Saving the World – with a Stink!

The latest from Nature (vol 602, p 202) on how to save the world: collect urine. This is, of course, a well-established technology – the ancient Romans did it. They collected it from special urinals through the city and did all sorts of things with it. One of the more interesting, according to Catullus, was to use it as a tooth whitener! The urine was also collected and taken to a fullonica (a laundry) and after dilution, was poured over dirty clothes. A worker would stand in a tub and stomp on the clothes – conceptually similar to a modern washing machine. It was similarly used to clean wool and remove the fats, etc, to prepare it for dyeing. It can be used to make leather soft, and when mordant dyeing, it can also make the dyes brighter. And, of course, if you feel so inclined, you could advance to medieval times and make saltpetre, which is essential for gunpowder. But urine uses come and they go, so how now do they save the world?

The lead, apparently, comes from Sweden, and in particular the island of Gotland. They are going to put some public flush-free urinals around the island and hope to collect about 70,000 litres of it. They are then going to dry this into chunks apparently with the texture of concrete, which they powder and compress into pellets for fertilizer. Currently, a local farmer uses the product from a pilot plant to grow barley which goes to a local brewery and thus forms a complete cycle. That is real recycling.

The problem here, of course, is it is necessary to separate the urine from the rest of the sewage. Either you need separate toilets, or you have an interesting design issue. There are, apparently, a number of similar projects in a number of different countries. Currently, it has been estimated that humans produce enough urine to replace about ¼ of our nitrogen and phosphate fertilizers. It also contains potassium and many  micronutrients. Also, by not flushing, we save a lot of water. As for problems, the first we face is we have to redesign our toilets and then design a way for how we treat it. The treatment will have to be dispersed, thus a building might have its own urine system. Currently, we have one sewage system that takes everything, but we cannot afford a further such system, especially since for a dispersed system sooner or later some people will put anything down the second system. As for “saving the world”, one estimate is that communities that do this could lower their overall greenhouse emissions by up to 47%, their energy consumption by up to 41%, fresh water usage by 50%, and nutrient  pollution from waste-water by up to 64%. The greenhouse emission savings go a very long way to saving the planet alone, provided everyone did it, because if properly managed, not only do you reduce methane production, but also the much more difficult nitrous oxide, which is more long-lived than carbon dioxide. Then, if you deal with this properly you could get more imaginative: bags to collect urine from cows! Fix the dairying greenhouse problem in one go.

Sounds good, so what’s the problem? Toilet design, to start with. What people come up with tends to be unwieldly, awkward to use, and outright smelly, especially if urine gets mixed with the faeces. A clever redesign of a toilet might overcome that, but now you have to collect the separate urine, with no additional water added. It will drain, but leave a smell. Either you collect in a tank that then has to be taken somewhere, or you re-pipe the building. Then what? In an urban setting, it is not practical to install a separate sewer system, and since it is about 95% water, transporting is very expensive for what you get. One trick is to hydrolyse the urine (because much of the nitrogen is present as urea) then add something like magnesium sulphate (maybe supplemented with some phosphate) and you get a precipitate of magnesium ammonium phosphate (struvite), which is an excellent slow-release fertilizer. The problem now is the phosphate in the urine is not balanced with the nitrogen (which is why supplanting it is desirable), you have lost the potassium, and does the average household want to do this every weekend? As you can see, saving the world is more difficult than it looks like at first sight.

Can Photovoltaics Provide our Electricity?

The difference between a scientific assessment and a politician’s statements is usually that the first has numbers attached to it, and that forces the analysis to come to some form of realism. You may have heard politicians say the answer to climate change is simple: solar energy. The sun, they say, has huge amounts of energy. That is true, but so what? We cannot simply pipe it to our homes and cars.

