Geoengineering: Shade the World

As you may have noticed when not concerned about a certain virus, global warming has not gone away. The virus did some good. I live on a hill and can look down on some roads, and during our lock-down the roads were strangely empty. Some people seemed to think we had found the answer to global warming, as much less petrol was bing burnt, but the fact is, even if nobody drove we were still producing net amounts of CO2 and other greenhouse gases, and even if we were not doing that, the amounts currently in the air are still out of equilibrium and would continue to melt ice and lead to high temperatures. In the northern hemisphere now you have a summer so maybe you notice.

So, what can we do? One proposal is to shade the Earth’s surface. The idea is that if you can reflect more incoming solar radiation back to space there is less energy on the surface and . . .  Yes, it is the ‘and’ wherein lies the difficulties. We get less radiation striking the surface, so we cool the surface, but then what? According to one paper recently published in Geophysical Research Letters (https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020GL087348 ) the answer is not good news. They have produced simulations of models, and focus on what are called storm tracks, which are relatively narrow zones in oceans where storms such as tropical cyclones and mid-latitude cyclones travel through prevailing winds. Such geoengineering, according to the models, would weaken these storms. Exactly why this is bad eludes me. I would have thought lower energy storms would be good; why do we want hundreds of thousands of citizens have their properties leveled by hurricanes, typhoons, or simply tropical cyclones as they are known in the Southern Hemisphere? This weakening happens through a smaller pole to equator temperature difference because most of the light reflected is over the tropics. Storms are heat engines at work, and the greater the temperature difference, the more force can be generated. The second law of thermodynamics at work. Fine. We are cooling the surface, and while it may seem that we are ignoring the ice melting of the polar regions, we are not because most of the heat comes from ocean currents, and they are heated by the tropics.

More examples: we would reduce wind extremes in midlatitudes, possibly lead to less efficient ventilation of air pollution, may possibly decrease low cloud cover the storm‐track regions and weaken poleward energy transport. In short, a reasonable amount of that is what we want to do anyway. It is also claimed we would get increased heat waves. I find that suspicious, given that less heat is available. It is claimed that such activities would alter the climate. Yes, but that is what we would be trying to do, namely alter it from what it might have been. It is also claimed that the models show there could possibly  be regional reductions in rainfall. Perhaps, but that sort of thing is happening anyway. Australia had dreadful bushfires this year. I gather forest fires were going well in North America also.

One aspect of this type of study that bothers me is it is all based on models. The words like ‘may’, ‘could’ and ‘possibly’ turn up frequently. That, to me, indicates the modelers don’t actually have a lot of confidence in their models. The second thing that bothers me is they have not looked at nature. Consider the data from Travis et al.(2002) Nature 418, 601.  For the three days 11-14 Sept. 2001 the average diurnal temperature ranges averaged from 4000 weather stations across the US increased on average 1.1 degrees C above the average from 1971 – 2000, with the highest temperatures on the 14th. They were on average 1.8 degrees C greater than the average for the two adjacent three-day periods. The three days with the increase were, of course, the days when all US aircraft were grounded and there were no jet contrails. Notice that this is the difference between day and night; at night the contrails retain heat better, while in daytime they reflect sunlight.  Unfortunately, what was not stated in the paper was what the temperatures were. One argument is that models show while the contrails reflect more light during the day, they keep in more heat during the night. Instead of calculations, why not show the actual data?

The second piece of information is that the eruption of Mount Pinatubo sent aerosols into the atmosphere and for about a year the average global temperature dropped 1 degree C. Most of that ash was at low latitudes in the northern hemisphere. There are weather reports from this period so that should give clues as to what would happen if we tried this geoengineering. This overall cooling was real and the world economies did not come to an end. The data from that could contribute to addressing the unkn owns.

So, what is the answer? In my opinion, the only real answer is to try it out for a short period and see what happens. Once the outcomes are evaluated we can then decide what to do. The advantage of sending dust into the stratosphere is it does not stay there. If it does not turn out well, it will not be worse than what volcanoes do anyway. The disadvantage is to be effective we have to keep doing it. Maybe from various points of view it is a bad idea, but let us make up our minds from evaluating proper information and not rely on models that are no better than the assumptions used. Which choice we make should be based on data, not on emotion.

What to do with Waste Plastics

One of the great environmental problems of our time is waste plastics, and there are apparently huge volumes floating around in the oceans of the world. These would generally get there by people throwing them away, so in principle this problem is solved if we can stop that irresponsible attitude. I can already hear the, “Good luck with that,” response. Serious fines for offenders would help, as would more frequent proper rubbish disposal bins. But this raises the question, what should we do with waste plastics?

