Geoengineering: Shade the World

As you may have noticed when not concerned about a certain virus, global warming has not gone away. The virus did some good. I live on a hill and can look down on some roads, and during our lock-down the roads were strangely empty. Some people seemed to think we had found the answer to global warming, as much less petrol was bing burnt, but the fact is, even if nobody drove we were still producing net amounts of CO2 and other greenhouse gases, and even if we were not doing that, the amounts currently in the air are still out of equilibrium and would continue to melt ice and lead to high temperatures. In the northern hemisphere now you have a summer so maybe you notice.

So, what can we do? One proposal is to shade the Earth’s surface. The idea is that if you can reflect more incoming solar radiation back to space there is less energy on the surface and . . .  Yes, it is the ‘and’ wherein lies the difficulties. We get less radiation striking the surface, so we cool the surface, but then what? According to one paper recently published in Geophysical Research Letters (https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020GL087348 ) the answer is not good news. They have produced simulations of models, and focus on what are called storm tracks, which are relatively narrow zones in oceans where storms such as tropical cyclones and mid-latitude cyclones travel through prevailing winds. Such geoengineering, according to the models, would weaken these storms. Exactly why this is bad eludes me. I would have thought lower energy storms would be good; why do we want hundreds of thousands of citizens have their properties leveled by hurricanes, typhoons, or simply tropical cyclones as they are known in the Southern Hemisphere? This weakening happens through a smaller pole to equator temperature difference because most of the light reflected is over the tropics. Storms are heat engines at work, and the greater the temperature difference, the more force can be generated. The second law of thermodynamics at work. Fine. We are cooling the surface, and while it may seem that we are ignoring the ice melting of the polar regions, we are not because most of the heat comes from ocean currents, and they are heated by the tropics.

More examples: we would reduce wind extremes in midlatitudes, possibly lead to less efficient ventilation of air pollution, may possibly decrease low cloud cover the storm‐track regions and weaken poleward energy transport. In short, a reasonable amount of that is what we want to do anyway. It is also claimed we would get increased heat waves. I find that suspicious, given that less heat is available. It is claimed that such activities would alter the climate. Yes, but that is what we would be trying to do, namely alter it from what it might have been. It is also claimed that the models show there could possibly  be regional reductions in rainfall. Perhaps, but that sort of thing is happening anyway. Australia had dreadful bushfires this year. I gather forest fires were going well in North America also.

One aspect of this type of study that bothers me is it is all based on models. The words like ‘may’, ‘could’ and ‘possibly’ turn up frequently. That, to me, indicates the modelers don’t actually have a lot of confidence in their models. The second thing that bothers me is they have not looked at nature. Consider the data from Travis et al.(2002) Nature 418, 601.  For the three days 11-14 Sept. 2001 the average diurnal temperature ranges averaged from 4000 weather stations across the US increased on average 1.1 degrees C above the average from 1971 – 2000, with the highest temperatures on the 14th. They were on average 1.8 degrees C greater than the average for the two adjacent three-day periods. The three days with the increase were, of course, the days when all US aircraft were grounded and there were no jet contrails. Notice that this is the difference between day and night; at night the contrails retain heat better, while in daytime they reflect sunlight.  Unfortunately, what was not stated in the paper was what the temperatures were. One argument is that models show while the contrails reflect more light during the day, they keep in more heat during the night. Instead of calculations, why not show the actual data?

The second piece of information is that the eruption of Mount Pinatubo sent aerosols into the atmosphere and for about a year the average global temperature dropped 1 degree C. Most of that ash was at low latitudes in the northern hemisphere. There are weather reports from this period so that should give clues as to what would happen if we tried this geoengineering. This overall cooling was real and the world economies did not come to an end. The data from that could contribute to addressing the unkn owns.

So, what is the answer? In my opinion, the only real answer is to try it out for a short period and see what happens. Once the outcomes are evaluated we can then decide what to do. The advantage of sending dust into the stratosphere is it does not stay there. If it does not turn out well, it will not be worse than what volcanoes do anyway. The disadvantage is to be effective we have to keep doing it. Maybe from various points of view it is a bad idea, but let us make up our minds from evaluating proper information and not rely on models that are no better than the assumptions used. Which choice we make should be based on data, not on emotion.

What to do with Waste Plastics

One of the great environmental problems of our time is waste plastics, and there are apparently huge volumes floating around in the oceans of the world. These would generally get there by people throwing them away, so in principle this problem is solved if we can stop that irresponsible attitude. I can already hear the, “Good luck with that,” response. Serious fines for offenders would help, as would more frequent proper rubbish disposal bins. But this raises the question, what should we do with waste plastics?

The first answer is it is unlikely there is a single answer because there are such a variety of plastics. Some, like polyester or polyethylene, can be reasonably easily recycled for low specification uses, but the problem here is there is a limit to how many plastic buckets, etc, can be sold. Technically, quite a high level of recycling can be achieved. Quite a while ago, during the first oil crisis, a client asked me to devise a means of recycling mixed coloured polyethylene so I devised a process that recovered a powder that could be used to make almost anything that virgin polyethylene could make, except maybe clear: there was always a slight beige colour from residual dyes etc that could not be got out, at least in a one-cycle process. Polyethylene degrades – you will all have seen it go brittle from sunlight. This shortens the chains and oxidizes parts and I was proud of this process because it got rid of all the degradation and short-chain material.

