Category: Sustainability/environmental

Categories
Sustainability/environmental

Coffee: emissions or waste?

Plastic free coffee? Is it possible? Is it desirable?

Plastic free July is nearly with us once again, prompting us to look again at the sustainability (or not) of the coffee we enjoy each day. Whether we drink our coffee at home or in a cafe, it is easy to see plastic items associated with the coffee. In a cafe there are the take-away, disposable, cups, together with the cartons of milk and perhaps, plastic cutlery. Even at home, we see the plastic packaging in the coffee bags that we buy or receive through the post and perhaps with the milk (or mylk) cartons that we ourselves are using. Some have argued that given that we are in a climate emergency, at this point we need to focus on the most urgent problem of all, the reduction of greenhouse gases. These are valid concerns and it is certainly true that the emissions costs associated with packaging and transporting items using low mass containers like plastic are lower than if the same product were transported in heavier, but more obviously sustainable, materials such as glass. Should this stop us from trying to reduce our plastic consumption and what hope is there that new technology can help us? These are questions we may like to ponder with a cup of coffee.

What is the problem for those of us who mostly brew and drink coffee at home? Here, the major sources of plastic packaging are likely to be in the bags that the coffee arrives in and in the packaging of the milk that we may use to accompany our coffee. Many speciality roasted coffee beans now arrive in LDPE plastic packaging. This is recyclable although most household collection services will not be able to process it. Fortunately there are places that you can take your coffee bags for recycling such as supermarket plastic bag recycling points. Alternatively, some coffee suppliers or roasters (eg. Dog & Hat) will offer to arrange recycling for you via Terracycle if you return the empty bags to them.

If you decide to buy your coffee in compostable packaging, look out for the “OK compost, home” label by Vincotte

Another popular packaging material for coffee bags is “compostable” packaging. This falls into two types, the compostable according to EN13432 and packaging that is fully home compostable (occasionally certified with the Vincotte OK Compost label). You can read more about the relative compostability of each type of packaging here, but it is worth noting that the majority of us do not have access to an industrial composting facility, nor can these bags be recycled with other plastic. Packaging that is only certified to EN13432 will not compost easily in a home composting environment. Be very careful when buying “compostable” packaging. Less commonly, coffee could arrive in cans, paper or even (in the case of supermarket instant coffee) glass packaging. These can be easily recycled but may have higher carbon emissions costs associated with them, both in terms of the cost of transport and in terms of the cost of manufacture of the packaging.

Milk cartons are often recyclable or even, in the case of glass milk bottles, reusable and then recyclable. Those of us using non-dairy ‘mylks’ could try to eliminate the plastic altogether by buying oats or soy beans from a zero waste shop and then making our own according to recipes you can find online.

So it seems that we have a problem: we still have a lot of waste material when we drink coffee. Can technology help us? Recently, a new form of plant based ‘plastic’ material has been demonstrated. This material is able to be formed and used in a similar way to commercial plastics and may be suitable for food packaging. Not only that, but the material is fully degradable, though more details are needed here before we can know whether this is degradable as we would understand it or degradable under certain conditions similar to the ‘industrially compostable’ packaging. Nonetheless it is highly encouraging that work is being done on materials that will provide the low carbon footprint and food-safety aspect of plastic combined with the reduced problems of landfill waste. While still a few years off, such technology may provide a longer term solution to our current waste/emissions problem.

There is a good (physics based) reason that dairy milk is often supplied in semi-opaque bottles: the packaging protects the milk within from UV light that would otherwise cause it to spoil.

Which leaves us with the initial objection. Given the state of our climate emergency with regards to greenhouse gases, should we really be concentrating on reducing greenhouse gas emissions rather than on reducing plastic waste? Fortunately, there are choices that you can make that will reduce the carbon cost of coffee, regardless of the packaging it arrives in. There are some well researched and thoughtful articles available about the carbon footprint of coffee and what you can do, including this series from United Baristas. However, it is worth noting that even if we do decide to prioritise greenhouse gas emissions, recent work has shown that the methane emissions of plastic as it degrades has been previously under appreciated. Perhaps what we can do is make choices that reflect our concern for the planet that we call home. Clearly this means reducing as far as practicable our greenhouse gas emissions, but it also means living as sustainably/zero waste as possible. We each need to find the balance that is suitable for the situation that we each find ourselves in. A significant benefit of Plastic free July is that it gives us an opportunity to examine how much of our lives are made easier, or in some cases possible, by the use of plastic, in short, how much we rely on it. It is not necessarily about changing our lives forever, though maybe we will find some changes good to carry on with, but becoming more aware of the problems that we really have.

Have you signed up for Plastic Free July? What are you doing to reduce the environmental impact you have while still enjoying a cup of coffee? And do you have a good recipe for oat milk? Do let me know either on Twitter, Facebook or in the comments below. In the meanwhile, a happy Plastic Free July to you all.

Categories
General Observations Science history Sustainability/environmental

Reflections, deviations…. coffee

The reflections from the surface of a cup of coffee of a building opposite a central London cafe. Towards the edges of the cup, the coffee bends upwards, revealed by the lines bending that would be expected to be straight.

A “flat white” could be ordered from many a coffee shop. A “flat black” may be a physical impossibility. We can realise this by gazing contemplatively, or perhaps even longingly, at a long black while it cools. Notice that the surface of the coffee is ever so slightly curved. Leaving aside the white mists that you may see skipping across the coffee surface, the coffee is flat in the middle of the cup but rises towards the edges. If you have noticed this, it is most probable that you did so because of the different way the light is reflected over the surface of the coffee. It is most obvious if you can arrange the reflections on the cup to reflect something supposedly straight: a window frame or a beam of strip light for example. The reflection is fairly clear and fairly straight until about 5mm from the edge of the cup where suddenly it bends. You can see an example of this in the photograph on the right.

The reason for the curvature is of course surface tension, which is the same effect that makes droplets form into shapes that are close to spheres. First investigated by Agnes Pockels and Lord Rayleigh in the nineteenth century, surface tension is caused by the fact that molecules at the surface of the water (in the coffee) will feel a net attraction to the other molecules within the water. There being no molecules of water above the surface of the cup, the surface molecules are pulled back towards the liquid in the cup. At the sides of the cup something slightly different is happening. There, the molecules in the water will be pulled back towards the liquid but will also experience the uncompensated attraction (or repulsion) from the atoms in the mug material. Exactly analogous to surface tension, but in the solid, the interaction of the surface energy of the mug with the surface tension of the liquid will pull the liquid into different shapes. It is for this reason that highly waterproof surfaces, such as fresh oak leaves, will form spherical drops of water, but wettable surfaces, such as an oak leaf in autumn, will accumulate flatter, less spherical droplets on the surface.

coffee, red wine, wet coffee stain, coffee spill, coffee ring
The interaction between the surface tension of the water and the surface energy of the solid surface it sits on determines the shape of the droplet. These drops of coffee and wine on paper were for an experiment about coffee ring formation. The droplets are: Drops of coffee (left), soapy coffee (middle) and red wine (right)

We see the effects of surface tension too when a bubble, or a small bit of dust, sits on the surface of the coffee. Again, looking at the light reflections, we see how the coffee, or tea, bends near the floating object showing how un-flat the surface really is. Bubbles are usually large enough that we can see them directly. In the photograph on this page for example, you can clearly see the reflections from the surface of the bubble together with the bent reflections of light from the surface of the liquid. However in the case of the dust, sometimes the dust is small enough that the reason that we see it is because of the change of the path of the light reflected from the surface. For a similar reason, the insects that skate the surface of a pond are visible because of the light patterns they make rather than their intrinsic visibility. Each time we are using the deviation of the light from its expected path in order to deduce the presence and shape of an object hidden to our view.

