrium, Europium, Terbium)

Rare earth elements are also used in consumer electronics of all kinds, medical applications, high-tech electronics, water treatment, nuclear reactor control, pigments, fertilizer, coatings, ceramics, glass, superalloys, petroleum catalysts, industrial and coal-plant pollution scrubbers, etc.

Geologic Occurrence and Mining
Rare earth elements might be better described as “dispersed earth elements”.   Because of their complex chemical properties, REEs do not occur in minerals with simple, distinct composition.  Instead, REEs occur as complex minerals showing a range of composition involving different REEs.  REEs occur in low concentrations, and separation of individual REEs is difficult. 

The great majority of rare-earth production is as a by-product of mining for another commodity.  This means that the cost of rare earth elements is generally subsidized by the principal mining product, and expansion of rare earth production volumes is difficult.

Most of the world’s rare earth element production and nearly all of the heavy REE (actinide) production comes from a single iron mine in Inner Mongolia.  In 2010, China cut its export quotas of REE, and declared an intention to reserve its production of REE for internal use.  The supply disruption caused extreme volatility in the price of REEs, and prompted the resumption of REE mining in other parts of the world.   Although REE are present in many parts of the world, there are only a handful of mines producing rare earth elements.  Mount Weld in Australia, and Mountain Pass in California are among the mines re-opened in the last two years. 

Production of rare earth elements as a by-product of other activity provides a substantial subsidy in the price of rare-earth elements.  The volume of production is a function of the production of the primary ore; this creates a barrier to expanding supply as a result of market demand.

Environmental Issues
Rare-earth elements generally occur with thorium and other radioactive or toxic elements.  Processing the ore requires finely grinding the ore, and chemical treatments to separate the rare-earth elements from the tailings.  Tailings are generally toxic and an environmental problem. 

The Mountain Pass mine in California has a rare earth oxide ore grade of 8.9% by weight, which is about 4% by volume.  Neodymium is about one-eighth of the total REE production.  The Mount Weld mine is one of the richest deposits of rare earth elements on earth, about 15.4% by weight.  Neodymium and Praseodymium comprise about one-quarter of the rare earth oxides.  For a sense of scale, in order to mine enough neodymium from these very rich mines, it will require generating about 10 to 90 metric tons of toxic, radioactive mining tailings for each large wind turbine.  (To be fair, other valuable elements are extracted with the neodymium.)

In the past, ore from the United States was sent to China for processing (also called beneficiation), and ore from Australia (as of my last information) is still being sent to Malaysia for processing.  The refined rare-earth metals are returned to the host country, and the toxic waste remains in China and Malaysia.  We have literally exported the environmental damage associated with our “green” energy.

Neodymium Supply and Demand for Wind Power
A USGS paper published in 2011 concluded that the United States would need 380 metric tonnes of Neodymium annually to meet a “market goal” of producing 20% of the country’s electricity from wind power by the year 2030.   Working from data from the US Energy Information Agency, I calculate a much larger number, requiring over 3100 metric tonnes of neodymium annually to meet this goal.  I have not yet resolved the source of the difference in the estimates.

My calculation of Neodymium demand for wind generation
         4,047,765 Gigawatt-Hours  --  US Net Electrical Generation (2012).
809,553  Gigawatt-Hours – 20% of annual electrical generation.
      27.2 % -- Current average wind capacity factor (efficiency: power generated/capacity).
339,608  Megawatts – Required capacity to provide 20% of US electrical generation.
  59, 075 Megawatts – Current installed wind generation capacity.
            280, 533 Megawatts – New capacity required to meet 20% goal.
             15,585 Megawatts – New-build capacity required annually, given 18 years from 2012 to 2030.
               3,117 Tonnes – Neodymium needed annually, at 200 kg Nd per megawatt.

The Mountain Pass Mine in California was the world’s principal source of rare earth elements 1970s though 1990s.  Mountain Pass recently re-opened after being closed for a decade due to competition from China.  

It is currently the United States' only domestic supply of rare earth elements.   Production targets announced by the company would suggest that neodymium production could reach 2000 to 2500 metric tonnes per year.  If the nation’s entire supply of neodymium were dedicated to wind power, production from Mountain Pass and another source might meet the demand.  However, neodymium is also a critical element in other technologies with growing demand – mobile telephones, computer screens, anti-lock brakes, glare-free mirrors, hybrid and electric cars, medical devices, and military technologies. 

