Carbon dioxide: the good, the bad, and the future

Carbon dioxide is a small molecule with the structure O=C=O

Carbon dioxide has been in and out of the news this summer for one reason or another, but why? Is this stuff helpful, or heinous?

It’s certainly a significant part of our history. Let’s take that history to its literal limits and start at the very beginning. To quote the great Terry Pratchett: “In the beginning, there was nothing, which exploded.”

(Probably.) This happened around 13.8 billion years ago. Afterwards, stuff flew around for a while (forgive me, cosmologists). Then, about 4.5 billion years ago, the Earth formed out of debris that had collected around our Sun. Temperatures on this early Earth were extremely hot, there was a lot of volcanic activity, and there might have been some liquid water. The atmosphere was mostly hydrogen and helium.

The early Earth was bashed about by other space stuff, and one big collision almost certainly resulted in the formation of the Moon. A lot of other debris vaporised on impact releasing gases, and substances trapped within the Earth started to escape from its crust. The result was Earth’s so-called second atmosphere.

ttps://nai.nasa.gov/articles/2018/6/5/habitability-of-the-young-earth-could-boost-the-chances-of-life-elsewhere/” target=”_blank” rel=”noopener”> An artist’s concept of the early Earth. Image credit: NASA. (Click image for more.)

[/caption]This is where carbon dioxide enters stage left… er… stage under? Anyway, it was there, right at this early point, along with water vapor, nitrogen, and smaller amounts of other gases. (Note, no oxygen, that is, O2. Significant amounts of that didn’t turn up for another 1.7 billion years, or 2.8 billion years ago.) In fact, carbon dioxide wasn’t just there, it made up most of Earth’s atmosphere, probably not so different from Mars’s atmosphere today.

The point being that carbon dioxide is not a new phenomenon. It is, in fact, the very definition of an old phenomenon. It’s been around, well, pretty much forever. And so has the greenhouse effect. The early Earth was hot. Really hot. Possibly 200 oC or so, because these atmospheric gases trapped the Sun’s heat. Over time, lots and lots of time, the carbon dioxide levels reduced as it became trapped in carbonate rocks, dissolved in the oceans and was utilised by lifeforms for photosynthesis.

Fast-forward a few billion years to the beginning of the twentieth century and atmospheric carbon dioxide levels were about 300 ppm (0.03%), tiny compared to oxygen (about 20%) and nitrogen (about 78%).

Chemists and carbon dioxide

Jan Baptist van Helmontge-2795″ src=”https://thechronicleflask.files.wordpress.com/2018/08/jan_baptista_van_helmont.jpg?w=300″ alt=”” width=”200″ height=”181″ /> Flemish chemist discovered that if he burned charcoal in a closed vessel, the mass of the resulting ash was much less than that of the original charcoal.

Let’s[/caption]Let’s pause there for a moment and have a little look at some human endeavours. In about 1640 Flemish chemist Jan Baptist van Helmont discovered that if he burned charcoal in a closed vessel, the mass of the resulting ash was much less than that of the original charcoal. He had no way of knowing, then, that he had formed and collected carbon dioxide gas, but he speculated that some of the charcoal had been transmuted into spiritus sylvestris, or “wild spirit”.

In 1754 Scottish chemist Joseph Black noticed that heating calcium carbonate, aka limestone, produced a gas which was heavier than air and which could “not sustain fire or animal life”. He called it “fixed air”, and he’s often credited with carbon dioxide’s discovery, although arguably van Helmont got there first. Black was also the first person to come up with the “limewater test“, where carbon dioxide is bubbled through a solution of calcium hydroxide. He used the test to demonstrate that carbon dioxide was produced by respiration, an experiment still carried out in schools more than 250 years later to show that the air we breathe out contains more carbon dioxide than the air we breathe in.

In 1772 that most famous of English chemists, Joseph Priestley, experimented with dripping sulfuric acid (or vitriolic acid, as he knew it) on chalk to produce a gas which could be dissolved in water. Priestley is often credited with the invention of soda water as a result (more on this in a bit), although physician Dr William Brownrigg probably discovered carbonated water earlier – but he never published his work.