A similar deviation of the expected path of light is seen in the phenomenon of gravitational lensing which has been used to infer the presence of black holes. Such a deviation even provided experimental evidence for Einstein’s (then) recently proposed General Theory of Relativity, just over 100 years ago on May 29, 1919. The idea that light had weight and would be deflected by a gravitational field was not new, indeed, even the Newtonian model of gravity predicted that light would be deflected as it went past a massive object*. The question was how much and, as an important secondary question, how to measure it. As Arthur Eddington later described in his book “Space, Time and Gravitation”*, according to Newton, any object thrown horizontally on the Earth’s surface would fall 16 feet (in his use of units, 4.88 m in SI) in one second. The same was true for light. However with Einstein’s theory, the predicted deflection of light was 32′ (9.75m). The difficulty for the experimentalist is that in the same second, the light would have travelled nearly 300 000 km. Detecting such a small deflection over such a large distance would be difficult, harder than seeing a grain of dust on the coffee surface. Which is where the light deflection comes in. Because if you watch as the light from a distant star travels past a massive and fairly large object, such as the Sun, you should be able to discern the small, but significant deflection. And on May 29th 1919 a total solar eclipse (which thereby blocked the extra and interfering light from the Sun) offered a perfect opportunity for Eddington and an expedition sent by the Royal Society and Royal Astronomical Society (to Brazil and West Africa) to attempt to measure such a deflection.

tea reflections, bubble on tea, surface tension, light bending
The way that light reflects off a surface of a cup of tea in this case, reveals the curvature of the tea surface. In this case the curvature is clearly due to the bubble in the centre. Sometimes you can see distortions on the surface caused by bits of dust which are difficult to see on their own.

Although the deflection was significant, working with large telescopes and photographic plates, the magnitude of the deflection of the light that they were looking for was still only 1/1500 of an inch on the photographic plate. Two groups at two different locations took multiple photographs of the eclipsed Sun and the stars around it in order to measure the position of the stars as seen behind the Sun and then compare that to the position of the stars when they had been photographed earlier in the year without the Sun between them and the Earth. Eddington describes the experiment:

“There is a marvellous spectacle above, and, as the photographs afterwards revealed, a wonderful prominence-flame is poised a hundred thousand miles above the surface of the sun. We have no time to snatch a glance at it. We are conscious only of the weird half-light of the landscape and the hush of nature, broken by the calls of the observers, and beat of the metronome ticking out the 302 seconds of totality.”

Finally after developing and comparing the images back in London, the team confirmed a deflection of 1″.98 +/- 0″.12 (Brazil) and 1″.61 +/- 0″.30 (W. Africa) for the stars closest to the Sun (NB. 1″ indicates 1 second of arc). Einstein’s theory had predicted a deflection of 1″.74, Newton’s theory had predicted 0″.87. The results of the light deflection were far more in agreement with Einstein’s new theory of General Relativity than with the classical Newtonian model.

The ‘wobble’ of a few of the stars on the photographic plates had confirmed a prediction of the theory of Relativity. Which could lead to the question: What do you see, or not, as the light dances off of your coffee?

*”Space, Time and Gravitation: an outline of the General Theory of Relativity”, Sir Arthur Eddington, Cambridge University Press, first printed 1920, 1968 edition.

Categories
Coffee review General Observations Science history slow Sustainability/environmental

Me time at Hétam

Iced chocolate at Hetam. The chocolate is sourced from Indonesia. At the time of visiting, drinks were only available in take-away cups, hopefully this will change as the cafe becomes more established and the pandemic restrictions that were in place at the time of visiting are eased.

In 2021, a new cafe opened up in Bangsar, Kuala Lumpur, Malaysia. Called Hetam, it is a cafe almost designed for the post-pandemic, Instagram age that we find ourselves living in. At the time of visiting, there was no ‘inside’ to this cafe, everything was outdoors: customer seating was outdoors, even the ordering and the counter were outdoors. Umbrellas provided some protection from the downpours as well as the hot sun that you can get in Kuala Lumpur. You order at a counter which is on the right of what looks like it used to be an ordinary house on the service road parallel to Jalan Maarof (between Lorong Maarof 5 and 6). The house is now the headquarters for the online section of Hetam and is where they package up their online sales. There are a small selection of edibles to the right of the cash till but the main focus is on the coffee, tea and chocolate. The coffee is roasted by Hetam. At the time of visiting, the coffee was a choice of either an Indonesian natural or a Brazilian washed coffee and available as any of the usual espresso based drinks. I found that the Indonesian worked better in the espresso but that when brewing with an Aeropress at home, the Brazilian came out on top. Various Japanese Genmaicha and Hojicha teas were available but each time, I focussed on the coffee. The chocolate also is sourced by Hetam mostly from Indonesia and is well worth trying.

The staff at Hetam were very friendly and knowledgable. When we first arrived, they talked us through checking-in using the MySejahtera (Covid-19) app when we didn’t have data on our phones (as of 1 May 2022, hopefully MySejahtera will be something you don’t need to use any more). This led to a conversation on the origins of Hetam and their hopes for the cafe for the future. We ordered a hot long black and an iced chocolate and took a seat in the side/back garden of the house. The space seems almost made for Instagram. Infact, perhaps it was. Carefully arranged bamboo adorns the sides of the garden. White pebbles form the floor while strategically placed bits of tree are scattered throughout the space leading to a certain, specific aesthetic. The first time that we enjoyed a coffee at Hetam, another couple were already there. As we sipped our coffee, the couple split into model and photographer and, with what appeared to be a well practised routine of recognisable Instagram poses, set about photographing each other against different backdrops. In subsequent visits, we enjoyed the place to ourselves.

The counter at Hetam is helpfully under a shelter, the other seats are mostly under umbrellas. You get a glimpse here of the ‘insta-ability’ of the cafe. Random dead logs form a counterpoint feature to the white pebbles of the seating area.

