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.

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The Year of Elements, and a Crisis

This is the International Year of the Periodic Table, and since it is almost over, one can debate how useful it was. I wonder how many readers were aware of this, and how many really understand what the periodic table means. Basically, it is a means of ordering elements with respect to their atomic number in a way that allows you to make predictions of properties. Atomic number counts how many protons and electrons a neutral atom has. The number of electrons and the way they are arranged determines the atom’s chemical properties, and thanks to quantum mechanics, these properties repeat according to a given pattern. So, if it were that obvious, why did it take so long to discover it?

There are two basic reasons. The first is it took a long time to discover what were elements. John Dalton, who put the concept of atoms on a sound footing, made a list that contained twenty-one, and some of those, like potash, were not elements, although they did contain atoms that were different from the others, and he inferred there was a new element present. The problem is, some elements are difficult to isolate from the molecules they are in so Dalton, unable to break them down, but seeing from their effect on flames knew they were different, labelled them as elements. The second problem is although the electron configurations appear to have common features, and there are repeats in behaviour, they are not exact repeats and sometimes some quite small differences in electron behaviour makes very significant differences to chemical properties. The most obvious example is the very common elements carbon and silicon. Both form dioxides of formula XO2. Carbon dioxide is a gas; you see silicon dioxide as quartz. (Extreme high-pressure forces CO2 to form a quartz structure, though, so the similarity does emerge when forced.) Both are extremely stable, and silicon does not readily form a monoxide, while carbon monoxide has an anomalous electronic structure. At the other end of the “family”, lead does not behave particularly like carbon or silicon, and while it forms a dioxide, this is not at all colourless like the others. The main oxide of lead is the monoxide, and this instability is used to make the anode work in lead acid batteries.

The reason I have gone on like this is to explain that while elements have periodic properties, these are only indicative of the potential, and in detail each element is unique in many ways. If you number them on the way down the column, there may be significant changes depending on whether the number is odd or even that are superimposed on a general change. As an example: copper, silver, gold. Thus copper and gold are coloured; silver is not. The properties of silicon are wildly different from those of carbon; there is an equally dramatic change in properties from germanium to tin. What this means is that it is very difficult to find a substitute material for an element that is used for a very specific property. Further, the amounts of given elements on the planet depend partly on how the planet accreted, thus we do not have much helium or neon, despite these being extremely common elements in the Universe as a whole, and partly on the fact that nucleosynthesis gives variable yields for different elements. The heavier elements in a periodic column are generally formed in lower amounts, while elements with a greater number of stable isotopes, or particularly stable isotopes, tend to be made in greater amounts. On the other hand, their general availability tends to depend on what routes there are for their isolation during geochemical processing. Some elements such as lead form a very insoluble sulphide and that separates from the rock during geothermal processing, but others are much more resistant and remain distributed throughout the rock in highly dilute forms, so even though they are there, they are not available in concentrated forms. The problem arises when we need some of these more difficult to obtain elements, yet they have specific uses. Thus a typical mobile phone contains more than thirty different elements

The Royal Society of Chemistry has found that at least six elements used in mobile phones are going out be mined out in at least 100 years. These have other uses as well. Gallium is used in microchips, but also in LEDs and solar panels. Arsenic is also used in microchips, but also used in wood preservation and, believe it or not, poultry feed. Silver is used in microelectrical components, but also in photochromic lenses, antibacterial clothing, mirrors, and other uses. Indium is used on touchscreens and microchips, but also in solar panels and specialist ball bearings. Yttrium is used for screen colours and backlighting, but also used for white LED lights, camera lenses, and anticancer drugs, e.g. against liver cancer. Finally, there is tantalum, used for surgical implants, turbine blades, hearing aids, pacemakers, and nosescaps for supersonic aircraft. Thus mobile phones will put a lot of stress on other manufacturing. To add to the problems, cell phones tend to have a life averaging two years. (There is the odd dinosaur like me who keeps using them until technology makes it difficult to keep doing it. I am on my third mobile phone.)A couple of other facts. 23% of UK households have an unused mobile phone. While in the UK, 52% of 16 – 24 year olds have TEN or more electronic devices in their home. The RSC estimates that in the UK there are as many as 40 million old and unused such devices in people’s homes. I have no doubt that many other countries, including the US, have the same problem. So, is the obvious answer we should promote recycling? There are recycling schemes around the world, but it is not clear what is being done with what is collected. Recovering the above elements from such a mixture is anything but easy. I suspect that the recyclers go for the gold and one or two other materials, and then discard the rest. I hope I am wrong, but from the chemical point of view, getting such small mounts of so many different elements from such a mix is anything but easy. Different elements tend to be in different parts of the phone, so the phones can be dismantled and the parts chemically processed separately but this is labour intensive. They can be melted down and separated chemically, but that is a very complicated process. No matter how you do it, the recovered elements will be very expensive. My guess is most are still not recovered. All we can hope is they are discarded somewhere where they will lie inertly until they can be used economically.

