A Solution to the Elements Shortage for Lithium Ion Batteries?

Global warming together with a possible energy crisis gives us problems for transport. One of the alleged solutions is battery powered cars. This gives three potential problems. One of these is how to generate sufficient electricity to power the batteries, but I shall leave that for the moment. The other two relate to chemistry. A battery (or fuel cell) has two basic electrodes: a cathode, which is positive, and an anode, which is negative. The difference in potential between these is the voltage, and is usually taken as the voltage at half discharge. The potential is caused by the ability to supply electrons to the anode while taking them at the cathode. At each there is a chemical oxidation/reduction reaction going on. The anode is most easily answered by oxidising a metal. Thus if we oxidise lithium we get Li  ➝ Li+  + e-. The electron disappears off to the circuit. We need something to accept an electron at the cathode, and that is Co+++, which gets reduced to the more stable Co++.  (Everything is a bit more complicated – I am just trying to highlight the problem.) Now superficially the cobalt could be replaced by a variety of elements, but the problem is the cobalt is embedded in a matrix. Most other ions have a substantial volume change of the ions, and if they are embedded in some cathode matrix, the stresses lead it to fall to bits. Cobalt seems to give the least stress, hence will give the batteries a longer life. So we have a problem of sorts: not enough easily accessible lithium, and not enough cobalt. There are also problems that can reduce the voltage or current, including side reactions and polarization.

In a fuel cell we can partly get over that. We need something at the cathode that will convert an input gas into an anion by accepting an electron, thus oxygen and water forms hydroxide. At the anode we need something that “burns”, i.e. goes to a higher valence state and gives up an electron. In my ebook “Red Gold”, a science friction story relating to the first attempt at permanent settlement of Mars, a portable power source was necessary. With no hidden oil fields on Mars, and no oxygen in the air to burn it if there were, I resorted to the fuel cell. The fuel cell chemistry I chose for Mars was to oxidize aluminium, which generates three electrons, and to reduce chlorine. The reason for these was that the settlement on Mars needed to make things from Martian resources, and the most available resource was the regolith, which is powdered rock. This was torn apart by nuclear fusion power, and the elements separated by magnetohydrodynamics, similar to what happens in a mass spectrometer. The net result is you get piles of elements. I chose aluminium because it has three electrons and hence more power capacity, and I chose chlorine because it is a liquid at Martian temperatures so no pressure vessel was required. Also, while oxygen might produce a slightly higher voltage, oxygen forms a protective coating on aluminium, and that stops that reaction.

An aluminium battery would have aluminium at the anode, and might have something in the electrolyte that could deposit more aluminium on it. Thus during a charge, you might get, if chlorine is the oxidiser,

4(Al2Cl7)-   + 3e-  → Al  +  7(AlCl4)-   

which deposits aluminium on the anode. During discharge the opposite happens and you burn aluminium off. Notice here the chlorine is actually tied up in chemical complexes and the battery has no free chlorine. Here, the electrolyte is aluminium chloride (Al2Cl6). For the fuel cell, we would be converting the gas to a complex at the cathode. That is not very practical on Earth, but the enclosed battery would be fine.

The main advantage of aluminium is that it gets rid of the supply problem. Aluminium is extremely common on Earth, as the continents are essentially made of aluminosilicates. The cathode can be simple carbon. A battery with this technology was proposed in 2015 (Nature 520: 325 – 328) that used graphite cathodes. It was claimed to manage 7,500 cycles without capacity decay, which looks good, but so far nobody seems to be taking this up.

Now, for an oddity. For discharge, we need to supply (AlCl4)- to the anode as it effectively supplies chlorine. Rather than have complicated chemistry at the cathode we can have an excess of AlCl4– from the start, and during charging, store it in the cathode structure. During discharge it is released. So now we need something to store it in. The graphite used for lithium-ion batteries comes to mind, but here is an oddity: you get twice the specific capacity, twice the cell efficiency and a 25% increase in voltage by using human hair! Next time you go to the hair dresser, note that in the long term that might be valuable. Of course, before we get too excited, we still need such batteries to be constructed and tested because so far we have no idea how such hair stands up to repeated cycles.

What we do not know about such batteries is how much dead weight has to be carried around and how small they can be made for a given charge. The point about cars is that eventually the critical point is how far will it go on one charge, how long does it take to safely recharge, how much volume of the vehicle does it take, and is it flammable? The advantage of the aluminium chloride system described above is that there are probably no side reactions, and a fire is somewhat unlikely. The materials are cheap. So, the question is, why hasn’t more been done on this system? My guess is that the current manufacturers know that lithium is working, so why change? The fact that eventually they will have to does not bother them. The accountants in charge think beyond the next quarter is long-term. Next year can look after itself. Except we know that when the problem strikes, it takes years to solve it. We should get prepared, but our economic system does  not encourage that.

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This and That from the Scientific World

One of the consequences of writing blogs like this is that one tends to be on the lookout for things to write about. This ends up with a collection of curiosities, some of which can be used, some of which eventually get thrown away, and a few I don’t know what to do about. They tend to be too short to write a blog post, but too interesting, at least to me, to ignore. So here is a “Miscellaneous” post.

COP 27.