The first answer is it is unlikely there is a single answer because there are such a variety of plastics. Some, like polyester or polyethylene, can be reasonably easily recycled for low specification uses, but the problem here is there is a limit to how many plastic buckets, etc, can be sold. Technically, quite a high level of recycling can be achieved. Quite a while ago, during the first oil crisis, a client asked me to devise a means of recycling mixed coloured polyethylene so I devised a process that recovered a powder that could be used to make almost anything that virgin polyethylene could make, except maybe clear: there was always a slight beige colour from residual dyes etc that could not be got out, at least in a one-cycle process. Polyethylene degrades – you will all have seen it go brittle from sunlight. This shortens the chains and oxidizes parts and I was proud of this process because it got rid of all the degradation and short-chain material.

A pilot plant was built, then the process was abandoned.  The reason was the oil prices tumbled, and there was no way the process could make money, particularly since big multinationals appeared to be dumping polyethylene into New Zealand. Some manufacturers loved this, and were able to export all sorts of plastic things, at least for a while. Part of the reason the process would have lost money, of course, was that despite getting the raw material rather cheaply, the yield at the end was lower because of the loss of the degradation products, but the killer was getting rid of the degradation products. They could be burnt for process heat, but that would need a specially designed burner, and there would still be the pigment remains to be disposed of. Good idea, but could not compete with the oil industry.

Another possible process is pyrolysis. This came to my attention when I recently saw a paper in the latest copy of “Energy and Fuels” put out by the American Chemical Society. Polyethylene gives a mix of oil, gas and carbonaceous solid, but you can get almost 80% in the form of oil that could be directly used as a diesel fuel after distillation. There appear to be a fraction that boils too high for the diesel range, and gets waxy, but those who have recalled a recent post by me will see that it would do well in the heavier marine heavy fuel oil. The resultant oil has a mix of linear alkanes and terminal alkenes, and the fragmentation is such that the double bond prefers the smaller fragment. There is also some miscellaneous stuff resulting from the oxidative degradation. Polypropylene, however, showed a lot more oxygen, with a range of alcohols, esters and also acids in addition to highly branched hydrocarbons, however, almost 20% was the single compound 2,4-dimethyl-1-heptene. It would manage with the light ends as petrol, and the heavier ends contributing to diesel. 

Polystyrene gave what corresponds more to a heavy oil, although 40% was actually styrene, which could be used to make more polystyrene. Importantly, the cetane rating for the oil from polyethylene was 73; for polypropylene, 61. Polystyrene oil was unsuitable for diesel, but if hydrogenated, the lower boiling cut would make a high octane petrol. The average pump diesel fuel has a cetane rating of about 50, and the higher the rating, the faster the engines can go, so pyrolysis of waste polyethylene and waste polypropylene will make an excellent diesel fuel, with the heavy ends going towards shipping.  However, the heavy ends of polystyrene would have to be dumped because they contain fluorinated material, presumably a consequence of additives, and you certainly do not want an exhaust stream rich in hydrogen fluoride. And here is the curse that plagues anything involving recycling: too many companies put in additives that will be impossible to remove, and which either prevent proper recycling or will have consequences that are at best highly unpleasant, while they offer no option for dealing with them.

How do we separate these plastics out? Fragment them, and stir in water. Polyethylene and polypropylene are the two plastics that float. Foam, of course, has to be omitted. So, will this end up being done? My guess is, not in the immediate future. In terms of economics, it cannot beat the entrenched oil industry, unless governments decide that cleaning up the environment is worth the effort.

Climate Change and International Transport

You probably feel that in terms of pollution and transport, shipping is one of the good guys. Think again. According to the Economist (March 11, 2017) the emissions of nitrogen and sulphur oxides from 15 of the world’s largest ships match those from all the cars on the planet. If the shipping industry were a country, it would rank as the sixth largest carbon dioxide emitter. Apparently 90%  of trade is seaborne, and in 2018, 90,000 ships burn two billion barrels of the dirtiest fuel oil, and contribute 2 – 3% of the world’s total greenhouse emissions. And shipping is excluded from the Paris agreement on climate change. (Exactly how they wangled that is unclear.) The International Maritime Organization wants to cut emissions by 50% by 2050, but prior to COVID-19, economic growth led to predictions of a six-fold increase by then!

