I shall add a little next Thursday, but these are excellent points that somehow seem to have got lost in the background noise
Monthly Archives: August 2019
The Hydrogen Economy to solve Climate Change?
One of the interesting aspects of climate change is the number of proposals put forward to solve it that do not take into account adverse consequences. There is a strong association of wishful thinking with some of these. On the other side are the gloomy ones, and maybe I fall into that category. What brought that thought to the fore was I have seen further claims for hydrogen as a solution. Why? Well, there are wild claims that wind and solar will solve everything. One problem with these is they tend to deliver their energy in pulses: solar during the day, wind when it is blowing. The net result is that if these can deliver adequate power for all times, there is serious overproduction required at other times. The problem then is how to store this energy. One way is to pump water uphill, but that requires large storage. In a country like New Zealand, where much of the electricity is hydro generated, you would just turn off that generation and use the hydro to manage power demand. However, that assumes there is not a large increase in electricity demand. One proposed solution is to generate hydrogen by electrolysing water. This is a well-understood technology, with no problems, given the power. There are, however, significant economic ones.
This is claimed to solve another problem; a very significant amount of domestic heating is obtained from burning gas. Now, all we have to do is burn hydrogen. We could also use hydrogen in vehicles. My big problem, having worked with hydrogen before, is that it leaks, and is extremely flammable. According to Wikipedia, the flammability range of hydrogen in air is between 4% and 75%; to detonate, the limits are 18.3 – 59% (each by volume), and a leak can support combustion at flow rates as low as 4 micrograms/second. Mixtures can ignite with very low energy input, 1/10 of that needed to ignite gasoline/air, and any static electric spark can ignite it.
The leak problem is made worse by the fact that hydrogen can embrittle metals, and thus create a way for it to escape. It is lighter than air, so it tends to accumulate at the ceilings of buildings, and its very wide explosive range is a broad hazard. The idea that hydrogen could be piped into houses to provide heating is not something I would want to see. The problem is made worse in that you might be sensible and cautious and not take it up, but your neighbour might. The consequences of that can impinge on you. Recently, in Christchurch, a house blew up, and reduced itself to a collection of boards, roofing material, etc., with only the foundations remaining more or less where they started. Several neighbours houses were severely damaged, and made effectively unliveable, at least without major repairs. By some miracle, nobody was killed, although a number had injuries. What apparently happened was a registered gasfitter had done some work on the house’s gas system, there was a natural gas leak, and something ignited it. My guess is, he has some explaining to do, but my point is if this can happen to a registered tradesman, what will happen if there is widespread use of something that leaks with orders of magnitude more ease?
There is a further irony. The objective behind using hydrogen is to help the greenhouse effect by reducing the amount of carbon dioxide we emit. Unfortunately, leaked hydrogen also magnifies the greenhouse effect. At first sight, this does not look right because greenhouse gases work because there is a change of dipole moment in the vibrational mode. This is needed because unless the transition involves a change of electric moment, it cannot absorb a photon. Hydrogen has only one vibrational mode and no electric moment, and no change of electric moment when it is stretched because of its symmetry, i.e.one end of H2 is exactly the same as the other end. There is a minor effect in that the molecule can be polarised for an instant in a collision with something else, but that is fairly harmless.
The problem lies in downstream consequences. One of the important greenhouse gases is methane, emitted by natural gas leaks, farm animals, other farm processes, anaerobic fermentation, etc. Methane is about 35 times more powerful than carbon dioxide as a greenhouse gas, and worse, it absorbs in otherwise transparent parts of the infrared spectrum. (The otherwise does not include other hydrocarbon gases.) However, methane is not as serious as it might be because it is short-lived. UV radiation in the upper atmosphere breaks water, directly or indirectly, into hydroxyl radicals and hydrogen radicals. The hydroxyl radicals rapidly degrade methane, and the hydrogen radicals react with oxygen in the air to make peroxyl radicals that also degrade methane. Molecular hydrogen reacts with both these sort of radicals, and thus indirectly preserves the methane.
There are, of course, other ways of using hydrogen, such as in chemical reactions, including upgrading biofuels, and it can be stored in chemical compounds. Hydrazine (N2H4) is an example of a liquid that could make a very useful fuel. (In the book, and film “The Martian”, the hero has hydrazine from the fuel tank of a rocket, so he catalytically converts it to hydrogen to burn to make water, and blows up his “dome”. It would have been so much easier to burn hydrazine, as it was, after all, from a rocket fuel tank.) Other options include storing hydrogen as hydrides, e.g. borohydrides, or as ammonia, which is cheaper to make than hydrazine, but it is also a gas, unlike hydrazine. The problem is usually how to deliver the hydrogen at a regular and controllable rate.
The use of hydrogen in a chemical manufacturing plant, or when handled with expertise, such as when used by NASA, is no problem. My concern would be for the average person doing repairs themselves to pipes conveying hydrogen, or worse still, plumbing incorrectly. As for having hydrogen as a fuel to be delivered at refuelling stations, I used this concept in my ebook “Puppeteer” to illustrate the potential danger if there are terrorists on the loose.
From August 22 – 28 Jonathon Munros will be discounted to 99c on Amazon in the US and 99p in the UK. The third book in a series, in which the evil Jonathon Munro violates the only reason his evil behaviour has as yet not been punished. He is to be replaced by an android, who learns to behave like the real man. However, Jonathon’s inherent evil has been underestimated, and the android, knowing of Jonathon’s obsession with sex, and knowing that sex is needed for reproduction, decides to start reproducing itself. What could possibly go right? A dystopian hard science fiction novel that, while the third of a series, stands alone as long as you accept the characters have a past, and a problem that makes the Terminator seem modest.