They agreed that some will pay the poorer nations for damage so far, although we have yet to see the money. There was NO promise by anyone to reduce emissions, and from my point of view, even worse o promise to investigate which technologies are worth going after. Finally, while at the conference there were a number of electric buses offering free rides, at the end of the conference these buses simply disappeared. Usual service (or lack thereof) resumed.

Fighting!

You may think that humans alone fight by throwing things at each other but you would be wrong. A film has been recorded ( https://doi.org/10.1038/d41586-022-03592-w) of two gloomy octopuses throwing things at each other, including clam shells. Octopuses are generally solitary animals, but in Jervis Bay, Australia, the gloomy octopus lives at very high densities, and it appears they irritate each other. When an object was thrown at another one, the throw was far stronger than when just clearing stuff out of the way and it tended to come from specific tentacles, the throwing ones. Further, octopuses on the receiving end ducked! A particularly interesting tactic was to throw silt over the other octopus. I have no idea what the outcome of these encounters were.

Exoplanets

The star HD 23472 has a mass of about 0.67 times that of our sun, and has a surface temperature of about 4,800 degrees K. Accordingly, it is a mid-range K type star, and it has at least five planets. Some of the properties of these include the semi-major axis a (distance from the star if the orbit is circular), the eccentricity e, the mass relative to Earth (M), the density ρ  and the inclination i. The following table gives some of the figures, taken from the NASA exoplanet archive.

Planet     a              e            M        ρ           i

b           0.116      0.07       8.32      6.15      88.9

c           0.165      0.06       3.41      3.10      89.1

d           0.043      0.07       0.55      7.50      88.0

e           0.068      0.07       0.72      7.50      88.6

f           0.091      0.07       0.77       3.0        88.1

The question then is, what to make of all that? The first thing to notice is all the planets are much closer to the star than Earth is to the sun. Is that significant? Maybe not, because another awkward point is that the inclinations are all approaching 90 degrees. The inclination is the angle the orbital plane of the planet makes with the equatorial plane of the star. Now planets usually lie on the equatorial plane because that was also the plane of the accretion disk, so something has either moved the planets, or moved the star. Moving the planets is most probable, and the reason the inclinations are all very similar is because they are close together, and they will probably be in some gravitational resonance with each other. What we see are two super Earths (b and c), two small planets closest to the star, which are small, but very dense. Technically, they are denser than Mercury in our system. There are also two planets (c and f) with densities a little lower than that of Mars.

The innermost part of the habitable zone of that star is calculated to be at 0.364 AU, the Earth-equivalent (where it gets the same radiation as Earth) at 0.5 AU, and the outer boundary of the habitable zone is at 0.767 AU. All of these planets lie well inside the habitable zone. The authors who characterised these planets (Barros, S. C. C. et al. Astron. Astrophys. 665, A154 (2022).) considered the two inner planets to be Mercury equivalents, presumably based on their densities, which approximate to pure iron. My guess is the densities are over-estimated, as the scope for error is fairly large, but they certainly look like Mercury equivalents that are somewhat bigger than our Mercury

Laughing Gas on Exoplanets

One of the targets of the search for exoplanets is to try and find planets that might carry life. The question is, how can you tell? At present, all we can do is to examine the spectra of atmospheres around the planet, and this is not without its difficulties. The most obvious problem is signal intensity. What we look for is specific signals in the infrared spectrum and these will arise from the vibrations of molecules. This can be done from absorptions if the planet transits across the star’s face or better (because the stellar intensity is less a problem) from starlight that passes through the planet’s atmosphere.

The next problem is to decide on what could signify life. Something like carbon dioxide or methane will be at best ambiguous. Carbon dioxide makes up a huge atmosphere on Venus, but we do not expect life there. Methane comes from anaerobic digestion (life) or geological activity (no life). So, the proposal is to look for laughing gas, better known as nitrous oxide. Nitrous oxide is made by some life forms, and oddly enough, it is a greenhouse gas that is becoming more of a problem from the overuse of agricultural fertilizer, as it is a decomposition product of ammonium nitrate. If nothing else, we might find planets with civilizations fighting climate change!

Reducing Electricity Usage in Your Refrigerator

When thinking about battling climate change, did you know that a major electricity consumer in your house is your refrigerator? The International Institute of Refrigeration (yes, there are institutes for just about everything) estimates that about 20% of all electricity used is expended on vapour compression refrigeration. The refrigerator works by compressing a vapour, often some sort of freon, or in industry, with ammonia, and when compressed it gives off heat. When you ship it somewhere else and expand it, the somewhere else gets colder. This is also the principle of the heat pump and various air conditioning units. Compress gas here to add heat from a heat exchanger; ship the gas there and expand it, where it cools a heat exchanger. The compression and expansion of gas moves heat from A to B, hence the name heat pump. Also, the refrigerant gases tend to be powerful greenhouse gases. One kilogram of R410a has the same greenhouse impact as two tonne of carbon dioxide. Refrigerants leak into the atmosphere from faulty equipment or when equipment is not properly disposed of.

It is possible to heat or cool without any gas through the Peltier effect. Basically, when electric current passes between two conductors, heating or cooling effects may be generated. There are commercial solid-state such cooling systems, but they suffer from high cost and poor efficiency, in part because the effect is restricted to the specific junction.