A pilot plant was built, then the process was abandoned.  The reason was the oil prices tumbled, and there was no way the process could make money, particularly since big multinationals appeared to be dumping polyethylene into New Zealand. Some manufacturers loved this, and were able to export all sorts of plastic things, at least for a while. Part of the reason the process would have lost money, of course, was that despite getting the raw material rather cheaply, the yield at the end was lower because of the loss of the degradation products, but the killer was getting rid of the degradation products. They could be burnt for process heat, but that would need a specially designed burner, and there would still be the pigment remains to be disposed of. Good idea, but could not compete with the oil industry.

Another possible process is pyrolysis. This came to my attention when I recently saw a paper in the latest copy of “Energy and Fuels” put out by the American Chemical Society. Polyethylene gives a mix of oil, gas and carbonaceous solid, but you can get almost 80% in the form of oil that could be directly used as a diesel fuel after distillation. There appear to be a fraction that boils too high for the diesel range, and gets waxy, but those who have recalled a recent post by me will see that it would do well in the heavier marine heavy fuel oil. The resultant oil has a mix of linear alkanes and terminal alkenes, and the fragmentation is such that the double bond prefers the smaller fragment. There is also some miscellaneous stuff resulting from the oxidative degradation. Polypropylene, however, showed a lot more oxygen, with a range of alcohols, esters and also acids in addition to highly branched hydrocarbons, however, almost 20% was the single compound 2,4-dimethyl-1-heptene. It would manage with the light ends as petrol, and the heavier ends contributing to diesel. 

Polystyrene gave what corresponds more to a heavy oil, although 40% was actually styrene, which could be used to make more polystyrene. Importantly, the cetane rating for the oil from polyethylene was 73; for polypropylene, 61. Polystyrene oil was unsuitable for diesel, but if hydrogenated, the lower boiling cut would make a high octane petrol. The average pump diesel fuel has a cetane rating of about 50, and the higher the rating, the faster the engines can go, so pyrolysis of waste polyethylene and waste polypropylene will make an excellent diesel fuel, with the heavy ends going towards shipping.  However, the heavy ends of polystyrene would have to be dumped because they contain fluorinated material, presumably a consequence of additives, and you certainly do not want an exhaust stream rich in hydrogen fluoride. And here is the curse that plagues anything involving recycling: too many companies put in additives that will be impossible to remove, and which either prevent proper recycling or will have consequences that are at best highly unpleasant, while they offer no option for dealing with them.

How do we separate these plastics out? Fragment them, and stir in water. Polyethylene and polypropylene are the two plastics that float. Foam, of course, has to be omitted. So, will this end up being done? My guess is, not in the immediate future. In terms of economics, it cannot beat the entrenched oil industry, unless governments decide that cleaning up the environment is worth the effort.

Climate Change and International Transport

You probably feel that in terms of pollution and transport, shipping is one of the good guys. Think again. According to the Economist (March 11, 2017) the emissions of nitrogen and sulphur oxides from 15 of the world’s largest ships match those from all the cars on the planet. If the shipping industry were a country, it would rank as the sixth largest carbon dioxide emitter. Apparently 90%  of trade is seaborne, and in 2018, 90,000 ships burn two billion barrels of the dirtiest fuel oil, and contribute 2 – 3% of the world’s total greenhouse emissions. And shipping is excluded from the Paris agreement on climate change. (Exactly how they wangled that is unclear.) The International Maritime Organization wants to cut emissions by 50% by 2050, but prior to COVID-19, economic growth led to predictions of a six-fold increase by then!

Part of the problem is the fuel: heavy bunker oil, which is what is left over after refining takes everything else it can use. Apparently it contains 3,500 times as much sulphur as diesel fuel does. Currently, the sale of these high sulphur fuels has been banned, and sulphur content must be reduced to 0.5% (down from 3.5%) and some ships have been fitted with expensive scrubbers to remove pollutants. That may seem great until you realize 80% of these scrubbers simply dump the scrubbed material, a carcinogenic mix of various pollutants, into the sea. They also increase fuel consumption by about 2%, thus increasing carbon dioxide missions.

On the 19th February, 2020, the Royal Society put out a document advocating ammonia as a zero-carbon fuel, and suggested that the maritime industry could be an early adopter. What do you think of that?

First, ammonia is currently made by compressing nitrogen and hydrogen at higher temperatures over a catalyst (The Haber process). The compression requires electricity, and the hydrogen is made by steam reforming natural gas, which is not carbon free, however it could be made by electrolysing water, which would be a use for “green” electricity”. The making of hydrogen this way may well be sound, but running the Haber process probably is not. The problem with this process is it really has to be carried out continuously, and solar energy is not available at night, and the wind does not always blow. However, leaving that aside, that part of the scheme is plausible. Ammonia can be burnt in a motor, or more efficiently in a fuel cell to make electricity. If you could make this work there are some ships that use diesel to make electricity to power motors, so that might work. Ammonia has an energy content of 3 kWh/litre (liquid hydrogen is 2/3 this) while heavy fuel oil has an energy content of 10 kWh/l. The energy efficiency of converting combustion energy to work is much higher in a fuel cell.

Of course by now you will have all worked out why this concept is a non-starter. The problem is the ship, its fuel tanks and motors, are part of the construction and are deep within the ship. The cost of conversion would be horrendous so it is most unlikely to happen. Equally, if we were serious about climate change, we could convert ships to use nuclear power. Various navies around the world have shown how this can be done safely. Don’t hold your breath waiting for the environmentalists to endorse that idea.

