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Australian National University (ANU) researchers are studying how to clean polluted water while extracting rare minerals, metals and scarce nutrients.
But why start from scratch when nature has already solved the problem?
“Prospectuses are already looking for a golden tint to gum leaves,” said plant scientist Associate Professor Caitlin Byrt cosmos. “Gum trees take up gold and accumulate it in their leaves. So it’s a cheap, quick and easy way to prospect for new gold deposits.”
Cutting down entire forests of eucalyptus for a few ounces will never be economically or environmentally sustainable, or pressure the local koala population.
But altering and mimicking the natural processes within trees that absorb, separate, transport and store minerals could solve a multitude of problems.
That is the goal. And a basic understanding of how it all works is established.
Now it’s time to turn that into a functional reality, says Byrt.
True blue ingenuity
What does Adblue, the diesel additive, have to do with it?
Australia recently experienced a supply crisis with the diesel additive AdBlue. Only a handful of nations, including Russia and China, produce it. The transport industry says it plunged into a crisis when it forecast shortages.
“AdBlue is a combination of super pure water and super pure urea,” says Byrt. “But humans release a few grams of urea and a lot of water as waste products every day.
“What if we could get creative – where every rest stop in the outback could collect deposits from drivers and give back something for their diesel tanks?”
Put simply, the molecules critical to the global economy are everywhere.
The numbers are enormous.
Globally, an estimated three million tons of phosphorus, 16.6 million tons of nitrogen and 6.3 million tons of potassium are trapped in urban wastewater. This includes enough organic ammonia and hydrogen molecules to power 158 million homes.
Then there is industrial wastewater. The Australian mining industry generates 500 million tonnes each year.
“Industrial wastewater can end up becoming a toxic mess,” Byrt says. “Effluents rich in metals such as copper, lithium and iron must be treated to recover these resources.”
Each element is immensely valuable – but only in its pure form.
The challenge is to find efficient and inexpensive ways to extract them before readily available mine deposits are depleted.
At the same time, the world’s water supplies are coming under increasing pressure. Polluted water must not stand idly by.
dr Byrt sees this as an opportunity.
Green technology to find rare minerals
From algae to acorn trees, plants are super-efficient solar-powered refineries.
Your cell membrane components can identify certain molecules, separate them from their environment and transport them to their desired location.
Plants do that. That’s how they live.
And that is exactly what is needed in mineral extraction and water purification.
“We investigated how plants can separate different target molecules and handle them differently in plant tissue,” says Byrt. “But that was all for crop applications like drought resistance, salt tolerance, and to promote basic plant biology.”
This research has new applications.
“Separation processes make it possible to take something that is a problematic environmental waste and extract target resources,” Byrt says. “It has the potential to enable a circular economy where those resources are reused and the end product is clean water.”
This is because plants share their resources.
Take cane. Squeeze it out and you get a sugar-rich liquid. Crush the stalk and you have a source of fiber. And the roots contain a whole separate collection of materials.
What if these otherwise underutilized parts of the plant could capture a valuable local mineral?
“We can develop new membrane technologies with precise separation capabilities that are not available in any other technology. And we can do that by borrowing from already developed plants.”
It’s not quite the same as picking gold nuggets from a berry bush, Byrt says.
But it’s a win-win-win scenario.
“You fix carbon while using solar radiation to power the process. They create a natural living environment and collect a vital resource,” she says. “Toxic dumps could become lush green lithium mines. And municipal sewage systems are a convenient source of potassium, phosphorus and nitrogen, which are becoming increasingly difficult to find.”
hyperaccumulators
Some plants are already harvesting minerals and molecules on near-industrial scales.
“There are species that can accumulate and compartmentalize up to 17 percent nickel,” says Byrt. “So it’s quite conceivable that a hybrid battery could be used as a solar-powered, carbon sequestering harvester in an area where there are a lot of gold particles dispersed in the environment.”
Unwanted money sinks could also become valuable raw materials.
“People have anecdotally said that $2 million worth of material can be trapped in a given mine tailings pile, but it causes $4 million worth of environmental problems,” Byrt explains.
It’s only trash because it’s a messy mix of materials. And his split hasn’t been economical so far.
“It’s only valuable if it’s pure,” Byrt says. “So it’s the separation challenge that we’re trying to overcome.”
Hyperaccumulating plants already have the techniques.
It is now a question of converting this into a highly scaled technology.
But plants alone cannot always be the solution.
“In some industries, like mine tailings, you just can’t grow anything,” Byrt says. “There is no creature that will survive that you are dealing with.”
But system know-how can still offer a solution.
“We will borrow mechanisms in living organisms and turn them into machines,” she says.
molecular manipulators
We are already doing this to a limited extent.
Desalination plants use membranes to remove the salt from seawater. And the US Army has ship-container-sized portable units that can process 17,000 liters of dirty water into drinking water every day.
“Plants can already perform these functions naturally,” says Byrt. “But not every plant can do what every other plant can do. It is about knowing which plants survive which conditions and which enable a certain process.”
Many species and subspecies have evolved different molecular mechanisms to suit their unique conditions.
“That means if you just take a copper-storing plant and expect it to work at harvesting nickel-rich soil, it won’t work. You need the right combination of biological functions.”
The ANU research team focuses its research on 10 target molecules.
Most are distributed among nutrients such as nitrogen, phosphorus and potassium.
“These molecules, these elements in their ionic form, come in a variety of different complexes,” she says. “Each of them requires a specific separation process designed for that.”
The minerals examined remain confidential for the time being, she adds.
“Our team understands what the parts of a plant do on a molecular level,” explains Byrt. “Each different cell type has its own biochemistry — the ability to have enzymes that can convert different molecules into different shapes. It also has its own membrane transport functions – allowing it to take in one thing and release another.”
When you understand this, anything from an algae bioreactor, a crop, a grove of trees, or a processing plant can be tailored to a specific product.
“It’s hidden from everyone’s eyes. Nature has already solved problems related to the management of these types of resources,” concludes Byrt. “Once understood, billions of years of accumulated biological skills can be applied to new technologies.”
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