There is an alternative. Some solid state materials can cool when they are subjected to strain, which is generated from an external field, such as  the electric or magnetic fields, or simply pressure. So far most efforts have been focused on the magnetic field, and one material, Mn3SnC apparently gives significant cooling,  but the magnetic field has to be greater than 2 tesla. That means expensive and bulky magnets, and additionally the refrigerator, if it used them, would have to be a “no-go” area for credit cards, and possibly people with a pacemaker. Even aside from direct messing with the pacemaker, losing all those bitcoin just because you wanted a cool beer could lead to medical problems.

However, there has been an advance. Wu et al. (Acta Materiala 237: 118154) have taken the Mn3SnC and coated it with a piezoelectric layer of lead zirconate titanate. Don’t ask me how they come up with these things; I have no idea, but this is certainly interesting. They probably do it by looking through the literature to find materials already known to have certain properties. Thus a piezoelectric effect is where you generate an electric voltage by applying pressure. Such effects are reversible so if you can generate a voltage by applying pressure to something, you can generate pressure by applying a potential difference. Recall that pressure also can generate a cooling effect. Accordingly, by applying an electric field to this coated material a cooling effect was obtained equivalent to that of a 3 tesla magnetic field. When the electric field is removed, the temperature returns to where it was. How useful will this be? Hard to tell right now. The temperature drop when applying a field of 0.8 kV/cm was slightly under 0.6 of a degree Centigrade, which is not a huge change while the voltage is tolerably high. Interestingly, if you apply a magnetic field you also get a temperature change, but in the opposite direction – instead of cooling, it heats. Why that is is unclear.

As you might guess, there is still a significant distance to go before we get to a refrigerator. First, you have to get the cooling into some other fluid that can transport it to where you need it. To do that you have to take the heat out of the cooling fluid, but that will heat up your unit, so you need another fluid to take the heat to where it can be dissipated. We have very roughly the same cycle as our present system except we are not compressing anything but we have two fluids. Except I rather think we will be, because pumping a fluid involves increasing its pressure so it flows. The alternative is to put the material across the rear wall of the refrigerator thus to cool the interior and have the heat dissipated out the back. The problem now is the change of temperature is rather small for the voltage. This is not so much a problem with fluids transporting it, but if the solids transport it, the solids are always heated by the environment so your temperature drop is from the room temperature. Half a degree is not very helpful, although you could increase the electric field. Unfortunately, to get a big enough temperature change you might be into the spark jumping region. Lightning in the kitchen! Finally, do you want the back of your refrigerator to be carrying even a kilovolt electric field? My guess is this effect may remain a curiosity for some length of time.

Economic Consequences of the Ukraine War

My last post mentioned the USSR collapse. One of the longer term consequences has been this Ukraine war. Currently, there have been problems of shelling of the Zaporizhzhia nuclear plant, and this appears to have happened in that our TV news has shown some of the smashed concrete, etc. The net result is the plant has shut down. Each side accuses the other of doing the shelling, but it seems to me that it had to be the Ukrainians. Russia has troops there, and no military command is going to put up with his side shelling his own troops. However, that is far from the total bad news. So far, Ukraine has been terribly lucky, but such luck cannot last indefinitely. There are consequences outside the actual war itself. The following is a summary of some of what was listed in the August edition of Chemistry World.

The Donbas area is Ukraine’s heavy industry area, and this includes the chemical industry. Recently, Russian air strikes at Sieverierodonetsk hit a nitric acid plant, and we saw images of the nitrogen dioxide gas spewing into the atmosphere.

Apparently, in 2017 Ukrainian shelling was around a chemical plant that contained 7 tonne of chlorine. Had a shell hit a critical tank, that would have been rather awkward. Right now, in the eastern Donbas there is a pipeline almost 700 km long that pipes ammonia. There are approximately 1.5 million people in danger from that pipeline should it burst; exactly how many depends on where it is broken. There are also just under  200,000 t of hazardous waste stored in various places. The question now is, with all this mess generated, in addition to demolished buildings and infrastructure, who will pay what to clean it up? It may or may not be fine for Western countries to use their taxes to produce weapons to give to Ukraine, but cleaning up the mess requires the money to go to Ukraine, not armament-making corporations at home.

The separation of the Donbas has led to many mines being closed, and these have filled with water. This has allowed mercury and sulphuric acid to be leached and then enter the water table. During 2019, a survey of industrial waste was made, and Ukraine apparently stores over 5.4 billion t of industrial waste, about half of which is in the Donbas. Ukraine has presumably inherited a certain amount, together with some of the attitudes, from the old Soviet Union. From experience, their attitude to environmental protection was not their strong point. I recall  one very warm sunny morning going for a walk around Tashkent. I turned a corner and saw rather a lot of rusty buildings, and also, unbelievably, a cloud. How could water droplets form during such a warm dry climate? The answer was fairly clear when I got closer. One slight whiff, and I knew what it was: the building was emitting hydrogen chloride into the atmosphere and the hydrochloric acid droplets were the reason for the rust.