However, converting to nuclear power has the same problem as converting to ammonia: a huge part of the ship has to be demolished and rebuilt, so that is a non-starter. So there is no way out? Not necessarily.  I have currently been spending my lockdown writing a chapter for a book in a series on hydrothermal treatment of algae. Now the interesting thing about the resultant biocrude is that while you can make very high octane petrol and high cetane diesel, there is a residue of heavy viscous fluid that can be mainly free of sulphur and nitrogen. What on earth could you do with that? It is a thick viscous oil, surprisingly like heavy bunker oil. Any guesses as to what I might be tempted to recommend?

Aircraft and Carbon Dioxide Emissions

Climate change requires significant changes to our lifestyle, and one of the more tricky problems to solve is air travel. Interestingly, you will find many environmentalists always telling everyone to cycle, but then spend tens of thousands of air miles going to environmental conferences. So, what can we do?

One solution is to reduce air travel. And there is no need in principle to adopt Greta Thunberg’s solution of sailing over the Atlantic. With a bit of investment, high speed rail can get you between the centres of reasonably close cities faster than aircraft, when you include the time taken to get to and from airports, and time wasted at airports. We can also reduce travel, but only so far. At first sight, things like conferences can be held online, but there are two difficulties: time-zone differences encourage doing something else, and second, the major benefit from conferences is not listening to set talks, but rather meeting people outside the formal program. For business, facing each other is a far improved way of negotiating because the real signals are unspoken. 

Some airlines are trying to improve their environmental credentials by planting trees to compensate for the carbon dioxide they emit. That is very noble of them, but apart from the fact it is their money doing it (and often it is not – it is the passengers who feel conscious stricken to donate more money for planting) it is something that should be done anyway. 

There has been talk of building electric aircraft. My personal opinion is this is not the solution. The problem is in terms of unit weight, jet fuel contains at least thirty times the energy density of the best batteries available. Even worse, for jet fuel, as you go further, you get lighter, but not with batteries. You could make a large aircraft fly, say, 1,000 to 2,000 km, as long as you did not want to carry much in the way of passengers or cargo. With thirty times the fuel weight for a long distance flight your aircraft would never get off the ground. However, the Israeli firm Eviation has developed a small electric aircraft for a load of 9 persons (plus two crew) powered by 920 kWh batteries with operating costs estimated at $200/hr. The range is about 540 nautical miles, or about 1,000 km. That could work for small regional flights, and it will be available soon.

Another option to be offered by Airbus is the E-Fan-X project. They will take a BAe 146 craft, which usually carries about 100 passengers, and which usually is powered by four Honeywell turbofan engines, and replace one of the inner ones with an electric-driven 2 MW propulsion fan motor. The idea is the takeoff, where the most power is required will use the normal jets, but the electric motor can manage the cruise. 

An alternative is to reduce fuel consumption. One possibility is the so-called blended wing, which is being looked at by NASA. This works; an example is the B2 bomber, however while it reduces fuel consumption by 20% it is most unlikely to come into commercial use any time soon. One reason is that there is probably no commercial airport that could accommodate the radically different design. It would also have to have extensive examination because so far the design has only had military applications, in which only very specific loads are involved. In principle, this, and other designs can reduce kerosene usage, but only by so much. Maybe overall, 25% is achievable, which does not solve anything.

Uranium 235 has an energy density that leaves kerosene for cold, but which airport wants it, and would you board it anyway? It could presumably be made to work, but I can’t see it happening anytime soon because nobody will take the associated political risk.

That leaves hydrogen. 1 kg of liquid hydrogen can provide the same energy as 3 kg of kerosene, so weight is not the problem, but keeping it cold enough and maintaining pressure will add weight. It cannot be stored in the aircraft wings because of the volatility. To keep it cold it is desirable to have minimum surface area of the tank. However, it is reasonably clean burning, giving only water and some nitrogen oxides. For a Boeing 747-400 aircraft, the full fuel load is 90 tonne less, but because the tanks have to be in the fuselage, they occupy about 30% of the passenger space.

That may work for the future, but the only real way to power current aircraft is to burn hydrocarbon fuel. More on that next week.

Nuclear Waste Management

It is now generally recognized (apart from a few recidivists and those with deep investment in the fossil fuel industries) that we have to find alternatives to fossil fuels as energy sources. There is great enthusiasm for solar and wind power, despite the obvious shortcomings for total replacement that are generally overlooked, but one of the obvious replacements, nuclear power, is shunned. There are two reasons: the danger of reactor explosions, such as at Chernobyl and Fukushima, both of which were caused by stupidity, which, unfortunately, is never in short supply, and the hazard of nuclear waste. Whether we can get around stupidity is debatable, but we should be able to design so that the effects are minimal. In this post I want to think about nuclear waste, and I am going to mainly consider the current standard reactor process. However, I argue the main problem is social: people are so against nuclear power it is difficult to get the required programs implemented.

The usual waste is extremely dangerous, and comprises two subsets: fissioned products, which tend to have shorter half-lives, e.g. strontium ninety has a half-life of 29.1 years, and actinides, which have longer half-lives, the plutonium 239 has a half-life of 24,000 years. Because of the latter, very long storage is required, and the usual thought is it has to be stored for a minimum of 100,000 years. My personal view is that is far too short if plutonium is present. If we are going to bury this, we need geological structures that will remain unchanged for that length of time. The amount of waste is fortunately not excessive; a plant that produces 1 GW (and earns more than $1 million/day) apparently produces 20 t/day. The good news is that there are plenty of rock formations that have not changed in 100 million years, so the problem now is to put the waste down in a form that will stay where you put it.

