The Non-Green Internet

Did you know that by reading this you are contributing to climate change. Oops! Seriously, it is claimed that by 2025 the internet will use a fifth of the world’s electricity, assuming no massive increase in the use of electric transport. And before you decide to stop reading this to save the climate, apart from the use of your computer, you make no difference whether you read it or not. On the other hand, apparently Bitcoin mining consumes the total electricity consumption of Switzerland, so steady on there. The infrastructure for the internet is always on, and the messages you send make no difference. Sorry but you cannot save the world by not sending that email, and of course had you posted a physical letter, there would have been significant greenhouse gas emissions from getting the letter from your desk to wherever.

People that store their work in the cloud do contribute. A major data centre consumes about 30 GWh per year, and the UK has about 450 data centres. After all, all this rubbish we write and record has to be stored somewhere. That raises the question, how many data centres will have to be built? These centres are where the “cloud” resides, and if everyone is busy filling them up, what happens when it is no longer so easy to build more? How long can we continue recording everything?

How much has to be recorded for posterity? All those pointless Facebook posts that make pointless comments (rude or otherwise) or show a few emoticons. If they were deleted after a few weeks, would anyone notice? The problem then, of course, is, who decides? Notice the recent fuss about Trump not being allowed to tweet. In my opinion, if they had done that to him when he became President he would have been more effective but that is another matter. The problem is, when you appoint a “Great Deleter” you open up so many cans of worms it is not funny. Some of what we store will be of interest historically, perhaps especially Trump’s tweets. Right now photos recovered from long ago fascinate many of us. I know that I recently downloaded a whole lot of photos of the area where my mother grew up, and where, still a long time ago, I drove her back to have a look around. So for me, it was of interest to hear her say what was there, where, and now be able to see it. Quite simply, in two lifetimes everything has changed remarkably, and what was there is no longer, other than in memories, and memories die. Also, storing photos in data centres takes up much less space than storing hard copies. Of the hard copies left, many have been lost, but how much of what is stored digitally will be available in a hundred years?

Much of what is stored digitally may become unreadable. In the scientific community, for example, the Royal Society for Chemistry has noted that computations carried out in the last century often use code that nobody now understands. Some of us have computer files written many years ago, but unless they were updated and converted into new formats they are unreadable other than on an ancient computer. Back to electricity, either we can go into our shell and try to live like the Amish, do something about electricity generation, or be like politicians and make encouraging speeches and hope all gets well. Apparently, Facebook, Apple, Google and others have committed to using 100% renewable electricity (although when is another question) and Microsoft claims that by 2050 it will have removed all the carbon emissions it has ever produced. These are noble aspirations, but so far, according to Greenpeace, only about 20% of the electricity used by the world’s data centres is renewable. Further, the data centres run uniform power consumption over the entire time. Solar is of little use during the night, and wind power fails when the wind is not blowing. If we rely heavily on such renewables, what happens when there are blackouts? And, of course, there is the question of the non-renewable resources used to build the computers in the cloud. So no, I do not think anyone will be reading my blogs in a hundred years. However, we should make more effort to generate electricity more sustainably. Unless we solve the fusion problem, I favour the liquid salt thorium-type reactor.

What are We Doing about Melting Ice? Nothing!

Over my more active years I often returned home from the UK with a flight to Los Angeles, and the flight inevitably flew over Greenland. For somewhat selfish reasons I tried to time my work visits in the northern summer, thus getting out of my winter, and the return flight left Heathrow in the middle of the day so with any luck there was good sunshine over Greenland. My navigation was such that I always managed to be at a window somewhere at the critical time, and I was convinced that by my last flight, Greenland was both dirtier and the ice was retreating. Dirt was from dust, not naughty Greenlanders, and it was turning the ice slightly browner, which made the ice less reflective, and thus would encourage melting. I was convinced I was seeing global warming in action during my last flight, which was about 2003.