Meanwhile, some more glum news. We all know that the sanctions in response to the Ukraine war has led to a gas shortage. What most people will not realize is what this is doing to the chemical industry. The problem for the chemical industry is that unlike most other industries, other than the very sophisticated, the chemical industry is extremely entangled and interlinked. A given company may make a very large amount of chemical A, which is then sold as a raw material to a number of other companies, who in turn may do the same thing. There are many different factories dependent on the same raw chemical and the material in a given chemical available to the public may have gone through several different steps in several different factories.

An important raw mixture is synthesis gas, which is a mix of carbon monoxide and hydrogen. The hydrogen may be separated and used in steps to make a variety of chemicals, such as ammonia, the base chemical for just about all nitrogen fertilizer, as well as a number of other uses. The synthesis gas is made by heating a mixture of methane gas and water. Further, almost all chemical processing requires heat, and by far the bulk of the heat is produced by burning gas. In Europe, the German government is asking people to cut back on gas usage. Domestic heating can survive simply by lowering the temperature, although how far down one is prepared to go during winter is another question. However, the chemical industry is not so easily handled. Many factories use multiple streams, and it is a simple matter to shut down such a stream, but you cannot easily reduce the amounts going through a stream because the reactions are highly dependent on pressure, and the plant is in a delicate balance between amount processed and heat generated.  A production unit is really only designed to operate one way, and that is continuously with a specific production rate. If you close it down, it may take a week to get it started again, to get the temperature gradients right. One possibility is the complete shutdown of the BASF plant at Ludwigshafen, the biggest chemical complex in the world. The German chemical industry uses about 135 TWhr of gas, or about 15% of the total in the country. The price of such gas has risen by up to a factor of eight since Russia was sanctioned, and more price rises are likely. That means companies have to try to pass on costs, but if they face international competition, that may not be possible. This war has consequences far beyond Ukraine.

A Plan to Counter Global Warming Must be Possible to Implement

Politicians seem to think that once there is a solution to the problem in theory, the problem is solved so they stop thinking about it. Let us look at a reality. We know we have a problem with global warming and we have to stop burning fossil fuels. The transport sector is a big problem, but electric vehicles will do the trick, and in theory that might be true, but as I have pointed out in previous posts there is this troublesome matter of raw materials. Now the International Energy Agency has brought a little unpleasantness to the table. They have reported that global battery and minerals supply chains need to expand ten-fold to meet the critical needs of 2030 if the plan is to at least maintain schedule. If we take the average size of a major producer as a “standard mine” according to the IEA we need 50 more such lithium mines, 60 more nickel mines, and 17 more cobalt mines operating fully by 2030. Generally speaking, a new mine needs about ten years between starting a feasibility study and serious production. See a problem here? Because of the costs and exposure, you need feasibility studies to ensure that there is sufficient ore where you can’t see, that there is an economic way of processing the ore, and you must have a clear plan on what to do with what to do with minerals you do not want, with materials like arsenates or other undesirables also being present. You also have to build new roads, pipe in water, provide electricity, and do a number of other things to make the mine work that are not directly part of the mine. This does not mean you cannot mine, but it does mean it won’t be quite as easy as some might have you think. We now want our mines not to be environmental disasters. The IEA report notes that ten years, and then adds several more years to get production up to capacity.

The environmental issues are not to be considered as irrelevant. Thus the major deposits of lithium tend to be around the Andes, typically in rather dry areas. Then lithium is obtained by pumping down water, dissolving the salts, then bringing them up and evaporating the brine. Once most of the lithium is obtained, something has to be done with the salty residue, and of course the process needs a lot of water. The very limited water already in some locations is badly needed by the local population and their farms. The salt residues would poison agriculture.

If we consider nickel, one possible method to get more from poorer ores is high-pressure acid leaching. The process uses acid at high temperatures and pressure and end up with nickel at a grade suitable for batteries. But nickel often occurs as a sulphide, which means as a byproduct you get hydrogen sulphide, and a number of other effluents that have to be treated. Additionally, the process requires a lot of heat, which means burning coal or oil. The alternative source to the sulphide deposits, as advocated by the IEA, is laterite, a clayish material that also contains a lot of iron and aluminium oxides. These metals could also be obtained, but at a cost. The estimate of getting nickel by this process is to double the cost of the nickel.

The reason can be seen from the nature of the laterite (https://researchrepository.murdoch.edu.au/id/eprint/4340/1/nickel_laterite_processing.pdf), which is a usually a weathered rock. At the top you have well weathered rock, more a clay, and is red limonite. The iron oxide content (the cause of the red colour) is over 50% while the nickel content is usually less than 0.8% and the cobalt less than 0.1%. Below that is yellow limonite, where the nickel and cobalt oxides double their concentration. Below that we get saprolite/serpentine/garnierite (like serpentine but with enhanced nickel concentration). These can have up to 3% nickel, mainly due to the garnierite, but the serpentine family are silicates, where the ferrous such as in olivine has been removed. The leaching of a serpentine is very difficult simply because silicates are very resistant. Try boiling your average piece of basalt in acid. There are other approaches and for those interested, the link above shows them. However, the main point is that much of the material does not contain nickel. Do y9ou simply dump it, or produce iron at a very much higher cost than usual?