Part of the problem is the fuel: heavy bunker oil, which is what is left over after refining takes everything else it can use. Apparently it contains 3,500 times as much sulphur as diesel fuel does. Currently, the sale of these high sulphur fuels has been banned, and sulphur content must be reduced to 0.5% (down from 3.5%) and some ships have been fitted with expensive scrubbers to remove pollutants. That may seem great until you realize 80% of these scrubbers simply dump the scrubbed material, a carcinogenic mix of various pollutants, into the sea. They also increase fuel consumption by about 2%, thus increasing carbon dioxide missions.

On the 19th February, 2020, the Royal Society put out a document advocating ammonia as a zero-carbon fuel, and suggested that the maritime industry could be an early adopter. What do you think of that?

First, ammonia is currently made by compressing nitrogen and hydrogen at higher temperatures over a catalyst (The Haber process). The compression requires electricity, and the hydrogen is made by steam reforming natural gas, which is not carbon free, however it could be made by electrolysing water, which would be a use for “green” electricity”. The making of hydrogen this way may well be sound, but running the Haber process probably is not. The problem with this process is it really has to be carried out continuously, and solar energy is not available at night, and the wind does not always blow. However, leaving that aside, that part of the scheme is plausible. Ammonia can be burnt in a motor, or more efficiently in a fuel cell to make electricity. If you could make this work there are some ships that use diesel to make electricity to power motors, so that might work. Ammonia has an energy content of 3 kWh/litre (liquid hydrogen is 2/3 this) while heavy fuel oil has an energy content of 10 kWh/l. The energy efficiency of converting combustion energy to work is much higher in a fuel cell.

Of course by now you will have all worked out why this concept is a non-starter. The problem is the ship, its fuel tanks and motors, are part of the construction and are deep within the ship. The cost of conversion would be horrendous so it is most unlikely to happen. Equally, if we were serious about climate change, we could convert ships to use nuclear power. Various navies around the world have shown how this can be done safely. Don’t hold your breath waiting for the environmentalists to endorse that idea.

However, converting to nuclear power has the same problem as converting to ammonia: a huge part of the ship has to be demolished and rebuilt, so that is a non-starter. So there is no way out? Not necessarily.  I have currently been spending my lockdown writing a chapter for a book in a series on hydrothermal treatment of algae. Now the interesting thing about the resultant biocrude is that while you can make very high octane petrol and high cetane diesel, there is a residue of heavy viscous fluid that can be mainly free of sulphur and nitrogen. What on earth could you do with that? It is a thick viscous oil, surprisingly like heavy bunker oil. Any guesses as to what I might be tempted to recommend?

Forests for storing carbon

One of the more annoying features of the climate change issue is the question of feedback, i.e. what are the consequences of what is inevitably going to happen? One important issue is whether we can fix carbon, at least temporarily, and the answer is, yes but . . .  The following illustrates some of the problems, based on a paper by McNicol et al. 2019. Environ. Res. Lett. 14 014004 .

We hear that forestry is a good place to store carbon. The first objection you hear will be that while the trees take carbon from the air, they eventually die and return the carbon to the air. Of course, if the forest is continuous, as the old trees die, new ones replace them, which means that if the trees are there, there is so much carbon dioxide taken from the atmosphere. New forests are net removers while they are growing; mature forests represent a constant fixed amount. Building things with the wood will add to the reduction of atmospheric carbon. Temperate rainforests can store up to 1500 t/ha of carbon, while something like 200 t/ha will commonly be stored in the top one meter of soil, particularly if there is plenty of rain. Peatlands store more carbon, as do deeper soils. Peatlands in the region can be up to six meters deep. The greatest concentration of organic carbon occurs where the ground is wettest, while slope is also important. To give some idea, the total mass of soil carbon calculated for the North Pacific coastal temperate rainforest was 4.5 billion tonnes of carbon. 

Soil carbon does not stay there. Soil is a rather remarkable mass of biological activity, the waste products of which return to the atmosphere as either methane or carbon dioxide. Increasing the temperature speeds this up, and an average increase of 1 degree Centigrade across the world could release 50 billion tonne of carbon into the atmosphere from this source alone by 2050. That is about five times as much as we produce annually through burning fossil fuels and through agricultural activities. On the other hand, if it rained more, an increase in water-saturated soil would lead to net storage. This is the issue of feedback I mentioned. Positive feedback would mean that as the temperature rose thanks to the carbon we have put in the air, the soil would put more there, and accelerate the heating. The negative feedback occurs where more rain falls in key places and holds more carbon in the soil. Which will it be?