The waste comes out in small ceramic pellets that have been heated at several hundred degrees Centigrade for a number of years. They are tough and can be dumped right then. The usual next step is to encase the radioactive nuclides in molten glass, which is then put into a stainless steel container, which is then put into a copper container. Provided there is no oxygen or sulphur-containing gas, copper simply does not react with anything found naturally in rock. The container then goes into a repository at a depth of several hundred meters in a hard rock, and that is further surrounded by bentonite clay, which is water-tight. 

That is the ideal. Unfortunately, so far there appear to be no such operational depositories, so the waste is buried in somewhat less desirable ways. There is a further problem in that a clay cannot be water-tight forever, and water-tightness may be a problem. A recent report (https://www.nature.com/articles/s41563-019-0579-x) has indicated a possible flaw that may make it necessary to revisit the current storage. When the glass or ceramic is placed in the steel cannister, as it cools a thin gap is created. If water gets into this gap, corrosion might occur, and if it does, the water gets progressively more acid, and that acid might start leaching waste. This is possible because when the waste is vitrified, it is distributed through the glass and some is at the glass surface. In my opinion there are various ways around this. The most obvious is to have only glass on the surface following vitrification, and that may mean two processes, the gap can be enclosed with silicone, and perhaps the steel could be enclosed in molten basalt. I do not know the answers, but I am reasonably convinced there is an answer.

We can do more. Reprocessing recovers plutonium and unburnt uranium, and it is possible to recover more fuel than you started with. This is because the initial fuel is uranium 235, but it would be surrounded by much more uranium 238; this is what absorbs a neutron and converts to plutonium 239. There will also be other useful radioactive isotopes there, such as americium for fire alarms, cobalt sixty for medical use, but of course there will remain a lot of rather noxious material. Most of the rest can be transmuted into more harmless material by irradiating them. Simple, so why don’t we do it? The basic reason is that most of the reactors currently used are of the light-water kind, and these cannot easily be so used. 

Different reactor designs can help the problem. Most current ones use a moderator to slow the neutrons. The advantages of this are stated to be that the required enrichment of uranium is much lower, and the plants are cheaper. The alternative of using fast neutrons (and no moderator) produce much less transuranic waste because the actinides are fissionable with fast neutrons. Paradoxically, Iran’s higher enrichment program could be used in fast neutron reactors and it would be much harder for them to produce bombs, but this seems not to be considered by the anti-Iran brigade. Molten salt reactors are claimed to produce less than one thousandth of the actinides. The actinides are the longest living waste, and they tend to be highly poisonous as well. So why are moderated reactors the predominant reactor? Possibly because they yield far more plutonium, and that is needed for bombs by the nuclear powers. It is alleged they are also cheaper. However, burning off these nuclides economically and safely is some distance away. It would involve a lot of money to set things up, and it would be preferable to develop much better robotic technology because you do not want to expose workers to the radiation while doing the processing. There is a further problem. If you have a large number of countries with nuclear power plants, using current technology, you have a large number of countries producing plutonium. The prospect of rogue countries developing bombs to blast out their neighbours is a deep problem, but there are ways around that. Unfortunately, that involves a somewhat radical change in the way some countries play politics.

Forests versus Fossil Fuels – a Debate on Effectiveness

The use of biomass for fuel has been advocated as a means of reducing carbon dioxide emissions, but some have argued it does nothing of the sort. There was a recent article in Physics World that discusses this issue, and here is a summary. First, the logic behind the case is simple. The carbon in trees all comes from the air. When the plant dies, it rots, releasing energy to the rotting agents, and much of the carbon is released back into the air. Burning it merely intercepts that cycle and gives the use of the energy to us as opposed to the microbes. A thermal power station in North Yorkshire is now burning enough biomass to generate 12% of the UK’s renewable energy. The power station claims it has changed from being one of the largest CO2 emitters in Europe to supporting the largest decarbonization project in Europe. So what could be wrong? 

My first response is that other than a short-term fix, burning it in a thermal power station is wrong because the biomass is more valuable for generating liquid fuels, for which there is no alternative. There are many alternative ways of generating electricity, and the electricity demand is so high that alternatives are going to be needed. There is no obvious replacement for liquid fuels in air transport, although the technology to make such fuels is yet to be developed properly. 

So, what can the critics carp on about? There were two criticisms about the calculated savings being based on the assumptions: (a) the CO2 released is immediately captured by growing plants, and (b) the biomass would have rotted and put its carbon back into the atmosphere anyway. The first is patently wrong, but so what? The critics claim it takes time for the CO2 to be reabsorbed, and that depends on fresh forest, or regrowth of the current forest. So replanting is obviously important, but equally there is quite some time used up in carbon reabsorption. According to the critics, this takes between 40 and a hundred years, then it is found that because biomass is a less energy-dense material during combustion, compared with coal you actually increase the CO2 emissions in the short-term. The reabsorption requires new forest to replace the old.

The next counter-argument was that the block should not be counted, but rather the landscape – if you only harvest 1% of the forest, the remaining 99% is busily absorbing carbon dioxide. The counter to that is that it would have been doing that anyway. The next objection is that older forests absorb carbon over a much longer period, and sequester more carbon than younger stands. Further, the wood that rots in the soil feeds microbes that otherwise will be eating their way through stored carbon in the soil. The problem is not so much that regrowth does not absorb carbon dioxide, but rather it does not reabsorb it fast enough to be meaningful for climate change.

