Microplastics

You may have heard that the ocean is full of plastics, and while full is an excessive word, there are huge amounts of plastics there, thanks to humans inability to look after some things when they have finished using them. Homo litterus is what we are. You may even have heard that these plastics degrade in light, and form microscopic particles that are having an adverse effect on the fish population. If that is it, as they say, “You aint heard nothin’ yet.”

According to an article in the Proceedings of the National Academy of Science, there is roughly 1100 tons of microplastics in the air over the Western US, and presumably there are corresponding amounts elsewhere. When you go for a walk in the wilderness to take in the fresh air, well, you also breathe in microplastics. 84% of that in the western US comes from roads outside the major cities, and 11% appear to be blowing in from the oceans. They stay airborne for about a week, and eventually settle somewhere. As to source, plastic bags and bottles photodegrade and break down into ever-smaller fragments. When you put clothes made from synthetic fibers into your washing machine, tiny microfibers get sloughed off and end up wherever the wastewater ends up. The microplastics end up in the sludge, and if that is sold off as fertilizer, it ends up in the soil. Otherwise, it ends up in the sea. The fragments of plastics get smaller, but they stay more or less as polymers, although nylons and polyesters will presumably hydrolyse eventually. However, at present there are so many plastics in the oceans that there may even be as much microplastics blowing out as plastics going in.

When waves crash and winds scour the seas, they launch seawater droplets into the air. If the water can evaporate before the drops fall, i.e. in the small drops, you are left with an aerosol that contains salts from the sea, organic matter, microalgae, and now microplastics.

Agricultural dust provided 5% of the microplastics, and these are effectively recycled, while cities only provided 0.4%. The rest mainly come from roads outside cities. When a car rolls down a road, tiny flecks come off the tyres, and tyre particles are included in the microplastics because at that size the difference between a plastic and an elastomer is trivial. Road traffic in cities does produce a huge amount of such microplastics, but these did not affect this study because in the city, buildings shield the wind and particles do not get lifted to the higher atmosphere. They will simply pollute the citizens’ air locally so city dwellers merely get theirs “fresher”.  Also, the argument goes, cars moving at 100 k/h impart a lot of energy but in cities cars drive much more slowly. I am not sure how they counted freeways/motorways/etc that go through cities. They are hardly rural, although around here at rush hour they can sometimes look like they think they ought to be parking lots.

Another reason for assigning tyre particles as microplastics is that apparently all sources are so thoroughly mixed up it is impossible to differentiate them. The situation may be worse in Europe because there they get rid of waste plastics by incorporating them in road-surface material, and hence as the surface wears, recycled waste particles get into the air.

Which raises the question, what to do? Option 1 is to do nothing and hope we can live with these microplastics. You can form your own ideas on this. The second is to ban them from certain uses. In New Zealand we have banned supermarket plastic bags and when I go shopping I have reusable bags that are made out of, er, plastics, but of course they don’t get thrown away or dumped in the rubbish. The third option is to destroy the used plastics.I happen to favour the third option, because it is the only way to get rid of the polymers. The first step in such a system would be to size reduce the objects and separate those that float on water from those that do not. Those that do can be pyrolysed to form hydrocarbon fuels that with a little hydrotreating can make good diesel or petrol, while those that sink can be broken down with hydrothermal pyrolysis to get much the same result. Hydrothermal treatment of wastewater sludge also makes fuel, and the residues, essentially carbonaceous solids, can be buried to return carbon to the ground. Such polymers will no longer exist as polymers. However, whatever we do, all that will happen is we limit the load. The question then is, how harmless are they? Given we have yet to notice effects, they cannot be too hazardous, but what is acceptable?

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.