The Need for, and the Problems of, Recycling

The modern economies rely on the supply of raw materials, and of these, elements are the most critical because there are no alternatives to them. Businesses will collapse if certain elements became unavailable, and the British Geological Society puts out a “risk list” of elements that have a risk of supply disruption. The list is debatable, because it includes political risk, thus the most risky from their perspective are the rare earth elements, the problem here being that China is essentially the main producer and reserve holder. These elements’ risk factors also depend on their demand, thus if there is no known use for something, it has zero risk because even if there is none of it, who cares? However, the overall conclusion is, we could have a problem. As in many such issues, not everyone agrees. Staff at the University of Geneva have published a report arguing that there is no shortage, at least for the foreseeable future. They argue you can mine over three kilometers below the Earth’s surface, or in the oceans. Whether you want to do this, or can even find the deposits, is less clear.

There is no shortage of elements but the bulk of them are distributed in very low concentrations in rock, or seawater. It may surprise some to know that there is plenty of gold in seawater. The problem is, it is rather dilute, and of course there are massive amounts of other materials. Thus there is about eleven tonnes of gold in a trillion tonnes of seawater. Good luck trying to get it out. Same with the rare earth elements. They are not especially rare; however they are particularly rare in workable deposits. Part of the problem is their chemistry has a certain similarity to aluminium, and as a result, they tend to be spread out amongst feldsic/granitic material and as microscopic inclusions (mixed with a lot of other stuff) in basalt. Rather interestingly, there are massive deposits on the Moon, where, as the Moon cooled down, the various rocks crystallised into solids, and one of the last of the liquids to solidify was KREEP, a mix of potassium (K), rare earth elements, and phosphate (P). This also indicates the reason why we have ore deposits on Earth: geological processing. Taking gold as an example, it, and silica dissolve in supercritical water, and as the water comes to the surface and cools down, the gold and the silica come out of solution, which is why you find gold in quartz veins. There are, of course, a variety of geological routes to make ores, but geology is a slow process, so once we run out of easy to find deposits, we have a deep problem. And on a planet such as Mars, there has not been so much geological processing, and no plate tectonics.

One way out of this is recycling, if you can work out how to do it and make a dollar. One big user of rare elements is mobile phones. Thus the “swipe-screen” uses indium/tin oxide, the electronics use copper, silver and gold for carrying current, tantalum for microcapacitors, and neodymium in the magnets. These are the critical elements, and in general there are no substitutes for their specific uses. However, the total number of elements used can be up to sixty. The problem for recycling is first, to get hold of the old ones, as opposed to have them lying about or thrown in the trash, and then to separate out what you want. If you simply melt them, you get a horrible mix. The process could be simplified if the phones could be split into parts, thus only the screens contain indium, but how do you do that?

Early on in my scientific career, I was asked by a company to devise a means of recycling coloured plastics. I did this, a pilot plant was built, a few bugs were ironed out and we could recycle coloured polyethylene to get a very light beige product that could be made into new coloured products by the addition of pigments, and the casual user would not know the difference between that and new plastics for most uses. So this should have been a success? Well, no. There were two problems. This was during the oil crisis of the seventies, and what had happened was that there was an oversupply of new polyethylene in the world. Such surplus was dumped on the New Zealand market, where “it would not do any harm”. That dumping made the venture economically unsustainable. Some time later, the dumping stopped, but by this time the original company had lost interest. Also, the manufacturers introduced more cross-linking, and in a quick demonstration, the process did not work without altering the conditions beyond what had been assumed. There were ways around that, but the warning was clear: the manufacturers were not being friendly to recycling as they kept their information close to their chests. Such changes really hinder recycling. However, that was not the worst: new laminates started appearing, and these were a horror for recycling because the two or more different plastics put together as layers do not separate easily, and any product made from a resultant mix will be of very low quality.

So, we can either have a problem with elements, or we can recycle. Recyclers tend not to have the high technology of the multinational corporations, so my recommendation is, manufacturers should be made to design their goods in a way that aids recycling. For example, a laptop or a mobile phone has lithium ion batteries. It is also essentially impossible to get the battery out when it dies and leave the item in a workable condition. It might suit the manufacturer to force the consumer to buy another laptop as opposed to a new battery, but as the technology matures, is that good enough? Similarly, if the motherboards could be removed/replaced, that would aid recycling and also reduce demand for new gadgets. When I was young, people fixed things. I think it is time to return to those times, and also make objects as recyclable as possible. The problem then is, how do you manage that in a market where competition rules, and the consumer does not think about recycling when he or she buys a new product?