As reported in “The Economist”, according to an analysis of 40 years of satellite data at Ohio State University, I was probably right. In the 1980s and 1990s, during Greenland summers it lost approximately 400 billion tonnes of ice each summer, by ice melting and by large glaciers shedding lumps of ice as icebergs into the sea. This was not critical at the time because it was more or less replenished by winter snowfalls, but by 2000 the ice was no longer being replenished and each year there was a loss approaching 100 billion t/a. By now the accumulated net ice loss is so great it has caused a noticeable change in the gravitational field over the island. Further, it is claimed that Greenland has hit the point of no return. Even if we stopped emitting all greenhouse gases now, it was claimed, more ice would be progressively lost than could be replaced.

So far the ice loss is raising the oceans by about a millimetre a year so, you may say, who cares? The problem is the end position is the sea will rise 7 metres. Oops. There is worse. Apparently greenhouse gases cause more effects at high latitudes, and there is a lot more ice on land at the Antarctic. If Antarctica went, Beijing would be under water. If only Greenland goes, most of New York would be under water, and just about all port cities would be in trouble. We lose cities, but more importantly we lose prime agricultural land at a time our population is expanding

So, what can be done? The obvious answer is, be prepared to move where we live. That would involve making huge amounts of concrete and steel, which would make huge amounts of carbon dioxide, which would make the overall problem worse. We could compensate for the loss of agricultural land, which is the most productive we have, by going to aquaculture but while some marine algae are the fastest growing plants on Earth, our bodies are not designed to digest them. We could farm animal life such as prawns and certain fish, and these would help, but whether productivity would be sufficient is another matter.

The next option is geoengineering, but we don’t know how to do it, and what the effects will be, and we are seemingly not trying to find out. We could slow the rate of ice melting, but how? If you answer, with some form of space shade, the problem is that orbital mechanics do not work in your favour. You could shade it some of the time, but so what? Slightly more promising might be to generate clouds in the summer, which would reflect more sunlight.

The next obvious answer (OK, obvious may not be the best word) is to cause more snow to fall in winter. Again, the question is, how? Generating clouds and seeding them in the winter might work, but again, how, and at what cost? The end result of all this is that we really don’t have many options. All the efforts at limiting emissions simply won’t work now, if the scientists at Ohio State are correct. Everyone has heard of tipping points. According to them, we passed one and did not notice until too late. Would anything work? Maybe, maybe not, but we won’t know unless we try, and wringing our hands and making trivial cuts to emissions is not the answer.

The Hangenberg Extinction

One problem of applying the scientific method to past events is there is seldom enough information to reach a proper conclusion. An obvious example is the mass extinction that we know occurred at the end of the Devonian period, and in particular, something called the Hangenberg event, which is linked to the extrinction of 44% of high-level vertebrate clades and 97% of vertebrate species. Only smaller species survived, namely sharks smaller than a meter in length and general fish less than ten centimeters in length. This is the time when most ammonites and trilobites, which had been successful for such a long time, failed to survive. One family of trilobites survived, only to be extinguished in the Permian extinction, another  of those that wiped out 90% of all species. 

So why did this happen? First, it is most likely the ecosystems had been stressed. The Hangenberg event occurred about 358 My ago, but before that, at about 382 My BP most jawless fish disappeared, while from 372 – 359 My BP there were a series of extinctions or climate changes known as the Kellwasser event (although it was almost certainly a number of events.) So for about 30 million years leading up to the Hangenberg event, there had been severe difficulties for life. At this stage, leaving aside insects and plants that had left the oceans, most life were in marine or freshwater environments and it was this life that appears to have suffered the most. That conclusion, however, may more reflect a relative paucity of land-based fossils. Climate change was almost certainly involved because over this period there was a series of sea level rises while the water became more anoxic. The causes of this are less than clear and there have been a numper of suggestions.