However, the major problems for each are they are all rather energy intensive, and the whole point of this is to reduce greenhouse emissions. The acid leach is very corrosive, and hence maintenance is expensive, while the effluents are troublesome for disposal. The disposal of the magnesium sulphate at sea is harmless, but the other materials with it may not be. Further, if the ore is somewhere like the interior of Australia, even finding water will be difficult.

Of course all these negatives can be overcome, with effort, if we are prepared to pay the price. Now, look around and ask yourself how much effort is going into establishing all those mines that are required? What are the governments doing? The short answer, as far as I can tell, is not much. They leave it to private industry. But private industry will be concerned that their balance sheets can only stand so much speculative expansion. My guess is that 2030 objectives will not be fulfilled.

Will We Do Anything To Stop Global Warming?

There is an interesting review on climate change (Matthews & Wynes, 2022, Science 376: 1404 – 1409). One point that comes up early is how did this sneak up on us? If you look at the graph on global temperatures, you will see that the summers in the 1940s were unusually hot, and the winters in the 1960 – 1980 period were unusually cool, with the net result that people living between 1940 – 1985 could be excused for thinking in terms of extremes instead of averages that the climate was fairly stable. As you will recall, at 1990 there was a major conference on climate change, and by 1992 goals were set to reduce emissions. It is just after this that temperatures have really started rising. In other words, once we “promised” to do something about it, we didn’t. At 1960 the CO2 levels in the atmosphere were about 320 ppm; by 1990 the CO2 levels were about 365 ppm, and at 2022 they are about 420 ppm. The levels of CO2 emissions have accelerated following the treaty in which much of the world undertook to reduce them. Therein lies out first problem. We are not reducing emissions; we are increasing them, even though we promised to do the opposite. (There was a small reduction in 2019-2020 as a result of the Covid lockdowns, but that has passed.) In short, our political promises are also based on hot air.

The current warming rate is approximately a quarter of a degree Centigrade per decade, which means that since we are now about 1.25 degrees warmer than the set 1850 baseline, we shall hit the 1.5 degrees warming somewhere just after 2030. Since that was the 1990 target not to be exceeded, failure seems inevitable. According to the models, to hold the temperature to 1.5 degrees C above our baseline we must not emit more than 360 Gt (billion tonne) of CO2. The IPCC considers we shall emit somewhere between 400 -650 Gt of CO2 before we get carbon neutral (and that assumes all governments actually follow up on their stated plans.) What we see is that current national targets are simply inadequate, always assuming they are kept. Unfortunately, there is a second problem: there are other greenhouse gases and some are persistent. The agricultural sector emits nitrous oxide, while industry emits a range of materials like sulphur hexafluoride, which may not be there in great quantity but it is reputedly 22,800 times more effective at trapping infrared radiation than CO2, and it stays in the atmosphere for approximately 3,200 years. These minor components cannot be ignored, and annual production is estimated at about 10,000 t/a. It is mainly used in electrical equipment, from whence it leaks.

Current infrastructure, such as electricity generators, industrial plant, ships, aircraft and land transport vehicles all have predictable lifetimes and emissions. These exceed that required to pass the 1.5 degree C barrier already unless some other mitigation occurs. Thus, the power stations already built will emit 846 Gt CO2, which is over twice our allowance. People are not going to abandon their cars. Another very important form of inertia is socio-political. To achieve the target, most fossil fuel has to stay in the ground, but politicians keep encouraging the development of new extraction. The average voter is also unhappy to see major tax increases to fund things that will strongly and adversely affect his way of life.

One way out might be carbon capture. The idea of absorbing CO2 from the atmosphere and burying it may seem attractive, but how is it done, at what cost in terms of money and energy required to do it, and who pays for it? Planting trees is a more acceptable concept. In New Zealand there is quite a bit of land that was logged by the early settlers, but has turned out to be rather indifferent farm land. The problem with knowing whether this is a potential solution or not is that it is impossible to know how much of such land can be planted, given that a lot is privately owned. However, planting trees is realistically something that could help, even if it does not solve the problem.

The article seems to feel that the solution must include actions such as lifestyle changes (carless days, reduced speed limits, reduced travel, a reduction of meat eating). My feeling is this would be a very difficult sell in a democracy, and it is not exactly encouraging to persuade some to purchase electric vehicles then be told they cannot use them. The article cites the need for urgency, and ignores the fact that we have had thirty years where governments have essentially ignored the problem. Even worse, the general public will not be impressed to find they are required to do something that adversely affects their lifestyle, only to find that a number of other countries have no interest in subjecting their citizens to such restrictions. The problem is no country can stop this disaster from happening; we all have to participate. But that does not mean we all have to give up our lifestyles, just to ensure that politicians can get away with their inability to get things done. In my opinion, society has to make changes, but they do not have to give up a reasonable lifestyle. We merely need to use our heads for something better than holding up a hat. And to show that we probably won’t succeed, the US Supreme Court has made another 6:3 ruling that appears to inhibit the US Federal Government from forcing certain states to reduce emissions. We shall cook. Yes, this might be a constitutional technicality that Congress could clear up easily, but who expects the current Congress to do anything helpful for civilization?

