Burying Carbon Dioxide, or Burying Cash?

In the last post, I expressed my doubt about the supply of metals for electric batteries. There is an alternative to giving up things that produce CO2 and that is to trap and sequester CO2. The idea is that for power stations the flu gases have the CO2 removed and pumped underground. That raises the question, how realistic is this? Chemistry World has an article that casts doubt, in my mind, that this can work. First, the size of the problem. One company aims to install 70 such plants, each capable of sequestering 1 million t of CO2. If these are actually realized, we almost reach 0.2% of what is required. Oops. Basically, we need to remove at least 1 billion t/a to stand still. This problem is large. There is also the problem of how we do it.

The simplest way is to pass the flu gases through amine solvents, with monoethanolamine the most common absorbent used. Leaving aside the problem of getting enough amine, which requires a major expansion of the chemical manufacturing industry, what happens is the amine absorbs CO2 and makes the amine carbonate, and the CO2 is recovered by heating the carbonate and regenerating the amine. However, the regeneration will never be perfect and there are losses. Leaving aside finding the raw materials actually synthesizing the amine takes about 0.8 MWh of energy, the inevitable losses mean we need up to 240 MWh every year to run a million tonne plant. We then need heat to decompose the amine carbonate, and that requires about 1 MWh per tonne of CO2 absorbed. Finally, we need a little less than 0.12 MWh per tonne of CO2 to compress it, transport it and inject it into the ground. If we wanted to inject 1 billion t of CO2, we need to generate something like 840 TWh of electricity. That is a lot of electricity.

We can do a little better with things called metal organic frameworks (MOFs).These can be made with a high surface energy to absorb CO2 and since they do not form strong chemical bonds the CO2 can be recovered at temperatures in the vicinity of  80 – 100 degrees C, which opens the possibility of using waste heat from power stations. That lowers the energy cost quite a bit. Without the waste heat the energy requirement is still significant, about half that of the amines. The comes the sting – the waste heat approach still leaves about 60% of what was absorbed, so it is not clear the waste heat has saved much. The addition of an extra step is also very expensive.

The CO2 content of effluent gases is between 4 – 15%; for ordinary air it is 0.04%, which makes it very much more difficult to capture. One proposal is to capture CO2 by bubbling air through a solution of potassium hydroxide, and then evaporating off the water and heating the potassium carbonate to decomposition temperature, which happens to be about 1200 degrees C. One might have thought that calcium oxide might be easier, which pyrolyses about 600 degrees C, but what do I know? This pyrolysis takes about 2.4 MWh per tonne of CO2, and if implemented, this pyrolysis route that absorbs CO2 from the air would require about 1.53 TWh of electricity per year for sequestering 1 million t of CO2.

When you need terawatt hours of electricity to run a plant capable of sequestering one million tonne of CO2, and you need to sequester a billion t, it becomes clear that this is going to take an awful lot of energy. That costs a lot money. In the UK, electricity costs between £35 – 65 per MWh, and we have been talking in terms of a million times that per plant. Who pays? Note this scheme has NO income stream; it sells nothing, so we have to assume it will be charged to the taxpayer. Lucky taxpayer!

One small-scale effort in Iceland offers a suggested route. It is not clear how they capture the CO2, but then they dissolve it in water and inject that into basalt, where the carbonic acid reacts with the olivine-type structures to make carbonates, where it is fixed indefinitely. That suggests that provided the concentration of CO2 is high enough, using pressure to dissolve it in water might be sufficient. That would dramatically lower the costs. Of course, the alternative is to crush the basalt and spread it in farmland, instead of lime. My preferred option to remove CO2 from the air is to grow plants. They work for free at the low concentrations. Further, if we select seaweed, we get the added benefit of improving the ecology for marine life. But that requires us to do something with the plants, or the seaweed. Which means more thinking and research. The benefit, though, is the scheme could at least earn revenue. The alternatives are to bankrupt the world or find some other way of solving this problem.

Will We Do Anything To Stop Global Warming?