Given the price volatility of neodymium, and environmental barriers to establishing new mines, I think it is unlikely that industry will establish significant sources of new supply in a timely fashion.  The lack of new supply will lead to shortages and limits on the growth of wind power by 2030.

Critical Elements for Photovotaic Solar Panels
Photovoltaic solar panels come in three varieties: silicon-based cells, polycrystalline thin-film devices, and multi-junction devices.   Silicon based solar cells are the most common but least efficient, representing 90% of the current market.  High efficiency solar cells are thin-film and multi-junction devices. 
Polycrystalline thin-film devices are made of layers of either cadmium-tellurium (CdTe) or copper-indium-gallium-selinide (CIGS).  Tellurium and indium are the critical elements.  Multi-junction devices utilize a different suite of exotic elements, including gallium, indium, and germanium.

Ninety percent of commercial tellurium is a by-product of copper production.  Tellurium is a trace element; 500 tons of copper must be processed to yield one pound of tellurium; a ratio of 1,000,000:1 (unverified reference in Wikipedia).  The primary process to recover tellurium is electrolysis, used on high-grade ores.  As the copper industry increasing utilizes lower-grade ores, solvent-based processes are preferred.  Unfortunately for tellurium supply, solvent-based extraction is less suited for recovery of tellurium.  Although incremental gains might be achieved by increasing the efficiency of the electrolysis process, in general, increasing the supply of tellurium will require a proportional increase in the supply of copper.   And a two-fold, three-fold, or ten-fold increase in copper production, in timely fashion to replace fossil fuels, is unlikely.

Indium, the critical component in CIGS solar cells, is similarly co-produced and derived from zinc mining.  In all, the exotic elements required for high-efficiency solar photovoltaic devices (tellurium, indium, gallium, and germanium) are of limited supply, and will ultimately constrain the growth of high-efficiency solar cells. 

The price of rare earth elements is volatile, due to rapid changes and uncertainties in supply and demand.  In May, 2010, the price of Neodymium was $42/kg.   During a time of increasing demand for wind turbines and hybrid cars, China indicated that it would set limits on REE exports, to retain sufficient supply for its own needs.  By May, 2011, the price of Nd rose to $284/kg, a nearly 700% rise.   By 2013, the market had settled to the range of $75 to $105/kg, a 65% drop from the earlier peak.  Similar price volatility exists for other rare elements.  A continuous price history is available on the internet, but is held by copyright.  The following chart was constructed by interpolation of data points in the public domain.

Tellurium prices rose from $30/kg in 2000 to $360/kg in 2011.  Following the bankruptcy of several solar cell manufacturers in 2012, tellurium dropped to the current price of $90/kg.  As with the rare earth elements, price uncertainty will be a barrier to investment to increase supply. 

Under conditions of such price volatility, it is very difficult for mining companies to make firm capital commitments for billion-dollar projects to expand supply. 


Renewable wind and solar energy are growing rapidly, as a result of dedicated efforts to reduce our dependence on fossil fuels.   However, electrical generation from wind and high-efficiency solar panels is dependent on a number of exotic elements, notably neodymium, tellurium and indium.   Expanding the supply of these elements is problematic, due to co-production with other minerals, environmental impacts and permitting delays, costs of establishing new mines, and volatile and uncertain pricing for the products.  

Part I of this post, "Limits on the Growth of Wind and Solar Power, Part I -- Area"
can be found here:

References and notes:
China controls 93 percent of all RE production, and 99 percent of certain elements (dysprosium & terbium).   No new articles since June 2011.

Neodymium is necessary for wind turbines and electric motors in hybrid cars.  China produces over 98% of world REE production.
A single 3.5 MW wind turbine contains 600 kg (>1300 pounds) of rare earth elements; a hybrid car contains about 5 kg of REE.

MIT Elisa Alonso  REE supply and demand study.

Evaluating Rare Earth Element Availability: A Case with Revolutionary Demand from Clean Technologies ,  Alonso, Environ. Sci. Technol., 2012, 46 (6), pp 3406–3414
Meeting the climate goal of 450 ppm CO2 will require 700% increased consumption of Neodymium, and 2600% increased consumption of dysprosium, over the next 25 years.