The climate warming is inevitable, but what happens to the weather? One suggestion is that where it is already wet, it will get wetter, whereas where it is dry, it will get dryer. That makes Australia less of “a lucky country”, which it proclaims itself to be.

Of course, simple soil is not the only source of greenhouse gas. Most people will have heard of methane occluded in tundra that is gradually thawing. Something has to be done, but politicians prepared to do anything are thin on the ground, and those who have analysed and recognized what few schemes might actually work and make a significant contribution towards solving it are even thinner on the ground.  There are conflicting issues, thus to store carbon you want trees on flat land to store more in the soil, but that is where the food comes from. So maybe planting trees on hills is better, because that land is less useful for food. What would you do?

An Imminent Water Crisis?

We have all heard the line “Water water everywhere, nor any drop to drink.” Well, soon we may have to rethink “everywhere”. There was a tolerably scary future hinted at by a recent letter in Nature (de Graaf, et al574: 90). It points out that groundwater is critically important for food production and currently pumping exceeds recharge from rainfall and rivers in many parts of the world. Further, when groundwater levels drop, discharges to streams declines or even stops completely, which reduces river flow, with potentially devastating effects on aquatic life. These authors claim that about 70% of pumped groundwater is used to sustain irrigation and hence food production. There are other problems, such as ground subsidence. If you take away matter from below you, then what you have between you and where you took it must eventually lower, but with land it does not have to do so evenly. Coastal flooding in some US cities is not really exacerbated by climate change to anywhere near the extent it is by the ground lowering due to groundwater removal. 

If the streams to rivers are not recharged, there is a slow desiccation of the nearby land. The billions of tonnes of water locked in soils and bedrock and various aquifers is the biggest single source of fresh water on the planet. Life essentially depends on this resource yet we are unthinkingly depleting it. Most people know that people in dry lands will experience worse conditions due to rising temperatures. What most don’t realise is the inability to properly recharge the aquifers they depend on will lead to even worse problems, not the least through the requirement for more water as temperatures increase.

The paper also provided maps that outline the size of the crisis, but in my opinion also shows a problem inherent in such studies: there was a map that showed the head decline that might lead to a crisis, which really indicates how much groundwater there is. Included is two-thirds of the South Island of New Zealand. Now for parts of Canterbury that may well be the case, but it also includes the West Coast of the South Island. The geology there may well indicate there is not much groundwater, and in fairness I have never heard of anyone drilling wells there, but there is not exactly a water shortage there because the Alps get roughly ten meters of rain a year. The problem for farming in that region is not a shortage of water but rather too much. It is true that farming in Canterbury is probably over-drawing on aquifers, but that is in part because the farmers took to dairying in an area unsuitable for that activity. Prior to the dairy rush, the area was quite prosperous at farming, but without irrigation. Farmers tended to grow grain in the warm dry summers, and would also run sheep. Now wool is not really wanted, so the farmers switched.

Of course, just because I can find a problem in one place does not mean the paper does not raise a valid point. I suspect that when producing a world map like that the authors go to whatever resources they can find and may not check associated issues. So, what are the real problems? In a recent article in Physics World it was stated that within thirty years almost 80% of lands that irrigate through groundwater will reach their limits as wells run dry. It also states that for the other 20% of areas that rely on pumped groundwater, surface flow of streams and rivers has already fallen. This includes cities that depend on pumped water for a water supply. The effects are already being felt in the mid-west of the US.

This raises the question of what can we do about this problem? The most obvious answer is to use less. Most people domestically use far more than necessary, and those who rely on stored rainwater will show how to use less. At the city level, do we really need the number of home pools? On a lesser scale, how many houses really do not waste water? Irrigation needs to be managed in such a way as to lose less by evaporation (i.e. something other than sprinklers.) We need farming methods that are better suited to the local climate, except that also has the problem that we then lose production volumes, and it is far from clear we can afford that.

For coastal cities, desalination offers an answer, but it costs $US1 per 1 – 2 tonne so it is not cheap, and in terms of electrical energy, if we use reverse osmosis, roughly 5 kWh is required, which means we have to significantly increase electrical production. Reverse osmosis works by using pressure to force water through a membrane that will not permit salts to pass, so in principle it could be turned off during peak loads, which might make it useful for a base loading source like nuclear power, but this is not so useful for places distant from the coast. There is another problem with desalination. The seawater should be sterile and the membranes have to be regularly cleaned, which leads to the release of biocides, salts, chelating agents, etc into the sea, which in turn is not particularly good for the local environment.We could pipe water from somewhere else, except we may be running out of “somewhere elses”, and anyway, that place may well be what is feeding the groundwater aquifer. The unfortunate end-result is we may have to give up using so much. We have a problem, Houston!