The name “Instagram” is apparently a derivation of a combination of “instant camera” and “telegram”. The idea being that a message is sent through an image acquired by an instant camera. The word camera is in turn derived (from both Latin and Greek) from the word for a chamber or a vault. Presumably this was a suitable name for the camera because early photographs were taken through a pin hole into a vaulted dark chamber. Which brings us into the realm of physics as the photograph is literally that which is written by light. Film cameras and even the old Polaroid instant cameras, could still, legitimately be said to take photographs. The light would fall onto a chemically active film and change it based on the exposure levels so that the image was written directly by the light. When it was developed, the negative would be the reverse of the places on the film ‘written’ by the photons of the light (for a description of the process and a recipe for developing film with coffee click here, opens as pdf). This is not true of the sort of “instant cameras” most would now use to upload an Instagram post. In the case of digital cameras, the photons of the light still activate a light sensitive electronic chip behind the camera lens, but much of the interpretation of the image is done using computer software. For example, many of the light sensitive cells in the camera are not colour sensitive, they are only sensitive to the number of photons that fall on them (the intensity of the light). Colour images are formed by considering neighbouring cells which each have a different coloured filter covering them. The relative intensity of the electronic response within each group of cells is then interpreted by the software as a different colour. At this point can it be said that the image is written by the light? The final image is a mixture of the light falling on the photoactive cells and the interpretation of that electrical data by the software in the phone or digital camera. The light directs the electrons within the device but does it write the image?

Table, pebbles and bamboo in the seating area of Hetam, KL.

There’s also the issue of what it means to have the image and to share it. The picture on the phone, the image shared through the screens, is a collection of data points that no one can hold. A photograph printed from film or even the negative is, in that sense, more tangible. In the case of the negative, what you hold is what was written by the photons, by the light, at the point at which the subject was seen. In either case though what does it mean to have, or even to share, that image? Erich Fromm in his book “To have or to be” contrasts a poem of Tennyson with a haiku of Basho*. In the former, Tennyson ‘plucks’ a flower out of a wall in order to study it. Basho in contrast looks “carefully” at the flower; paying attention to it but not possessing it. Fromm questions our mode of being, suggesting that Tennyson could be compared “to the Western scientist who seeks the truth by means of dismembering life.” Is this fair? Does our desire to possess an image, pluck a flower or to ‘capture’ a moment and thereby ‘keep’ it necessarily imply that we would seek truth by means of dismembering life?

Which may take us to a consideration of those dead tree branches on the gleaming stones. They appear like petrified wood, wood that has been preserved for years through a process of fossilisation. We cannot own such objects, they outlast us. If we photograph it we cannot keep that moment, what does it mean to us if we don’t look carefully at the instant but rather try to pluck it for posterity?

So finally back to Hetam. While it may be ideal for Instagram, and while it will definitely be worth a few good photo ‘captures’, the space is also ideal for contemplation. For sitting with a coffee, enjoying the moment, appreciating the surroundings, both aesthetic and people, and for being rather than having. A friendly, outdoor and relaxed cafe, what more could you want?

Hetam is on Jalaan Maarof just next to the Petronas petrol station on the service road to Jalan Maarof.

*”To have or to be” by Erich Fromm, Jonathan Cape publishers, 1976 (1978)

Categories
Coffee cup science General Observations Science history Sustainability/environmental

Pure Percolation

Pure over boxed
The Pure Over in its box. The glass base is designed with an inbuilt filter, avoiding the need for disposable paper filters but making the physics of percolation unavoidable.

It was entirely appropriate that the first coffee I tried in the Pure Over coffee brewer was the directly traded La Lomita Colombian from Ricardo Canal via Amoret Coffee. Ricardo was a special guest at one of the Coffee and Science evenings we held at Amoret Coffee in Notting Hill (pre-pandemic) where, among other things, he spoke about how he is using Biochar on his coffee farm. Biochar is a porous, charcoal based material that can help to provide the coffee plants with nutrients as well as water, thereby reducing the amount of fertiliser the plants need. To understand how it works, we need to understand a bit about percolation, which of course we also need to understand in order to brew better coffee in the Pure Over. Indeed, there are enough similarities, and an extension to a quirk of how espressos are brewed, that it is worth spending a little more time thinking about this process and the connections revealed as we brew our coffee.

Percolation recurs in many of the brew methods we use for making coffee. The V60, Chemex, Kalita wave, percolators and the espresso itself, all rely at some point on water flowing through a bed of ground coffee. The flavour of the resultant cup is dependent on the amount of coffee surface that the flowing water is exposed to together with the time that it is in contact with the coffee. What this means is that grain size, or the degree to which you grind your coffee, is critical.

Playing with brewing coffee, we know some things by experience. Firstly, frequently, the flow through a coarse grind of coffee will be quite fast (probably too fast to make a good cup). Secondly, we know that for any particular brew method, the more water we pour into the brewer, the faster the water initially comes through. We also know that we can affect the flow rate of water through the coffee if we increase the area of the coffee bed, or decrease its thickness. These observations were quantified into an equation by Henri Darcy in 1856. Darcy’s work had been as an engineer, designing and building public works such as the aqueduct that brought drinking water into the city of Dijon in the 1840s. Darcy received significant recognition at the time for his work including the Légion d’honneur, but it is more for a later set of experiments and particularly for his equation that we remember him today. In the 1850s Darcy was working on the problem of water purification. Passing water through a bed of sand is still used as a method of purifying the water today. Darcy used a series of cylinders filled with sand to investigate how quickly water trickled through the sand bed in order to come up with a proper quantification of those things that we too know by experience with our coffee filters. You can read about the mathematics of Darcy’s equation here.

espresso puck
An espresso puck. The compact structure nonetheless allows water to percolate through it at high pressure.

Darcy found that the flow rate of water through the sand bed increased when the porosity of the bed was higher (fine, dense sand would delay the flow of the water more than coarse, loosely packed sand). If there was a greater pressure on the water at the top of the bed (ie. more water is on top of the sand), the flow rate through the bed would increase too. Conversely the flow would get slower as the water was made more viscous. This is something we too know from experience: try to pour honey through the coffee grounds and it just won’t work.

For us to apply Darcy’s insights into making better coffee, it means that we need to think about the grind size. Too coarse and there will be lots of empty space through the bed of grounds: the porosity is high, and the water will flow straight through. Too fine and the flow rate will decrease so much that rather than just the sweet and slightly acidic solubles that first come out of any coffee extraction*, there could be too much of the bitter organic compounds that come out later, changing the character of the cup. With coffee we have an additional concern. Unlike sand, coffee grinds will swell, and splinter, as water is added to them, closing up any narrower paths and lengthening the brew time. This also means that, unless we properly wet the grounds prior to filtering our coffee, the extraction will be non-uniform and not reproducible. Another reason to bloom coffee thoroughly before brewing.

