Biofuels from Algae

In the previous post, I described work that I had done on making biofuels from lignin related materials, but I have also looked at algae, and here hydrothermal processing makes a lot of sense, if for no other reason than algae is always gathered wet. There are two distinct classes: microalgae and macroalga. The reason for distinguishing these has nothing to do with size, but rather with composition. Microalgae have the rather unusual property of being comprised of up to 25% nucleic acid, and the bulk of the rest is lipid or protein, and the mix is adjustable. The reason is microalgae are primarily devoted to reproduction, and if the supply of nitrogen and phosphate is surplus to requirements, they absorb what they can and reproduce, mainly making more nucleic acid and protein. Their energy storage medium is the lipid fraction, so given nutrient-rich conditions, they contain very little free lipids. Lipids are glycerol that is esterified by three fatty acids, in microalgae primarily palmitic (C16) and stearic (C18), with some other interesting acids like the omega-three acids. In principle, microalga would be very nutritious, but the high levels of nucleic acid give them some unfortunate side effects. Maybe genetic engineering could reduce this amount. Macroalgae, on the other hand, are largely carbohydrate in composition. Their structural polysaccharides are of industrial interest, although they also contain a lot of cellulose. The lipid nature of microalgae makes them very interesting when thinking of diesel fuel, where straight-chain hydrocarbons are optimal.

Microalgae have been heavily researched, and are usually grown in various tubes by those carrying out research on making biofuels. Occasionally they have been grown in ponds, which in my opinion is much more preferable, if for no other reason than it is cheaper. The ideal way to grow them seems to be to feed them plenty of nutrients, which leads them to reproduce but produce little in the way of hydrocarbons (but see below) then starve them. They cannot shut down their photosystems, so they continue to take on carbon dioxide and reduce the carbon all the way to lipids. The unimaginative thing to do then is to extract the microalgae and make “biodiesel”, a process that involves extracting the lipids, usually with a solvent such as a volatile hydrocarbon, distilling off the solvent, then reacting that with methanolic potassium hydroxide to make the methyl esters plus glycerol, and if you do this right, an aqueous phase separates out and you can recover your esters and blend them with diesel. The reason I say “unimaginative” is that when you get around to doing this, you find there are problems, and you get ferocious emulsions. These can be avoided by drying the algae, but now the eventual fuel is starting to get expensive, especially since the microalgae are very difficult to harvest in the first place. To move around in the water, they have to have a density that is essentially the same as water, so centrifuging is difficult, and since they are by nature somewhat slimy, they clog filters. There are ways of harvesting them, but that starts to get more expensive. The reason why hydrothermal processing makes so much sense is it is not necessary to dry them; the process works well if they are merely concentrated.

The venture I was involved in helping had the excellent idea of using microalgae that grow in sewage treatment plants, where besides producing the products from the algae, the pollution was also cleaned up, at least it is if the microalgae are not simply sent out into the environment. (We also can recover phosphate, which may be important in the future.). There are problems here, in that because it is so nutrient-rich the fraction of extractable lipids is close to zero. However, if hydrothermal liquefaction is used, the yield of hydrocarbons goes up to the vicinity of over 20%, of which about half are aromatic, and thus suitable for high-octane petrol. Presumably, the lipids were in the form of lipoprotein, or maybe only partially substituted glycerol, which would produce emulsifying agents. Also made are some nitrogen-rich chemicals that are about an order of magnitude more valuable than diesel. The hydrocarbons are C15 and C17 alpha unsaturated hydrocarbons, which could be used directly as a high-cetane diesel (if one hydrogenated the one double bond, you would have a linear saturated hydrocarbon with presumably a cetane rating of 100), and some aromatic hydrocarbons that would give an octane rating well over a hundred. The lipid fraction can be increased by growing them under nutrient-deprived conditions. They cannot reproduce, so they make lipids, and swell, until eventually they die. Once swollen, they are easier to handle as well. And if nothing else, there will be no shortage of sewage in the future.

Macroalgae will process a little like land plants. They are a lot easier to handle and harvest, but there is a problem in obtaining them in bulk: by and large, they only grow in a narrow band around the coast, and only on some rocks, and then only under good marine conditions. If the wave action is too strong, often there are few present. However, they can live in the open ocean. An example is the Sargasso Sea, and it appears that there are about twenty million tonne of them in the Atlantic where the Amazonian nutrients get out to sea. However, in the 1970s the US navy showed they could be grown on rafts in the open ocean with a little nutrient support. It may well also be that free-floating macroalgae can be grown, although of course the algae will move with the currents.