According to a recent article by Lennon et al in Nature Sustainability the International Technology Roadmap has estimated that to get photovoltaics to replace other forms of power it needs a peak output of 60 TW by 2050. Of course, one still needs a huge battery storage system because the sun does not shine at night, and domestic electricity peaks tend to be near dawn and dusk, not in the middle of the day, but let us put that aside for the moment. Let us concentrate on the material demands of generating it. If that does not add up, what follows is immaterial because we can’t use it, at least on the required scale.

First, consider copper. From Zhang et al. 2021(Energy and Environmental Science, 14: 5587) the auxiliary systems (cables, transformers, connections in modules) require 2,800 kg/MW,  which, to get to 60 TW, requires 168 million t. That is about 20% of the estimated global reserves. Similarly, the amount of silver would be about 90,000 t, which is about 16% of the estimated known world reserves, but three times the supply available now. The estimate for silver is that 1 TW would consume between 53 – 117% of current silver production. As can be seen, 60 TW will be a problem. Indium usage tends to be 50% higher than that of silver, and there are some indications it could be even higher. Global reserves of indium could be as low as 2.7% those of silver. The most optimistic estimate for bismuth usage is that 1 TW would consume 50% of the global bismuth supply. On top of that, you may ask why is the global supply so large? That is because these metals are currently used for other things as well as PV modules, and the other uses are increasing in sales volume. Thus the touch screens on your mobile phones rely on indium. Further, although more indium and bismuth are used in these PV modules, bismuth has only about 2/3 the global reserves of silver. We need more of these elements and there is much less available. The total resource level is not that great, and when we have mined those resources, what then? Anyone who says, “Recycle them,” should be asked how they propose to do that. Thus a given mobile phone has tiny amounts of indium, and of a large number of other elements. Separating them all will be extremely difficult, but when the known resources are gone, now what?

However, the problem does not stop there. It is one thing to have, say, silver sulphide dispersed through various rocks, and another to having silver in a form ready for use in a photovoltaic.

Not only that, but there is material not directly involved in electricity generation. Thus aluminium is used in mountings, frames, inverters and in many other energy technologies. Now refining aluminium is rather energy intensive. There are two main steps: refining bauxite into alumina, then electrolysing the alumina. A tonne of aluminium ingot requires about 63 GJ of energy to make. Just for photovoltaics we need an extra 486 Mt of aluminium, which requires 30.6 quadrillion Joules. This is a huge amount of energy, so a lot of fossil fuel will have to be burned with the corresponding effect on climate change. We can cut this back by using recycled aluminium, but the recycled aluminium is currently being used. Unless there is a surplus of recycled material or potentially recyclable material, recycling adds nothing because the uses it is taken from will have to use virgin material.

We can have substitution. Replacing aluminium with steel reduces the energy demand to make the metal, but increases the loss due to corrosion, and because it is heavier, increases transport greenhouse gas emissions. It is possible to reduce demands by making things lighter, but there is limited scope here because simple costs have led to most of these cherries already having been picked.

On top of that, we have ignored another elephant in the room. Silicon comes from silica, which is very inert. There is no shortage of silica and rocks are made of that bound to metal oxides. However, the making of silicon is very energy intensive. To make high grade silicon we need 1 – 1.5 GJ of energy per tonne of silicon. We need 13 t of silicon per MW, so 60 TW of energy requires 780 billion t of silicon, or a minimum of another 780 quadrillion J of energy. We shall make a lot of greenhouse gases making these collectors.

An Ebook Discount and Something Different: Music!

From February 10 – 17, Scaevola’s Triumph will be discounted to 99c/99p on amazon.com and amazon.uk.

So far, the bizarre prophecy has worked, and Scaevola finds himself on a technically advanced alien planet where he is considered a primitive, yet it is losing a war. According to Pallas Athene, only he can save this civilization from extermination, and his use of strategy is needed to win this war. But what can he do, when at first he cannot even open the door to his apartment? A story of strategy and tactics in an interstellar war under relativistic physics. If you set off on a mission, when you return everyone who sent you is long dead. Book III of a series. http://www.amazon.com/dp/B00O0GS7LO

And now for the something different. A side hobby of mine is composing music, and I like to amuse myself by playing it, not necessarily very well. Anyway, I have decided to make some of what I play to myself available in case anyone is interested. Go to https://ianmiller.co.nz/music then scroll to the bottom.  I have listed in what I call Suite number 2 six short piano pieces that I like to play. The only connection, apart from being short, is they are in different time signatures, thus try number 5, in 5/4 time. Click on them and it takes you to a sheet music sale site, but it also has .mp3 files you can listen to.