Let us consider the options where we either do it or we do not. If we do, assume we replant the same area, and fresh vegetation is sufficient to maintain the soil carbon. In year 1 we release x t CO2. After year 40, say, it has been all absorbed, but we burn again and release x t CO2. By year 80, it is all reabsorbed, so we burn again. There is a net x t CO2 in the air. Had we not done this, in each of years 1, 40 and 80 we burn kx t CO2, giving us now 3kx t CO2, where k is some number <1 to counter the greater efficiency of burning coal. Within this scenario eventually the biofuel must save CO2. That we could burn coal and plant fresh forests is irrelevant because in the above scenario we only replace what was there. We can always plant fresh forest.

Planting more works in both options. This is a bit oversimplified, but it is aimed to show that you have to integrate what happens over sufficient time to eliminate the effect of non-smoothness in the functions, and count everything. In my example above it could be argued I do not know whether there will be a reduction in soil carbon, but if that is troublesome, at least we have focused attention on what we need to know. It is putting numbers on a closed system, even if idealized, that shows the key facts in their proper light. 

Recycling Lithium Ion Batteries

One of the biggest contributors to greenhouse warming is transport, and the solution that seems to be advocated is to switch to electric vehicles as they do not release CO2, and the usual option is to use the lithium ion battery A problem that I highlighted in a previous blog is we don’t have enough cobalt, and we run out of a lot of other things if we do not recycle. A recent review in Nature (https://doi.org/10.1038/s41586-019-1682-5)   covered recycling and the following depends on that review. The number of vehicles in the world is estimated to reach 2 billion by 2035 and if all are powered by lithium ion batteries the total pack wastes would be 500 million tonnes, and occupy a billion cubic meters. Since the batteries last about nine years, we eventually get drowned in dead batteries, unless we recycle. Also, dead lithium ion batteries are a fire hazard. 

There are two initial approaches, assuming we get the batteries cleanly out of the vehicle. One is to crush the whole and burn off the graphite, plastics, electrolyte, etc, which gives an alloy of Co, Cu, Fe and Ni, together with a slag that contains aluminium and manganese oxides, and some lithium carbonate. This loses over half the mass of the batteries and contributes to more greenhouse warming, which was what we were trying to avoid. Much of the lithium is often lost this way to, and finally, we generate a certain amount of hydrogen fluoride, a very toxic gas. The problem then is to find a use for an alloy of unknown composition. Alternatively, the alloy can be treated with chlorine, or acid, to dissolve it and get the salts of the elements.

The alternative is to disassemble the batteries, and some remaining electricity can be salvaged. It is imperative to avoid short-circuiting the pack, to prevent thermal runaway, which produces hydrofluoric acid and carcinogenic materials, while fire is a continual hazard. A further complication is that total discharge is not desirable because copper can dissolve into the electrolyte, contaminating the materials that could be recycled. There is a further problem that bedevils recycling and arises from free market economics: different manufacturers offer different batteries with different physical configurations, cell types and even different chemistries. Some cells have planar electrodes, others are tightly coiled and there are about five basic types of chemistries used. All have lithium, but additionally: cobalt oxide, iron phosphorus oxide, manganese oxide, nickel/cobalt.aluminium oxide, then there are a variety of cell manufacturers that use oxides of lithium/manganese/cobalt in various mixes. 

Disassembling starts with removing and the wiring, bus bars, and miscellaneous external electronics without short-circuiting the battery, and this gets you to the modules. These may have sealants that are difficult to remove, and then you may find the cells inside stuck together with adhesive, the components may be soldered, and we cannot guarantee zero charge. Then if you get to the cell, clean separation of the cathode, anode, and electrolyte may be difficult, we might encounter nanoparticles which provide a real health risk, the electrolyte may generate hydrogen fluoride and the actual chemistry of the cell may be unclear. The metals in principle available for recycling are cobalt, nickel, lithium, manganese and aluminium, and there is also graphite.

Suppose we try to automate? Automation requires a precisely structured environment, in which the robot makes a pre-programmed repetitive action. In principle, machine sorting would be possible if the batteries had some sort of label that would specify precisely what it was. Reading and directing to a suitable processing stream would be simple, but as yet there are no such labels, which, perforce, must be readable at end of life. It would help recycling if there were some standardised designs, but good luck trying to get that in a market economy. If you opt for manual disssembling, this is very laboour intensive and not a particularly healthy occupation.

If the various parts were separated, metal recovery can be carried out chemically, usually by treating the parts with sulphuric acid and hydrogen peroxide. The next part is to try to separate them, and how you go about that depends on what you think the mixture is. Essentially, you wish to precipitate one material and leave the others, or maybe precipitate two. Perhaps easier is to try to reform the most complex cathode by taking a mix of Ni, Mn, and Co that has been recovered as hydroxides, analysing it and making up what is deficient with new material, then heat treating to make the desired cathode material. This assumes you have physically separated the anodes and cathodes previously.

If the cathodes and anodes have been recovered, in principle they can be directly recycled to make new anodes and cathodes, however the old chemistry is retained. Cathode strips are soaked in N-methylpyrrolidine (NMP) then ultrasonicated to make the powder to be used to reformulate a cathode. Here, it is important that only one type is used, and it means new improved versions are not made. This works best when the state of the battery before recycling was good. Direct recycling is less likely to work for batteries that are old and of unknown provenance. NMP is a rather expensive solvent and somewhat toxic. Direct recycling is the most complicated process.