The reason for picking on algae is partly that some are the fastest-growing plants on the planet. They will take more carbon dioxide from the atmosphere more quickly than any other plant, the sunlight absorbed by the plant is converted to chemical energy, not heat, and finally, the use of the oceans is not competing with any other use, and in fact may assist fish growth.

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Alternative​ Sources for Fuel: Rubbish

As most people have noticed, there is finally some awakening relating to climate change and the need to switch from fossil fuels, not that politicians are exactly accepting such trends, and indeed they seem to have heads firmly buried in the sand. The difficulty is there are no easy solutions, and as I remarked in a previous post, we need multiple solutions.

So what to do? I got into the matter after the first “energy crisis” in the 1970s. I worked for the New Zealand national chemistry laboratory, and I was given the task of looking at biofuels. My first consideration was that because biomass varies so much, oil would always be cheaper than anything else, and the problem was ultimately so big, one needed to start by solving two problems. My concept was that a good place to start was with municipal rubbish: they pay you to take it away, and they pay a lot. Which leads to the question, how can you handle rubbish and get something back from it? The following is restricted to municipal rubbish. Commercial waste is different because it is usually one rather awkward thing that has specific disposal issues. For example, demolition waste that is basically concrete rubble is useless for recovering energy.

The simplest way is to burn it. You can take it as is, burn it, use the heat in part to recover electricity, and dump the resultant ash, which will include metal oxides, and maybe even metals. The drawback is you should take the glass out first because it can make a slag that blocks air inlets and messes with the combustion. If you are going to do that, you might as well take out the cans as well because they can be recycled. The other drawback is the problem of noxious fumes, etc. These can be caught, or the generators can be separated out first. There are a number of such plants operating throughout the world so they work, and could be considered a base case. There have also been quite satisfactory means of separating the components of municipal refuse, and there is plenty of operational experience, so having to separate is not a big issue. Citizens can also separate, although their accuracy and cooperativeness is an issue.

There are three other technologies that have similarities, in that they basically involve pyrolysis. Simple pyrolysis of waste gives an awful mix, although pyrolysis of waste plastics is a potential source of fuel. Polystyrene gives styrene, which if hydrogenated gives ethylbenzene, a very high-octane petrol. Pyrolysis of polyethylene gives a very good diesel, but pvc and polyurethanes give noxious fumes. Pyrolysis always leaves carbon, which can either be burned or buried to fix carbon. (The charcoal generator is a sort of wood pyrolysis system.)

The next step up is the gasifier. In this, the pyrolysis is carried out by extreme heat, usually generated by burning some of it in air, or oxygen. The most spectacular option I ever saw was the “Purox” system that used oxygen to maintain the heat by burning the char that got to the bottom. It took everything and ended up with a slag that could be used as road fill. I went to see the plant, but it was down for maintenance. I was a little suspicious at the time because nobody was working on it, which is not what you expect for maintenance. Its product was supposed to be synthesis gas. Other plants tended to use air to burn waste to provide the heat, but the problem with this is that the produced gas is full of nitrogen, which means it is a low-quality gas.

The route that took my interest was high-pressure liquefaction, using hydrogen to upgrade the product. I saw a small bench-top unit working, and the product looked impressive. It was supposed to be upgraded to a 35 t/d pilot plant, to take up all of a small city’s rubbish, but the company decided not to proceed, largely because suddenly OPEC lost its cohesion and the price of oil dropped like a stone. Which is why biofuels will never stand up in their own right: it is always cheaper to pump oil from the ground than make it, and it is always cheaper to refine it in a large refinery than in a small-scale plant. This may seem to have engineering difficulties, but this process is essentially the same as the Bergius process that helped keep the German synthetic fuels going in WW II. The process works.

So where does that leave us? I still think municipal waste is a good way to start an attack on climate change, except what some places seem to be doing is shipping their wastes to dump somewhere else, like Africa. The point is, it is possible to make hydrocarbon fuels, and the vehicles that are being sold now will need to be fuelled for a number of years. The current feedstock prices for a Municipal Waste processing plant is about MINUS $100/t. Coupled with a tax on oil, that could lead to money being made. The technologies are there on the bench scale, we need more non-fossil fuel, and we badly need to get rid of rubbish. So why don’t we do something? Because our neo-liberal economics says, let the market decide. But the market cannot recognise long-term options. That is our problem with climate change. The market sets prices, but that is ALL it does, and it does not care if civilization eradicates itself in five years time. The market is an economic form of evolution, and evolution leads to massive extinction events, when life forms are unsuitable for changing situations. The dinosaurs were just too big to support themselves when food supplies became too difficult to obtain by a rather abrupt climate change. Our coming climate change won’t be as abrupt nor as devastating, but it will not be pleasant either. And it won’t be avoided by the market because the market, through the fact that fossil fuels are the cheapest, is the CAUSE of what is coming. But that needs its own post.

