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.

Energy from the Sea. A Difficult Environmental Choice.

If you have many problems and you are forced to do something, it makes sense to choose any option that solves more than one problem. So now, thanks to a certain virus, changes to our economic system will be forced on us, so why not do something about carbon emissions at the same time? The enthusiast will tell us science offers us a number of options, so let’s get on with it. The enthusiast trots out what supports his view, but what about what he does not say? Look at the following.

An assessment from the US Energy Information Administration states the world will use 21,000 TWh of electricity in 2020. According to the International Energy Agency, the waves in the world’s oceans store about 80,000 TWh. Of course much of that is, well, out at sea, but they estimate about 4,000 TWh could be harvested. While that is less than 20% of what is needed, it is still a huge amount. They are a little coy on how this could be done, though. Wave power depends on wave height (the amplitude of the wave) and how fast the waves are moving (the phase velocity). One point is that waves usually move to the coast, and there are many parts of the world where there are usually waves of reasonable amplitude so an energy source is there.

Ocean currents also have power, and the oceans are really one giant heat engine. One estimate claimed that 0.1% of the power of the Gulf Stream running along the East Coast of the US would be equivalent to 150 nuclear power stations. Yes, but the obvious problem is the cross-sectional area of the Gulf Stream. Enormous amounts of energy may be present, but the water is moving fairly slowly, so a huge area has to be trapped to get that energy. 

It is simpler to extract energy from tides, if you can find appropriate places. If a partial dam can be put across a narrow river mouth that has broad low-lying ground behind it, quite significant flows can be generated for most of the day. Further, unlike solar and wind power, tides are very predictable. Tides vary in amplitude, with a record apparently going to the Bay of Fundy in Canada: 15 meters in height.

So why don’t we use these forms of energy? Waves and tides are guaranteed renewable and we do not have to do anything to generate them. A surprising fraction of the population lives close to the sea, so transmission costs for them would be straightforward. Similarly, tidal power works well even at low water speeds because compared with wind, water is much denser, and the equipment lasts longer. La Rance, in France, has been operational since 1966. They also do not take up valuable agricultural land. On the other hand, they disturb sea life. A number of fish appear to use the Earth’s magnetic field to navigate and nobody knows if EMF emissions have an effect on marine life. Turbine blades most certainly will. They also tend to be needed near cities, which means they disturb fishing boats and commercial ships.

There are basically two problems. One is engineering. The sea is not a very forgiving place, and when storms come, the water has serious power. The history of wave power is littered with washed up structures, smashed to pieces in storms. Apparently an underwater turbine was put in the Bay of Fundy, but it lasted less than a month. There is a second technical problem: how to make electricity? The usual way would be to move wire through a magnetic field, which is the usual form of a generator/dynamo. The issue here is salt water must be kept completely out, which is less than easy. Since waves go up and down, an alternative is to have some sort of float that mechanically transmits the energy to a generator on shore. That can be made to work on a small scale, but it is less desirable on a larger scale.The second problem is financial. Since history is littered with failed attempts, investors get wary, and perhaps rightly so. There may be huge energies present, but they are dispersed over huge areas, which means power densities are low, and the economics usually become unattractive. Further, while the environmentalists plead for something like this, inevitably it will be, “Somewhere else, please. Not in my line of sight.” So, my guess is this is not a practical solution now or anytime in the reasonable future other than for small specialized efforts.

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?

Aircraft and Carbon Dioxide Emissions

Climate change requires significant changes to our lifestyle, and one of the more tricky problems to solve is air travel. Interestingly, you will find many environmentalists always telling everyone to cycle, but then spend tens of thousands of air miles going to environmental conferences. So, what can we do?

One solution is to reduce air travel. And there is no need in principle to adopt Greta Thunberg’s solution of sailing over the Atlantic. With a bit of investment, high speed rail can get you between the centres of reasonably close cities faster than aircraft, when you include the time taken to get to and from airports, and time wasted at airports. We can also reduce travel, but only so far. At first sight, things like conferences can be held online, but there are two difficulties: time-zone differences encourage doing something else, and second, the major benefit from conferences is not listening to set talks, but rather meeting people outside the formal program. For business, facing each other is a far improved way of negotiating because the real signals are unspoken. 

Some airlines are trying to improve their environmental credentials by planting trees to compensate for the carbon dioxide they emit. That is very noble of them, but apart from the fact it is their money doing it (and often it is not – it is the passengers who feel conscious stricken to donate more money for planting) it is something that should be done anyway. 