In the late 1700s carbon dioxide became more widely known as “carbonic acid gas”, as seen in this article dated 1853. In 1823 Humphry Davy and Michael Faraday manged to produce liquified carbon dioxide at high pressures. Adrien-Jean-Pierre Thilorier was the first to describe solid carbon dioxide, in 1835. The name carbon dioxide was first used around 1869, when the term “dioxide” came into use.

com/P/Priestley_Joseph/PriestleyJoseph-MakingCarbonatedWater1772.htm” target=”_blank” rel=”noopener”> A diagram from Priestly’s letter: “Impregnating Water with Fixed Air”. Printed for J. Johnson, No. 72, in St. Pauls Church-Yard, 1772. (Click image for paper)

Back to Priestle

[/caption]Back to Priestley for a moment. In the late 1800s, a glass of volcanic spring water was a common treatment for digestive problems and general ailments. But what if you didn’t happen to live near a volcanic spring? Joseph Black, you’ll remember, had established that CO2 was produced by living organisms, so it occurred to Priestly that perhaps he could hang a vessel of water over a fermentation vat at a brewery and collect the gas that way.

But it wasn’t very efficient. As Priestly himself said, “the surface of the fixed air is exposed to the common air, and is considerably mixed with it, [and] water will not imbibe so much of it by the process above described.”

It was then that he tried his experiment with vitriolic acid, which allowed for much greater control over the carbonation process. Priestly proposed that the resulting “water impregnated with fixed air” might have a number of medical applications. In particular, perhaps because the water had an acidic taste in a similar way that lemon-infused water does, he thought it might be an effective treatment for scurvy. Legend has it that he gave the method to Captain Cook for his second voyage to the Pacific for this reason. It wouldn’t have helped of course, but it does mean that Cook and his crew were some of the first people to produce carbonated water for the express purpose of drinking a fizzy drink.

Refreshing fizz

You will have noticed that, despite all his work, there is no fizzy drink brand named Priestly (at least, not that I know of).

Joseph Priestley is credited with developing the first method for making carbonated water.

But there is one called Schweppes. That’s because a German watchmaker named Johann Jacob Schweppe spotted Priestley’s paper and worked out a simpler, more efficient process, using sodium bicarbonate and tartaric acid. He went on to found the Schweppes Company in Geneva in 1783.

Today, carbonated drinks are made a little differently. You may have heard about carbon dioxide shortages this summer in the U.K. These arose because these days carbon dioxide is actually collected as a by-product of other processes. In fact, after several bits of quite simple chemistry that add up to a really elegant sequence.

From fertiliser to fizzy drinks

It all begins, or more accurately ends, with ammonia fertiliser. As any GCSE science student who’s been even half paying attention can tell you, ammonia is made by reacting hydrogen with nitrogen during the Haber process. Nitrogen is easy to get hold of – as I’ve already said it makes up nearly 80% of our atmosphere – but hydrogen has to be made from hydrocarbons. Usually natural gas, or methane.

This involves another well-known process, called steam reforming, in which steam is reacted with methane at high temperatures in the presence of a nickel catalyst. This produces carbon monoxide, a highly toxic gas. But no problem! React that carbon monoxide with more water in the presence of a slightly different catalyst and you get even more hydrogen. And some carbon dioxide.

Fear not, nothing is wasted here! The CO2 is captured and liquified for all sorts of food-related and industrial uses, not least of which is fizzy drinks. This works well for all concerned because steam reforming produces large amounts of pure carbon dioxide. If you’re going to add it to food and drinks after all, you wouldn’t want a product contaminated with other gases.

Carbon dioxide is a by-product of fertiliser manufacture.

We ended up with a problem this summer in the U.K. because ammonia production plants operate on a schedule which is linked to the planting season. Farmers don’t usually apply fertiliser in the summer – when they’re either harvesting or about to harvest crops – so many ammonia plants shut down for maintenance in April, May, and June. This naturally leads to reduction in the amount of available carbon dioxide, but it’s not normally a problem because the downtime is relatively short and enough is produced the rest of year to keep manufacturers supplied.

This year, though, natural-gas prices were higher, while the price of ammonia stayed roughly the same. This meant that ammonia plants were in no great hurry to reopen, and that meant many didn’t start supplying carbon dioxide in July, just when a huge heatwave hit the UK, coinciding with the World Cup football (which tends to generate a big demand for fizzy pop, for some reason).