One possibility is an asteroid collision, and while impact craters can be found they cannot be dated sufficiently closely to be associated with any specific event. A more likely effect questions why anoxic? The climate  should have no direct effect on this, although the reverse is possible. The question is really was it the seas only that became anoxic? One possibility is that on land the late Devonian saw a dramatic change in plant life. In the early Devonian, plants had made it to land, but they were small leafy plants like liverworts and mosses. In the late Devonian they developed stems that could move water and nutrients, and suddenly huge plants emerged. One argument is that this caused a flood of nutrients through the weathering of rocks caused by the extensive root systems to flow down into the sea, which caused algal blooms, which led to anoxic conditions. Meanwhile, the huge forests of the Devonian may have reduced carbon dioxide levels, which would lead to glaciation, and the sea level fall in the very late Devonian. However, it does not explain sea level rise earlier. That may have arisen from extensive volcanism that occurred around 372 My ago, which would enhance greehouse warming. You can take your pick from these explanations because even the experts in the field are unsure.

Accordingly, a new theory has just emerged, namely Earth was bombarded by cosmic rays from a nearby supernova (Fields, et al., arXiv:2007.01887v1, 3rd July, 2020). This has the advantage that we can see why it is global. The specific event would be a core-collapse supernova. If this occurred within 33 light years from Earth, it would probably extinguish all life on Earth, but one about twice as far away, 66 light years, would exterminate much life, but not all. The mechanism is in part ozone depletion, but there is the possibility of enhanced nitrogen fixation in the atmosphere, which might lead to algal blooms. One of the good things about such a proposition is it is testable. Such an event would bombard Earth with isotopes that would otherwise be difficult to obtain, and one would be plutonium 244. There is no naturally occurring plutonium on Earth, so if some atoms were found in the fossils or in accompanying rock, that would support the supernova event.

So, is that what happened? My personal view is that is unlikely, and the reason I say that is that most of the damage would be done to life on land, and as I gather, the insects expanded into the Carboniferous period. The seas would be relatively protected because the incoming flux would be protected by the water. The nitrate fixation might cause an algal bloom and while a lot of energy would be required to saturate the world’s oceans, maybe there was sufficient. The finding of plutonium in the associated deposits would be definitive, however. The typical deposits were black shales overlaid by sandstone, and are easy to locate, so if there is plutonium in them, there is the answer. If there is not, does that mean the proposition is wrong? That is more difficult to answer, but the more samples that are examined from widespread sources, the more trouble for the proposition.

My preferred explanation is the ecological one, namely the development of tree ferns, etc. The Devonian extinction was slow, taking 24 million years, and while most marine extinctions occurred during what is called the Hangenberg event, the word event may be misleading. That specific period took 100,000 – 300,000 years, which is plenty of time for an ecological disaster to kill off that which cannot adapt. To put it into perspective, Homo Sapiens has been around for only 30,000 years, and effective for only about 10,000 years. Look at the ecological change. Now, think what will happen if we let climate change get out of control. We are already causing serious extinction of many species, but the loss of habitat if the seas rise will dwarf what we have done so far because our booming population has to eat. We should learn from the late Devonian.

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 ( ) 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.

Energy from the Sea. A Difficult Environmental Choice.

If you have many problems and you are forced to do something, it makes sense to choose any option that solves more than one problem. So now, thanks to a certain virus, changes to our economic system will be forced on us, so why not do something about carbon emissions at the same time? The enthusiast will tell us science offers us a number of options, so let’s get on with it. The enthusiast trots out what supports his view, but what about what he does not say? Look at the following.

An assessment from the US Energy Information Administration states the world will use 21,000 TWh of electricity in 2020. According to the International Energy Agency, the waves in the world’s oceans store about 80,000 TWh. Of course much of that is, well, out at sea, but they estimate about 4,000 TWh could be harvested. While that is less than 20% of what is needed, it is still a huge amount. They are a little coy on how this could be done, though. Wave power depends on wave height (the amplitude of the wave) and how fast the waves are moving (the phase velocity). One point is that waves usually move to the coast, and there are many parts of the world where there are usually waves of reasonable amplitude so an energy source is there.

Ocean currents also have power, and the oceans are really one giant heat engine. One estimate claimed that 0.1% of the power of the Gulf Stream running along the East Coast of the US would be equivalent to 150 nuclear power stations. Yes, but the obvious problem is the cross-sectional area of the Gulf Stream. Enormous amounts of energy may be present, but the water is moving fairly slowly, so a huge area has to be trapped to get that energy. 