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

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

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

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

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

Banana-skin Science

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

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

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

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

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

The Case for Hydrogen in Transport

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

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

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

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

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

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

“Green” Electricity

Before thinking about how to replace fossil fuels for electricity, we need to look at how the power demand varies through the day. Not unexpectedly, this varies depending on where you live, but if you take various parts of the US as an example of industrialized usage, there is a baseline that involves minimal usage at about 0500 hrs, and that baseline varies by up to 30% seasonally. The difference between day and night can vary by up to 60%, the biggest variation is in hot summer and is due to the use of air conditioning. This means there is a huge difference between peak demand and minimum demand, which in turn means that difference has to be supplied by generation that can be turned on and off. The big thermal plants do not turn on and off easily. You can run the plant without producing electricity, but now you are simply burning fuel for no purpose.

The most responsive generators are the gas turbine and hydroelectricity. Hydro is an obvious “green” source for load smoothing; you simply shut the gate, save water, and stop generating, but most suitable hydro sites are already used. Wind power is also useful; you simply let wind pass if you do not want power, but it runs into trouble when you need power and there is no wind. Solar means you charge batteries during the day and used the power later, but in a previous post I showed it is impossible to make enough batteries to power our vehicle fleet, so how do we make an even greater supply of batteries? A further alternative is to run your base load near maximum usage, and use the surplus to make something like hydrogen when it is not needed. More on hydrogen in a later post.

The “inconvenient truth” for some is the only general major base load provider to replace coal and gas for electricity generation is nuclear. Unfortunately, nuclear has a bad press. Other downsides include, currently, it is too expensive. Most people think it is too dangerous and it is too likely to leak radiation. Actually, the smoke from coal combustion also is cancer inducing to lungs, while in the US there are around 13,000 premature deaths per year due to coal, and 23,000 annually in Europe. Coal is nowhere nearly as safe as people think. So far, nuclear power has a death rate of 0.07 deaths per terawatt-hour of electricity, or about 1 death per 14 years. That figure is enhanced substantially due to stupidity at Chernobyl. Fukushima has 1 death attributed to it, although there are claims that the stresses of it on those who had to move caused a further 2,200. Up to 2004 (18 years later) 78 died from Chernobyl. This is not good, but it is avoidable.

Current reserves of uranium total 5.3 million tonne, about a third of which are in Australia. However, only about 36,000 t of that is U235, which is what is fissile, and has to be enriched. The depleted uranium waste from the enrichment process goes into armour-piercing military rounds. What happens in most nuclear power stations is the enriched uranium rods generate heat, then have to be taken away to be reprocessed, which involves removing the plutonium for weapons. A long time ago, when I was at school, we had a visiting energy expert who told us that in the future the world would develop breeder reactors, and the enriched uranium would produce more fuel in the form of plutonium than it consumed in making electricity, The need to feed the military complex means that did not happen.

What is possible is a new generation of reactor, based on the fuel being dissolved in molten salt. The reactor is now at thermal equilibrium so it is impossible to have a melt-down – there is nothing to melt. The one catch is the issue of corrosion. That can undoubtedly be dealt with, but we have yet to learn the real long-term issues. China is currently testing one demonstration plant, and it is designed to simply provide the boiling pressurized water to run an existing power plant. The idea is simply the coal-firing is removed, this heat source is plugged in and everything else continues working. As the U238 gets converted to plutonium, it also fissions and generates heat to make electricity. What the surplus neutrons in the reactor do is also to burn “hot” isotopes, so the waste disposal problems are far less. Finally, once going, it can also take thorium as a fuel, and there is far more thorium in the world. Simple fission could keep us going for centuries.

Arguably, nuclear is not “green”. My argument is we either use it or not, but it alone has any chance of providing the levels of electricity we need and replace fossil fuel burning.

Ultimately, fusion power would solve all our energy problems. There is only one problem with it: we do not know how to make it work. There is also one general problem. To change our ways, we shall have to spend a very large amount of money, and basically replace about two thirds of our existing electricity generating infrastructure. The alternative is to do nothing and then rebuild all our major coastal cities when the ice sheets collapse. That is also expensive. We have a choice, but unfortunately our politicians seem to want to do nothing and leave the problem for our grandchildren.