The future did not seem to work!

When I started my career in chemistry as an undergraduate, chemists were an optimistic bunch, and everyone supported this view. Eventually, so it was felt, chemists would provide a substance to do just about anything people wanted, provided the laws of physics and chemistry permitted it. Thus something that was repelled by gravity was out, but a surprising lot was in. There was a shortage of chemists, and good paying jobs were guaranteed.

By the time I had finished my PhD, governments and businesses everywhere decided they had enough chemists for the time being thank you. The exciting future could be put on hold. For the time being, let us all stick to what we have. Of course there were still jobs; they were just an awfully lot harder to find. The golden days for jobs were over; as it happened, that was not the only thing that was over. In some people’s eyes, chemicals were about to become national villains.

There was an element of unthinking optimism from some. I recall in one of my undergraduate lectures where the structure of penicillin was discussed. Penicillin is a member of a class of chemicals called beta lactams, and the question of bacterial tolerance was discussed. The structure of penicillin is (https://en.wikipedia.org/wiki/Penicillin) where R defines the carboxylic acid to that amide. The answer to bacterial tolerance was simple: there is almost an infinite number of possible carboxylic acids (the variation is changing R) so chemists could always be a step ahead of the bugs. You might notice a flaw in that argument. Suppose the enzymes of the bug attacked the lactam end of the molecule and ignored the carboxylic acid amide? Yes, when bacteria learned to do that, the effectiveness of all penicillins disappears. Fortunately for us, this seems to be a more difficult achievement, and penicillins still have their uses.

The next question is, why did this happen? The answer is simple: stupidity. People stopped restricting the use to countering important infections. They started to be available “over the counter” in some places, and they were used intermittently by some, or as prophylactics by others. Not using the full course meant that some bacteria were not eliminated, and since they were the most resistant ones, thanks to evolution when they entered the environment, they conveyed some of the resistance. This was made worse by agricultural use where low levels were used to promote growth. If that was not a recipe to breed resistance, what was?

The next “disaster” to happen was the recognition of ozone depletion, caused by the presence of chlorofluorocarbons, which on photolysis in the upper atmosphere created free radicals that destroyed ozone. The chlorofluorocarbons arose from spray cans, essential for hair spray and graffiti. This problem appears to have been successfully solved, not by banning spray cans, not by requesting restraint from users, but rather by replacing the chlorofluorocarbons with hydrocarbon propellant.

One problem we have not addressed, despite the fact that everyone knows it is there, is rubbish in the environment. What inspired this post was the announcement that rubbish has been found in the bottom of the Marianna trench. Hardly surprising; heavy things sink. But some also floats. The amounts of waste plastic in the oceans is simply horrendous, and only too much of it is killing fish and sea mammals. What starts off as a useful idea can end up generating a nightmare if people do not treat it properly. One example that might happen comes from a news report this week: a new type of plastic bottle has been developed that is extremely slippery, and hence you can more easily get out the last bit of ketchup. Now, how will this be recycled? I once developed a reasonably sophisticated process for recycling plastics, and the major nightmare is the multi-layered plastics with hopelessly incompatible properties. This material has at least three different components, and at least one of them appears to be just about totally incompatible with everything else, which is where the special slipperiness comes from. So, what will happen to all these bottles?

Then last problem to be listed here is climate change. The problem is that some of the more important people, such as some politicians, do not believe in it sufficiently to do anything about it. The last thing a politician wants to do is irritate those who fund his election campaign. Accordingly, that problem may be insoluble in practice.

The common problem here is that things tend to get used without thinking of the consequences of what is likely to happen. Where things have gone wrong is people. The potential failure of antibiotics is simply due to greed from the agricultural sector; there was no need for its use as a growth promoter when the downside is the return of bacterial dominance. The filling of the oceans with plastic bags is just sloth. Yes, the bag is useful, but the bag does not have to end in the sea. Climate change is a bit more difficult, but again people are the problem, this time in voting for politicians that announce they don’t believe in it. If everybody agreed not to vote for anyone who refused to take action, I bet there would be action. But people don’t want to do that, because action will involve increased taxes and a requirement to be better citizens.

Which raises the question, do we need more science? In the most recent edition of Nature there was an interesting comment: people pay taxes for one of two reasons, namely they feel extremely generous and want to good in the world, or alternatively, they pay them because they will go to jail if they don’t. This was followed by the comment to scientists: do you feel your work is so important someone should be thrown into jail if they don’t fund it? That puts things into perspective, doesn’t it? What about adding if they question who the discovery will benefit.