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)

Fuel for Legacy Vehicles in a “Carbon-free” Environment

Electric vehicles will not solve our emissions problem: there are over a billion petroleum driven vehicles, and they will not go away any time soon. Additionally, people have a current investment, and while billionaires might throw away their vehicles, most ordinary people will not change unless they can sell what they have, which in turn means someone else is using it. This suggests the combustion motor is not yet finished, and the CO2emissions will continue for a long time yet. That gives us a rather awkward problem, and as noted in the previous posts on global warming, there is no quick fix. One of the more obvious contributions could be biofuels. Yes, you still burn carbon, but the carbon came from the atmosphere. There will also be processing energy, but often that can come from the byproducts of the process. At this point I should add a caveat: I have spent quite a bit of my professional life researching this route so perhaps I have a degree of bias.

The first point is that it will be wrong to take grain and make alcohol for fuel, other than as a way of getting rid of spare or spoiled grain. The world will also have a food shortage, especially if the sea levels start rising, because much of the most productive land is low-lying. If we want to grow biomass, we need an area of land roughly equivalent to the area used for food production, and that land is not there. There are wastelands, but they tend to be non-productive. However, that does not mean we cannot grow biomass for fuel; it merely states there is nowhere nearly enough. Again, there is no single fix.

What you get depends critically on how you do it, and what your biomass is. Of the various processes, I prefer hydrothermal processing, which involves heating the biomass in water up to supercritical temperatures with some additional conditions. In effect, this greatly accelerates the processes that formed oil naturally. Corresponding pyrolysis will break down plastics, and in general high quality fuel is obtainable. The organic fraction of municipal refuse could also be used to make fuel, and in my ebook “Biofuel” I calculated that refuse could produce roughly seven litres per week per person. Not huge, but still a contribution, and it helps solve the landfill problem. However, the best options that I can think of include macroalgae and microalgae. Macroalgae would have to be cultivated, but in the 1970s the US navy carried out an exercise that grew macroalgae on “submerged rafts” in the open Pacific, with nutrients from the sea floor brought up from wind and wave action. Currently there is work being carried out growing microalgae in tanks, etc, in various parts of the world. In principle, microalgae could be grown in the open ocean, if we knew how to harvest it.

I was involved in one project that used microalgae grown in sewage treatment plants. Here there should have been a double benefit – sewage has to be treated so the ponds are already there, and the process cleans up the nitrogen and phosphate that would otherwise be dumped into the sea, thus polluting it. The process could also use sewage sludge, and the phosphate, in principle, was recoverable. A downside was that the system would need more area than the average treatment plant because the residence time is somewhat longer than the current time, which seems designed to remove the worst of the oxygen demand then chuck everything out to sea, or wherever. This process went nowhere; the venture needed to refinance and unfortunately they left it too late, namely shortly after the Lehman collapse.

From the technical point of view, this hydrothermal technology is rather immature. What you get can critically depend on exactly how you do it. You end up with a thick brown fluid, from which you can obtain a number of products. Your petrol fraction is generally light aromatics, with a research octane number (RON) of about 140, and the diesel fraction can have a cetane number approaching 100 (because the main components are straight chain C15 or C17 saturated hydrocarbons. Cetane is the C16 equivalent.) These are superb fuels, however while current motors would run very well on them, they are not optimal.

We can consider ethanol as an example. It has an RON somewhere in the vicinity of 120 – 130. People say ethanol is not much of a fuel because its energy content is significantly lower than hydrocarbons, and that is correct, but energy is not the whole story because efficiency also counts. The average petrol motor is rather inefficient and most of the energy comes out as heat. The work you can get out depends on the change of pressure times volume, so the efficiency can be significantly improved by increasing the compression ratio. However, if the compression is too great, you get pre-ignition. The modern motor is designed to run well with an octane number of about 91, with some a bit higher. That is because they are designed to use the most of the distillate from crude oil. Another advantage of ethanol is you can blend in some water with it, which absorbs heat and dramatically increases the pressure. So ethanol and oxygenates can be used.

So the story with biofuels is very similar to the problems with electric vehicles; the best options badly need more research and development. At present, it looks as if they will not get it in time. Once you have your process, it usually takes at least ten years to get a demonstration plant operating. Not a good thought, is it?