Some Unanswered Questions from the Lunar Rocks

In the previous post I hinted that some of what we found from our study of moon rocks raises issues of self-consistency when viewed in terms of the standard paradigm. To summarize the relevant points of that paradigm, the argument goes that the dust in the accretion disk that was left behind after the star formed accreted into Mars-sized bodies that we shall call embryos, and these moved around in highly elliptical orbits and eventually collided to form planets. While these were all mixed up – simulations suggest what made Earth included bodies from outside Mars’ current orbit, and closer to the star than Mercury’s current orbit. These collisions were extraordinarily violent, and the Earth formed from a cloud of silicate vapours that condensed to a ball of boiling silicates at a little under 3000 degrees C. Metallic iron boils at 2862 degrees C, so it was effectively refluxing, and under these conditions it would extract elements such as tungsten and gold that dissolve in iron and take them with it to the core. About sixty million years after Earth formed, one remaining embryo struck Earth, a huge amount of silicates were sent into space, and the Moon condensed from this. The core of this embryo was supposedly iron, and it migrated into the Earth to join our core, leaving the Moon a ball of silicate vapour that had originated from Earth and condensed from something like 10,000 degrees C. You may now see a minor problem for Earth: if this iron took out all the gold, tungsten, etc, how come we can find it? One possibility is the metals formed chemical compounds. That is unlikely because at those temperatures elements that form only moderate-strength chemical bonds would not survive, and since gold is remarkably unreactive, that explanation won’t work. Another problem is that the Moon has very little water and no nitrogen. This easily explained through their being lost to space from the silicate vapours, but where did the Earth get its volatiles? And if the Moon did condense from such high temperatures, the last silicate to condense would be fayalite, but that was not included in the Apollo rocks, or if it were, nothing was made of that. This alone is not necessarily indicative, though, because fayalite is denser than the other olivines, and if there were liquid silicates for long enough it would presumably sink.

The standard paradigm invokes what is called “the late veneer”; after everything was over, Earth got bombarded with carbonaceous asteroids, which contain water, nitrogen, and some of these otherwise awkward metals. It is now that we enter one of the less endearing aspects of modern science: everything tends to be compartmentalised, and the little sub-disciplines all adhere to the paradigm and add small findings that support their view, even if they do not do so particularly well, and there is a reluctance to look at the overall picture. The net result is that while many of the findings can be made to seemingly provide answers to their isolated problems, there is an overall problem with self-consistency. Further, clues that the fundamental proposition might be wrong are carefully shelved.

The first problem was noted at the beginning of the century: the isotope ratios of metals like osmium from such chondrites are different from our osmium. There are various hand-waving argument to the extent that it could just manage if it were mixed with enough of our mantle, but leaving whether the maths are right aside, nobody seems to have noticed the only reason we are postulating this late veneer is that originally the iron stripped all the osmium from the mantle. You cannot dilute A with B if B is not there. There are a number of other reasons, one of which is the nitrogen of such chondrites has more 15N than our nitrogen. Another is to get the amounts of material here we need a huge amount of carbonaceous asteroids, but they have to come through the ordinary asteroids without perturbing them. That takes some believing.

But there is worse. All the rocks found by the Apollo program have none of the required materials and none of the asteroidal isotope signatures. The argument seems to be, they “bounced off” the Moon. But the Moon also has some fairly ferocious craters, so why did the impactors that caused them not bounce off? Let’s suppose they did bounce off, but they did not bounce off the Earth (because the only reason we argue for this is that we need them, so it is said, to account for our supply of certain metals). Now the isotope ratios of the oxygen atoms on the Moon have a value, and that value is constant over rocks that come from deep within the Moon, thanks to volcanism, and for the rocks from the highlands, so that is a lunar value. How can that be the same as Earth’s if Earth subsequently got heavily bombarded with asteroids that we know have different values? My answer, in my ebook “Planetary Formation and Biogenesis” is simple: there were no embryo impacts in forming Earth therefore the iron vapours did not extract out the heavy elements, and there were no significant number asteroid impacts. Almost everything came here when Earth accreted, and while there have been impacts, they made a trivial contribution to Earth’s supply of matter.