Don’t Look Up

No, I am not going to discuss the film, the merits of which you can decide for yourself. However, it might be worth considering some of the things it says about the way we consider and treat science. What the film is supposed to say is that those in society with the power to do something about a crisis wilfully avoid taking action. Consider the excuses for doing nothing.

The film presents a wipe-out event that we will be struck by a comet. The probability of this happening is assessed at 99.8%. So it is not 100%? What we have to recognize that scientific measurements have errors in them. Statistically we make lots of measurements and use a statistical analysis, and while someone in the movie says “Scientists never like to say 100%” that is wrong too. Scientists do not like or dislike; they report the mathematics, and a statistical spread cannot give a 100% because that denies the initial spread. Further, that 0.2% is not physically meaningful either because the errors due to instruments are not randomly probable, but nobody is going to waste time working out the error function for every piece of equipment. Statistical analysis takes care of that. To gain perspective, consider a bag of 1000 50 calibre bullets. You are assured two are blank. One is placed into a gun. What amount of money do you need, if you survive, to put your head in front of the barrel when it is fired?

A second problem for scientists is that long-term realities will be ignored by the public. This more relevant to something like climate change. What are you prepared to do to avoid a major problem fifty years down the track? For many, not a lot, so they ignore the problem on the grounds that it can be dealt with “later”. Related to this are the economic considerations. One response is we cannot afford to do something. When we hear that we seldom see what the costs are of not doing said something. Again, the response might be, but you do not absolutely know that will solve the problem. No, we do not, but that is because we do not think there will be one simple solution for a problem like climate change.

Another response is to rely on technological changes. For an approaching comet, there are probably no other choices. You either construct some space vehicle that will push the comet off course or it strikes you. To make that work, a major investment in development work would be required, since we do not have such a vehicle now. As it happens, for this scenario NASA is doing work, and around the end of September a space vehicle weighing 550 kg will slam into an asteroid called Dimorphos. This is part of a double asteroid system, and we will be able to follow the effect of the impact in fine detail because it will alter the orbital characteristics of Dimorphos as paired with Didymos, the larger companion. The problem with something like climate change is that while technology might fix it, we are not doing the research and development needed to make it work.

Society seems to work against science, simply because people do not trust it. Over 5 million have died with Covid 19, yet we have many very active antivaxxers trying to persuade others not to be vaccinated. The interesting question is why? It is one thing to refuse to be vaccinated yourself, but why impose these views on others?  In their effort το persuade others they spread completely stupid stories. Recall the story that Bill Gates was inserting nano-trackers into the vaccine so he could know what everyone was doing? There are also stories with an element of truth but with no comprehension of relevance. Like our 98.8% above, they focus on the 0.2%. There is a tiny segment of the populations that respond adversely to certain vaccines. The medical profession knows this, and can look out for them and treat them properly if such an event occurs. These stories totally ignore what would happen to these far more sensitive people if the virus struck them. Finally, there is a tendency for navel-gazing. Consider our experiment on Dimorphos. There is a view, “What right have we to change the solar system?” If we took this view to the limit, we would still be hunter-gatherers and our biggest problem would be that lion in the shrubbery planning on eating us. Dimorphos is a lump of rock. It does not have feelings. It is not planning its future. The allied question, do your sensitivities about the Universe and the pristine nature of rocks in it give you the right to prevent the killing of billions of innocent people who do not share your view?

Did a Galactic-Scale Collision Lead to Us?