Can We Feed an Expanded Population?

One argument you often see is that our farmland can easily feed even more people and that our technology will see that famines are a thing of the past. I am going to suggest that this may be an overenthusiastic view of our ability. First, the world is losing a surprising amount of good soil every year, to water and wind erosion. Seawater rising will remove a lot of prime agricultural land, but there is a much worse problem that needs attention. The 18th May edition of Science had some information that might give cause to rethink any optimistic view. Our high intensity agriculture depends on keeping pests, weeds and fungi at bay, and much of that currently depends on the heavy use of certain chemicals. The problem is what we are trying to keep at bay are gradually evolving resistance to our agents.

Looking at fungicides first, there are basically four classes of fungicides licensed for use, and some of these, such as the azoles, have a number of variations, but the variations tend to be those to differentiate the compounds from someone else’s, and to get around patents. The fundamental activity usually comes from one chemical group. As an example from antibiotics, there are a large number of variation on penicillin, but they all have beta lactams, and it is the beta lactams that give the functionality, so when bugs evolve that can tolerate beta lactams, the whole set of such penicillin-like drugs becomes ineffective. For fungi, the industrial scale production of single crops in some regions optimises the chance of a fungus developing a resistance, and there appears to be the possibility of gene transfer between fungi.

This has some other downstream issues. Thus medical advances lead to people having a much better chance of survival through cancer treatments, but they then become more susceptible to fungi. Apparently Candida auris is now resistant to all clinical antifungals, and is a worse threat in hospitals because it can survive most standard decontamination procedures. A number of other fungi are very threatening in clinical situations.

So what can be done about fungi? Obviously, seeking new antifungals is desirable, but this is a slow process because before letting such new chemicals out into the environment, we have to be confident that there will really be benefits and the chemicals are sufficiently effective under all circumstances, and we also need to know there are no unintended consequences.

Insecticides and herbicides (and following the article in Science, these will be collectively termed pesticides) have the same problem. It was estimated that even now the evolution of such resistance costs billions of dollars in the US. With regard to weeds, in 1996 plants were produced that were not harmed by glyphosate, and the effectiveness of this led to over 90% of US maize, soy and cotton being planted with such plants. (Some will recall the fact that some were bred so the plants did not produce viable seed, and further seed had to be purchased from the company that developed the plant.) Now there are at least forty serious weeds that have developed resistance to glyphosate. Plants have been engineered that are resistant to chemicals mimicking previous herbicides but the weeds are defeating that. Weed species have evolved to resist every known herbicide, and no herbicide has been developed with a new mode of action over the last thirty years.

In agriculture, it is easy to see how this situation could arise. When you spray a crop, not every part of every plant gets the same amount of spray. Some of what you don’t want will survive in places where the dose was less than enough. From the farmer’s point of view, this does not matter because enough of the pests have been dealt with that his return is not hurt by the few that survive. However, the fact that some always survive is just what evolution needs to develop life forms capable of resisting the chemicals.

So, what to do? Obviously, more effort is required, but here we meet some problems that might be intractable. Major companies have to invest large amounts of money to provide a possible solution, and they will only do so when there are likely to be guaranteed very large sales. However, to defeat resistance, it is most desirable to pulse agents, thus using agent A one year, agent B the next, and no repeat for a number of years. That maximises the chance of avoiding the generation of further resistance, but what company wants to participate in the sort of sales future? We could try natural procedures and live with the fact that yields are lower, but that implies we really do not want to eat that much more, which in turn suggests population growth needs to be curbed. Unfortunately, there are no easy answers.

Agricultural Fix for Climate Change?

One of the sadder aspects of our problem with climate change is that the politicians simply do not appreciate the magnitude of the problem, which is illustrated by a briefing in the journal Nature (554, 404). It is all very well to say that emissions must be curbed, and fast, but there is a further problem. What is there is still there. The Intergovernmental Panel on Climate Change has argued that carbon emissions must peak in the next couple of decades, and then fall steeply if we want to avoid a 2 Centigrade degree rise in average temperatures. So how do we get a steep decline?

The 2015 Paris agreement settled on negative emissions. That sounds good, until you start putting numbers on what has to be done. Consider the simple approach of putting silicates onto the land, where they will be weathered to produce silica and calcium/magnesium/iron bicarbonate or carbonate.