The Electric Vehicle as a Solution to the Greenhouse Problem

Further to the discussion on climate change, in New Zealand now the argument is that we must reduce our greenhouse emissions by converting our vehicle fleet to electric vehicles. So, what about the world? Let us look at the details. Currently, there are estimated to be 1.2 billion vehicles on the roads, and by 2035 there will be two billion, assuming current trends continue. However, let us forget about such trends, and look at what it would take to switch 1.2 billion electric vehicles to electric. Obviously, at the price of them, that is not going to happen overnight, but how feasible is this in the long run?

For a scoping analysis, we need numbers, and the following is a “back of the envelope” type analysis. This is designed not to give answers, but at least to visualise the size of the problem. To start, we have to assume a battery size per vehicle, so I am going to assume each vehicle will have an 85 kWh battery assembly. A number of vehicles now have more than this, but equally many have less. However, for initial “back of the envelope” scoping, details are ignored. For the current purposes I shall assume an 85 kWh battery assembly and focus n the batteries.

First, we need a graphite anode, which, from web-provided data will require approximately 40 million t of graphite. Since Turkey alone has reserves of about 90 million t, strictly speaking, graphite is not a problem, although from a chemical point of view, what might be called graphite is not necessarily suitable. However, if there are impurities, they can be cleaned up. So far, not a limiting factor.

Next, each battery assembly will use about 6 kg of lithium, and using the best figures from Tesla, at least 17 kg of cobalt. This does not look too serious until we get to multiplying by 1.2 billion, which gets us to 7.2 million tonne of lithium, and 20.4 million t of cobalt. World production of lithium is 43,000 t/a, while that of cobalt is 110,000 t/a, and most of the cobalt goes to other uses already known. So overnight conversion is not possible. The world reserves of lithium are about 16 million t, so there is enough lithium, although since most of the reserves are not actually in production, presumably due to the difficulty in purifying the materials, we can assume a significant price increase would be required. Worse, the known reserves for cobalt are 7,100,000 so it is not possible to power these vehicles with our current “best battery technology”. There are alternatives, such as manganese based cathode additives, but with current technology they only have about 2/3 the power density and they can only last for about half the number of power cycles, so maybe this is not an answer.

Then comes the problem of how to power these vehicles. Let us suppose they use about ¼ of their energy on high-use days and they recharge for the next day. That requires about 24 billion kWhr of electricity generated that day for this purpose. World electricity production is currently a little over 21,000 TWh, Up to a point, that indicates “no problem”, except that over 1/3 of that came from coal, while gas and oil burning added to coal brought the fossil fuels contribution up to 2/3 of world energy production, and coal burning was the fastest growing contribution to energy demand. Also, of course, this is additional electricity we need. Global energy demand rose by 900 TWh in 2018. (Electricity statistics from the International Energy Agency.) So switching to electric vehicles will increase coal burning, which increases the emission of greenhouse gases, counter to the very problem you are trying to solve. Obviously, electricity supply is not a problem for transport, but it clearly overwhelms transport in contributing to the greenhouse gas problem. Germany closing its nuclear power stations is not a useful contribution to the problem.

It is frequently argued that solar power is the way to collect the necessary transport electricity. According to Wikipedia, the most productive solar power plant is in China’s Tengger desert, which produces 1.547 GW from 43 square kilometers. If we assume that it can operate like this for 6 hrs per day, we have 9.3 Gwh/day. The Earth has plenty of area, however, the 110,000 square km required is a significant fraction. Further, most places do not have such a friendly desert close by. Many have proposed that solar panels of the roof of houses could store power through the day and charge the vehicle at night, but to do that we have just doubled the battery requirements, and these are strained already. The solar panels could feed the grid through the day and charge the vehicles through the night when peak power demand has fallen away, so that would solve part of the problem, but now the solar panels have to make sense in terms of generating electricity for general purposes. Note that if we develop fusion power, which would solve a lot of energy requirements, it is most unlikely a fusion power plant could have its energy output varied too much, which would mean they would have run continuously through the night. At this point, charging electric cars would greatly assist the use of fusion power.