The real problem is costs. As we reduce the cobalt content, we reduce the value of the metals. Direct recycling may seem good, but if it results in an inferior product, who will buy it? Every step in a process incurs costs, and also produces is own waste stream, including a high level of greenhouse gases. If we accept the Nature review, 2% of the world’s cars would eventually represent a stream of waste that would encircle the planet so we have to do something, but the value of the metals in a lithium ion battery is less than 10% of the cost of the battery, and with all the toxic components, the environmental cost of such electric vehicles is far greater than people think. All the steps generate their own waste streams that have to be dealt with, and most steps would generate their own greenhouse gases. The problem with recycling is that since it usually makes products of inferior quality because of the cost of separating out all the “foreign” material, economics means that in a market economy, only a modest fraction actually gets recycled.

Protesting on Climate Change

It is interesting these days to see the level of protest; so many people want to protest against doing something. In many cases, that is fair as what they are protesting about should not happen, but then the problem comes, what happens when they get the rhythm, and what sort of protests get results as opposed to the protestors just making a nuisance of themselves? Recently, there were widespread protests here against the inaction of governments on the issue of climate change and that is a fair enough target of protest but how should they go about it? Blocking major roads to prevent traffic from going home after work simply leads to the production of more greenhouse gas. Then there were people here who used superglue to attach themselves to windows. My view on that is they should have been identified so that any bills for damages could be sent, then they be left there. Since they glued their hands, they would need friends to even feed them and a couple of cold fronts were coming.

What I find interesting is that one of the proposed ways of attacking climate change is to plant trees and they even protest about that. They argue the trees grow, then get cut down and the CO2 is returned to the atmosphere so we are no further ahead. In my opinion, that is wrong. First, we buy time. The trees can stand for a reasonable length of time, and further, when we cut them down, we can use the wood to build houses, etc. Leaves fall and return some carbon to the soil. And, of course, when we cut them down, we can replant. But most important, from my point of view, is we can do this now. There is no king hit that will deal with climate change so we shall have to do a very large number of things and unfortunately we don’t actually know how to do many of them beneficially. There is nothing like getting started on what you can do, and that you know what the consequences of doing it are.

Another objection noted in our local paper was that, wait for it, had we started thirty years ago when we knew about the problem this might have worked, but now we need more trees than we can reasonably plant quickly. Well, maybe. It does take time to get the necessary seedlings. The argument seems to be, we can’t solve the entire crisis this way, so why bother? Yes, I know there is no king hit, but if you are going to solve this crisis with a number of different approaches, getting started now is better than not doing anything. As the callers for doing nothing argue, we only have the problem because we did nothing some time ago. Yes, it is true we have wasted a lot of time, but why will wasting more now be beneficial?

Another argument seems to be, the land is too valuable for food production to waste on planting trees. Well, if I look out the window from where I am writing this, I see a range of somewhat tortured hills that stand between 300 to 700 meters above the valley floor, and these hills proceed as hills and steep valleys for a considerable distance. They are largely devoid of big trees, despite the fact that this whole area was initially heavily forested. When the settlers came, the valley was cleared of forest for farmland (farming has now long gone, having been replaced by urban development) then the hillsides were denuded of forest for timber. Now there is light scrub in places, but the big trees are long gone, and this is typical of a lot of land here. Planting trees would stabilise a lot of such steep hillsides, which are often prone to severe erosion, especially with heavy rain, which is expected to become more common over time due to climate change, at least here. For such country where harvesting trees becomes unlikely, by planting a judicious mix of trees such a forest could be self-sustaining so once established and it would store carbon indefinitely.

There are additional benefits of forests. An article in he recent Physics World mentioned that forests decrease the effect of storms, the reason being that the rough land surface offers a frictional restraint on wind speed. The forest has to be reasonably large, and of course the beneficial effects tend to apply to places distant from the coast. The forests also offer a benefit to rainfall through evapotranspiration and it is notable that many areas that are now facing desertification in Africa once had reasonable rainfall and extensive forests. It should be emphasised that forests may also reduce total rainfall by reducing the effect of heavy tropical storms, however in general these do little to provide water in a useful form as the water runs off very quickly. Forests are also beneficial in that they hold up water from heavy rains and allow it to be absorbed by the soil, and hence be available later, and of course, reduce heavy erosion. Also, in areas prone to severe flooding, and we have seen many examples of flooded urban areas on television recently, by holding up the water and thus spreading its movement over more time, the effects of such floods are mitigated. To my mind, anything that achieves more than one benefit is far more worthwhile to pursue.

As for the argument that when the trees mature, they will be harvested and eventually the carbon will return to the atmosphere, I have two responses. First, at least some of it can be stored in buildings, where it will remain for quite some time. Second, you could burn it for fuel or convert it to biofuel, in which case the carbon will return quickly, several decades in the future, but it displaces fossil carbon you would have otherwise converted to CO2, so you are still ahead. Finally, you have bought time to develop new means of solving this problem. And, at the same time, you do generate a future resource, in some cases from land that is otherwise producing nothing except erosion. From my point of view, it probably does not matter whether we act because I shall be dead by the time the really worst of the consequences arrive. However, I would like my grandchildren’s children to have a reasonable chance at life, and that means that we must stop protesting against change because our society cannot continue this way. Change will come; the issue is, what sort of change? Let us control it and make it beneficial.