Energy Sustainability

Sustainability is the buzzword. Our society must use solar energy, lithium-ion batteries, etc to save the planet, at least that is what they say. But have they done their sums?. Lost in this debate is the fact that many of the technologies use relatively difficult to obtain elements. In a previous post I argued that battery technology was in trouble because there is a shortage of cobalt, required to make the cathode work for a reasonable number of cycles. Others argue that we could obtain sufficient elements. But if we are going to be sustainable, we have to be sustainable for an indefinite length of time, and mining is not sustainable; you can only dig up the ore once. Of course, there are plenty of elements left. There is more gold in the sea than has ever been mined; the problem is that it is too dilute. Similarly, most elements are present in a lump of basalt; just not much of anything useful and it is extremely difficult to get it out. The original copper mines of Cyprus, where even lumps of copper could occasionally be found, are all worked out, at least to the extent that mining is no longer profitable there.

The answer is to recycle, right? Well, according to an article [Charpentier Poncelet, A. et al. Nature Sustain. https://doi.org/10.1038/s41893-022- 00895-8 (2022)] there are troubles. The problem is that even if we recycle, every time we do something we lose some of the metal. Losses here refer to material emitted into the environment, stored in waste-disposal facilities, or diluted in material where the specific characteristics of the elements are no longer required. The authors define a lifetime as the average duration of their use, from mining through to being entirely lost. As with any such definition-dependent study, there will be some points where you disagree.

The first loss for many elements lies in the production state. Quite often it is only economical to obtain one or two elements, and the remaining minor components of the ore disappear in slag. These losses are mainly important for specialty elements. Production losses account for 30% of rare earth metals, 50% for cobalt, 70% for indium, and greater than 95% for arsenic, gallium, germanium, hafnium, selenium and tellurium. So most of those elements critical for certain electronic and photo-electric effects are simply thrown out. We are a wasteful lot.

Manufacturing and use incur very few losses. There are some, but because materials are purified ready for use, pieces that are not immediately used can be remelted and used. There are exceptions. 80% of barium is lost through use; it is used in drilling muds.

The largest losses come from the waste management and recycling stage. Metals undergoing multiple life cycles are still lost this way; it just takes longer to lose them. Recycling losses occur when the metal accumulates in a dust (zinc) or slag(e.g. chromium or vanadium), or get lost in another stream, thus copper is prone to dissolve in an iron stream. Longest lifetimes occur for non-ferrous metals (8 to 76 years) precious metals (4 to 192 years), and ferrous metals (8 to 154 years). The longest lifetimes are for gold and iron.

Now for the problem areas. Lithium has a life-cycle use of 7 years, then it is all gone. But lithium-ion batteries last about this long, which suggests that as yet (if these data are correct) there is very little real recycling of lithium. Elements like gallium and tellurium last less than a year, while indium manages a year. Before you protest that most of the indium goes into swipeable mobile phone screens and mobile phones last longer than a year, at least for some of us, remember that losses occur through being discarded at the mining stage, where the miner/processor can’t be bothered. Of the fifteen metals most lost during mining/processing, thirteen are critical for sustainable energy, such as cobalt (lithium-ion batteries), neodymium (permanent magnets), indium, gallium, germanium, selenium and tellurium (solar cells) and scandium (solid oxide fuel cells). If we look at the recycled content of “new material” lithium is less than 1% as is indium. Gallium and tellurium are seemingly not recycled. Why are they not recycled? Metals that are recycled tend to be like iron, aluminium, the precious metals and copper. It is reasonably easy to find uses for them where purity is not critical. Recycling and purifying most of the others requires technical skill and significant investment. If we think of lithium-ion batteries, the lithium reacts with water, and if it starts burning it is unlikely to be put out. Some items may have over a dozen elements, and some are highly toxic, and not to be in the hands of the amateur. What we see happening is that the “easy” metals are recycled by organizations that are really low-technology organizations. It is not an area attractive to the highly skilled because the economic risk/return is just not worth it, while the less-skilled simply cannot do it safely.

Banana-skin Science

Every now and again we find something that looks weird, but just maybe there is something in it. And while reading it, one wonders, how on Earth did they come up with this? The paper in question was Silva et. al. 2022. Chemical Science 13: 1774. What they did was to take dried biomass powder and exposed it to a flash of 14.5 ms duration from a high-power xenon flash lamp. That type of chemistry was first developed to study the very short-lived intermediates generated in photochemistry, when light excites the molecule to a high energy state, where it can decay through unusual rearrangements. This type of study has been going on since the 1960s and equipment has steadily been improving and being made more powerful. However, it is most unusual to find it used for something that ordinary heat would do far more cheaply. Anyway, 1 kg of such dried powder generated about 100 litres of hydrogen and 330 g of biochar. So, what else was weird? The biomass was dried banana skin! Ecuador, sit up and take notice. But before you do, note that flash xenon lamps are not going to be an exceptionally economical way of providing heat. That is the point; this very expensive source of light was actually merely providing heat.

There are three ways of doing pyrolysis. In the previous post I pointed out that if you took cellulose and eliminated all the oxygen in the form of water, you were left with carbon. If you eliminate the oxygen as carbon monoxide you are left with hydrogen. If you eliminate it as carbon dioxide you get hydrogen and hydrocarbon. In practice what you get depends on how you do it. Slow pyrolysis at moderate heat mainly makes charcoal and water, with some gas. It may come as a surprise to some but ordinary charcoal is not carbon; it is about 1/3 oxygen, some minor bits and pieces such as nitrogen, phosphorus, potassium, and sulphur, and the rest carbon.