To summarise the use of electricity to power road transport using independent vehicles, there would need to be a significant increase in electricity production, but it is still a modest fraction of what we already generate. The reason it is so significant to New Zealand is that much of New Zealand electricity is renewable anyway, thanks to the heavy investment in hydropower. Unfortunately, that does not count because it was all installed prior to 1990. Those who turned off coal plants to switch to gas that had suddenly became available around 1990 did well out of these protocols, while those who had to resort to thermal because the hydro was fully utilised did not. However, in general the real greenhouse problem lies with the much bigger thermal power station emissions, especially the coal-fired stations. The limits to growth of electric vehicles currently lie with battery technology, and for electric vehicles to make more than a modest contribution to the transport problems, we need a fundamentally different form of battery or fuel cell. However, to power them, we need to develop far more productive electricity generation that does emit greenhouse gases.

Finally, I have yet to mention the contribution of biofuels. I shall do that later, but if you want a deeper perspective than in my blogs, my ebook “Biofuels” is 99c this week at Smashwords, in all formats. (https://www.smashwords.com/books/view/454344.)  Three other fictional ebooks are also on discount. (Go to https://www.smashwords.com/profile/view/IanMiller)

Cold Fusion

My second post-doc. was at Southampton University, and one of the leading physical chemists there was Martin Fleischmann, who had an excellent record for clever and careful work. There would be no doubt that if he measured something, it would be accurate and very well done. In the academic world he was a rising star until he scored a career “own goal”. In 1989, he and Stanley Pons claimed to have observed nuclear fusion through a remarkably simple experiment: they passed electricity through samples of deuterium oxide (heavy water) using palladium electrodes. They reported the generation of net heat in significant excess of what would be expected from the power loss due to the resistance of the solution. Whatever else happened, I have no doubt that Fleischmann correctly measured and accounted for the heat. From then on, the story gets murky. Pons and Fleischmann claimed the heat had to come from nuclear fusion, but obviously there was not very much of it. According to “Physics World”, they also claimed the production of neutrons and tritium. I do not recall any actual detection of neutrons, and I doubt the equipment they had would have been at all suitable for that. Tritium might seem to imply neutron production, thus a neutron hitting deuterium might well make tritium, but tritium (even heavier hydrogen) could well have been a contaminant in their deuterium, or maybe they never detected it.

The significance, of course, was that deuterium fusion would be an inexhaustible source of clean energy. You may notice that the Earth has plenty of water, and while the fraction that is deuterium is small, it is nevertheless a very large amount in total, and the energy in going to 4-helium is huge. The physicists, quite rightly, did not believe this. The problem is the nuclei strongly repel each other due to the positive electric fields until they get to about 1,000 – 10,000 times closer than they are in molecules. Nuclear fusion usually works by either extreme pressure squeezing the nuclei together, or extreme temperature giving the nuclei sufficient energy that they overcome the repulsion, or both.

What happened next was that many people tried to reproduce the experiment, and failed, with the result this became considered an example of pathological science. Of course, the problem always was that if anything happened, it happened only very slightly, and while heat was supposedly obtained and measured by a calorimeter, that could happen from extremely minute amounts of fusion. Equally, if it were that minute, it might seem to be useless, however, experimental science doesn’t work that way either. As a general rule, if you can find an effect that occurs, quite often once you work out why, you can alter conditions and boost the effect. The problem occurs when you cannot get an effect.

The criticisms included there were no signs of neutrons. That in itself is, in my opinion, meaningless. In the usual high energy, and more importantly, high momentum reactions, if you react two deuterium nuclei, some of the time the energy is such that the helium isotope 3He is formed, plus a neutron. If you believe the catalyst is squeezing the atoms closer together in a matrix of metal, that neutron might strike another deuterium nucleus before it can get out and form tritium. Another reason might be that the mechanism in the catalyst was that the metal brought the nuclei together in some form of metal hydride complex, and the fusion occurred through quantum tunnelling, which, being a low momentum event, might not eject a neutron. 4He is very stable. True, getting the deuterium atoms close enough is highly improbable, but until you know the structure of the hydride complex, you cannot be absolutely sure. As it was, it was claimed that tritium was found, but it might well have been that the tritium was always there. As to why it was not reproducible, normally palladium absorbs about 0.7 hydrogen atoms per palladium atom in the metal lattice. The claim was that fusion required a minimum of 0.875 deuterium atoms per palladium atom. The defensive argument was the surface of the catalyst was not adequate, and the original claim included the warning that not all electrodes worked, and they only worked for so long. We now see a problem. If the electrode does not absorb and react with sufficient deuterium, you do not expect an effect. Worse, if a special form of palladium is required, that rectifying itself during hydridization could be the source of the heat, i.e.the heat is real, but it is of chemical origin and not nuclear.