Why do we have a planet that we can walk around on, and generally mess up? As most of us know, the atoms we use, apart from hydrogen, will have originated in a nova or supernova, and some of the planet possibly even from collisions of neutron stars. These powerful events send clouds of dust into gas clouds, but then what? We call it dust, but the particle size is mainly like smoke. Telescopes like the Hubble space telescope have photographed huge clouds of gas and dust in space. These can be quite large, thus the Orion molecular cloud complex is hundreds of light years across. These giant clouds can sit there and do very little, or then start forming stars. The question then is, what starts it? The hydrogen and helium, which are by far the predominant components, with hydrogen masses about ten thousand times as much as anything else except helium, are always colliding with each other, and with dust molecules, but they always bounce back because there is no way to lose their kinetic energy. The gas has been around for 13.6 billion years, so why does it collapse suddenly?

To make things slightly more complicated, the cloud does not collapse on itself. Rather, sections collapse to form stars. The section that formed our solar system would probably have been a few thousand astronomical units across (an astronomical unit, AU, is the distance between Earth and the Sun), and this is a trivial fraction of such giant clouds. So what happens is sections collapse, leaving the cloud with “holes”, a little like a Swiss cheese.

For us, about 4.6 billion years ago such a piece of a gigantic gas cloud started to collapse upon itself, which eventually led to the formation of the solar system, and us. Perhaps we should thank whatever caused that collapse. A common explanation is that a nearby supernova sent a shockwave through the gas, and that may well be correct for a specific situation, but there is another source of disruption: galactic collisions. We have observed these elsewhere, and invariably such collisions lead to a good generation of stars. Major galaxies do not collide that often because they are so far away from each other. As an example, in about five billion years, Andromeda will collide with the Milky Way. That may well initiate a lot of formation of new stars as long as there is plenty of gas and dust clouds left.

However, there are some galactic collisions that are a bit more frequent. There is something called the Sagittarius Dwarf Spheroidal Galaxy which is approximately a tenth the diameter of the Milky Way. It comprises four main globular clusters and is spiralling around our galaxy on a polar orbit about 50,000 light years from the galactic core and passes through the plane of the Milky Way periodically. It apparently did this about five to six billion years ago, then about two billion years ago, and one billion years ago. Coupled with that, a team of astronomers have argued that star formation in the Milky Way peaked at around 5.7, 1.9 and 1 billion years ago. The argument appears to be that such star formation arose about the same time that the dwarf galaxy passed through the Milky Way. In this context, some of our nearest stars fit ths hypothesis. Thus Tau Ceti, EZ Aquarii,  and Alpha Centauri A and B are about 5.8 billion years old, Procyon is about 1.7 billion years old, while Epsilon Eridani is about 900 million years old.

However, if we look at other local stars, we find Earth, Lacaille 9352 and Proxima Centauri are about 4.5 billion years old, Epsilon Indi is about 1.3 years old, Alpha Ophiuchi A is about 750 million years old, Sirius is about 230 million years old, and Wolf 359 is between 100 – 300 million years old. Of course, a galaxy passing through another galaxy will consume a lot of time, so it is not clear what to make of this. There is always a temptation to correlate and assume causation, and that is unsound. On the other hand, the more massive Milky Way may have stripped some gas from the smaller galaxy, and a wave of gas and dust on a different orbit could have long term effects.

In case you think the stars in a galaxy are on well-behaved orbits around the centre, that is wrong. Because the galaxy formed from the collision and absorption of smaller galaxies the motion is actually quite chaotic, but because stars are so far apart by and large they ignore each other. Thus Kapteyn’s Star orbits the galactic centre and is quite close to our Sun, except it is going in the opposite direction. We “meet again” on the other side of the galaxy in about 120 million years. So to summarize, we still don’t know what caused this solar system to form but we should be thankful that we got what we did. Our system happens to be just about right for our life to form, but as you will see, when it comes out, from the second edition of my ebook “Planetary Formation and Biogenesis” there are a lot of things that could have gone wrong. Let’s not help more things to go wrong.