There is one more factor in brewing our coffee however that Darcy’s equation, which is valid for more stable systems, overlooks. Darcy assumed a constant flow rate of water through the sand bed, but coffee is different. In his book about espresso*, Illy showed that the flow of the water through an espresso puck was not constant over time. Something really interesting was happening when you looked carefully at an espresso puck. Ground coffee can come in a large distribution of sizes. In addition to the grind that we are aiming for, we also get a whole load of smaller particles called ‘fines’. Sometimes this is desirable, but with espresso, and by extension with our filter coffees, these fines add a twist to the physics of the percolation. As the espresso water is pushed through the coffee puck, the fines get pushed down through the puck between the ‘grains’ of the coffee grinds. This reduces the flow rate of the water until the point at which they get stuck. This will have the effect of increasing the contact time between the coffee and the water and so allowing more flavour solubles to be extracted. But crucially, these fines remain somewhat mobile. If you were to turn the whole espresso puck upside down (and Illy had a machine that allowed him to do this in-situ), the fines would again go on the move. Migrating from the new top of the puck to the new bottom. Filling the voids between the slightly too coarse grains. Complicating the simplifications in Darcy’s equation, but adding flavour to our brew.

Watch House coffee Bermondsey
There is a fountain on the wall (right hand side) of the Watch House cafe in Bermondsey. Many public fountains in London date from the 1850s emphasising just what a problem access to drinkable water once was.

Which leaves the connection between the farming method and the coffee. Biochar is formed by burning carbon containing waste (such as plant matter) in a low oxygen environment. Burying the resultant charcoal is therefore a way of storing carbon, and preventing its release into the atmosphere, for many years. But it is not just good for carbon storage. The buried charcoal is highly porous and traps nutrients within its structure so that the plants growing near it can be fertilised more efficiently. Moreover, the fact that it is porous, just like the coffee or sand beds, means that it traps water for a long time. Consider how long it takes a used filter full of coffee grounds to completely dry out! The water gets trapped within the porous structure and does not evaporate easily. This aspect of the biochar means that, as well as nutrients, the plants that grow nearby get a good source of reliable water. The ancient civilisations of the Amazon region used something similar to biochar in their farming techniques resulting in soil now known as “Terra Preta”, an extremely rich form of soil that improves plant growth. On his farm, Ricardo is going fully circular and making his biochar out of old coffee trees. The old trees thereby giving new opportunities to the fresh growth. It is a carbon capture scheme that reduces the need for fertilisers and that relies on percolation physics to work to best effect for the plants.

It seemed a moment of perfect coffee-physics poetry to use coffee grown on a farm using these techniques while initially experimenting with my own, percolation sensitive, Pure Over brewer. Percolation physics and interconnectedness all in one cup.

*Illy and Viani (Eds), “Espresso Coffee”, 2nd Edition, (2005)

Categories
Coffee Roasters General Sustainability/environmental

Packaging, all about substance

The OK Vincotte or OK Compost HOME labels are for items that are suitable for “home” composting. This label was on a coffee bag from Amoret Coffee

Who would have thought that buying coffee to drink at home could be such a moral minefield? There are issues of sustainability: for the people involved in the coffee process through to the planet. Issues of transportation and the balance between supporting local independents or larger companies with different sustainability policies. And in amongst all this are issues of packaging the final product. How does your freshly roasted coffee arrive? Is it in a bag that you have no choice but to dispose of in the ordinary rubbish, or in a bag (or even bottle) that can be re-used and recycled or composted?

As many of us are buying more coffee on-line at the moment, I thought that it may be helpful to have a list of roasters who have gone to some effort in thinking about the sustainability of their final packaging. Of course many other issues are involved in your decision about which coffee to purchase. This list is only intended as a place to collate information on coffee bean packaging. The list is not definitive, so if you know of a roaster (or if you are a roaster) who is not currently featured on this list but you think ought to be, please let me know as I will be updating the page regularly. Similarly if you notice a mistake, please get in touch (e-mail, Twitter, Facebook).

One more caveat. We each need to decide what we consider a ‘good’, or sustainable packaging. The issue is highly complex. Some of us will have the ability to compost at home, some will have access to an industrial composting bin, some will go to supermarkets regularly and would prefer to recycle plastic together with other plastic bags. And then of course there is the problem that packaging is just one part of a whole relationship between farmer, supplier, roaster, customer and planet. It requires thought and consideration on our part as consumers, on the part of the coffee roasters and, I think, it requires kindness on all our parts, appreciating the efforts of those who are trying to improve things while recognising that there is currently no perfect solution.

In alphabetical order:

Compostable (Home)

Very few items marked “compostable” are, in reality, “home” compostable. Properly home compostable items are certified by the “Ok Compost, Vincotte“/OK compost-HOME labels.

Amoret – Notting Hill, London and online. Coffees (including directly traded coffees) are supplied in bags certified as home compostable (OK Compost). Owing to supply problems during the pandemic, some bags of coffee have been packaged in EN13432 (industrially) compostable bags instead but a recent addition of a new supplier should hopefully solve these supply problems.

Coromandel Coast – online. Shade grown coffee from India, coffee orders online come in a Natureflex bag within a recyclable cardboard box. Natureflex is certified as ASTM D6400 but also listed as “home” compostable and indeed composted in my worm bin composter in 17 weeks (packaging was from Roasting House in that instance).

Roasting House – online. Delivery by bike in the Nottingham area. Ground coffee is supplied in home compostable packaging. Whole beans are supplied in recycled and recyclable bags (see below). You can read more about their latest packaging policies here.

Compostable (Industrial)/Biodegradable

Most packaging that is marked compostable (or biodegradable), but that is not marked as home compostable, will require specialist facilities to compost/degrade such as industrial composting. Compostable items should be certified by (BS) EN 13432 and/or ASTM D6400.

Coromandel Coast – Croydon and online. Bags of coffee purchased in Filtr, the coffee shop associated with Coromandel Coast in Croydon, are supplied in industrially compostable packaging. For coffee purchased online see above.

Dear Green – Glasgow and online. “Together we can all make a difference”. Next year, COP26 will go to Glasgow and Dear Green are ready, organising the 2018 Glasgow Coffee festival to be re-usable cup only. Coffee is supplied in biodegradable packaging.

Glen Lyon Coffee – Perthshire and online. Glen Lyon coffee made a commitment to zero waste in 2017 and use OK Compost Industrial certified coffee bags for their 250g and 500g packaging. 1kg bags are designed to compost within 3 months in a home composting environment. They offer a ‘drop box’ for customers to return their bags for composting. You can read further details about their dedication to sustainability here.

Recyclable

Several roasters have opted for recyclable packaging and quite a few are using the Dutch Coffee Pack bags which are additionally carbon neutral (via offsetting which you can read about here). Be careful with the “recyclable” label as it may, or may not, be suitable for collection with your household waste. Look for the recycling labels on the bags. PET plastic (label 1) is often collected with the street based collections but LDPE (label 4) should be taken to a supermarket where they provide recycling for plastic bags.

Atkinsons – Lancaster, Manchester and online – Established in 1837 as a tea merchant in Lancaster, Atkinsons now sell tea and coffee using recyclable packaging which is also carbon neutral.

Casa Espresso – online – Great Taste award winner for 3 years in a row, coffee is supplied in recyclable and carbon neutral packaging.

Chipp Coffee – online – In addition to using recyclable packaging, you can read more about the ethical and sustainability policies of Chipp Coffee here.