There has been talk of building electric aircraft. My personal opinion is this is not the solution. The problem is in terms of unit weight, jet fuel contains at least thirty times the energy density of the best batteries available. Even worse, for jet fuel, as you go further, you get lighter, but not with batteries. You could make a large aircraft fly, say, 1,000 to 2,000 km, as long as you did not want to carry much in the way of passengers or cargo. With thirty times the fuel weight for a long distance flight your aircraft would never get off the ground. However, the Israeli firm Eviation has developed a small electric aircraft for a load of 9 persons (plus two crew) powered by 920 kWh batteries with operating costs estimated at $200/hr. The range is about 540 nautical miles, or about 1,000 km. That could work for small regional flights, and it will be available soon.

Another option to be offered by Airbus is the E-Fan-X project. They will take a BAe 146 craft, which usually carries about 100 passengers, and which usually is powered by four Honeywell turbofan engines, and replace one of the inner ones with an electric-driven 2 MW propulsion fan motor. The idea is the takeoff, where the most power is required will use the normal jets, but the electric motor can manage the cruise. 

An alternative is to reduce fuel consumption. One possibility is the so-called blended wing, which is being looked at by NASA. This works; an example is the B2 bomber, however while it reduces fuel consumption by 20% it is most unlikely to come into commercial use any time soon. One reason is that there is probably no commercial airport that could accommodate the radically different design. It would also have to have extensive examination because so far the design has only had military applications, in which only very specific loads are involved. In principle, this, and other designs can reduce kerosene usage, but only by so much. Maybe overall, 25% is achievable, which does not solve anything.

Uranium 235 has an energy density that leaves kerosene for cold, but which airport wants it, and would you board it anyway? It could presumably be made to work, but I can’t see it happening anytime soon because nobody will take the associated political risk.

That leaves hydrogen. 1 kg of liquid hydrogen can provide the same energy as 3 kg of kerosene, so weight is not the problem, but keeping it cold enough and maintaining pressure will add weight. It cannot be stored in the aircraft wings because of the volatility. To keep it cold it is desirable to have minimum surface area of the tank. However, it is reasonably clean burning, giving only water and some nitrogen oxides. For a Boeing 747-400 aircraft, the full fuel load is 90 tonne less, but because the tanks have to be in the fuselage, they occupy about 30% of the passenger space.

That may work for the future, but the only real way to power current aircraft is to burn hydrocarbon fuel. More on that next week.

Molten Salt Nuclear Reactors

In the previous post, I outlined two reasons why nuclear power is overlooked, if not shunned, despite the fact it will clearly reduce greenhouse gas emissions. I discussed wastes as a problem, and while they are a problem, as I tried to show they are in principle reasonably easily dealt with. There is a need for more work and there are difficulties, but there is no reason this problem cannot be overcome. The other reason is the danger of the Chernobyl/Fukushima type explosion. In the case of Chernobyl, it needed a frightening number of totally stupid decisions to be made, and you might expect that since it was a training exercise there would be people there who knew what they were doing to supervise. But no, and worse, the operating instructions were unintelligible, having been amended with strike-outs and hand-written “corrections” that nobody could understand. You might have thought the supervisor would check to see everything was available and correct before starting, but as I noted, there has never been a shortage of stupidity.

The nuclear reaction, which generates the heat, is initiated by a fissile nucleus absorbing a neutron and splitting, and then keeping going by providing more neutrons. These neutrons either split further fissile nuclei, such as 235U, or they get absorbed by something else, such as 238U, which converts that nucleus to something else, in this case eventually 239Pu. The splitting of nuclei produces the heat, and to run at constant temperature, it is necessary to have a means of removing that amount of heat continuously. The rate of neutron absorption is determined by the “concentration” of fissile material and the amount of neutrons absorbed by something else, such as water, graphite and a number of other materials. The disaster happens when the reaction goes too quickly, and there is too much heat generated for the cooling medium. The metal melts and drips to the bottom of the reactor, where it flows together to form a large blob that is out of the cooling circuit. As the amount builds up it gets hotter and hotter, and we have a disaster.

The idea of the molten salt reactor is there are no metal rods. The material can be put in as a salt in solution, so the concentration automatically determines the operating temperature. The reactor can be moderated with graphite, beryllium oxide, or a number of others, or it can be run unmoderated. Temperatures can get up to 1400 degrees C, which, from basic thermodynamics, gives exceptional power efficiency, and finally, reactors can be relatively small. The initial design was apparently for aircraft propulsion, and you guessed it: bombers. The salts are usually fluorides because low-valence fluorides boil at very high temperatures, they are poor neutron absorbers, and their chemical bonds are exceptionally strong, which limits corrosion, and they are exceptionally inert chemically. In one sense they are extremely safe, although since beryllium fluoride is often used, its extreme toxicity requires careful handling. But the big main advantage of this sort of reactor, besides avoiding the meltdown, is it burns actinides and so if it makes plutonium, that is added to the fuel. More energy! It also burns some of the fission wastes, and such burning of wastes also releases energy. It can be powered by thorium (with some uranium to get the starting neutrons) which does not make anything suitable for making bombs. Further, the fission products in the thorium cycle have far shorter half-lives. Research on this started in the 1960s and essentially stopped. Guess why! There are other fourth generation reactors being designed, and some nuclear engineers may well disagree with my preference, but it is imperative, in my opinion, that we adopt some. We badly need some means of generating large amounts of electricity without burning fossil fuels. Whatever we decide to do, while the physics is well understood, the engineering may not be, and this must be solved if we are to avoid a planet-wide overheating. The politicians have to ensure this job gets done.