The Hydrogen Economy

Now that climate change has finally struck home to at least some politicians, we have the problem, what to do next. An obvious point could be that while the politicians made grandiose promises about it thirty years ago, and then for economic reasons did nothing, they could at least have carried out research so they knew what their options are so that when they finally got around to doing something, they knew what to do. Right now, they don’t. One of the possibilities for transport is the use of hydrogen, but is that helpful? If so, where? The first point is you have to make your hydrogen. That is easy: you pass electricity through water. There is no shortage of water but you still have to generate your electricity. This raises the question, how, and at what cost? The good news is that generating hydrogen merely consumes energy so it can be turned down or off at peak load periods, but the difficulty now is the renewables everyone is so happy about offer erratic loads. As an example, Germany is turning off its nuclear power stations and finds it has to burn more coal, especially when the wind is not blowing. 

Assume we have the electricity and we have hydrogen, now what? The hydrogen could be burned directly in a compression motor, or used to power fuel cells. The latter is far more energy efficient, and we can probably manage about 70% overall efficiency. The reason the fuel cell is more desirable than the battery is simply that the battery cannot contain the desired energy density. The advantages of hydrogen include it is light and when burned (including in a fuel cell) all it makes is water. Water is a very powerful greenhouse gas, but the atmosphere has a way of promptly removing excess: rain.

However, hydrogen does have some disadvantages. A hydrogen-air mix is explosive over a rather wide mix ratio. Even outside this ratio, it has a clear flammability and an exceptionally fast flame speed, it leaks far faster than any other gas other than, possibly, helium, and it is odourless and colourless so you may not know it is there. But suppose you put that behind you, there are still clear problems. A small fuel cell car would need approximately 1 kg of hydrogen to drive 100 km. Now, suppose we need a range of 500 km. The storage of 5 kg of hydrogen would take up most of the boot space if you use a tank that is pressurised to 700 bar. (1 bar is atmospheric pressure.) That requires a lot of energy to compress the gas, and it adds a significant weight to the reinforced tank, which you most certainly do not want to rupture. The volume is important for a small car. You wish to go on holiday, then find your boot is occupied by a massive gas tank. However, this is trivial for very large machines, and a company in the US makes hydrogen powered forklifts. Here, a very heavy counterballancing weight is required so a monstrous steel tank is actually an asset. I previously wrote a blog post on hydrogen for vehicles, here.

There are different possible ways to store hydrogen. For those with a technical bent, the objective is to have something that absorbs hydrogen and binds it with an energy of between 15 – 20 kJ/mol. That is fairly weak. If you can mange that range you can store hydrogen at up to 100 bar with good reversibility. If you bind it in metal hydrides, you get a better density of storage at atmospheric pressure, but the difficulty is then to get the hydrogen back out. Most of the proposed metal organic absorbers bind it too weakly and you can’t get enough in. The metals that strongly absorb can be made to release it easier if the metal is present as nanoparticles, and to prevent these clumping, they can be embedded into carbon. There is an issue here, though, that the required volume is starting to become large for a given usage range because there are so many components that are not hydrogen.

There is another problem with hydrogen that most overlook: how do you deliver it to filling stations? Pressurizing won’t work because you can’t get enough into any container to be worth it. You could ship liquefied hydrogen, but it is only a liquid at or below -253 degrees Centigrade. It takes a lot of energy to cool that far, a lot to keep it that cold, and the part that most people will not realize is that at those very low temperatures for very light atoms, there are some effects of quantum mechanics that have to be taken into account. One problem is that hydrogen occurs as two isomers: ortho and para hydrogen. (Isomers are where there are at last two distinctly different forms with the same components, that may or may not readily interconvert.)  These arise because the hydrogen molecule comprises two protons bound by two electrons. The protons have what we call nuclear spin and as a consequence, have a magnetic moment. In ortho hydrogen, the spins are aligned; in para they are opposed. At room temperature, the hydrogen is 75% in the ortho form, but this is of higher energy than the para form. Accordingly, if you just cool hydrogen to the liquid form, you get the room temperature mix. This slowly converts to the para form, but it gives off heat as it does so. That means a tank of liquid hydrogen slowly builds up pressure. To be used as liquid hydrogen it is probably best to let it switch to the para form first, but that takes a lot more energy maintaining the low temperatures while the conversion is going on. Currently, liquefying hydrogen takes 12 kWh of power per kilogram of hydrogen, which is about 25% that of what you get from a fuel cell. In practice, you may need almost that much again to keep it cold, and since this power has to be electrical, we have an even greater demand for electricity.

So, is there an answer? My feeling is still that hydrogen is not the most desirable material for a fuel cell, from the point of view of usage in transport. The reason it is pursued is that it is easiest to make a fuel cell work with hydrogen. There are alternatives. Two that come to mind are ammonia and methanol. Both can drive fuel cells, and ammonia reacts to give water and nitrogen while methanol reacts to give water and carbon dioxide. Currently, the ammonia cell may be more efficient, but ammonia is somewhat difficult to make, although there is evidence it can be made from hydrogen and nitrogen under mild conditions. The methanol fuel cell has a problem that too much of the methanol sneaks through the membrane that keeps the two sides of the cell separate, and carbon monoxide tends to poison electrodes. Methanol could be made by the reduction of carbon dioxide from the air with solar energy.