Fried Hats – Amsterdam and online – recyclable but also re-usable. The coffee comes in bottles that can be re-used before ultimately being recycled.

Good Coffee Cartel – online – Coffee in a can, but this time a re-usable and recyclable can containing speciality coffee beans.

Manumit coffee – online – “Manumit”, a historical verb meaning to set a slave free. Manumit coffee works with people who have been subject to exploitation and modern slavery so that they can rebuild their lives. Their coffee comes in recyclable and carbon neutral, Dutch Coffee Pack packaging

New Ground – Oxford, Selfridges and online. Providing opportunities for ex-offenders to develop new skills and employment, coffee is provided in recyclable packaging.

Paddy and Scotts Suffolk based, various outlets and online – Coffee packaging is described as PET recyclable or compostable. Check labelling on package. More info here.

Rave Coffee – Cirencester and online – Rave coffee have been conscientious in describing the reasoning behind their policy of using recyclable (LDPE (4)) bags, You can read about the rationale here.

Roasting House – For whole beans, Roasting House supply the coffee in (recycled and) recyclable paper packaging. Ground coffee is supplied in home compostable packaging (see composting section).

Runnerbean Coffee – Berkshire based Runnerbean coffee uses recyclable (LDPE label 4) coffee bags and, additionally runs a tree planting scheme to offset their carbon footprint. They had been using compostable bags until recent supply problems, check their website for the latest details.

Steampunk coffee – online. I’m reliably informed that their coffee is supplied in recyclable packaging but have been unable to confirm.

This list will be updated regularly. Please do get in touch if you would like to suggest a coffee roasting company who should be included: email, Twitter, Facebook.

Categories
Coffee cup science General slow Sustainability/environmental

Coffee and science: a problem shared?

coffee and Caffeine at Sharps
What is the future of coffee? Science? Our society? Are these things held together more closely than we imagine?

There is a lot of science in coffee (and a lot of coffee in science). And there are also many scientists who are keen coffee drinkers and vice versa. But is there more in common between these two fields than even this? Could a shared problem be hiding a different (shared) problem?

One issue for coffee drinkers is reliability and reproducibility. How can we ensure that we get a good cup each time we visit a café or brew our own? In a similar way, how do we ensure that our experimental results in science are correct and reproducible? It is a fairly fundamental tenet of science that an experiment should be able to be reproduced in another lab with similar equipment. The suggestion is that this is not always happening, we have a ‘reliability’ problem in science (and sometimes in coffee).

A possible solution, in both fields, is some form of automation. In the world of coffee this is quite obviously just by making coffee via a machine. There have been several attempts to make reproducibly good coffee using an automated pour over machine. In the world of experimental science, it is not quite so clearly an automation process but is described instead as “data sharing”. The results of all experiments, or at least those that are published, should be shared (uploaded with the published paper) so that others can examine the data in more detail and form their own conclusions†.

For both coffee and science, it is suggested that this opening up of our process so that it is more transparent or reliable, will increase the reproducibility of good results and, crucially, mean that we get those results faster. We will get reproducibly good coffee without having to queue so long in the morning; we will make discoveries more quickly and have faster progress in science.

It seems that the problem that we thought we had, reproducibility, is perhaps not the one that we are actually aiming to solve. The problem we seem to be interested in is ensuring faster progress.

coffee under the microscope
We can look at coffee under the microscope (here are two different coffees ground to the same degree). But do we need to look more closely at the process of making good coffee or of doing science?

But an emphasis on faster progress can undermine our initial ideal of a reproducibly good result. For scientific research the emphasis on getting results quickly (at least within the time frame of the science funding cycle) has led to predictable problems. There are cases that I know about where results that were contrary to those that were wanted were suppressed. Not permanently. No, that would be demonstrably scientific fraud. No, suppressed just long enough for the first ‘ground breaking’ paper to be published. Then, after a suitable length of time, the second paper showing the problems with the first can follow up. Those involved get two papers (at least), and rapid progress is shown to be happening in the field. Would data transparency help here? Clearly not, because the initial set of data would still be suppressed until it was wanted those few months later.

What we need is a change in the structure of how science is done. We need to value scientific integrity and so trust that other scientists do too. We know that the current situation whereby promotions, funding etc are determined by the number of papers in ‘good’ journals, can act to undermine scientific integrity. This needs to change if the reliability issue is to be addressed. In the type of case described above, there would be no consequences for the people who kept their names on the paper(s) published. The only consequences would be if anyone refused to have their name on the paper as they knew it was misleading. And even then, the consequences would be to that person/those people in terms of their CV, and publication list, not those who published the paper and of course, shared the data.

coffee at Watch House
A good pour over takes time.
What are we looking for in coffee, in science? Is progress an aim of itself?

For the coffee, there are already discussions about whether the increase in throughput offered by automated coffee brewing techniques really contributes to the coffee experience that the cafés are trying to encourage. Can we really expect someone to slow down, take in the aroma, the mouthfeel, the taste and flavour if we rush the cup through to them on a production line? Isn’t part of the enjoyment of something to have to wait for it (hence lent before Easter; fasting before a feast)?

It is not that automation necessarily is bad. We can get a genuinely all round good coffee in a café that utilises a machine based pour over (perhaps). We can also get genuinely reproducible data in a situation where data is routinely shared. It’s just that data sharing does not solve the reproducibility problem, nor does automation give us continually good coffee. What makes the difference is a café that cares about the product that they are serving; scientists that care about the integrity of the research that they are doing. Automation processes give us faster results, they do not, automatically, give us better science (coffee).

Moreover, our desire for faster progress obscures questions that we should be asking if we slowed down a little. What is a good coffee experience? Who (if anyone) should own the scientific data shared? Is our desire for good coffee, quickly and (relatively) cheaply obtained, an aspect of that consumerism that is damaging for the planet’s ecological health? How much do we need to trust each other (and take responsibility for our own integrity) for our society, including our scientific society, to function? Is faster progress in and of itself, a “good” to aim for?

And perhaps, there is a final, more fundamental question. Have we become so accustomed to seeing ourselves and our work as merely a cog in a machine that we have become inured to the dehumanisation of society which seems to us almost natural and itself progress? Is this what we want for society?

The process of making a good cup of coffee indeed shares many things with the process of doing science. Perhaps this should not be surprising, both are practises embedded in our society. Certainly our view of the society that we live in can be informed by slowing down with our coffee as we enjoy a little science (or should that be the other way round)?

 

†It is not quite an automation process in the sense that the data is taken by a machine and then uploaded. However, it is still a dehumanisation process. At the root of the concept is the idea that the human experimenter can be taken out of the process. I would be happy to expand on this in the comments but for the sake of readability haven’t done so here.