Rare Earth prices
2013 Nd prices ranged from $74/kg to $105/kg, current price (1/3/14) of $90/kg.
2013 Dy prices dropped from $780/kg to $605/kg.

17 elelments.   Two mines outside China are planned for start-up in 2012: Mountain Pass, Molycorp, California, and Mount Weld, Lynas, Australia.  [Mountain Pass re-opened April 2011.]
China sharply reduced REE export quotas, briefly embargoed exports of REE to Japan in 2010, in response to a territorial dispute.
Hybrid  car contains about 5 pounds of REE in its magnets and battery electrodes.  Other uses include earbud speakers and phosphor laptop displays.
Every Megawatt of wind power requires about a half-ton of REE.  Projections of growth of wind power call for 10,000 MW of new turbines, but “there just isn’t the supply” ( Keith Delaney, the executive director of the Rare Earth Industry and Technology Association).

May 2010:  Nd $19/pound  =  $41.80/kg
May 2011:  Nd $129/pound  =  $283.80/kg
2011, US gets 92% of REE from China; only US mine, (Molycorp, Mountain Pass, CA, closed 2002) re-opened April 2011.  The mine suffered waste-water leaks from 1984 to 1998.
List of REE and uses.
Chart showing REE composition at Mountain Pass. Nd is about 1/8 of total REE production. 

China cut export quotas 35% in 2010; established limits on pollutants and emissions in tailings from REE mining in Oct, 2010.

China owns 50% of known REE deposits, but produces 98% of REE production.
Summary of Alonso MIT study, 2600% increase in demand for dysprosium;  700% increase in demand for neodymium in 25 years.

Good Infographic, much information.    Pricing 2008 – 2011 for dysprosium, europium, terbium oxides; all show huge price increases.
Reserves; China 50%; CIS 17%; US 12%.  Total world reserves REE oxides 114 million tons, USGS.
2010 production: 133,000 tonnes; expected 2015 production 210,000 tonnes.

Several web-pages of textbook type information.  
Typical hybrid car contains 28 kg REE.  [Note difference from MIT study.]
Green technologies:  exhaust catalysts (Ce, La),  Wind Turbines (Nd, Pr, Dy, Tb).
Compact Fluorescent lights, LEDs (Y, Eu, Tb).
Also Consumer electronics of all kinds, Medical applications, high-tech electronics, water treatment, nuclear reactor control, pigments, fertilizer, coatings, ceramics, glass, superalloys, petroleum catalysts, industrial and coal-plant pollution scrubbers, etc.
More than 200 minerals contain essential or significant REE. 
REE occur in alkaline intrusive igneous complexes, i.e. low-calcium granitoid rocks and pegmatites.
Other commercial sources are apatite and loparite Russia, REE-bearing clays (LongNan clay, Jiangxi Province),

Monazite is a rare-earth phosphate.  Occurs in pegmatites and placer deposits (density 4.6 to 5.7).  Often contains Thorium, and is radioactive.
Placers are found in India, Australia, Brazil, Sri Lanka, Malaysia, Nigeria, Florida and N.Carolina;  pegmatites in Wyoming, New Mexico, Virginia, Colorado, Maine, N. Carolina; Bolivia, Madagasgar, Norway, Austria, Switzerland, Brazil, and Finland.

Good description of why REE are “rare” – essentially dispersed, rarely concentrated in economic deposits.
Long, pedantic article.
REE occur in pegmatitic, and secondary deposits.  Hydrothermal deposits are possible near plutons, but long-distance hydrothermal transport is unlikely.
LongNan Jiangxi  -- Chinese Iron Mine
Relative abundances of REE in different mines.   Mountain Pass and Mount Weld have negligible dysprosium, Thulium, Holmium, but are enriched in neodymium.
Contains an article:  “How Green Is Green?”   R.E. Beauford, April 16, 2011, compares wind energy to coal-fired plants.   Largely a diatribe against coal-fired plants; good statistics on pollutants.   Disappointingly simplistic view of pure “clean” wind power.

USGS REE in Alaska.  Bokan mountain is one of few known deposits where Heavy REE can be commercially produced.   Bokan Mountain is a former uranium mine.  Granite host rock in rift setting.

USGS general report on REE in the United States, and world perspective.

USGS report on wind energy 2010 – 2030, and required resources (reported as average annual consumption), including REE.   380 metric tons of Neodymium required annually to meet a market goal of 20% wind energy by 2030.   [I question this number; it is much too low.   My calculation is 3100 metric tonnes per year.]