In an experiment (Beerling et al. 2018. Nature Plants: 4: 138 – 147) applied 3.5 t/ha of wollastonite powder (calcium silicate) to some New Hampshire land, which led to a 50% increase in the delivery of weathered calcium and silica to a stream. This was accompanied by a decrease in soil acidity and a decreased release of soil aluminium. So, carbon dioxide was taken from the atmosphere while improving the soil quality. Global cropland totals 12 million square km and additionally 1 – 10 million square km of marginal land is available.

Wollastonite is not the most readily available rock, but there is unlimited basalt. There are massive amounts of olivine, and this is potentially able to capture 0.8 – 0.9 t CO2 per tonne of applied rock, but olivines also tend to have higher levels of nickel and chromium. The authors suggest continental flood basalts, which have lower amounts of nickel and chromium and higher amounts of phosphorus, but now the carbon capture potential is about 0.3 t CO2 per tonne of applied rock. This suggests that applying 10 – 50 t /ha/y of rock to an area of farmland about the size of Texas could sequester 0.2 – 1.1 billion tonne (Gt) of CO2. That is a significant reduction, but of course about 1/3 of that would currently be emitted in the grinding/transportation. Suppose we wanted to put it on all agricultural land? There is a hundred hectares to a square kilometre, so in the worst case we would need to grind and apply 60 Gt of basalt per year.

The problem could be lessened if the 7 – 17 Gt of silicate waste were used. For example, it is estimated that quarrying for construction generates an estimated 3 Gt of “fines” that are too small to be used. There is about 1.4 – 5.9 Gt of construction/demolition waste dumped each year. Cement in particular is particularly suitable. Up to half a Gt of steel slag is produced each year, and this contains weatherable elements plus some fertiliser, such as phosphate. Besides these wastes, in some places there are historically accumulated dumps of material, although these materials are probably already sequestering CO2, so perhaps they should not be counted

A further benefit from this is that the silica will replenish eroded soil and aid replacement of further soil organic carbon, as the world’s cropland soil is eroding far faster than it can be replaced (about 5 t/ha/y). Such weathered material provides silicic acid for plants, which strengthens stems, and it is suggested that this might reduce the effect of pests.

To summarise, here is a method that could in theory take CO2 from the air, but think of the problems. Let us assume the most encouraging figures. Humanity currently burns about 9 Gt of carbon a year. To absorb all of that, we would have to apply 109 Gt of powdered basalt a year, and burn no carbon while we are doing it. That is 109 billion tonne of basalt, which is not a soft rock, and do that while running the risk of some serious adverse environmental issues, and try to avoid having a lot of silicosis amongst the workers. All of this is not going to be easy. Worse, as far as CO2 levels are concerned, that is merely standing still.

There is one other related option. The rock peridotite is a mantle rock, but occasionally there are large surface deposits. It is a relatively soft rock on the surface, and it is one of the faster rocks for sequestering carbon dioxide. For that reason, it tends to be rather rare because when it does get to the surface, it weathers and erodes relatively quickly under the effect of water and carbon dioxide. However, one proposal is to drill into a deposit and fracture hydraulically, and force CO2 in, where it will form dolomite. The problem here tends to be with location. One of the bigger masses of peridotite is in the Oman desert, which is not rich in water, nor in local CO2.

Thinking about this shows some of the problems of modifying a planet. People seem to think changing Mars into somewhere pleasant to live in would be easy. In my novel Red Gold I offered the suggestion that to do that you would need a dead minimum of at least a petatonne (a million billion tonne) of nitrogen to have enough pressure to have a tolerable outside air pressure that would last through the winter. Where do you find that?

Another small commercial break: from May 3 – 10, for those in the US and the UK, A Face on Cydonia will be at 99c or 99p respectively. For everyone else, Amazon requires it to be $2.99 – still a bargain!

How Earth Cools

As you may have seen at the end of my last post, I received an objection to the existence of a greenhouse effect on the grounds that it violated the thermodynamics of heat transfer, and if you read what it says it is essentially focused on heat conduction. The reason I am bothering with this post is that it is an opportunity to consider how theories and explanations should be formed. We start by noting that mathematics does not determine what happens; it calculates what happens provided the background premises are correct.