Categories
Coffee review General Observations slow Sustainability/environmental Tea

To stay or to go at Cafe from Crisis

coffee commercial St volcano
Cafe from Crisis on Commercial Street, E1. Notice the arches…

It was not what I had expected. Entering the door of the Cafe from Crisis, you go up a ramp with a bench running alongside it before the counter looms in front of you with a large café space opening up to your right (previously partially obscured from your view by the wall for the ramp). Perhaps it is fitting that my expectations were wrong. Many of us have ideas about the homeless (why they are homeless, what homelessness is etc) that may not match fully with the reality. And this café is, after all, in the head office of Crisis, a UK national charity working with the homeless and homelessness.

The coffee is roasted by Volcano and there are a large number of food options (including vegan and veggie) and cakes at the counter. A selection of keep cups are also arranged in a rack on the left of the counter, should you not have one yet. We ordered an Americano and tea (to stay) and took our numbered wooden spoon to the table so that they could find us. Although it was late lunchtime and busy, the drinks arrived fairly quickly with the coffee in a (Crisis themed?) red cup. Apparently serving coffee in red cups make us perceive the coffee as warmer than if it is served in a blue cup. Whether this is true or not, the warm brew was very welcome on this cold January day. The café is situated on a street corner which means that it has many windows, each topped with a shallow arch. The building looks fairly modern from the outside, but the arches were reminiscent of the way that older buildings can be dated by the window style, along with other features. The Cure played in the background which entertained my tea drinking companion but made me wonder about the ideas of Pythagoras on the psychological impacts of different sorts of music (and whether it affected the ability to find thought connections in a café).

plant in a coffee cup
It turns out there are many things to notice in this photo. From the bricks to the self-defence tactics of plants. But what about the nature of the home of the plant?

As we sat, enjoyed our drinks and looked around, we noticed that some plants had found a home in coffee cups placed on the tables around. Small plants in plastic pots (a nod to the anthropocene as pointed out by @lifelearner47 on twitter) were dotted around the café. Did they move from an espresso to a long black cup as they grew larger? Perhaps it was the spiky plant in one of the pots, but my mind immediately jumped to hermit crabs and their search for a new shell each time they grew a bit bigger. Marine hermit crabs  have been shown to be happy in any old discarded shell. Normally these are the ex-homes of gastropods that have, well, “moved on” would be a euphemism, but marine based hermit crabs have been known to make their shells out of all sorts of things including our plastic litter. Land based hermit crabs however are far more demanding and only move into shells that have been specially remodelled by earlier generations of hermit crabs for their own use. This means that land based hermit crabs have to develop a social awareness of other hermit crabs when they want to swap shells.

Apparently the interaction goes something like this: A group of hermit crabs come together in a small-ish area and begin to scope each other out. The loose collection becomes a cluster as the crabs explore whether one of the larger crabs can be evicted from its shell. As the process of eviction is about to occur, the remaining crabs (which can number quite a few, 10 or more) literally ‘line up’ in order of shell size so that, when the largest is evicted, each crab can move up to the next sized shell leaving the smallest, most undesirable shell on the seashore and the poor evicted crab, shell-less.

Several questions arise but one is, do the crabs make decisions, “to stay or to go” based on how advanced the eviction process is? So, say a crab wanders into an area with an unusually large number of crabs in it (perhaps 4) but the crabs are all lined up in a queue ready to swap into each others shells. Do the crabs coming into the area stick around for a long time or do they head off somewhere else? Or, conversely, what if they enter an area where there are more than the usual number of ‘colleagues’, but they are all scattered about, not yet ready to evict the largest crab. What would our incoming crab do then?

coffee red cup Crisis
What would you learn if you noticed the connections your mind was forming while enjoying a coffee?

These questions were addressed by a group working with the terrestrial hermit crabs of Costa Rica. By defining five cells on the beach, each with a different arrangement of (empty but inaccessible) shells that the incoming hermit crab may want, the researchers found that the incoming hermits were making some strikingly sensible decisions. When the crab came into a region of scattered shells (that the incomer mistook for fellow crabs owing to a trick with a combination of loctite glue and partially burying the empty shells that the researchers used to fool the incomers), the incomer tended to stick around, waiting for an opportunity to swap a shell. If the incomer came but saw that the queue of shells had already formed, it still stayed a bit longer in the region relative to a control area devoid of shells, but it did tend to leave it after some time, perhaps to look for new shells elsewhere. The researchers concluded that when the crab came into an area and thought it had a pretty good chance of inserting itself into a good queue position, it would stay in the area waiting for the eviction to occur and the shell swapping process to start. However when the crab came into an area where the queue had already formed, it was unlikely to be able to get a good position in the queue and so would investigate the situation for a bit before wandering off elsewhere in the search of a new shell in a different area.

Does this have any relevance to a café trying to do a bit to address the problems of homelessness and the homeless in our city and country? I will leave that to each reader to ponder. However, it was a great opportunity to learn something new about our world, which only happened because I stopped to notice something in a café and then wondered how hermit crabs get their homes. It’s always good to slow down and notice things. What will you see next?

Cafe from Crisis (London) is at 64 Commercial Street, E1 6LT.

Categories
Coffee review Observations Science history Sustainability/environmental Tea

A post in need of a Curator(s) Coffee, Fitzrovia

espresso Curators
A deliciously intense and fruity espresso from the ‘specials’ menu at Curators Coffee.

Curators Coffee in Margaret St in Fitzrovia has been there for years. A great location just off of Oxford St, with plenty of seating and good coffee, and so it is perfect to pop into, unless you are like me and avoid the Oxford St area as much as possible. Which perhaps explains the rarity of my visits. I first popped into Curators Coffee a couple of years back (before the laws on allergen information came in) when I remember enjoying a lovely long black but couldn’t have a cake because the people behind the counter that day couldn’t tell me which (if any) cakes contained nuts. At the time, I sat upstairs and noticed the graphene type arrangement of hexagons around the back of the space and the Bramah’s 300 years of coffee makers book in a rack at the back. I had wanted to return to properly cafe-physics review the place at a later date (and try the cake) but circumstances (and Oxford St avoidance) meant that I never got round to it. Until very recently.

This time, I noticed that there were three single origin coffees available to try as espresso. Glancing at the tasting notes it was a fairly quick decision: “chocolate”. And although this time I had just had lunch and so passed on the cake, it appears that the espresso choices regularly rotate, offering an incentive to come back again and try something new. Although the café is quite large, with plenty of seating, it seems that it is also very popular. And so there were no spaces remaining upstairs. Fortunately, there were more seats downstairs and so, taking our table number with us, we made our way down the stairs and found a table at the window, as if it was waiting for us.

UFO in Curators Coffee Fitzrovia
A UFO reflected in the window? Why? What? Why (again)? It is small details such as this that reward you as you put down your smart phone and notice your surroundings.

Perhaps it is obvious that a café called Curators should have art work adorning the walls. That, and the spotlights that highlighted the work immediately caught our interest, (although it was odd to see that one of the rows of spotlights was almost devoid of bulbs). The exhibition downstairs seemed to have a tilt towards street art and a couple of decorated aerosol cans were on the windowsill priced at £15 each. Was this the time to consider why an aerosol gets cooler as you spray the walls with it?