 July 2013 article.  More about China’s domination of REE production.   Australian mine now operating.

All of the world’s Heavy REE (including dysprosium come from Chinese sources, primarily the Bayan Obo iron mine in Inner Mongolia.

Rare earth prices
Trial subscription

Rare earth prices –trial subscription

Neodymium price elevated by 1400 percent 2010 to 2011.   Declined by 33 percent by Feb., 2012.

Penn State Energy Institue REE news; latest article 2011.

Environmental problems with Chinese REE mining.   “Baiyunebo in Inner Mongolia, where most of the world’s rare earth is mined, along with iron ore.”   REE tailings have ruined farmlands and aquifers.

Bokan Mountain report.   Concentrations of REE are measured in low tens to hundreds ppm.

interesting science blog

REE occurrences in the US

USGS studies gold-rush era mine tailing for REE.

Mountain pass project description

Molycorp Mountain Pass page
Graph of Mountain Pass production targets, and types of REE.

2011 Energy Department study reports supply challenges for five REE, (dysprosium, terbium, europium, neodymium, and yttrium) may affect clean energy technologies in coming years. 
Research for replacements is on-going.
Ditto, Energy Dept report, shortages until 2015.

More search for alternatives to REE

REE showed huge weekly changes:   47% for yttria, 35% for terbium.   Other increases in the range of 25%.
REE prices climb as China shuts illegal mines.

Weakening prices delays production from new mine in Australia.
REE prices are up recently, but significantly below a year ago.

Concerns about toxic waste from proposed REE mining in Malaysia, particularly thorium.    Examples of toxic residues in China.

Every megawatt of wind power requires 200 kg of neodymium.

Indium tin oxide is key element in solar panels.   Known indium reserves will satisfy only 20 years demand, and indium is expensive and subject to volatile pricing.   Half of the supply comes from China.
Zinc oxide is less efficient but available and cheaper.   Use of zinc oxide is still in the research realm, with application and integration methods not yet established.

Article date Nov 2011.   European Union study shows expected supply problems with REE critical to renewable energy and cleaner transport.    The study showed that five metals:  dysprosium, neodymium, tellurium, gallium, and indium, are at the highest risk of supply bottlenecks, due to high demand, concentration of supply and political risk.  Solar energy technologies will require 50% of the world supply of teluriumj, and 25% of the supply of indium. 

NERL Silicon based solar cells represent 90% of sales in 2011.   15 GW of Si-based Solar cells manufactured in 2011, 10x more than any other solar technology.
Polycrystalline thin-film devices
CdTe devices and CIGS (copper-indium-gallium-selenide) devices
Multijunction devices (gallium, indium, phosphorus, arsenic, germanium)

The US would need 400 t of tellurium for every gigawatt of solar energy (sic).
Total known world tellurium supply of 48,000 t would be hopelessly out of kilter if the world went solar.
General rule, 1 t of neodymium needed for one megawatt of wind power.
So far, attempts to use less neodymium have not worked.
Electric cars also require other REE.
Geologists seen as being in short supply!  Only 4000 world wide.

Talks hopefully about 100,000,000 electric cars in America by 2040, requiring 250 billion kWhrs. 
Equivalent of 30 1000-MW nukes, 75 combined cycle 800 MW gas plants or 250,000 1 MW turbines.
--Only 5% of electrical production in the US.

Knowledgeable article from power-hitter in metals industry.   Article is generally critical of analyses that show there is enough tellurium for solar power growth.
Market fundamentals for tellurium are an enigma.  No general agreement on size of global supply, rate of production, or locations of production.
90% of available tellurium is as a byproduct of copper.   Recovery of tellurium depends on the smelting process used.  The copper industry is actually moving away from processes that recover tellurium, in order to process lower-grade ores.
USGS estimate of global tellurium production in 2007 – 500 t. 
Maximum tellurium availability – 3200 t/year (calculation of author), most likely maximum 1600 t/yr, as calculated by NERL (1997).
USGS speculates that 1200 t/yr could be produced by separation from copper.

Tellurium is produced by “electro-winning” beneficiation process, from higher-grade ores.  As high-grade ores are exhausted, miners are shifting to a solvent-leaching process to treat lower-grade ores.  Solvent leaching “does not lend itself” to recovery of tellurium.