I should add at this point I am not advocating that this worked, but merely that the criticisms aimed at it were not exactly valid. Very soon the debate degenerated into scoffing and personal insults rather than facts. Science was not working at all well then. Further, if we accept that there was heat generated, and I am convinced that Martin Fleischmann, whatever his other faults, was a very careful and honest chemist and would have measured that heat properly, then there is something we don’t understand. What it was is another matter, and it is an unfortunate human characteristic that the scientific community, rather than try to work out what had happened, preferred to scoff.

However, the issue is not entirely dead. It appears that Google put $10 million of its money to clear the issue up. Now, the research team that has been using that money still have not found fusion, but they have discovered that the absorption of hydrogen by palladium works in a way thus far unrecognised. At first that may not seem very exciting, nevertheless getting hydrogen in and out of metals could be an important aspect of a hydrogen fuel system as the hydrogen is stored at more moderate pressures than in a high-pressure vessel. The point here, of course, is that understanding what has happened, even in a failed experiment, can be critically important. Sure, the actual initial objective might never be reached, but sometimes it is the something else that leads to real benefits. Quite frequently, in science, success stories actually started out as something else although, through embarrassment, it is seldom admitted.

Finally, there is another form of cold fusion that really works. If the electrons around deuterium and tritium are replaced with muons, the nuclei in a molecule come very much closer together, and nuclear fusion does occur through quantum tunnelling and the full fusion energy is generated. There are, unfortunately, three problems. The first is to maintain a decent number of muons. These are made through the decay of pions, which in turn are made in colliders. This means very considerable amounts of energy are spent getting your muons. The second is that muons have a very short life – about 2 microseconds. The third is if they lose some energy they fall into the helium atom and stay there, thus taking themselves out of play. Apparently a muon can catalyse up to 150 fusions, which looks good, but the best so far is that to get 1 MW of net energy, you have to put 4 MW in to make the muons. Thus to get really large amounts of energy, extremely huge generators are required just to drive the generation. Yes, you get net power but the cost is far too great. For the moment, that is not a productive source.

What do we need for life?

One question that intrigues man people is, is there life in the Universe besides what we see? Logic would say, almost certainly yes. The reason is we know there is a non-zero probability that it can form elswhere because it did here. That probability may be small but there is an enormous number of stars in the Universe (something in excess of 10^22 that we can see) that the conditions that led to life here must be reproduced a very large number of times. Of course, while there are such a large number of stars, by far the most are at such an extraordinarily large distance from us that they are essentially irrelevant. For the bulk of them, it took the light more than ten billion years to get here. But if we were to look for life nearby, where would we look? To answer that, we need to ask ourselves, what conditions are needed to get life started? The issue is NOT where can life exist, but rather where can it form. We know life can be found now on Earth in a wide range of environments, but that does not mean it can form there. It can migrate from somewhere else, gradually evolving systems needed to stabilize it to the new environment. The most obvious example is life emerging from the water to live on land. Nobody suggests life did not start in water because you need a solution to move nutrients around.

The first question to ask is, what are the most difficult things to achieve for life to get started? I think the four hardest things to get started are reproduction, energy transport, solubilization, and catalysis. Catalysis is required to make the chemical reactions that are desirable to go faster, and thus get more of the available resources going in the desired direction. (In this, when I use the word “desired” I mean to get on a right track to where life can get going and then support that choice during subsequent evolution. I do not mean to imply some sort of planning or directing.) Solubilization is required because many of the chemicals with functions that will be needed are not soluble in water, and hence they would simply settle out as a layer of brown gunk, which, as an aside, is what happens in many experiments designed to simulate the origin of life. What needs to happen is that something joins on at a place that does not spoil the function and then conveys solubility. Energy transport is a critical problem: if you do not have something that stores energy, functionality is restricted to microdistances from energy inputs.

Each of these critical functions, as well as reproduction, as I shall show below, depend on forming phosphate esters. Thus energy transport is mediated by adenosine tripolyphosphate (ATP), solubilisation of many of the most primitive cofactors that do not contain a lot of nitrogen or hydroxyl groups is aided by an attached adenosine monophosphate (AMP), initial catalysts came from ribozymes, RNA would be the initial source of reproduction, and both ribozymes and RNA (the latter is effectively just far longer strands of the former) are both constructed of AMP or the equivalent with different nucleobases. The commonality is the ribose and phosphate ester.