Outside the window, a staircase leading up to the street outside had railings in straight lines leading up towards a blue sky. Inside, a space craft was reflected in the window.

Indeed, on checking again, there was a spacecraft, like a cartoon of a stereotypical little UFO, drawn onto the wall behind my accomplice’s head and reflected in the window next to it. What could it mean? Regardless of whether some UFO incidents are associated with visitors from other planets, there are a large number of scientific thought trains we can take when considering a UFO reflected in a window. To start with, how likely is it that we are alone in the universe or that there are many other intelligent life forms in other planetary systems?

The question has been answered on the basis of probability for many years. But recently, we have been finding more planets orbiting stars and crucially, more planets that are in the ‘habitable’ zone around other stars. Assuming that life elsewhere needs similar conditions to the earth’s in order to thrive, the idea of life elsewhere is becoming increasingly real.

canali Curators Coffee
If you see straight lines such as this, it is fairly sensible to infer that they were built by an intelligent life-form. Can you see canals on Mars?

Closer to home, there were even suggestions that Mars may support flowing water, thought to be a host for bacteria based life. And although these interpretations of the flow patterns observed on the Martian surface have more recently been contested (could they instead be flowing sand?), we continue to send probes (such as the Insight probe that landed recently) to the red planet to investigate its geology. Did Mars once host life?  Mars of course has a resonance in science fiction for being the planet hosting extra-terrestrial life. HG Wells imagined the Martians landing just south of London, and eventually being killed off by exposure to bacteria on earth that they had not experienced in their Martian habitat. Could life on Mars suggest a (tenuous) further link to this café on Margaret St?

Perhaps one reason that people started to imagine (intelligent) life on Mars came about because of an interesting mistranslation of an astronomical observation. While gazing at Mars in 1877, Schiaparelli noted ‘canali’ on the Martian surface. The correct translation of this in this context into English is “channels” but what the observation came to be known as was “canals”. Canals imply an intelligent builder, and hence life on Mars. Later observers also saw these ‘canals’ and a popular myth was born. It is a useful lesson for us all, sometimes how we see something can be influenced by the language we use to describe it.

soya hot chocolate, Curators
We photograph our coffee, and share it with our online friends. But would putting down our phone in a cafe be worth something for the planet as well as for ourselves? How many batteries do we need?

And then one final thought train, prompted by photographing the cafe with my mobile phone. The whole probability argument rests on two assumptions. The first is that there are other planetary systems (which we are finding). The second is that life is fairly easy to start, or at least, that the chances of producing life are not restricted to one planet a short distance away from the Sun; we are not unique. As yet we don’t know whether this assumption is justified but discoveries such as the deep sea hydrothermal vents challenge our preconceptions about the requirements for life and suggest that life could start more than once, and so could very well start on other planets, not just ours. In these vents, bacteria are known to convert what we think of as toxic chemicals into energy in a process known as chemosynthesis without the need of sunlight or other ingredients that we had thought essential to life. Could similar hydrothermal vents on other planets host new life forms?

And in a related way, what is going on with these vents? Is new life being created even now in the deep sea? In which case, what do we think about deep sea mining? If our aim is to reduce our carbon dioxide emissions by using more re-usable objects and renewable energy sources, we will require more batteries and batteries require (among other things) cobalt. If we are all to keep using mobile phones to photograph cafés, we too need the batteries which rely on these elements. A number of companies have realised that there is a vast untapped resource under the sea if only we could dredge it up. This may be easier or ultimately cheaper than recycling the old batteries. It may destroy a few hydrothermal vents or stir up the sea bed but what concern is that to us if we can gain access to more cobalt to allow us to have more batteries to allow us to all be ‘greener’.

Indeed, of what concern is that to us?

Curators Coffee is at 51 Margaret St, W1W 8SG

Categories
Coffee review Coffee Roasters Observations Science history slow Sustainability/environmental

A Story with many layers, Clapham Junction

Story Coffee St John's Hill Clapham
The doorway to Story, or a story depending on how you look at it.

A “ghost sign” above the door to Story Coffee on St John’s Hill ensures that you know that you have arrived at the correct place. “Peterkin Custard, Self-Raising Flour – Corn Flour, can be obtained here”, only now it is coffee rather than custard that is sold in the shop beneath. The sign is an indicator to the many tales that could be discerned while exploring the coffee within. I had had a couple of attempts to visit Story Coffee (thwarted for a variety of reasons) before Brian’s Coffee Spot’s review appeared a couple of days after one of my attempted visits. Suitably re-motivated, another trip was attempted (address checked, closing times checked) and this time we were in luck. Although a pour over is listed on the menu, sadly this was not available on our visit and so I enjoyed a lovely long black instead (Red Brick, Square Mile) while looking at the cakes on offer. There was plenty of seating in which to shelter from the rain outside and many things to notice in this friendly café. In addition to the cakes and lunch menu, a box on the counter housed “eat grub” protein bars, protein bars made of cricket powder. Are insects the future for humans to eat protein sustainably?

glass jar at Story
Through a glass darkly?
The distortions produced by the refractive indices of air, water and glass and the shape of the glass produces interesting effects on our view through it.

The tables were well arranged for people to sit chatting while enjoying their beverages and it is always an excellent thing (from a personal point of view) to encounter a café with a no laptop (or tablet) at the tables policy. Complementary tap water was available in jugs placed on each table while it was also nice to note that Story branded re-usable cups were on sale from the counter. Many things we noted can be seen in the gallery pictures in the review on Brian’s Coffee Spot: the funky fans, the egg shaped light shades, the light introduced by the large glass window panes (though it was a much fairer day on Brian’s visit than on ours). Each had its contribution to a thought train, the way the glass water jar bent the light coming through, the concept of a Prandtl boundary layer in fluids (and its connection to both fans and coffee cups). Moreover there were hexagons, which for someone who has worked on the periphery of the graphene craze, are always thought provoking.

Apart from hexagons decorating the top of the stools, there were hexagons lining the counter made of cut logs, each showing the rings from the tree that was felled. Rather than a flat surface, these hexagons were made to be different thicknesses on the wall, rather like the hexagonal columns of the Giant’s Causeway. It is a subtle thing that may have implications for the space that is otherwise surrounded by flat, solid, walls. Such spaces can become echo-y and yet, the music and conversation in Story was not overly distracting presumably because features such as the uneven hexagonal wall reflected the sound waves such that they destructively interfered rather than echoed around the room.

every tree tells a story, but which story
A macroscopic crystal of hexagonally cut logs forms the side of the counter.

Each log in the hexagonal decoration was cut with its cross-section showing a number of tree rings. We know that we can age a tree by counting the rings (though each of these would be underestimated as they have been trimmed into hexagons post-drying), but what more do the tree rings, and the trees themselves have to tell us? The rings are caused by the rapid growth of large cells during spring followed by a slower growth of smaller cells as the year progresses. But this method of growth means that the cut logs have more to tell us than just their age. The spacing between the rings can tell of the weather the tree experienced during that year, were there many years of drought for example? Such clues, from the relative density of the tree rings, can help researchers learn about the climate in previous centuries, but conversely, reading the climate report in the rings can indicate in which year a tree was felled and so the age of a building for example.

coffee at Story
Many stories start with a coffee.