The IPCC Orders Action

The Intergovernmental Panel on Climate Change has produced Part 3 of a report, and with only about 2900 pages, that has one stark message: we need aggressive action to curb greenhouse gas emission AND we need aggressive action to absorb CO2 from the atmosphere, and the action must start now, not some indefinite time in the future. As I recall, this problem was highlighted thirty years ago, and in that thirty years, emissions have increased. There was not even a hint of a reduction. To give some idea of how seriously some take this matter, Germany closed down its nuclear power plants, and now it threatens not to use Russian gas, but instead burn lignite. We cannot do much worse than that can we?

Maybe we can, and maybe we are. According to an article by Lawrence et al. (Front. For. Glob. Change https://doi.org/10.3389/ffgc.2022.756115 (2022) tropical rain forests not only secrete carbon and take it out of circulation, saving around 0.5 of a degree C, but they also physically cool the planet by a further 0.5 degrees C. What the trees do is to emit much humidity from their leaves, with the result that they cool themselves (similar to sweating) and this humidity creates clouds, which reflect sunlight back to space. This is the sort of a geo-engineering proposal often made, but the trees do it for free. So, what are we doing? Why, cutting down the rain forests. Apparently a third has been removed, and another third has been heavily logged so it is not as functional as it should be. We are supposed to be trying to hold the temperatures to an increase of no more than 1.5 degrees C, we are nearly there already, so do we really need another degree of heating added in for no good reason?

According to the IPCC, carbon emissions will have to decline rapidly after 2025, halve by 2030, and hit “net zero” by the early 2050s. Given current efforts, a warming of 3 degrees is forecast. Emissions from existing and planned projects already exceed the allowable carbon budget. But even going to zero emissions will not suffice in the short term. Nations also need to extract carbon dioxide from the atmosphere.

So, what can we do? First, consider the problem. For our electricity, which has a little under 750 GW global capacity, wind power provides a little over 6%; solar provides a little over 2%, hydropower about 16%, nuclear about 10%. For fuels, earth consumes about 3.8 trillion cubic meters of natural gas, 35.4 billion barrels of oil, and 8.5 billion t of coal a year. Why we have a problem should be clear. Currently, about 2/3 of our electricity comes from burning fossil fuel. Worse, you don’t build a coal-fired power station today and turn it off tomorrow. Wind turbines need solid support. Making a tonne of cement produces roughly 800 kg of CO2, making a tonne of steel releases 1.85 t of CO2; combined they sum to about 16% of the world’s CO2 production. Wind power might be “green” but look at the CO2 emitted making and installing the equipment. Solar is free, but the demand for electricity is when solar is weak or non-existent, so massive storage is required, and that gets expensive, both in terms of money and in CO2 emissions for making the batteries. The point is, all new infrastructure is going to involve a lot of CO2 emissions before any energy is generated.

Transport is a particularly difficult problem. I think it is a common problem, but where I live the cities expanded significantly after WW 2, and they expanded with the automobile in mind. The net result is it is most people get around by car. Most people have access to a car, and that is petrol driven. The electric vehicle that might replace the petrol-driven car costs (here, at least) over twice that of the petrol driven car and you cannot really convert them. The reason is the electric vehicle needs a huge mass of batteries to have a useful driving range. Further, as I pointed out in a previous post, we cannot have everyone driving electric cars because we do not have the cobalt to make the batteries, and we still need ships and aircraft, which use a rather small fraction of the oil cut. We have to do something with the rest of the fuel cut. You may have noticed that large electricity production above and how so much comes from fossil fuels. Transport uses about 25% of the total energy production. That means to convert transport to electricity, we need to expand electricity generation by about another 250 GW. That is easy to write down, but just think of all the CO2 emitted by making the concrete and steel to build the power stations. Our current wind power would have to expand by a factor of 5.5 and we have to hope there are no still days. Of course, you may legitimately argue that if we charged batteries at night that would even the base load and you do not need all the additional installation. That is true, except green electricity generation  usually is not optimal for base loads.

My view is it cannot be done the way the enthusiasts want it done. We shall never get everybody to cooperate sufficiently to achieve the necessary reductions because society simply cannot afford it. We need a different approach, and in some  later posts, I shall try to offer some suggestions.

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.

Seaweed and Climate Change

A happy and prosperous New Year to you all. The Great New Zealand Summer Vacation is coming to an end, so I have made an attempt at returning to normality. I hope all is well with you all.