Which brings us back to our atmosphere…

Carbon dioxide calamity?

Isn’t there, you may be thinking, too much carbon dioxide in our atmosphere? In fact, that heatwave you just mentioned, wasn’t that a global warming thing?  Can’t we just… extract carbon dioxide from our air and solve everyone’s problems? Well, yes and no. Remember earlier when I said that at the beginning of the twentieth century and atmospheric carbon dioxide levels were about 300 ppm (0.03%)?

Over the last hundred years atmospheric carbon dioxide levels have increased from 0.03% to 0.04%

Today, a little over 100 years later, levels are about 0.04%. This is a significant increase in a relatively short period of time, but it’s still only a tiny fraction of our atmosphere (an important tiny fraction nonetheless – we’ll get to that in a minute).

It is possible to distill gases from our air by cooling air down until it liquefies and then separating the different components by their boiling points. For example Nitrogen, N2, boils at a chilly -196 oC whereas oxygen, O2, boils at a mere 183 oC.

But there’s a problem: CO2 doesn’t have a liquid state at standard pressures. It forms a solid, which sublimes directly into a gas. For this reason carbon dioxide is usually removed from cryogenic distillation mixtures, because it would freeze solid and plug up the equipment. There are other ways to extract carbon dioxide from air but although they have important applications (keep reading) they’re not practical ways to produce large volumes of the gas for the food and drink industries.

Back to the environment for a moment: why is that teeny 0.04% causing us such headaches? How can a mere 400 CO2 molecules bouncing around with a million other molecules cause such huge problems?

For that, I need to take a little diversion to talk about infrared radiation, or IR.

Infrared radiation was first discovered by the astronomer William Herschel in 1800. He was trying to observe sun spots when he noticed that his red filter seemed to get particularly hot. In what I’ve always thought was a rather amazing intuitive leap, he then passed sunlight through a prism to split it, held a thermometer just beyond the red light that he could see with his eyes, and discovered that the thermometer showed a higher temperature than when placed in the visible spectrum.

He concluded that there must be an invisible form of light beyond the visible spectrum, and indeed there is: infrared light. It turns out that slightly more than half of the total energy from the Sun arrives on Earth in the form of infrared radiation.

What has this got to do with carbon dioxide? It turns out that carbon dioxide, or rather the double bonds O=C=O, absorb a lot of infrared radiation. By contrast, oxygen and nitrogen, which make up well over 90% of Earth’s atmosphere, don’t absorb infrared.

CO2 molecules also re-emit IR but, having bounced around a bit, not necessarily in the same direction and – and this is the reason that tiny amounts of carbon dioxide cause not so tiny problems – they transfer energy to other molecules in the atmosphere in the process. Think of each CO2 molecule as a drunkard stumbling through a pub, knocking over people’s pints and causing a huge bar brawl. A single disruptive individual can, indirectly, cause a lot of others to find themselves bruised and bleeding and wondering what the hell just happened.

Like carbon dioxide, water vapour also absorbs infrared, but it has a relatively short lifetime in our atmosphere.

Water vapor becomes important here too, because while O2 and N2 don’t absorb infrared, water vapour does. Water vapour has a relatively short lifetime in our atmosphere (about ten days compared to a decade for carbon dioxide) so its overall warming effect is less. Except that once carbon dioxide is thrown into the mix it transfers extra heat to the water, keeping it vapour (rather than, say, precipitating as rain) for longer and pushing up the temperature of the system even more.

Basically, carbon dioxide molecules trap heat near the planet’s surface. This is why carbon dioxide is described as a greenhouse gas and increasing levels are causing global warming. There are people who are still arguing this isn’t the case, but truly, they’ve got the wrong end of the (hockey) stick.

It’s not even a new concept. Over 100 years ago, in 1912, a short piece was published in the Rodney and Otamatea Times which said: “The furnaces of the world are now burning about 2,000,000,000 tons of coal a year. When this is burned, uniting with oxygen, it adds about  7,000,000,000 tons of carbon dioxide to the atmosphere yearly. This tends to make the air a more effective blanket for the earth and to raise its temperature.”