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?

Transport System Fuel. Some passing Comments

In the previous series of posts, I have discussed the question of how we should power our transport systems that currently rely on fossil fuels, and since this will be a brief post, because I have been at a conference for most of this week, I thought it would be useful to have a summary. There are two basic objectives: ensure that there are economic transport options, and reduce the damage we have caused to the environment. The latter one is important in that we must not simply move the problem.

At this stage we can envisage two types of power: heat/combustion and electrical. The combustion source of power is what we have developed from oil, and many of the motors, especially the spark ignition motors, have been designed to optimise the amount of the oil that can be so used. The compression of most spark ignition engines is considerably lower than it could be if the octane rating was higher. These motors will be with us for some time; a car bought now will probably still be on the road in twenty years so what do we do? We shall probably continue with oil, but biofuels do offer an alternative. Some people say biofuels themselves have a net CO2 output in their manufacture. Maybe, but it is not necessary; the main reason would be that the emphasis is put onto producing the appropriate liquids because they are worth more than process heat. Process heating can be provided from a number of other sources. The advantages of biofuels are they power existing vehicles, they can be CO2 neutral, or fairly close to it, we can design the system so it produces aircraft fuel and there is really no alternative for air transport, and there are no recycling problems following usage. The major disadvantages are that the necessary technology has not really been scaled up so a lot of work is required, it will always be more expensive than oil until oil supplies run down so there is a poor economic reason to do this unless missions are taxed, and the use of the land for biofuels will put pressure on food production. The answers are straightforward: do the development work, use the tax system to change the economic bias, and use biomass from the oceans.

There are alternatives, mainly gases, but again, most of them involve carbon. These could be made by reducing CO2, presumably through using photolysis of water (thus a sort of synthetic photosynthesis) or through electricity and to get the scale we really need a very significant source of electricity. Nuclear power, or better still, fusion energy would work, but nuclear power has a relative disappointing reputation, and fusion power is still a dream. Hydrazine would make a truly interesting fuel, although its toxicity would not endear it to many. Hydrogen can work well for buses, etc, that have direct city routes.

Electricity can be delivered by direct lines (the preferred option for trains, trams, etc.), but otherwise it must be by batteries or fuel cells. The two are conceptually very similar. Both depend on a chemical reaction that can be very loosely described as “burning” something but generating electricity instead of heat. In the fuel cell, the material being “burnt” is added from somewhere else, and the oxidising agent, which may be air, must also be added. In the battery, nothing is added, and when what is there is used, it is regenerated by charging.

Something like lithium is almost certainly restricted to batteries because it is highly reactive. Lithium fires are very difficult to put out. The lithium ion battery is the only one that has been developed to a reasonable level, and part of the reason for that is that the original market was for mobile phones and laptops. There are potential shortages of materials for lithium ion batteries, but they would never cut in for those original uses. However, as shown in my previous post, recycling of lithium ion batteries will be very difficult to solve the problem for motor vehicle batteries. One alternative for batteries is sodium, obtainable from salt, and no chance of shortage.

The fuel cell offers some different options. A lot has been made of hydrogen as the fuel of the future, and some buses use it in California. It can be used in a combustion motor, but the efficiencies are much better for fuel cells. The technology is here, and hydrogen-powered fuel cell cars can be purchased, and these can manage 500 km on  single charge, and can totally refuel in about 5 minutes. The problem again is, hydrogen refuelling is harder to find. Methanol would be easier to distribute, but methanol fuel cells as of yet cannot sustain a high power take-off. Ammonia fuel cells are claimed to work almost as well as hydrogen and would be the cheapest to operate. Another possibility I advocated in one of my SF novels is the aluminium/chlorine cell, as aluminium is cheap, although chlorine is a little more dangerous.

My conclusions:

(a)  We need a lot more research because most options are not sufficiently well developed,

(b)  None will out-compete oil for price. For domestic transport, taxes on oil are already there, so the competitors need this tax to not apply

(c)  We need biofuels, if for no other reason that maintaining existing vehicles and air transport

(d)  Such biofuel must come at least partly from the ocean,

(e)  We need an alternative to the lithium ion battery,

(f)  We badly need more research on different fuel cells, especially something like the ammonia cell.