Last year a paper in Nature Communications (https://doi.org/10.1038/s41467-021-22837-2) caught my eye for two reasons. First, it was so littered with similar abbreviations I found it difficult to follow. The second was that they seemed to conclude the idea of growing seaweed to absorb carbon dioxide would not work, but  they seemed to refuse to consider any option by which it might work. We know that much of seaweed biomass arises from photo-fixing CO2, as does biomass from all other plants. So there are problems. There were also problems ten thousand years ago for our ancestors in Anatolia or in the so-called fertile crescent wanting to grow some of those slightly bulky grass seeds for food. They addressed those problems and got to work. It might have been slow, but soon they had the start of a wheat industry.

So, what was the problem? The paper considered the Sargasso Sea as an example of massive seaweed growth. One of the first objections the paper presented was that the old seaweed fronds get coated with life forms such as bryozoans that have calcium carbonate coatings. They then state that by making this solid lime (Ca++ + CO3 -> CaCO3, a solid) it releases CO2 by reducing seawater alkalinity. The assertion was from a reference, and no evidence was supplied that it is true in the Sargasso. What this does is to deflect the obvious: for each molecule of lime formed, a molecule of CO2 was removed from the environment, not added to it as seemingly claimed. Associated with this is the statement that the lime shields the fronds from sunlight and hence reduces photosynthesis. Can we do anything about this? We could try harvesting the old fronds and keep growing new ones. Further, just as our ancestors found that by careful management they could improve the grain size (wild wheat is not very impressive) we could “weed” to improve the quality of the stock.

I don’t get the next criticism. While calcification on seaweed was bad because it liberated CO2 (so they say) they then go on to say that growing seaweed reduces the phytoplankton, and then the calcification of that gets reduced, which liberates more CO2. Here we have increased calcification and decreased calcification both increase CO2. Really?

Another criticism is that the seaweeds let out other dissolved carbon, which is not particulate carbon. That is true, but so what? The dissolved sugars are not acidic. Microalgae will gobble them up, but again, so what?

The next criticism is if we manage to reduce the CO2 levels in the ocean, we cannot calculate what is going on, and the atmosphere may not be able to replenish the levels for a up to a hundred years. Given the turbulence during storms I find this hard to believe, but if it is true, again, so what? We are busy saving the ocean food chains. Ocean acidification is on the verge of wiping out all shellfish that rely on forming aragonite for their shells. Reducing that acidity should be a good thing.

They then criticise the proposal because growing forests on land reduces the albedo, and by making the land darker, makes the locality warmer. They then say the Sargasso floating seaweed increases the albedo of that part of the ocean, and hence reflects more light back to space, which reduces heat generation. Surely this is good? But wait. They then point out that other proposals have seaweed growing in deep water and this won’t happen. In other words, some aspect of some completely different proposal is a reason not to proceed with this one. Then they conclude by saying they need more money to get more detailed information. I agree more detailed information would be helpful, but they should acknowledge possible solutions to their problems. Thus ocean fertilization and harvesting mature seaweed could change their conclusions completely. I suspect the problem is they want to measure things, possibly remotely, but they do not want to actually do things, which involves a lot more effort, specifically on location. But for me, the real annoyance is that everyone by now knows that global warming is a problem. Growing seaweed might help solve that problem. We need to know whether it will contribute to a solution or merely transfer the problem. They may not have the answers, but they at least should identify the questions that need answers.

Climate Change and Political inertness

Since the season of goodwill and general cheerfulness is approaching, it seems wrong to present even more bad news for this rather dismal year, yet we cannot hide from it, The problem was presented in Nature ( https://doi.org/10.1038/d41586-021-03758-y  and relates to the Thwaites glacier. This glacier flows off the Antarctic continent into the Southern ocean. The glacier is 120 kilometers wide and about two thirds of this flows into the Southern Ocean, but one third runs into its eastern ice shelf. Here, the flow grinds to a halt because the ice out at sea hits an underwater mountain that is about 40 kilometres offshore. The Mountain is stopping the ice from flowing.

