Car Science #10: devil's advocate lettuce
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So, as you might have noticed from the last couple of editions, rather than try and summarise tons of complicated stuff in one go, a lot of which doesn't necessarily fit together or deserves its own long discussion, I'm gonna try and keep Car Science to looking at one, recent piece of research and the stuff around it. I think that works for a) making a newsletter I can actually realistically produce every week and b) making something reasonably readable. Sometimes reading 15-30 papers isn't gonna happen. Sometimes that time has to be used for teetering on the edge of a breakdown and watching Buzzfeed Unsolved. And it means some of the stuff I've passed up for being too long to get into in a summary gets a chance to be given space.
This week's issue looks at why, of all the dang things, people keep inventing floating leaves that make fuel 'out of thin air.'
Science is odd. You get the same thing recurring a lot, sometimes - that could be like carcinization, the strange evolutionary process whereby things keep evolving into shitty crabs, because all the evidence points multiple researchers down the same path. Or it could be because research is a business and certain things attract more funding at any particular time.
The answer's probably somewhere between the two, which is that some promising fields crop up and there'll be an angle that if you work it into your pitch you're more likely to get a grant for. But there's something particularly notable about the current trend for inventing artificial leaves.
As you'll know if you've been awake at any point in the 21st century (and if this is how you find out then: sorry) we have a problem with an increasing concentration of carbon dioxide and other greenhouse gases causing global warming and anthropogenic climate change. One of the reasons the situation is so severe is that we have combined adding huge amounts of CO2 to the atmosphere that had previously been safely sequestered underground as fossil fuels with stripping away large amounts of forest and sea grass and meadows and kelp that previously acted as carbon sinks.
The most effective carbon capture method available to us already exists: it's fields of sea grass. It's actually more effective than the rainforest - thirty five times more. Sea grass meadows have been severely depleted but there are ways to regrow them, saving animals like dugongs and providing an effective carbon sink. All without needing any fresh water at all, which is going to increasingly be a problem for us as the earth warms and salination increases. Because the land is getting hotter and less snow is falling in winter to form glacier meltwater, more water is ending up in the sea faster, so a carbon sink that thrives in brine is particularly good.
The other ones we have, of course, are just plants in general. Plants very effectively sequester carbon dioxide and the process they do it by, photosynthesis, is currently very interesting to science. If we could passively, with artificial leaves, remove carbon from the air and potentially make something useful to us like hydrogen or synth gas then that's a very useful process to the, uh, petrochemical industry which has rarely been all that interested in botany.
There aren't many botanists at all these days, which is one of the problems with trying to deal with Our Current Situation. But there is lots of petrochemical funding and I'm not saying every attempt to engineer an artificial leaf is a sinister plot from Big Oil because there are genuinely useful applications to them but there is a sad disconnect between plants that can do this very efficiently and have existed for hundreds of millions of years and trying to make something that does it nearly half as well.
Anyway, so: trying to engineer ourselves out of this mess we've made it is, I guess and if actually making fake plastic trees might feel like the writing is really getting lazy then, well. It's still happening.
What is an artificial leaf?
Defining what makes an artificial leaf, in science terms, is more than just the plastic plant section of IKEA. For it to be classed as an artificial leaf it's got to be doing some version of what leaves do, which is being a photo-electro-catalytic cell, basically. Using sunlight (or an equivalent light source) to make a reaction happen and change something, a bit like the process that plants do via photosynthesis.
Here at Car Science we talk a lot about rearranging hydrocarbons because well, there's a lot of it going round. You'll remember from all the synthetic fuels stuff that basically smashing different orders of hydrogen and carbon atoms together makes whatever you fucking like if you can make it happen and photosynthesis is just another one of those processes. A really efficient one that plants have super got the hang of.
Plants capture carbon dioxide from the air and then split hydrogen from water to make glucose, with some leftover oxygen as the emission. Which is extremely like the process to make synthetic fuel, except it's done in the cells of a leaf not in a complicated and energy-intensive manufacturing process.
Artificial leaves take that principal of something that can end-to-end use sunlight for energy and (usually) water and make something else. Often, they don't look like leaves at all because they're complicated photo-electro-catalytic setups that involve layered arrays. But some of them have started looking a lot closer, like this Cambridge University study I've linked to in Car Science before that created a plastic-enclosed leaf light enough to float on water.
That leaf makes synth gas, which can be converted to a natural gas alternative or even further refined into synthetic fuel depending on how many levels of fannydangle you want to go through once you've got it. As you can imagine, something the size of an A5 piece of paper doesn't make a huge amount of synth gas before it needs emptying so I wouldn't call the process mature or efficient yet but it is impressive that a technology went from something that had to sit on a lab table to something light enough to float in just a few years.