If you do very fast pyrolysis, called ablative pyrolysis, you can get almost all liquids and gas. I once saw this done in a lab in Colorado where a tautly held (like a hacksaw blade) electrically heated hot wire cut through wood like butter, the wire continually moving so the uncondensed liquids (which most would call smoke) and gas were swept out. There was essentially no sign of “burnt wood”, and no black. The basic idea of ablative pyrolysis is you fire wood dust or small chips at a plate at an appropriate angle to the path so the wood sweeps across it and the gas is swept away by the gas stream (which can be recycled gas) propelling the wood. Now the paper I referenced above claimed much faster pyrolysis, but got much more charcoal. The question is, why? The simple answer, in my opinion, is nothing was sweeping the product away so it hung around and got charred.

The products varied depending on the power from the lamp, which depended on the applied voltage. At what I assume was maximum voltage the major products were (apart from carbon) hydrogen and carbon monoxide. 100 litres of hydrogen, and a bit more carbon monoxide were formed, which is a good synthesis gas mix. There were also 10 litres of methane, and about 40 litres of carbon dioxide that would have to be scrubbed out. The biomass had to be reduced to 20 μm size and placed on a surface as a layer 50 μm thick. My personal view is that is near impossible to scale this up to useful sizes. It uses light as an energy source, which is difficult to generate so almost certainly the process is a net energy consumer. In short, this so-called “breakthrough” could have been carried out to give better yields of whatever was required far more cheaply by people a hundred years ago.

Perhaps the idea of using light, however, is not so retrograde. The trick would be to devise apparatus that with pyrolyse wood ablatively (or not if you want charcoal) using light focused by large mirrors. The source, the sun, is free until it hits the mirrors. Most of us will have ignited paper with a magnifying glass. Keep the oxygen out and just maybe you have something that will make chemical intermediates that you can call “green”.

Biofuels to Power Transport

No sooner do I post something than someone says something to contradict the post. In this case, immediately after the last post, an airline came out and said it would be zero carbon by some time in the not-too-distant future. They talked about, amongst other things, hydrogen. There is no doubt hydrogen could power an aircraft, as it also powers rockets that go into space. That is liquid hydrogen, and once the craft takes off, it burns for a matter of minutes. I still think it would be very risky for aircraft to try to hold the pressures that could be generated for hours. If you do contain it, the extra weight and volume occupied would make such travel extremely expensive, while sitting above a tank of hydrogen is risky.

Hydrocarbons make by far the best aircraft fuel, and one alternative source of them is from biomass. I should caution that I have been working in this area of scientific research on and off for decades (more off than on because of the need to earn money.) With that caveat, I ask you to consider the following:

C6H12O6  ->  2 CO2 +2H2O + “C4H8”

That is idealized, but the message is a molecule of glucose (from water plus cellulose) can give two molecules each of CO2 and water, plus two thirds of the starting carbon as a hydrocarbon, which would be useful as a fuel. If you were to add enough hydrogen to convert the CO2 to a fuel you get more fuel. Actually, you do not need much hydrogen because we usually get quite a few aromatics, thus if we took two “C4H8” and make xylene or ethyl benzene (both products that are made in simple liquefactions) these total C8H10, which gives us a surplus of three H2 molecules. The point here is that in each of these cases we could imagine the energy coming from solar, but if you use biomass, much of the energy is collected for you by nature. Of course, if you take the oxygen out as water you are left with carbon. In practice there are a lot of options, and what you get tends to depend on how you do it. Biomass also contains lignin, which is a phenolic material. This is much richer in hydrocarbon material, but also it is much harder to remove the oxygen.

In my opinion, there are four basic approaches to making hydrocarbon fuels from biomass. The first, which everyone refers to, is pyrolysis. You heat the biomass, you get a lot of charcoal, but you also get liquids. These still tend to have a lot of oxygen in them, and I do not approve of this because the yields of anything useful are too low unless you want to make charcoal, or carbon, say for metal refining, steel making, electrodes for batteries, etc. There is an exception to that statement, but that needs a further post.

The second is to gasify the biomass, preferably by forcing oxygen into it and partially burning it. This gives you what chemists call synthesis gas, and you can make fuels through a further process called the Fischer-Tropsch process. Germany used that during the war, and Sasol in South Africa Sasol, but in both cases coal was the source of carbon. Biomass would work, and in the 1970s Union Carbide built such a gasifier, but that came to nothing when the oil price collapsed.

The third is high-pressure hydrogenation. The biomass is slurried in oil and heated to something over 400 degrees Centigrade in then presence of a nickel catalyst and hydrogen. A good quality oil is obtained, and in the 1980s there was a proposal to use the refuse of the town of Worcester, Mass. to operate a 50 t/d plant. Again, this came to nothing when the price of oil slumped.