So where does that leave us? In my opinion, what we need more than anything else is progress on better performing methanol or ammonia fuel cells, or some better fuel cell. My preference for the fuel cell is simply an issue of weight and power density, and I do not see hydrogen as being useful for light vehicles. The very heavy machines are a different matter, and batteries will never adequately power them. The problem of energy production in the future is a real one, and I feel we need to do a lot more research to pick the better options. We should have been doing this over the last thirty years, but we didn’t. However, there is no point in moaning about time wasted; we are here, and we have to act with a lot more urgency. However, it is not right to use the easiest but not very good options; we need to get these problems right.

The Hydrogen Economy to solve Climate Change?

One of the interesting aspects of climate change is the number of proposals put forward to solve it that do not take into account adverse consequences. There is a strong association of wishful thinking with some of these. On the other side are the gloomy ones, and maybe I fall into that category. What brought that thought to the fore was I have seen further claims for hydrogen as a solution. Why? Well, there are wild claims that wind and solar will solve everything. One problem with these is they tend to deliver their energy in pulses: solar during the day, wind when it is blowing. The net result is that if these can deliver adequate power for all times, there is serious overproduction required at other times. The problem then is how to store this energy. One way is to pump water uphill, but that requires large storage. In a country like New Zealand, where much of the electricity is hydro generated, you would just turn off that generation and use the hydro to manage power demand. However, that assumes there is not a large increase in electricity demand. One proposed solution is to generate hydrogen by electrolysing water. This is a well-understood technology, with no problems, given the power. There are, however, significant economic ones.

This is claimed to solve another problem; a very significant amount of domestic heating is obtained from burning gas. Now, all we have to do is burn hydrogen. We could also use hydrogen in vehicles. My big problem, having worked with hydrogen before, is that it leaks, and is extremely flammable. According to Wikipedia, the flammability range of hydrogen in air is between 4% and 75%; to detonate, the limits are 18.3 – 59% (each by volume), and a leak can support combustion at flow rates as low as 4 micrograms/second. Mixtures can ignite with very low energy input, 1/10 of that needed to ignite gasoline/air, and any static electric spark can ignite it.

The leak problem is made worse by the fact that hydrogen can embrittle metals, and thus create a way for it to escape. It is lighter than air, so it tends to accumulate at the ceilings of buildings, and its very wide explosive range is a broad hazard. The idea that hydrogen could be piped into houses to provide heating is not something I would want to see. The problem is made worse in that you might be sensible and cautious and not take it up, but your neighbour might. The consequences of that can impinge on you. Recently, in Christchurch, a house blew up, and reduced itself to a collection of boards, roofing material, etc., with only the foundations remaining more or less where they started. Several neighbours houses were severely damaged, and made effectively unliveable, at least without major repairs. By some miracle, nobody was killed, although a number had injuries. What apparently happened was a registered gasfitter had done some work on the house’s gas system, there was a natural gas leak, and something ignited it. My guess is, he has some explaining to do, but my point is if this can happen to a registered tradesman, what will happen if there is widespread use of something that leaks with orders of magnitude more ease?

There is a further irony. The objective behind using hydrogen is to help the greenhouse effect by reducing the amount of carbon dioxide we emit. Unfortunately, leaked hydrogen also magnifies the greenhouse effect. At first sight, this does not look right because greenhouse gases work because there is a change of dipole moment in the vibrational mode. This is needed because unless the transition involves a change of electric moment, it cannot absorb a photon. Hydrogen has only one vibrational mode and no electric moment, and no change of electric moment when it is stretched because of its symmetry, i.e.one end of H2 is exactly the same as the other end. There is a minor effect in that the molecule can be polarised for an instant in a collision with something else, but that is fairly harmless.

The problem lies in downstream consequences. One of the important greenhouse gases is methane, emitted by natural gas leaks, farm animals, other farm processes, anaerobic fermentation, etc. Methane is about 35 times more powerful than carbon dioxide as a greenhouse gas, and worse, it absorbs in otherwise transparent parts of the infrared spectrum. (The otherwise does not include other hydrocarbon gases.) However, methane is not as serious as it might be because it is short-lived. UV radiation in the upper atmosphere breaks water, directly or indirectly, into hydroxyl radicals and hydrogen radicals. The hydroxyl radicals rapidly degrade methane, and the hydrogen radicals react with oxygen in the air to make peroxyl radicals that also degrade methane. Molecular hydrogen reacts with both these sort of radicals, and thus indirectly preserves the methane.

There are, of course, other ways of using hydrogen, such as in chemical reactions, including upgrading biofuels, and it can be stored in chemical compounds. Hydrazine (N2H4) is an example of a liquid that could make a very useful fuel. (In the book, and film “The Martian”, the hero has hydrazine from the fuel tank of a rocket, so he catalytically converts it to hydrogen to burn to make water, and blows up his “dome”. It would have been so much easier to burn hydrazine, as it was, after all, from a rocket fuel tank.) Other options include storing hydrogen as hydrides, e.g. borohydrides, or as ammonia, which is cheaper to make than hydrazine, but it is also a gas, unlike hydrazine. The problem is usually how to deliver the hydrogen at a regular and controllable rate.

The use of hydrogen in a chemical manufacturing plant, or when handled with expertise, such as when used by NASA, is no problem. My concern would be for the average person doing repairs themselves to pipes conveying hydrogen, or worse still, plumbing incorrectly. As for having hydrogen as a fuel to be delivered at refuelling stations, I used this concept in my ebook “Puppeteer” to illustrate the potential danger if there are terrorists on the loose.