Catalysis is an interesting problem. Currently, enzymes are used, but life could not have started that way. The reason lies in the complexity of enzymes. The enzyme that will digest other protein, and hence make chemicals available from failed attempts at guessing the structure of a useful enzyme, has a precise sequence of three hundred and fifteen amino acids. There are twenty different common amino acids used (and in abiogenic situations, a lot more available) and these occur in D- and L- configurations, except for glycine, which means the probability of getting this enzyme is two in 39^315. That number is incredibly improbable. It makes selecting a specific proton in the entire Universe trivial in comparison. Worse, that catalyses ONE reaction only. That is not how initial catalysis happened.

Now, look at the problem of reproduction. Once a polymer is formed that can generate some of whatever requirements life needs, if it cannot copy itself, then it is a one-off wonder, and eventually it will degrade and be lost without a trace. Reproduction involves the need to transfer information, which in this case is some sort of a pattern. The problem here is the transfer must be accurate, but not too accurate initially, and we need different entities. By that I mean, if you just reproduced the same entity, such as in polyethene, you have two units of information: what it is and how long it is, but that second one is rather useless because life has no way of measuring the length without having a very large set of reference molecules. What life here chose appears to have been RNA, at least to start with. RNA has two purines and two pyrimidines, and it pairs them in a double helix. When reproduction occurs, one strand is the negative of the other, but if the negative pairs, we now have two strands that are equivalent to each original strand. (you retain the original.) There are four variations possible from the canonical units at any given position, and once you have many millions of units, a lot of information can be coded.

Why ribonucleic acid? The requirement is to be able to transfer information reliably, but not too accurately (I shall explain why not in a later post.) To do that, the polymer strands have to bind, and this occurs through what we call hydrogen bonds, which each give a binding energy of about 13 kJ/mol. These are chosen because they are weak enough to be ruptured, but strong enough you can get preferences. Thus adenine binds with uracil through two hydrogen bonds, which generates a little over 26 kJ/mol. (For comparison, a carbon-carbon bond is about 360 kJ/mol.) To get the 26 kJ/mol. the two hydrogen bonds have to be formed, and that can only happen of the entities have the right groups in the correct rigid configuration. When guanine bonds with cytosine, three such hydrogen bonds are formed, and the attraction is just under 40 kJ/mol. Guanine can also bind with uracil generating 26 kJ/mol., so information transfer is not necessarily totally accurate.

This binding through hydrogen bonds is critical. The bonding is strong enough to give a significant preference for each mer, but once the polymer gets long enough, the total energy (the sum of the energy of the individual pairs) holding the strands together gets to be those energies above multiplied by the number of pairs. If you have a million pairs, the strength of diamond becomes trivial, yet to reproduce, the strands must be separated. Hydrogen bonds can be separated because as the strands start to separate, water also hydrogen bonds and thus makes up for the linking energy. However, that alone is insufficient because the strand itself would be insoluble in water, and if so, the two strands linked together would remain insoluble (for those who know what this means, entropy strongly favours keeping the strands together). To achieve this, we need something that joins the mers into a chain, adds solubility, forms stable chemical bonds in general but is equally capable of being broken so that if the information creates something that is useless, we can recycle the chemicals. Only phosphate fills these requirements, but phosphate does not bind nucleobases together. Something intermediate is required, and that something is ribose.

In the next posts on this topic, I shall show you where this leads in seeing where life might be.

Asteroid (101955) Bennu

The results of the OSIRIS-REx probe have now started to be made public, and while this probe was launched to answer questions about carbonaceous asteroids, and while some information has been obtained that is most certainly interesting, what it has mainly done, in my opinion, is to raise more questions. As is often the case with scientific experiments and observations.

Bennu is a carbonaceous asteroid with a semimajor axis of about 1.26 AU, where 1 AU is the Earth-Sun distance. Its eccentricity is 0.2, which means it is Earth-crossing and could collide with Earth. According to Wikipedia, it has a 1 in 2700 chance of impacting Earth between 2175 – 2199. I guess I shall never know, but it would be a threat. It has a diameter of approximately 500 meters, and a mass of somewhere in the vicinity of 7 x 10^10 kg, which means an impact would be extremely damaging near where it struck, but it would not be an extinction event. (The Chicxulub impactor would have been between five to seven orders of magnitude bigger.) So, what do we know about it?