Unfortunately, thanks to the warmer water flowing underneath, that part of the glacier is becoming unstuck from the mountain, and this is causing cracking and fracturing across parts of the ice shelf. The fractures are propagating through the ice at several kilometres per year, and are heading towards thinner ice, which may lead to the whole lot shattering. To add to the problem there is tidal flexing as the glacier starts to separate from the rock and the “up and down” movement with the tides causes the glacier to flex further upstream, including where it is over land. Because of this flexing, warm water from the Southern Ocean could make its way beneath the glacier more easily.

Current estimates are that this mass of ice over the water could shatter within five years, which would release an huge mass of icebergs into the Southern Ocean, and the whole glacier could start flowing much faster into the sea. That means sea level rise. Currently the Thwaites already loses around fifty billion tonnes of ice each year and causes 4% of global sea level rise. If this eastern ice shelf collapses, ice would flow three times faster into the sea. If the glacier were to collapse completely sea levels would rise 65 centimetres. The glacier itself is moving towards the sea at about a mile each year. This is a fairly fast moving glacier.

So, what do we do about it. In this case it is probably impossible to do much. There is no way to stop a glacier moving. The only possible thing to do to stop the sea level rise would be to somehow engineer more snow to fall further inland to Antarctica. Fifty billion tonnes of snow each year would cancel out the sea level rise, but we all know that is not about to happen any time soon. But not to worry. Senator Manchin does not believe in climate change as a hazard, and he will torpedo President Biden’s efforts to get the US to do something. This Senator wants to burn more coal, and this one man will torpedo everyone else’s limited efforts. So is the Senator right? No. We might not be able to stop the Thwaites, but there are worse problems downstream we can still stop if we act before they become activated. Of course, he is not alone. Australia is selling more coal, China is building more coal-foired power stations, Germany has turned of nuclear to burn lignite. A cartoon in our paper had it: the Devil was reading about our activities and he said, “Aw, no fun. They’re not even pretending to try now.”

The nature of the problem is what we call hysteresis. If you have an equilibrium, such as when there is no change of temperature in an object over time, this arises because the heat loss equals the heat input. Now, suppose you increase the heat input a little. Now we are out of equilibrium, but since the heat loss depends on the temperature what you expect is the temperature will rise to reach the equilibrium position corresponding to where the heat loss now equals the heat input. Unfortunately, it doesn’t quite work like that. Suppose I have a lump of iron, and I increase the amount of heat going into it. The surface may well get warmer, but heat then starts flowing into the inside of the object. It takes time before the object reaches the new temperature. With something like ice, it is worse. The ice will warm, but once it gets to its melting point the increased heat flowing in starts to melt the ice. The ice stays at the same temperature. If we increase the heat flow inwards there is no change, other than the ice melts faster. Then, when it has all melted, suddenly the temperature starts to increase quickly.

To some extent, that is what has happened on our planet. Our greenhouse effect has been slowing the heat loss to space, and since the heat input remains the same, effectively the system is absorbing more heat. However, to start with all that happened was the surface of the oceans warmed up and some ice melted. So we ignored the problem because we observed no change in temperature, and poured more heat in. All that did was warm more water and melt more ice. The problem then is that we have now reached the point where the increase in heat that we are pouring into the Earth is starting to reach the point where the effects that absorbed heat without altering our temperature too much have now reached the end of their capacity. We are now going to make major changes to the planet, and we cannot stop them because the forces are already in place to generate far more heat.

Another characteristic of hysteresis is you cannot reverse what you have done simply by stopping increasing the heat input. Because the ice is melting because the water is above its freezing point, if we stopped adding heat now and stopped all greenhouse emissions, the oceans are still warm and the melting continues. However, there are thresholds. One calculation (Nature 585 (2020) p 538) indicated that for every degree of global temperature rise up to 2 degrees above pre-industrial levels will lead to 1.3 metres of sea-level rise. Between 2 – 6 degrees of warming it doubles to 2.4 metres per degree, and between 6 – 9 degrees, we get an extra 10 meters per degree. Further, the nature of hysteresis is that this is irreversible. If we want to turn it around we have to reduce global temperatures to one degree below what they were in 1850.

With that dismal thought, I wish you all a very Merry Christmas and all the best for 2022. This will be my last post for the year, and as usual I shall resume in mid-January. Finally, there are still my ebooks on the Smashwords sale.