字幕表 動画を再生する 英語字幕をプリント Some plants are totally metal… and I'm not just talking about venus fly traps. There are plants that literally ooze metal! And we're farming them! But first, we gotta back it up a little bit. In the ground beneath our feet, there can be all kinds of different metals. Not in the form you and I might picture them, like in a can or in your car, but in a much more unrefined, elemental form. And turns out, some plants have evolved to absorb lots of metal from these soils, through their roots. These helpful superstars are called hyperaccumulators, and there are lots of different kinds. After sucking up all that tasty metal, hyperaccumulating plants do just that—they accumulate that metal in their bodies. (If you can call them that. Do plants have bodies? Whatever, you get the point.) Now the metal is inside them, it's literally running through their vascular structures in their sap, or even their shoots, seeds, and leaves. So now, we can extract it from the plant, which has so handily brought it all together for us. A group of researchers working on a small trial farm on the Malaysian side of the island of Borneo is already trying this with a plant that accumulates nickel. Every six to twelve months or so, the farmer can harvest about this length of metal-filled plant tissue, and through purification, then have all this metal, no mining required. Nickel in particular is an essential component of stainless steel, like what you might see in your kitchen, and we're seeing increasing demand for both it and its derivatives for things like electric car batteries and even your cell phone. But mining it - just like mining other heavy metals and rare earth elements - is extremely destructive. Not only because you're literally cutting open the earth, but because you're leaving behind some really intense chemical pollution as you refine it, too. The process we humans have traditionally used to extract the metal from its raw form in the ground is called “smelting,” and it involves lots of energy-intensive heating and melting, plus purifying chemicals and lots of waste products. So, as our world's boundless appetite for things like cobalt, zinc, and other heavy metals continues to grow, we're seeing a serious environmental impact. That comes in the form of water, soil and air pollution - not only from smelting's byproducts, but also from the metal itself, which can be really poisonous when inhaled or ingested. So, being able to farm these metals, instead? Yes, please. The plants are basically natural, solar-powered smelters: they do the whole thing for us in a totally self-contained way. And this concept is called “bioharvesting,” or more specifically, “phytomining.” Which basically means we're farming metal, which just sounds way too cool for this reality. But that's not all. Because remember that pollution I was just talking about? In addition to being a sustainable source of heavy metals and maybe eventually rare earth elements, they can also be used to clean up heavy metal pollution. Another research group has been studying copper- and zinc- accumulating plants. They've shown that plants - specifically Brassica juncea, a kind of mustard plant and Sedum alfredii, a common Asian herb, could uptake heavy metals from a polluted copper-zinc mine. This helped clean up the site, a process called phytoremediation. Then the team was able to process those plant tissues and use the bio-accumulated metal to make carbon nanotubes and carbon zinc-oxide nanoparticles, both of which can be used to advance all kinds of exciting electronics and energy technologies. So, not only did you clean up the pollution, but you then were able to still use that material instead of having to find a way of safely disposing of it, and you made something really useful out of it. It kinda feels like we could really be on our way to getting this recycling thing down, you guys. Exciting as it is, all of this is still in its beginning stages. Scientists are working hard on optimizing growing techniques and understanding ideal growth and accumulation conditions to make this phytomining thing a really strong competitor to the existing methods. They even say with further development of the science, they think this process could expand all over the globe... really changing what we mean when we say a "grassroots solution." One last fact: scientists think that it may have been helpful for hyperaccumulators to evolve the ability to store these metals in their tissues so they would be toxic to predators. Pretty cool. If you want more surprising melding of nature and tech check out my other video on graphene-enhanced mushrooms over here. And keep coming back to Seeker for all of your news on botanical advancements. As always, thanks so much for watching, and I'll see you next time!