This summer has seen record high temperatures and some scientists have been warning of a “Hothouse Earth” scenario.

This 1912 piece suggested we might start to see effects in “centuries”. In fact, we’re seeing the results now. As I mentioned earlier, this summer has seen record high temperatures and some scientists have been warning of “Hothouse Earth” scenario, where rising temperatures cause serious disruptions to ecosystems, society, and economies. The authors stressed it’s not inevitable, but preventing it will require a collective effort. They even published a companion document which included several possible solutions which, oddly enough, garnered rather fewer column inches than the “we’re all going to die” angle.

Don’t despair, DO something…

But I’m going to mention it, because it brings us back to CO2. There’s too much of it in our atmosphere. How can we deal with that? It’s simple really: first, stop adding more, i.e. stop burning fossil fuels. We have other technologies for producing energy. The reason we’re still stuck on fossil fuels at this stage is politics and money, and even the most obese of the fat cats are starting to realise that money isn’t much use if you don’t have a habitable planet. Well, most of them. (There’s probably no hope for some people, but we can at least hope that their damage-doing days are limited.)

There are some other, perhaps less obvious, sources of carbon dioxide and other greenhouse gases that might also be reduced, such as livestock, cement for building materials and general waste.

Forrests trap carbon dioxide in land carbon sinks. More biodiverse systems generally store more carbon.

And then, we’re back to taking the CO2 out of the atmosphere. How? Halting deforestation would allow more CO2 to be trapped in so-called land carbon sinks. Likewise, good agricultural soil management helps to trap carbon underground. More biodiverse systems generally store more carbon, so if we could try to stop wiping out land and coastal systems, that would be groovy too. Finally, there’s the technological solution: carbon capture and storage, or CSS.

This, in essence, involves removing CO2 from the atmosphere and storing it in geological formations. The same thing the Earth has done for millenia, but more quickly. It can also be linked to bio-energy production in a process known as BECCS. It sounds like the perfect solution, but right now it’s energy intensive and expensive, and there are concerns that BECCS projects could end up competing with agriculture and damaging conservation efforts.

A new answer from an ancient substance?

Forming magnesite, or magnesium carbonate, may be one way to trap carbon dioxide.

Some brand new research might offer yet another solution. It’s another carbon-capture technology which involves magnesium carbonate, or magnesite (MgCO3). Magnesite forms slowly on the Earth’s surface, over hundreds of thousands of years, trapping carbon dioxide in its structure as it does.

It can easily be made quickly at high temperatures, but of course if you have to heat things up, you need energy, which might end up putting as much CO2 back in as you’re managing to take out. Recently a team of researchers at Trent University in Canada have found a way to form magnesite quickly at room temperature using polystyrene microspheres.

This isn’t something which would make much difference if, say, you covered the roof of everyone’s house with the microspheres, but it could be used in fuel-burning power generators (which could be burning renewables or even waste materials) to effectively scrub the carbon dioxide from their emissions. That technology on its own would make a huge difference.

And so here we are. Carbon dioxide is one of the oldest substances there is, as “natural” as they come. From breathing to fizzy drinks to our climate, it’s entwined in every aspect of our everyday existence. It is both friend and foe. Will we work out ways to save ourselves from too much of it in our atmosphere? Personally, I’m optimistic, so long as we support scientists and engineers rather than fight them…


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Any old ions?

The other day, thanks to an expedition to the swimming pool, I found myself drying my hair twice in one day. As I did so it occurred to me that the process was a lot faster at home with my old, battered hair dryer that it had been in the pool changing rooms.

I pondered variables (what can I say, I’m a scientist). I hadn’t washed my hair at the pool, I’d just rinsed it (hence the need to wash it again later) which meant no shampoo and, critically, no conditioner. Does conditioner’s presumably slightly hydrophobic nature help your hair to shrug off extra moisture? This didn’t seem like it ought to make that much difference. It seemed much more likely that the difference was simply due to the hair dryer itself.

hair-dryer

My battered old hair dryer.

And this got me thinking about the nature of my much-loved, rather battered, bright red hair dryer.

I’m going to ‘fess up here. I didn’t buy this hair dryer because I’d carefully researched its specifications and features and decided it was the best model for the job. No, if I’m honest I bought it because it was red and all the others were boring black and silver. Rational eh?