It is simpler to extract energy from tides, if you can find appropriate places. If a partial dam can be put across a narrow river mouth that has broad low-lying ground behind it, quite significant flows can be generated for most of the day. Further, unlike solar and wind power, tides are very predictable. Tides vary in amplitude, with a record apparently going to the Bay of Fundy in Canada: 15 meters in height.

So why don’t we use these forms of energy? Waves and tides are guaranteed renewable and we do not have to do anything to generate them. A surprising fraction of the population lives close to the sea, so transmission costs for them would be straightforward. Similarly, tidal power works well even at low water speeds because compared with wind, water is much denser, and the equipment lasts longer. La Rance, in France, has been operational since 1966. They also do not take up valuable agricultural land. On the other hand, they disturb sea life. A number of fish appear to use the Earth’s magnetic field to navigate and nobody knows if EMF emissions have an effect on marine life. Turbine blades most certainly will. They also tend to be needed near cities, which means they disturb fishing boats and commercial ships.

There are basically two problems. One is engineering. The sea is not a very forgiving place, and when storms come, the water has serious power. The history of wave power is littered with washed up structures, smashed to pieces in storms. Apparently an underwater turbine was put in the Bay of Fundy, but it lasted less than a month. There is a second technical problem: how to make electricity? The usual way would be to move wire through a magnetic field, which is the usual form of a generator/dynamo. The issue here is salt water must be kept completely out, which is less than easy. Since waves go up and down, an alternative is to have some sort of float that mechanically transmits the energy to a generator on shore. That can be made to work on a small scale, but it is less desirable on a larger scale.The second problem is financial. Since history is littered with failed attempts, investors get wary, and perhaps rightly so. There may be huge energies present, but they are dispersed over huge areas, which means power densities are low, and the economics usually become unattractive. Further, while the environmentalists plead for something like this, inevitably it will be, “Somewhere else, please. Not in my line of sight.” So, my guess is this is not a practical solution now or anytime in the reasonable future other than for small specialized efforts.

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.

Molten Salt Nuclear Reactors

In the previous post, I outlined two reasons why nuclear power is overlooked, if not shunned, despite the fact it will clearly reduce greenhouse gas emissions. I discussed wastes as a problem, and while they are a problem, as I tried to show they are in principle reasonably easily dealt with. There is a need for more work and there are difficulties, but there is no reason this problem cannot be overcome. The other reason is the danger of the Chernobyl/Fukushima type explosion. In the case of Chernobyl, it needed a frightening number of totally stupid decisions to be made, and you might expect that since it was a training exercise there would be people there who knew what they were doing to supervise. But no, and worse, the operating instructions were unintelligible, having been amended with strike-outs and hand-written “corrections” that nobody could understand. You might have thought the supervisor would check to see everything was available and correct before starting, but as I noted, there has never been a shortage of stupidity.

The nuclear reaction, which generates the heat, is initiated by a fissile nucleus absorbing a neutron and splitting, and then keeping going by providing more neutrons. These neutrons either split further fissile nuclei, such as 235U, or they get absorbed by something else, such as 238U, which converts that nucleus to something else, in this case eventually 239Pu. The splitting of nuclei produces the heat, and to run at constant temperature, it is necessary to have a means of removing that amount of heat continuously. The rate of neutron absorption is determined by the “concentration” of fissile material and the amount of neutrons absorbed by something else, such as water, graphite and a number of other materials. The disaster happens when the reaction goes too quickly, and there is too much heat generated for the cooling medium. The metal melts and drips to the bottom of the reactor, where it flows together to form a large blob that is out of the cooling circuit. As the amount builds up it gets hotter and hotter, and we have a disaster.