The fourth is hydrothermal liquefaction. Again, what you get depends on what you put in but basically there are two main fractions from woody biomass: hydrocarbons and phenolics. The phenolics (which includes aromatic ethers) need to be hydrogenated, but the hydrocarbons are directly usable, with distillation. The petrol fraction is a high octane, and the heavier hydrocarbons qualify as very high-quality jet fuel. If you use microalgae or animal residues, you also end up with a high cetane diesel cut, and nitrogenous chemicals. Of particular interest from the point of view of jet fuel, in New Zealand they once planted Pinus Radiata which grew very quickly, and had up to 15% terpene content, most of which would make excellent jet fuel, but to improve the quality of the wood, they bred the terpenes more or less out of the trees.

The point of this is that growing biomass could help remove carbon dioxide from the atmosphere and make the fuels needed to keep a realistic number of heritage cars on the road and power long-distance air transport, while being carbon neutral. This needs plenty of engineering development, but in the long run it may be a lot cheaper than just throwing everything we have away and then finding we can’t replace it because there are shortages of elements.

The Case for Hydrogen in Transport

In the last post I looked at the problem of generating electricity, and found that one of the problems is demand smoothing One approach to this is to look at the transport problem, the other major energy demand system. Currently we fill our tanks with petroleum derived products, and everything is set for that. However, battery-powered cars would remove the need for petrol, and if they were charged overnight, they would help this smoothing problem. The biggest single problem is that this cannot be done because there is not enough of some of the necessary elements to make it work. Poorer quality batteries could be made, but there is another possibility: the fuel cell.

The idea is simple. When electricity is not in high demand, the surplus is used to electrolyse water to hydrogen and oxygen. The hydrogen is stored, and when introduced to a fuel cell it burns to make water while generating electricity. Superficially, this is ideal, but there are problems. One is similar to the battery – the electrodes tend to be made of platinum, and platinum is neither cheap nor common. However, new electrodes may solve this problem. Platinum has the advantage that it is very unreactive, but the periodic servicing of the cell and the replacing of electrodes is realistic, and of course recycling can be carried out because unlike the battery, it would be possible to merely recycle the electrodes. (We could also use pressurised hydrogen in an internal combustion engine, with serious redesign, but the efficiency is simply too low.)

One major problem is storing the hydrogen. If we store it as a gas, very high pressures are needed to get a realistic mass to volume ratio, and hydrogen embrittles metals, so the tanks, etc., may need servicing as well. We could store it as a liquid, but the boiling point is -259 oC. Carting this stuff around would be a challenge, and to make matters worse, hydrogen occurs in two forms, ortho and para, which arise because the nuclear spins can be either aligned or not. Because the molecule is so small there is an energy difference between these, and the equilibrium ratio is different at liquid temperatures to room temperatures. The mix will slowly re-equilibrate at the low temperature, give off heat, boil off some hydrogen, and increase the pressure. This is less of a problem if you have a major user, because surplus pressure is relieved when hydrogen is drawn off for use, and if there is a good flow-through, no problem. It may be a problem if hydrogen is being shipped around.

The obvious alternative is not to ship it around, but ship the electricity instead. In such a scenario for smaller users, such as cars, the hydrogen is generated at the service station, stored under pressure, and more is generated to maintain the pressure. That would require a rather large tank, but it is doable. Toyota apparently think the problem can be overcome because they are now marketing the Mirai, a car powered by hydrogen fuel cells. Again, the take-up may be limited to fleet operators, who send the vehicles out of central sites. Apparently, the range is 500 km and it uses 4.6 kg of hydrogen. Hydrogen is the smallest atom so low weight is easy, except the vehicle will have a lot of weight and volume tied up with the gas pressurized storage. The question then is, how many fuel stations will have this very large hydrogen storage? If you are running a vehicle fleet or buses around the city, then your staff can refill as well, which gets them to and from work, but the vehicle will not be much use for holidays unless there are a lot of such stations.

Another possible use is in aircraft, but I don’t see that, except maybe small short-haul flights driven by electric motors with propellors. Hydrogen would burn well enough, but the secret of hydrocarbons for aircraft is they have a good energy density and they store the liquids in the wings. The tanks required to hold hydrogen would add so much weight to the wings they might fall off. If the main hull is used, where do the passengers and freight go? Another possibility is to power ships. Now you would have to use liquid hydrogen, which would require extremely powerful refrigeration. That is unlikely to be economic compared with nuclear propulsion that we have now.

The real problem is not so much how do you power a ship, or anything else for that matter, but rather what do you do with the current fleet? There are approximately 1.4 billion motor vehicles in the world and they run on oil. Let us say that in a hundred years everyone will use fuel cell-driven cars, say. What do we do in the meantime? Here, the cheapest new electric car costs about three times the cost of the cheapest petrol driven car. Trade vans and larger vehicles can come down to about 1.5 times the price, in part due to tax differences. But you may have noticed that government debt has become somewhat large of late, due to the printing of large amounts of money that governments have promptly spent. That sort of encouragement will probably be limited in the future, particularly as a consequence of shortages arising from sanctions. In terms of cost, I rather think that many people will be hanging on to their petrol-powered vehicles, even if the price of fuel increases, because the difference in the price of fuel is still a few tens of dollars a week tops, whereas discarding the vehicle and buying a new electric one involves tens of thousands of dollars, and with the current general price increases, most people will not have those spare dollars to throw away. Accordingly, in my opinion we should focus some attention on finding an alternative to fossil fuels to power our heritage fleet.