However, I do remember something about this particular hair dryer, and you can just about see a reference to this feature on the photo. Namely, it apparently contains an “ionic generator”. The little dial that you can see in the middle of the photo (set to orange, which if I recall correctly means, ‘maximum ions’) apparently adjusts the ion levels.

At the time I did try to find out exactly what the technology might be. I recall it was difficult – there didn’t seem to be much information out there – and since to be honest I didn’t care that much so long as it dried my hair, and it wasn’t particularly expensive (and it was red, RED!) I bought it anyway.

It only takes a quick glance at Amazon to see that the idea has not gone away. There are lots of ‘ionic’ hair dryers on the market, making claims such as, “Ionic conditioning with 90 per cent more ions“, “Heat-balancing ionic technology for condition and shine and a frizz-free finish“, “stylish dryer with ionic technology–seals in moisture to the hair cuticle for increased shine and silky, glossy hair” and the simple “4X More Ions“.

Hm.

Ok, well first of all what are ions? Whereas most people have a faint idea what atoms and molecules are, far fewer are confident to describe ions – despite the fact that they are firmly a part of the compulsory GCSE Science syllabus and were, of course, also included in  O-level Chemistry before that. Exactly why this should be is tricky to explain. Possibly it’s simply because ‘atoms’ and ‘molecules’ do occasionally crop up in everyday speech, whereas ions are that bit more obscure. Possibly it’s because children learn about atoms in the most basic terms quite early on, and come back to the idea regularly, but ions only turn up relatively briefly (unless, of course, you choose to study A-level Chemistry). There may be an element (hoho) of confusion over the fact that element 26 is called ‘iron’, which in most English accents sounds the same as ‘ion’. And just to really confound everyone, there are such things as iron ions.

But I think the most likely is that ions are a bit tricky to understand.

I’ll have a go.

Ions are charged particles.

There, that was easy, wasn’t it?

What do you mean, what does ‘charged’ mean? It means they have either a positive or negative charge.

What do you mean, ‘what does that mean’?

Oh all right. All right. Back to basics.

helium atom

A helium atom containing a tiny nucleus made up of two protons and two neutrons (red and blue), surrounded by an ‘electron cloud’. 1 fm = 0.0000000000010 millimetres.

First of all we need to understand a bit about atoms. Atoms are made up of two parts. There is the nucleus, which is made up of protons and neutrons (except for hydrogen’s nucleus, which is just a proton) and then, whizzing around that, are electrons. Electrons are quite fiddly things that behave frankly very oddly. In particular, they don’t actually drift around atoms in stately orbits as shown in most diagrams. In fact, they are sort of there and sort of not-there at the same time, and chemists talk about an ‘electron cloud’ as a result. An electron cloud need not contain lots of electrons (this depends on the size of the atom) – it just describes an area where you might find one or more electrons.

Anyway, that’s all a bit complicated and for our purposes it doesn’t really matter – all we need to know is that there’s a nucleus in the middle and electrons around it.

Electrons have a negative charge, protons have a positive charge, and neutrons have no charge. It’s quite difficult to rigorously define what I mean by ‘charge’ without getting into some tricky maths and physics. If you are ok with the idea of negative numbers (who hasn’t had an overdraft at some point or another?) then think of it like this: electrons are -1 and protons are +1 (and neutrons are 0). If you have one proton and one electron, the overall ‘balance’ is zero – their charges cancel each other out. In the case of helium, there are two protons and two electrons. This neat bit of balancing is no accident: it’s the case for all atoms. Carbon has 6 protons and 6 electrons. Oxygen has 8 protons and 8 electrons. Calcium has 20 protons and 20 electrons, and so on.

If the electrons and protons aren’t balanced for some reason (usually as a result of a chemical reaction) then the thing that you were calling an atom a moment ago stops being an atom and becomes, wait for it….

An ion!

Oxygen atoms have 8 protons and 8 electrons, but oxygen ions (properly called oxide ions) have 8 protons and 10 electrons. Which means they have a bit more minus than plus. They are, if you like, a bit overdrawn. If you add it up, you find the number works out as -2. And so we say that oxide ions have a charge of -2, and chemists (who are lazy) write this as O2-. Which is not, we must be careful here, the same thing as O2. That means two oxygen atoms joined together, to make an oxygen molecule. What do you mean it’s confusing?