The idea of the molten salt reactor is there are no metal rods. The material can be put in as a salt in solution, so the concentration automatically determines the operating temperature. The reactor can be moderated with graphite, beryllium oxide, or a number of others, or it can be run unmoderated. Temperatures can get up to 1400 degrees C, which, from basic thermodynamics, gives exceptional power efficiency, and finally, reactors can be relatively small. The initial design was apparently for aircraft propulsion, and you guessed it: bombers. The salts are usually fluorides because low-valence fluorides boil at very high temperatures, they are poor neutron absorbers, and their chemical bonds are exceptionally strong, which limits corrosion, and they are exceptionally inert chemically. In one sense they are extremely safe, although since beryllium fluoride is often used, its extreme toxicity requires careful handling. But the big main advantage of this sort of reactor, besides avoiding the meltdown, is it burns actinides and so if it makes plutonium, that is added to the fuel. More energy! It also burns some of the fission wastes, and such burning of wastes also releases energy. It can be powered by thorium (with some uranium to get the starting neutrons) which does not make anything suitable for making bombs. Further, the fission products in the thorium cycle have far shorter half-lives. Research on this started in the 1960s and essentially stopped. Guess why! There are other fourth generation reactors being designed, and some nuclear engineers may well disagree with my preference, but it is imperative, in my opinion, that we adopt some. We badly need some means of generating large amounts of electricity without burning fossil fuels. Whatever we decide to do, while the physics is well understood, the engineering may not be, and this must be solved if we are to avoid a planet-wide overheating. The politicians have to ensure this job gets done.

Forests for storing carbon

One of the more annoying features of the climate change issue is the question of feedback, i.e. what are the consequences of what is inevitably going to happen? One important issue is whether we can fix carbon, at least temporarily, and the answer is, yes but . . .  The following illustrates some of the problems, based on a paper by McNicol et al. 2019. Environ. Res. Lett. 14 014004 .

We hear that forestry is a good place to store carbon. The first objection you hear will be that while the trees take carbon from the air, they eventually die and return the carbon to the air. Of course, if the forest is continuous, as the old trees die, new ones replace them, which means that if the trees are there, there is so much carbon dioxide taken from the atmosphere. New forests are net removers while they are growing; mature forests represent a constant fixed amount. Building things with the wood will add to the reduction of atmospheric carbon. Temperate rainforests can store up to 1500 t/ha of carbon, while something like 200 t/ha will commonly be stored in the top one meter of soil, particularly if there is plenty of rain. Peatlands store more carbon, as do deeper soils. Peatlands in the region can be up to six meters deep. The greatest concentration of organic carbon occurs where the ground is wettest, while slope is also important. To give some idea, the total mass of soil carbon calculated for the North Pacific coastal temperate rainforest was 4.5 billion tonnes of carbon. 

Soil carbon does not stay there. Soil is a rather remarkable mass of biological activity, the waste products of which return to the atmosphere as either methane or carbon dioxide. Increasing the temperature speeds this up, and an average increase of 1 degree Centigrade across the world could release 50 billion tonne of carbon into the atmosphere from this source alone by 2050. That is about five times as much as we produce annually through burning fossil fuels and through agricultural activities. On the other hand, if it rained more, an increase in water-saturated soil would lead to net storage. This is the issue of feedback I mentioned. Positive feedback would mean that as the temperature rose thanks to the carbon we have put in the air, the soil would put more there, and accelerate the heating. The negative feedback occurs where more rain falls in key places and holds more carbon in the soil. Which will it be?

The climate warming is inevitable, but what happens to the weather? One suggestion is that where it is already wet, it will get wetter, whereas where it is dry, it will get dryer. That makes Australia less of “a lucky country”, which it proclaims itself to be.

Of course, simple soil is not the only source of greenhouse gas. Most people will have heard of methane occluded in tundra that is gradually thawing. Something has to be done, but politicians prepared to do anything are thin on the ground, and those who have analysed and recognized what few schemes might actually work and make a significant contribution towards solving it are even thinner on the ground.  There are conflicting issues, thus to store carbon you want trees on flat land to store more in the soil, but that is where the food comes from. So maybe planting trees on hills is better, because that land is less useful for food. What would you do?

Transport System Fuel. Some passing Comments

In the previous series of posts, I have discussed the question of how we should power our transport systems that currently rely on fossil fuels, and since this will be a brief post, because I have been at a conference for most of this week, I thought it would be useful to have a summary. There are two basic objectives: ensure that there are economic transport options, and reduce the damage we have caused to the environment. The latter one is important in that we must not simply move the problem.