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.
Biofuels as Alternative Fuel Sources
In the previous post I suggested that municipal refuse could be converted to liquid fuels of similar nature to modern hydrocarbon fuels from oil. There are some who think transport can be readily electrified, but three other considerations suggest not. The first is that, as noted by Physics World, a publication by the Institute of Physics, there is a very good chance that a car sold today will still be being used twenty years out. The second is that electric vehicles also have considerable greenhouse emissions. The actual running of the car is free of emissions, but you still have to make the car, which has significant emissions and may exceed that of the standard car; you have to generate the electricity, and the majority of the world’s electricity is generated from fossil fuels, and much from coal; and finally you have to make the batteries, and this is also a serious emitter. There are also parts of the vehicle fleet that will not easily electrify, such as the big road trailers that go into remote Australia, heavy construction equipment, simply because the extra mass to store the batteries would be horrendous, and recharge is not simple in remote places. Shipping will continue to use oil, as will aircraft, and as noted in a previous post, so will much of the vehicle fleet because it is not possible to make satisfactory batteries for replacement vehicles because with current technology there is insufficient cobalt. So what else can replace fossil fuel?
One such possibility is biofuels. The case for biofuels is that in principle their combustion is carbon neutral: their carbon may return to the air, but it came from the air. The energy source is essentially solar, and that is not going to run out soon. The problem then is that biomass is a strange mix of different chemicals. Worse, we eat biomass, and we must not remove our food supply.
The first problem that gives biofuels a bad name is the urge to take the low hanging fruit, especially for tax benefits. Palm oil for biodiesel has made a terrible mess of the Indonesian rain forests, and for what benefit (apart from clipping the tax ticket?) Corn for ethanol similarly makes little sense exceptfor the case where the corn would otherwise go to waste. The problem in part is that corn also utilises so little of the sunlight; most of the plant is simply wasted, and often burned. Seed oils do make sense for specialist uses, such as drying oils in paint, or in cosmetics, or as a feedstock to make other specialist chemicals, but something like “biodiesel” from palm oil makes the overall situation worse, not better. It will never replace the carbon fixed in the rain forest.
Forestry is another interesting case. We are much better off to use the logs for timber in construction: it is worth more, and at the same time it fixes carbon in the buildings. However, if you have ever seen forestry, you will know there is an awful lot of biomass just left to rot: the branches, twigs, stumps, roots, leaves/needles, etc. That is essentially free to use. There are big problems in that it packs extremely badly, so transport costs for any distance are too great.
From a technical point of view, the processes to use woody biomass would come down to the same ones for municipal wastes as noted in the previous post, except that gasification is unlikely to be suitable. A significant plant was put up in the US to gasify biomass and use the gas for a modified Fischer-Tropsch process, but it failed. There were probably several reasons for this, but one is immediately obvious: if we rely on market forces we cannot compete with oil. There are two reasons for that. The first is that the oil is “free” originally, and since liquids can be pumped, it is easily handled, while the second is there is a huge infrastructure to process oil. The cost per unit mass of product becomes lower, usually the ratio of the throughput rates to the power of 0.6. The reason for this is simple. Costs of processing plant are proportional (all other things being equal) to the area of the container, which is proportional to r squared, while the production rate is proportional to volume, which is proportional to rcubed. The huge oil processing plants are extremely efficient, and no much smaller biomass processing unit can have any hope of matching it. The reason for the 0.6 as opposed to 0.66666 is that there are also some extra savings. Control equipment, gauges, etc tend to cost much the same because they are the same, and pumps, etc, tend to be excessively costly when small. The six-tenths rule is, of course, only a rough approximation, but it is a guide.
My approach to this, when I started, was to consider biomass hydrothermal liquefaction. The concept here was that if we merely heated the biomass up with water and simple catalysts under pressure to approaching the critical point, we could end up with liquids. These would have to be refined, but that could be done in a large central plant, while the initial processing could be done in smaller units that could be, with effort, portable. One of the surprises from this was that a certain fraction was already effectively a very high-grade fuel, at least for petrol craft or jet engines without further refining. Exactly what you got depended on catalysts, and a case could also be made to add certain other chemicals to enhance certain products. A lot more work would be needed to get such technology operational, but needing more work is not a reason to discard the concept if saving the world is at stake.
So why did I stop doing this work? Basically, because I felt the desire to change my working environment, and because the funding for this work was drying up. Regarding my working environment, there is a funny story there – well, sort of funny, but it did not feel that way then. The journal Naturedid a quick survey of science in New Zealand. I worked in a Government laboratory, and I had the rather dubious honour of having Head Office describe me in Natureas “an eccentric”. Why? Because I was trying to promote an industry based on a by-product of a synthetic fuels plant constructed at Motunui that would make a key starting material for high-temperature plastics. I suppose some of my antics were unusual, for example there was a program on national television of the dangers of flammable foam plastics, so I went there and pointed out they did not haveto be flammable. I had a piece of foam I had made in the lab that afternoon in the palm of my hand and I fired a gas torch at it so the foam was in my hand, yet yellow-hot on the outside. I held it there for quite some time, until everyone got bored. Anyway, when your employer decides you are eccentric, it felt like time to quit and start up by myself. There were two consequences of this. Before I left, the technical staff made me a brass “eggcup” with a large glass egg in it. One of my prized possessions. The second was I got a letter of apology from Head Office, in which it was explained they did not mean I was eccentric, but rather my ideas were. Not a great improvement, as seen by me. I suppose there was a further example of eccentric behaviour. The laboratory was set up with the purpose of promoting the New Zealand economy by finding new industrial opportunities. I suppose it was somewhat eccentric to actually be following “the Prime Directive”.
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.