One more example then. Calcium atoms have 20 protons and 20 electrons, but calcium ions have 20 protons and 18 electrons. Add that up and you get +2. We say that calcium ions have a charge of +2, and write Ca2+(and there’s no such thing as Ca2, so that’s one less thing to worry about).

Where have we got to? Ions are charged particles, and that means that they either have a positive charge or a negative charge. These charges are typically between 1 and 3, positive or negative.

mineral water label

Fizzy mineral water, chock full of lovely ions.

Ions are very important, because they form during chemical reactions and many everyday substances are made up of ions. For example table salt, sodium chloride, is made up of Cl ions and Na+ ions.

Tap water, and indeed bottled water, are full of ions. Tap water has chloride ions (chlorinated water is a jolly good thing, assuming you don’t want typhoid, and is definitely not harmful regardless of what your nearest quack might try and tell you). It might also have fluoride ions, which are also very good for your general health (again, there’s lots of nonsense spread about this). Both tap and mineral water usually contain some sodium ions and some calcium ions. The ion balance does affect the taste – the more sodium there is the more salty the water tastes, for example – but that’s about it really. The ions don’t give the water any special properties except, perhaps, the ability to conduct electricity (which pure water, as in just H2O, actually does really badly).

Having explained ions, let’s get back to hair dryers for a moment. Ionic hair dryers claim to produce streams of negatively-charged ions. They usually claim to use something like the mineral tourmaline to do this, but despite much searching I struggled to find out much about how this was supposed to work or, most crucially, what the negative ions actually are. Negative ions are not a thing in and of themselves. They must be ions formed from atoms, so which element? Or elements?

After much hunting I eventually came upon an interesting piece written by Andrew Alden, at about.com. He explains that tourmaline has an interesting trick called pyroelectricity, which means that it does become charged when heated. The ancient Greeks even knew about this: in 314 BC Theoprastus noticed that tourmaline (called lyngourion at the time) attracted sawdust and bits of straw when heated.

Ed Trollope, from Things We Don’t Know, helpfully explained this pyroelectric effect as follows: the crystal structure of tourmaline becomes polarised (in other words the charges already in the structure become unevenly distributed) if you change its temperature. This results in a voltage across the crystal, which in turn leads to a small current being generated.

But I’m still unclear what the ions, if they exist, actually are. And the problem is that if you search for this, the first umpteen links are all pure and utter nonsense. Tourmaline is a complicated mineral that contains a whole host of different metal ions as well as oxygen, OH (hydroxide) and fluorine. Does it produce oxide ions, O2-? These are very reactive and wouldn’t hang around for any useful length of time. And if they did they would surely be harmful. Presumably they would cause the production of ozone (definitely not a good thing). Are the manufacturers using the word ‘ions’ when they actually mean ‘electrons’? They are not the same thing of course, but perhaps ‘ions’ seemed like a friendlier word.

Electrons would reduce static in your hair, but then static is short-lived anyway. Would it speed up drying time? None of the explanations I’ve actually seen for this including, most memorably, “The negative ions break down water molecules to one-fifth of their size” (errrr, what?), provide a really satisfactory, scientific explanation as to why it should. Or why it should ‘seal water into the hair’, whatever that means. It is feasible that the reduction of static could help keep the hair strands separate, which might help, but surely brushing or even running your fingers through your hair would have a much bigger effect. What I’m also not clear on is whether the tourmaline in your hair dryer carries on producing streams of ions/electrons indefinitely, or whether it becomes degraded over time. Which you would expect, if the charged particles are coming from the tourmaline itself. Is my battered old hair dryer really doing anything at all anymore, if it ever did?

It’s all very unsatisfactory. My best guess? Ionic hair dryers do reduce static build-up in hair, which would leave it smoother immediately after drying. Conditioner and styling products will also help with this mind you, and will probably have a more significant effect. The rest, I strongly suspect, is pure woo. And my hair dryer dries my hair faster simply because it runs hotter and with a faster airflow than the cheap, basic models in the swimming pool changing rooms.

But if you know better, I’d genuinely love to hear from you.