At this stage we can envisage two types of power: heat/combustion and electrical. The combustion source of power is what we have developed from oil, and many of the motors, especially the spark ignition motors, have been designed to optimise the amount of the oil that can be so used. The compression of most spark ignition engines is considerably lower than it could be if the octane rating was higher. These motors will be with us for some time; a car bought now will probably still be on the road in twenty years so what do we do? We shall probably continue with oil, but biofuels do offer an alternative. Some people say biofuels themselves have a net CO2 output in their manufacture. Maybe, but it is not necessary; the main reason would be that the emphasis is put onto producing the appropriate liquids because they are worth more than process heat. Process heating can be provided from a number of other sources. The advantages of biofuels are they power existing vehicles, they can be CO2 neutral, or fairly close to it, we can design the system so it produces aircraft fuel and there is really no alternative for air transport, and there are no recycling problems following usage. The major disadvantages are that the necessary technology has not really been scaled up so a lot of work is required, it will always be more expensive than oil until oil supplies run down so there is a poor economic reason to do this unless missions are taxed, and the use of the land for biofuels will put pressure on food production. The answers are straightforward: do the development work, use the tax system to change the economic bias, and use biomass from the oceans.

There are alternatives, mainly gases, but again, most of them involve carbon. These could be made by reducing CO2, presumably through using photolysis of water (thus a sort of synthetic photosynthesis) or through electricity and to get the scale we really need a very significant source of electricity. Nuclear power, or better still, fusion energy would work, but nuclear power has a relative disappointing reputation, and fusion power is still a dream. Hydrazine would make a truly interesting fuel, although its toxicity would not endear it to many. Hydrogen can work well for buses, etc, that have direct city routes.

Electricity can be delivered by direct lines (the preferred option for trains, trams, etc.), but otherwise it must be by batteries or fuel cells. The two are conceptually very similar. Both depend on a chemical reaction that can be very loosely described as “burning” something but generating electricity instead of heat. In the fuel cell, the material being “burnt” is added from somewhere else, and the oxidising agent, which may be air, must also be added. In the battery, nothing is added, and when what is there is used, it is regenerated by charging.

Something like lithium is almost certainly restricted to batteries because it is highly reactive. Lithium fires are very difficult to put out. The lithium ion battery is the only one that has been developed to a reasonable level, and part of the reason for that is that the original market was for mobile phones and laptops. There are potential shortages of materials for lithium ion batteries, but they would never cut in for those original uses. However, as shown in my previous post, recycling of lithium ion batteries will be very difficult to solve the problem for motor vehicle batteries. One alternative for batteries is sodium, obtainable from salt, and no chance of shortage.

The fuel cell offers some different options. A lot has been made of hydrogen as the fuel of the future, and some buses use it in California. It can be used in a combustion motor, but the efficiencies are much better for fuel cells. The technology is here, and hydrogen-powered fuel cell cars can be purchased, and these can manage 500 km on  single charge, and can totally refuel in about 5 minutes. The problem again is, hydrogen refuelling is harder to find. Methanol would be easier to distribute, but methanol fuel cells as of yet cannot sustain a high power take-off. Ammonia fuel cells are claimed to work almost as well as hydrogen and would be the cheapest to operate. Another possibility I advocated in one of my SF novels is the aluminium/chlorine cell, as aluminium is cheap, although chlorine is a little more dangerous.

My conclusions:

(a)  We need a lot more research because most options are not sufficiently well developed,

(b)  None will out-compete oil for price. For domestic transport, taxes on oil are already there, so the competitors need this tax to not apply

(c)  We need biofuels, if for no other reason that maintaining existing vehicles and air transport

(d)  Such biofuel must come at least partly from the ocean,

(e)  We need an alternative to the lithium ion battery,

(f)  We badly need more research on different fuel cells, especially something like the ammonia cell.

Yes, I gree that is a little superficial, but I have been at a conference, and gave two presentations. I need to come back down a little 🙂