It is described as a rubble pile, although what that means varies in terms of who says it. It is generally not considered to be an original accretion, and it is usually assumed to have formed inside a much larger planetoid which provided heat and pressure to form more complex minerals. Exactly why they are so sure of this is a puzzle to me, because we do not know what the minerals are, and how they are bound into the asteroid. Carbonaceous asteroids usually are found in the outer asteroid belt, and the assumption is this was dislodged inwards as a result of the collision that formed it. Standard theory assumes there were such collisions, but it also assumes such collisions led to planetary formation, and the rather awkward fact that there are no planets in the asteroid belt tends to be overlooked. These collisions are doing a lot of work, first making protoplanets then planets, and second, smashing up protoplanets to make asteroids, with no explanation why two different results arise other than “we need two different results”. Note that the collision velocities in the asteroid belt would be much milder than for the rocky planets, so smashing is more likely the closer to the star. Its relevance to planetary formation may be low since it did not form a planet, and there are no planets that have compositions that could realistically be considered to have come from such a chemical composition.

It is often said that Earth was bombarded with carbonaceous chondrites early on, and that is where the reduced carbon and nitrogen came from to sustain life, as well as the amino acids and nucleobases used to create life. Additionally, it is asserted that the iron and a number of other metals that dissolve in iron that we have on the surface must have come from asteroids, the reason being that in the early formation of Earth, the whole was a mass of boiling silicates in which such metals would dissolve in iron and go to the core. That we have them means something else must have brought them later. This shows one of the major faults of science, in my opinion. Rather than take the observation as a reason to go back and question whether the boiling silicates might be wrong, they introduce a further variable. Unfortunately, this “late veneer”  is misleading because the advocates have refused to accept that we have fragments of asteroids as meteorites. Their isotopes show they could only have contributed the right amount of metals, etc, if they were emulsified in all of Earth’s silicates. But wait. Why would these be emulsified and not go to the core while the original metals were not emulsified and did go to the core?

These asteroids are also believed by many to be the origin of life. They have very small amounts of amino acids and nucleobases, but they have a much wider range of amino acids than are used by our life. If they were the source, why did we not use them? Even more convincing, the nitrogen in the meteorite fragments has more 15N than Earth’s nitrogen. Ours is of solar composition; the asteroids apparently processed it. There is no way to reduce the level of heavy isotopes so these asteroids cannot be the source.

Now, what does a rubble pile conjure up in your mind? I originally considered it to be, well, a pile of rubble, loosely adhering, but Bennu cannot be that. First, consider the escape velocity, which is more than 20 cm/sec in the polar regions but reduces down to 10 cm/sec at the equator, due to the centrifugal force of its rotation. That is not much, and anything loose would be lost in any impact. Yet the surface is littered with boulders, three more than 40 m long. Any significant shock would seemingly dislodge such boulders, especially smaller ones, but there they are, some half buried. There are also impact craters, some up to 150 meters in diameter. Whatever hit it to create that and excavate a hole 150 m in diameter must have delivered a shock wave that should impart more than 10 cm s−1 to a loosely lying boulder, although there is one possible exception, which is when the whole structure was sufficiently flexible to give without fragmenting and absorb the energy by converting it to heat while adding to the kinetic energy of the whole.

Which brings us back to the rubble pile. Bennu’s relative density is 1.19, so if placed in water it would not float, but it would not sink very quickly either. For comparison, it is less than half that of granite and about a third of many basalts. CI asteroidal material has a bulk density of 1.57, while CM asteroidal material has a bulk density of 2.2.  Accordingly, it is concluded that Bennu has a lot of voids in it, which is where the concept of the rubble pile comes to bear. On the other hand, there is considerable stiffness, so something is restricting movement.

So what do we not know about this asteroid? First, we have only a modest idea of what it is made of, although a sample return might be possible. It may well be made entirely of large boulders plus the obvious voids put together with something sticking the boulders together, but what is the something? If made of boulders, what are the boulders made of? It never got hot enough out there to melt silicates, so whatever they are must b held together by some agent, but what? How resilient is that something, and how many times can it be used before it fails? This is important in case we decide it would be desirable to alter its orbit to avoid a collision with Earth. What holds the boulders together? This is important if we want to know how planets form, and whether such an asteroid will be useful in any way. (If, for example, we were to build a giant space station, the nitrogen, organic material and water in such an asteroid would be invaluable.) More to do to unravel this mystery.