And then there is more, trees will grow at an average rate per year so that, as a rough guide, the circumference of a mature (but not old) tree increases by 2.5cm per year¹. There is therefore something in the idea that you can have a good guess at how old a tree is by hugging it. But this assumes that the tree is growing in its optimum conditions, far enough from any neighbouring trees so as not to be crowded into growing more slowly. So the absolute density of tree rings must also give a clue as to whether this tree was in a dense forest or an open clearing. Which is reminiscent of something else that living trees can tell you if you listen to them closely enough: trees will grow so that their leaves are exposed to the maximum amount of light. For us in the UK, this means that the crown of a tree will frequently tip towards the south (where the Sun is most often) and there will be more leaf growth (and consequently more branches) in a southerly direction². But again, we only see this if the tree has room to grow on its own, without the crowding, and competition, of too many neighbours. A solitary tree helps us to know which direction we are walking in.

empty coffee cup Story St John's Hill
While many coffees could also tell a story. It depends on how you read them.

Which all points to the idea that there are many stories being told all around us all of the time, the ones we hear depend on what we choose to pay attention to. So what about the story behind the ghost sign above the door? The Peterkin custard company was a venture by J. Arthur Rank in an attempt to start a milling company in the mould of his father’s (Rank Hovis McDougall, later bought by Premier Foods). The company failed and Rank went on to form the Rank Organisation that was responsible for many films made throughout the 40s and 50s as well as running a chain of cinemas around the UK. Truly a sign concealing many stories.

 

Story Coffee is at 115 St John’s Hill, SW11 1SZ

¹Collins complete guide to British Trees, Collins, 2007

²The Walker’s Guide to Outdoor Clues and Signs, Tristan Gooley, Hodder and Stoughton, 2014

 

 

 

 

Categories
General Home experiments Observations Science history Sustainability/environmental

Air raising

Small waves seen from Lindisfarne
How do clouds form? How does temperature vary with altitude, and what does coffee have to do with any of it?

You put a drop of alcohol on your hand and feel your hand get cooler as the alcohol evaporates, but what has this to do with coffee, climate and physics?

Erasmus Darwin (1731-1802) was the grandfather of Charles of “Origin of the Species” fame. As a member of the Lunar Society (so-called because the members used to meet on evenings on which there was a full moon so that they could continue their discussions into the night and still see their way home) he would conduct all sorts of scientific experiments and propose various imaginative inventions. Other members of the Lunar Society included Matthew Boulton, Josiah Wedgwood and Joseph Priestley. The society was a great example of what can happen when a group of people who are interested in how things work get together and investigate things, partly just for the sake of it.

One of the things that Darwin had noticed was that when ether* evaporates from your hand, it cools it down, just as alcohol does. Darwin considered that in order to evaporate, the ether (or alcohol or even water) needed the heat that was provided by his hand, hence his hand started to feel cooler. But then he considered the corollary, if water (ether or alcohol) were to condense, would it not give off heat? He started to form an explanation of how clouds form: As moist air rises, it cools and expands until the moisture in the air starts to condense into droplets, clouds.

hole in water alcohol
There are several cool things you can notice with evaporating alcohol. Here a hole has been created in a thin layer of coffee by evaporating some gin. You can see the video of the effect here.

As with many such ideas, we can do a ‘back of the envelope’ calculation to see if Darwin could be correct, which is where we could also bring in coffee. The arabica growing regions are in the “bean belt” between 25 °N and 30 °S. In the sub-tropical region of that belt, between about 16-24°, the arabica is best grown at an altitude between 550-1100 m (1800-3600 ft). In the more equatorial regions (< 10º), the arabica is grown between 1100-1920m (3600-6300 ft). It makes sense that in the hotter, equatorial regions, the arabica needs to be grown at higher altitude so that the air is cooler, but can we calculate how much cooler it should be and then compare to how much cooler it is?

We do this by assuming that we can define a parcel of air that we will allow to rise (in our rough calculation of what is going on)¹. We assume that the parcel stays intact as it rises but that its temperature and pressure can vary as they would for an ideal gas. Assuming that the air parcel does not encounter friction as it rises (so we have a reversible process), what we are left with is that the rate of change of temperature with height (dT/dz) is given by the ratio of the gravitational acceleration (g) to the specific heat of the air at constant pressure (Cp) or, to express it mathematically:

dT/dz = -g/Cp = Γa

Γa is known as the adiabatic lapse rate and because it only depends on the gravitational acceleration and the specific heat of the gas at constant pressure (which we know/can measure), we can calculate it exactly. For dry air, the rate of change of temperature with height for an air parcel is -9.8 Kelvin/Km.

contrail, sunset
Contrails are caused by condensing water droplets behind aeroplanes.

So, a difference in mountain height of 1000 m would lead to a temperature drop of 9.8 ºC. Does this explain why coffee grows in the hills of Mexico at around 1000 m but the mountains of Columbia at around 1900 m? Not really. If you take the mountains of Columbia as an example, the average temperature at 1000 m is about 24ºC all year, but climb to 2000 m and the temperature only drops to 17-22ºC. How can we reconcile this with our calculation?

Firstly of course we have not considered microclimate and the heating effects of the sides or plateaus of the mountains together with the local weather patterns that will form in different regions of the world. But we have also missed something slightly more fundamental in our calculation, and something that will take us back to Erasmus Darwin: the air is not dry.

Specific heat is the amount of energy that is required to increase the temperature of a substance by one degree. Dry air has a different specific heat to that of air containing water vapour and so the adiabatic lapse rate (g/Cp) will be different. Additionally however we have Erasmus Darwin’s deduction from his ether: water vapour that condenses into water droplets will release heat. Condensing water vapour out of moist air will therefore affect the adiabatic lapse rate and, because there are now droplets of water in our air parcel, there will be clouds. When we calculate the temperature variation with height for water-saturated air, it is as low as 0.5 ºC/100 m (or 5 K/Km), more in keeping with the variations that we observe in the coffee growing regions†.

We have gone from having our head in the clouds and arrived back at our observations of evaporating liquids. It is fascinating what Erasmus Darwin was able to deduce about the way the world worked from what he noticed in his every-day life. Ideas that he could then either calculate, or experiment with to test. We have very varied lives and very varied approaches to coffee brewing. What will you notice? What will you deduce? How can you test it?

 

*ether could refer to a number of chemicals but given that Erasmus Darwin was a medical doctor, is it possible that the ether he refers to was the ether that is used as an anaesthetic?

†Though actually we still haven’t accounted for microclimate/weather patterns and so it is still very much a ‘rough’ calculation. The calculation would be far better tested by using weather balloons etc. as indeed it has been.

¹The calculation can be found in “Introduction to Atmospheric Physics”, David Andrews, Cambridge University Press