Yes, I gree that is a little superficial, but I have been at a conference, and gave two presentations. I need to come back down a little 🙂

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!

Protesting on Climate Change

It is interesting these days to see the level of protest; so many people want to protest against doing something. In many cases, that is fair as what they are protesting about should not happen, but then the problem comes, what happens when they get the rhythm, and what sort of protests get results as opposed to the protestors just making a nuisance of themselves? Recently, there were widespread protests here against the inaction of governments on the issue of climate change and that is a fair enough target of protest but how should they go about it? Blocking major roads to prevent traffic from going home after work simply leads to the production of more greenhouse gas. Then there were people here who used superglue to attach themselves to windows. My view on that is they should have been identified so that any bills for damages could be sent, then they be left there. Since they glued their hands, they would need friends to even feed them and a couple of cold fronts were coming.

What I find interesting is that one of the proposed ways of attacking climate change is to plant trees and they even protest about that. They argue the trees grow, then get cut down and the CO2 is returned to the atmosphere so we are no further ahead. In my opinion, that is wrong. First, we buy time. The trees can stand for a reasonable length of time, and further, when we cut them down, we can use the wood to build houses, etc. Leaves fall and return some carbon to the soil. And, of course, when we cut them down, we can replant. But most important, from my point of view, is we can do this now. There is no king hit that will deal with climate change so we shall have to do a very large number of things and unfortunately we don’t actually know how to do many of them beneficially. There is nothing like getting started on what you can do, and that you know what the consequences of doing it are.

Another objection noted in our local paper was that, wait for it, had we started thirty years ago when we knew about the problem this might have worked, but now we need more trees than we can reasonably plant quickly. Well, maybe. It does take time to get the necessary seedlings. The argument seems to be, we can’t solve the entire crisis this way, so why bother? Yes, I know there is no king hit, but if you are going to solve this crisis with a number of different approaches, getting started now is better than not doing anything. As the callers for doing nothing argue, we only have the problem because we did nothing some time ago. Yes, it is true we have wasted a lot of time, but why will wasting more now be beneficial?

Another argument seems to be, the land is too valuable for food production to waste on planting trees. Well, if I look out the window from where I am writing this, I see a range of somewhat tortured hills that stand between 300 to 700 meters above the valley floor, and these hills proceed as hills and steep valleys for a considerable distance. They are largely devoid of big trees, despite the fact that this whole area was initially heavily forested. When the settlers came, the valley was cleared of forest for farmland (farming has now long gone, having been replaced by urban development) then the hillsides were denuded of forest for timber. Now there is light scrub in places, but the big trees are long gone, and this is typical of a lot of land here. Planting trees would stabilise a lot of such steep hillsides, which are often prone to severe erosion, especially with heavy rain, which is expected to become more common over time due to climate change, at least here. For such country where harvesting trees becomes unlikely, by planting a judicious mix of trees such a forest could be self-sustaining so once established and it would store carbon indefinitely.

There are additional benefits of forests. An article in he recent Physics World mentioned that forests decrease the effect of storms, the reason being that the rough land surface offers a frictional restraint on wind speed. The forest has to be reasonably large, and of course the beneficial effects tend to apply to places distant from the coast. The forests also offer a benefit to rainfall through evapotranspiration and it is notable that many areas that are now facing desertification in Africa once had reasonable rainfall and extensive forests. It should be emphasised that forests may also reduce total rainfall by reducing the effect of heavy tropical storms, however in general these do little to provide water in a useful form as the water runs off very quickly. Forests are also beneficial in that they hold up water from heavy rains and allow it to be absorbed by the soil, and hence be available later, and of course, reduce heavy erosion. Also, in areas prone to severe flooding, and we have seen many examples of flooded urban areas on television recently, by holding up the water and thus spreading its movement over more time, the effects of such floods are mitigated. To my mind, anything that achieves more than one benefit is far more worthwhile to pursue.

As for the argument that when the trees mature, they will be harvested and eventually the carbon will return to the atmosphere, I have two responses. First, at least some of it can be stored in buildings, where it will remain for quite some time. Second, you could burn it for fuel or convert it to biofuel, in which case the carbon will return quickly, several decades in the future, but it displaces fossil carbon you would have otherwise converted to CO2, so you are still ahead. Finally, you have bought time to develop new means of solving this problem. And, at the same time, you do generate a future resource, in some cases from land that is otherwise producing nothing except erosion. From my point of view, it probably does not matter whether we act because I shall be dead by the time the really worst of the consequences arrive. However, I would like my grandchildren’s children to have a reasonable chance at life, and that means that we must stop protesting against change because our society cannot continue this way. Change will come; the issue is, what sort of change? Let us control it and make it beneficial.

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.