The objection mentioned convection as a complicating feature. Actually, the transfer of heat in the lower atmosphere is largely dependent on the evaporation and condensation of water, and wind transferring the heat from one place to another, and it is these, and ocean currents, that are the problems for the ice caps. Further, as I shall show, heat conduction cannot be relevant to the major cooling of the upper atmosphere. But first, let me show you how complicated heat conduction is. The correct equation for one-dimensional heat conduction is represented by a partial differential equation of the Laplace type, (which I would quote if I knew how to get such an equation into this limited htm formatting) and the simplest form only works as written when the medium is homogenous. Since the atmosphere thins out with height, this clearly needs modification, and for those who know anything about partial differential equations, they become a nightmare once the system becomes anything but absolutely simple. Such equations also apply to convection and evaporative transfer, once corrected for the nightmare of non-homogeneity and motion in three dimensions. Good luck with that!

This form of heat transfer is irrelevant to the so-called greenhouse effect. To show why, I start by considering what heat is, and that is random kinetic energy. The molecules are bouncing around, colliding with each other, and the collisions are elastic, which means energy is conserved, as is momentum. Most of the collisions are glancing, and that means from momentum conservation that we get a range of velocities distributed about an “average”. Heat is transferred because fast moving molecules collide with slower ones, and speed them up. The objection noted heat does not flow from cold to hot spontaneously. That is true because momentum is conserved in collisions. A molecule does not speed up when hit by a slower molecule. That is why that equation has heat going only in one way.

Now, suppose with this mechanism, we get to the top of the atmosphere. What happens then? No more heat can be transferred because there are no molecules to collide with in space. If heat pours in, and nothing goes out, eventually we become infinitely hot. Obviously that does not happen, and the reason becomes obvious when we ask how the heat gets in in the first place. The heat from the sun comes from the effects of solar radiation. Something like 1.36 kW/m^2 comes in on a surface in space at right angles to the line from the sun, but the average is much less on the surface of earth as the angle is at best normal only at noon, and if the sun is overhead. About a quarter of that is directly reflected to space, and that may increase if the cloud cover increases. The important point here is that light is not heat. When it is absorbed, it will direct an electronic transition, but that energy will eventually decay into heat. Initially, however, the material goes to an excited state, but its temperature remains constant, because the energy has not been randomised. Now we see that if energy comes in as radiation, it follows to get an equilibrium, equivalent energy must go out, and as radiation, not heat, because that is the only way it can get out in a vacuum.

The ground continuously sends radiation (mainly infrared) upwards and the intensity is proportional to the fourth power of the temperature. The average temperature is thus determined through radiant energy in equals radiant out. The radiance for a given material, which is described as a grey body radiator, is also dependent on its nature. The radiation occurs because any change of dipole moment leads to electromagnetic radiation, but the dipoles must change between quantised energy states. What that means is they come from motion that can be described in one way or another as a wave, and the waves change to longer wavelengths when they radiate. The reason the waves representing ground states switch to shorter wavelengths is that the heat energy from collisions can excite them, similar in a way to when you pluck a guitar string. Thus the body cools by heat exciting some vibratory states, which collapse by radiation leaving them. (This is similar to the guitar string losing energy by emitting sound, except that the guitar string emits continuous decaying sound; the quantised state lets it go all at once as one photon.)

Such changes are reversible; if the wave has collapsed to a longer wavelength when energy is radiated away, then if a photon of the same frequency is returned, that excites the state. That slows cooling because the next photon emitted from the ground did not need heat to excite it, and hence that same heat remains. The reason there is back radiation is that certain frequencies of infrared radiation leaving the ground get absorbed by molecules in the atmosphere when their molecular vibrational or rotational excited states have a different electric moment from the ground state. Carbon dioxide has two such vibrational states that absorb mildly, and one that does not. Water is a much stronger absorber, and methane has more states available to it. Agriculture offers N2O, which is bad because it is harder to remove than carbon dioxide, and the worst are chlorocarbons and fluorocarbons, because the vibrations have stronger dipole moment changes. Each of these different materials has vibrations at different frequencies, which make them even more problematical as radiation at more frequencies are slowed in their escape to space. The excited states decay and emit photons in random directions, hence only about half of that continues on it way to space, the rest returning to the ground. Of that that goes upwards, it will be absorbed by more molecules, and the same will happen, and of course some coming back from up there with be absorbed at a lower level and half of that will go back up. In detail, there is some rather difficult calculus, but the effect could be described as a field of oscillators.

So the take-away message is the physics are well understood, the effect of the greenhouse gases is it slows the cooling process, so the ground stays warmer than it would if they were not there. Now the good thing about a theory is that it should predict things. Here we can make a prediction. In winter, in the absence of wind, the night should be warmer if there is cloud cover, because water is a strong greenhouse material. Go outside one evening and see.