Money Does Grow On Trees
So, you like your phone, electric car and other modern gadgets but hate that the metals come from filthy mines with exploited workforces and tremendous amounts of pollutants that are a massive driving force towards our inevitable climate doom? Luckily, many scientists are in the same boat, but using a quirk of biology, they could replace these mines with forests. Miners could put down their shovels and instead become conservationists, caring for the forest and collecting the gold, nickel and copper crops that will power an eco-friendly future. Is this a way to herald an eco-friendly tech future, or is this just a pipe dream?
Before we get into the fantastic possibilities of plant mining, why are our mines so terrible? Well, there are four huge problems, logistics, land use, carbon footprint and processing. Let me explain.
Our modern tech needs metals like gold, nickel, copper, lithium and neodymium, to name just a few. Sadly they aren’t? in equal concentrations worldwide, and often the sites with the richest metal ores are in critical natural areas, for example, the Amazon rainforest’s massive copper mines. This means that a lot of logistics are needed to get all the right materials to the factory to make your phone or laptop. This increases the carbon footprint of our tech dramatically, simply through awkward logistics.
But you’ve probably guessed that mines in places like the Amazon aren’t a good idea. This is where land use comes in, because they are a leading cause of deforestation. Not only do you need to flatten the area of the mine, but also the roads, workers village and farms to feed said workers. Suddenly you are setting up a massive city in the middle of a fragile rainforest, then small towns grow on the connecting roads to other cities, and slowly the rainforest completely disappears. That’s right, the metals in your gadgets could be driving deforestation.
So, we have wrecked a vital ecosystem and burnt a tonne of fuel to get this metal, so what? Well, we aren’t done yet, because we haven’t refined out the metal. All you have is a lump of rock, you need to heat that up to incredible temperatures and skim off the molten metal. To do this, you need vast refineries that use immense amounts of energy. These can release some particularly toxic gasses into the air, not to mention all the CO² from the energy production. But after all this polluting, surely this has to be the end of the climate nightmares associated with mines?
Nope! You see, some mines pump vast amounts of water into the ground to get at the precious metals. But this can leach metals and toxic compounds into surrounding waterways, poisoning entire ecosystems.
So we are all agreed, mines suck, but how can trees help? Well, it’s all to do with how life has a habit of hoarding. Let me explain.
Have you ever been told not to overeat fish because it has a lot of mercury in it? Well, mercury and other heavy elements are known to bioaccumulate in animals. So, when the mercury rich runoff from volcanoes, coal plants and mines (oh, look, another reason they are terrible) goes into the ocean, krill, muscles and other filter feeders absorb it into their cells, now, they don’t mean to, it’s just that cell mechanics can get confused. For example, strontium, a radioactive element associated with nuclear fallout, is absorbed by humans in the same way as calcium because our cells get tricked into thinking it’s calcium. People exposed to strontium end up with huge amounts of it in their teeth and bones, turning them radioactive.
But the concentration of mercury in the water is incredibly low, and filter feeders tend to be short-lived, so they can’t accumulate much in their tissues. But their predators, particularly the longer-lived ones like Tuna or Salmon, can accumulate a lot in their tissues because they eat tonnes of these tiny critters. This means the higher up the food chain you go, the higher the mercury contamination, and we are at the top of that food chain! Overeat contaminated Tuna, and you could overdose on mercury and get permanent nervous system damage.
So maybe think twice about having those sushi rolls for lunch every day?
But rather than digging up our precious metals, why don’t we use some form of bioaccumulation to gather up what we need from our local environment? This is precisely what the scientists have set out to do, except, rather than using delicious seafood, they are using some rather incredible trees.
Trees might not be on top of the food chain, but they can still be magnificent bio-accumulators. Their roots run deep and interact with the water table, and the mycorrhizal fungi that grow on their roots can break down rocks and soil, releasing locked up metals. They are also incredibly long-lived, giving them lots of time to accumulate. So, in theory, trees could extract a vast amount of gold, copper, nickel and other essential metals from the soil and waterways. But there’s a catch, not all trees are good at keeping a hold of these metals.
But some trees are particularly good at it. Pycnandra acuminata is a species of Caledonia tree with green latex sap that is 25% nickel! All you need to do is bleed the tree like they do with Maple trees, refine the sap (a lot easier and eco-friendlier than refining ore) and hey presto, you have nickel! Species like this are so good at accumulating metals that they have been called hyperaccumulators!
But this is a rare tree on a small island, there are only around 700 Pycnandra acuminata in existence. But other hyperaccumulators exist, such as the macadamia, which pumps manganese into its leaves, a crucial ingredient for metal alloys. As we find more and more trees that accumulate different elements, we can either selectively breed or genetically modify them to be sturdier and more efficient, eventually, to the point where these plant mines are cheaper and easier to run than actual mines. At least, that’s the end goal.
An important thing to remember here, while these trees need specific soil conditions, climate, and a supply of their chosen metal, it doesn’t limit them to their natural habitat. We can modify them to cope with colder or hotter weather, wetter or dryer climates, enabling them to grow in places they couldn’t before. You could even use them to recycle the metals in rubbish dumps by growing them nearby so that they both share the same water table. What I’m getting at here is that the nickel that runs your phone doesn’t have to come from a mine. It could come from a Pycnandra acuminata tree in your city, one that has been modified to thrive there and extract the metals local to you, drastically reducing logistics. This makes the metal cheaper and more eco-friendly.
This decentralisation could end or ease international trade. All your gadgets could be entirely homegrown and homebuilt. No more relying upon foreign mines, factories and fuel-guzzling shipping! While this might upset some countries that rely on this trade, it could boost the economy of many countries and drastically lower our overall climate impact.
So, it sounds like a good idea, doesn’t it?! Close down all the mines, we will replace them with extraordinary forests of metal-eating trees!
Well… You might want to think again.
Sadly, I can’t find any figures on how much land these forests would take up. But if you’re going to replace all the worlds mines with trees, I can imagine you’ll need a considerable amount of them, taking up an awful lot of land with a small number of tree species. We’re already doing this with the Palm Oil industry, vast swathes of rainforest cut down and replaced with a single plant and it is causing an ecological nightmare.
Not only do these Palm farms crash biodiversity by using up huge amounts of land, fragmenting and reducing vital rainforests, but it also leaves the tiny bit of ecosystem left incredibly vulnerable. It only takes a single disease or a slight predator-prey imbalance to send the whole ecosystem out of whack, wiping out species and farmers livelihoods. We can’t just go planting these metal gathering trees anywhere. We need to think about it. Otherwise, our solution will be just as terrible as the problem.
Having a wide variety of trees that all find different metals is one solution because it could keep the biodiversity of the mining forests high. But remember that animals eat stuff off these trees. Bugs will eat the nickel rich sap, wild boar could then eat these, become hyperaccumulators themselves, and finally, we eat the boar and get sick. It’s the seafood all over again!
There likely is a combination of plant mining farmland, plant mining vertical farming and traditional mining that will be the least harmful to the environment. But this is still a new field of research. We can’t be sure what that perfect balance is yet.
So, money does grow on trees! Some of our most precious metals, which enable our twenty-first century lives, could be harvested from hyperaccumulator trees with minimal impact on the environment. But only if we can pull off an ecological balancing act.