What artificial leaves have over regular leaves is that they really only do one thing. They're not part of an organism that's trying to balance stuff - trees don't always need or want to make the maximum amount of glucose all the time whereas artificial leaves don't give a shit about that and can run as high as they can for as long as possible. As a consequence, you can end up with ones that, relative to the same area on a tree, absorb much more CO2. Like this one, from Toyota Central Labs.
Doesn't look a lot like a leaf really, does it? But it does absorb a lot of carbon, more than the same square metre of cedar forest. And it certainly makes a lot more fuel-relevant chemicals because plants, well, they don't do that.* The leaf can convert solar energy to chemical energy at an efficiency rate of about 10.5%. That's pretty dogshit for photovoltaics (20% is good for most modern panels, at the lab stage there's 60%+) but of course, a solar panel is just generating electricity and putting it somewhere where it could be used in other things (that probably have fairly high efficiency) compared to converting it to a chemical fuel. And the solar panel, in all fairness, is not capturing any CO2.
Chemically storing CO2 using systems that power themselves is a really cool concept. The business case for it is where it begins to get, shall we say, sketchier to justify.
Nothing new under the sun
The drive for artificial leaves isn't about sequestration. It's about a non-fossil fuel alternative. Jet planes fuelled by artificial leaves, the carbon cycled out of and then back into the air to aim for neutrality.
It's a nice concept and if we had started here then we wouldn't be in this mess. But like a lot of things it's not enough to be carbon neutral now - and neutrality is a long way off realisable for synthetic fuels once you account for their movement and storage and refining. The idea of "fuels out of thin air" is, sure, nice but the fact is it takes equipment and infrastructure and maintenance.
Even if we get back to non-artificial leaves, there's a carbon cost to cultivation. It's why biofuels have to come from non-farmed feedstocks to approach anything like carbon efficiency. These new technological cultivars have the same problem, which is that leaves exist as a system not in isolation.**
Not to get too organic chickpea soup at you but our problems have been created by not caring what the wider consequences of actions are. And now those consequences happen in thinner and thinner margins of operation because the wriggle room we have before total climate apocalypse is in negative numbers.
The research that prompted me to pick this for a newsletter was this: a step towards solar fuels out of thin air
It's a new wafer-thin (picture at the very top of this newsletter) product that does something a little bit different. It's not using a photosynthesis-style process that captures carbon and is fed with liquid water, it's basically moisture farming for hydrogen.
That's interesting, especially as a passive process that uses air moisture. Here in dank, January London I reckon stringing a few of these up in my lounge might be pretty useful. On the other hand there is a problem, which is that if moisture in the air can reach the semiconductor coating then hydrogen, famously extremely difficult to contain, can definitely get away from it. So the process can only happen in sealed containers, so far at least.
That doesn't mean it's totally naff and it could be a very interesting way of producing green hydrogen from a solar source that doesn't have the same nonsensical losses as generating hundreds of gWh of solar power only to use it to make hydrogen by electrolysis and end up with a potential 80% (at best) of the energy you'd originally generated. And it seems very likely green hydrogen has some role in future processes, in industry as a natural gas replacement even if it doesn't play a part in transport.
Maybe I'm getting old and curmudgeonly, it is a surprisingly large number birthday all too soon. But there's a bit of me that can't help feeling a bit 'wish Gen X authors would use less blunt metaphors, I'm sure I thought Douglas Copeland was good at one point' about the idea of all these millions being plunged into artificial leaves for this far-distant (and not physically realisable) concept of free, clean fuel out of thin air when right now we could do with more, y'know, actual plants.
To end this on a different note (well, maybe the same note but whatever, it's where my brain's gone) I've been watching a lot of Alexis Dahl's excellent content about Michigan and was wondering when I'd come across something about the auto industry. If you're interested in cars, this video about how Ford and GM razed the Michigan forest to build Detroit and the nascent automotive industry is well. It's a more blunt lens on 'cars vs trees' than you might normally see but still, a worthwhile bit of history to learn.
Anyway. I don't know if there's a miracle cure in engineering the trees we've lost. It feels sad to think of doing that - maybe it could be our short term fix, a time-buying carbon sink to give us (and plants) space to gasp a breath through the smog. But like everything miraculous, fuels out of thin air is a phrase that can't be resisted and shouldn't be believed.
See you next week
Hazel
x
*This isn't totally true because glucose very much is a fuel. And actually something very promising is that glycerin can be used to run diesel engines with virtually no conversion needed - Formula E used to do this with Aquafuel, made out of brine-farmed algae. All of that seems to have gone away in favour of hydrogen discussions in the past half-decade or so, which is unfortunate because it's the more readily available and scalable solution, as things stand with hydrogen production efficiency and storage challenges.
**Except for a bunch of freaky plants like the amorphophallus corpse flower which grows this weird ass green tree thing in its first phase which is actually just one leaf and honestly. That thing is fucked up. But maybe fucked up and stinking of rotting flesh is where we're at right now so who am I to rule it out.