From Wikipedia:  One gigawatt of CdTe PV modules would require about 66 tonnes of Tellurium (at current efficiencies).
Installed electric generation in the US today is 1,100 GW – implied requirement would be 67,600 tonnes of tellurium, without considering capacity factor. (my conclusion)

Good discussion of the limited availability of dispersed elements, i.e. those that are mined only in association with another mineral.   Example Gallium.

The US would need 400 tons of Tellurium per Gigawatt of solar energy.

Typically, 500 tons of copper ore yields one pound of tellurium.  Year-end price 2000 was $14/lb, but by 2006 reached $100/lb.

US tellurium Price, production imports and exports.   Price per kg, rises from $82 in 2007 to $360 in 2011.

2013 price of tellurium has fallen from near $140/kg to current price of $90/kg (1/3/14).

Tellurium price volatility.   Tellurium traded as high as $350/kg in 2011, ranged from below $100 to over $300/kg in 2012.   March 2013 pricing at $100 - $140/kg, due to bankruptcy of solar power companies in 2012, reducing demand.

Very good site.    Nd,Pr, Dy, Tb are used in hybrid cars.

Each Toyota Prius contains about 1 kg of Nd, and the battery contains 10 to 15 kg lanthanum.

Rare earth based solar panels.

100,000 metric tons REE global production in 2012, source IHS Chemical.   Global growth expected to be 7.6 percent annually (doubling rate every 9 years).

Terbium, europium, and yttrium needed for fluorescent light bulbs.

Indium used in PV panels.   Research suggests possibility of replacing Indium with Zinc.

Projects being considered for development today are in the range of 0.2% to 12% Total Rare Earth Oxide ore grade.  Heavy REO enrichment is defined as HREO/TREO.   Heavy REO enrichment of proposed projects ranges from 0.6% to 55%. 

Mountain Pass mine – mostly LREE.   Rare earth oxides average about 8.9% of the ore by mass.  Ce, La, Nd, and Pr comprise about 99% of the REE output.
Mount Weld mine has one of the highest REE ore grades on the planet, about 15.4% by weight.   Nd and Pr are about 23.8% of oxides. 

The importance of Tellurium is still not recognized.   “Tellurium forms many compounds, but none that are commercially important.”

Despite doubling of supply due to improved extraction, the DOE expects a supply shortfall by 2025.

Cadmium – Tellurium PV panels have an efficiency rating of 11% to 13%, as compared to amorphous silicon panels, which have an efficiency of 7% - 9%.

CdTe PV panels represented about 8% of the solar PV panels installed in 2011.

CdTe PV panels are the cheapest on the market; CIGS (indium) are the most laboratory efficient panels.

Germanium Is a by-product of zinc mining.
Rare-earth ore from the United States was formerly sent to China for beneficiation.  Lack of beneficiation alternatives contributed to the shutdown of Mt. Pass mine in California.
Dr. Susan Karl, USGS geologist , personal communication, 8/13/13
Australia still sends rare-earth ore to Malaysia for beneficiation
Dr. Susan Karl, USGS geologist, personal communication, 8/15/13
Tellurium Fact Sheet; UKERC, UK Energy Research Centre

USGS claim that only 380 metric tonnes of Nd per year are needed to reach 20% of electrical generation by 2030 needs a reality check ---
1)      Doesn’t make sense from supply point of view.  We know Nd supply is tight, but Mountain Pass will produce about 2300 tonnes of Nd per year.
2)      Other sources say that about 1 ton of Nd is needed in every wind turbine.  Surely we need more than 380 turbines per year to supply 20% of the US electrical demand.  Particularly when considering the capacity factor.  Assuming a 30% capacity factor, we would need a nameplate wind generation capacity of 60% of the US electrical demand, to produce 20% of our electricity.  

Good Neodymium fact sheet, lots of uses.   Associated pages on scientific properties of Nd and Nd oxide.

British Geological Survey REE report.  Contains forecast of supply and demand.

Good report on REE, contains market forecast from Brit Geol Survey,  and  Mountain Pass REE composition  from USGS report.
Rare earth prices have been artificially low since the 1990s, as the result of Chinese REE production [as a by-product of iron mining] exceeding demand.
Price table for REE from 2002 through 2011.

Rare Earth Elements—Critical Resources for High Technology

USGS REE fact sheet.    


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