This post is written by Monica Cesinger, a microbiologist at UC Berkeley passionate about using biotechnology to build a more sustainable future.
Imagine: A picogram-sized organism that can efficiently mine the megatons of critical metals we need to power the world economy. Biomining may sound like science fiction, but this technology is both feasible and primed to play a critical role in ensuring our clean energy future.
To reach net-zero emissions, we will require 3.5 times more critical minerals by 2050 than we use today, for everything from electric vehicles and batteries to solar panels and wind turbines. This increase is estimated to require $800Billion of investment by 2040, but it’s more than “just” scaling old approaches. Mineral extraction is a destructive process: It can damage waterways, landscapes, and animal populations. A continued decrease in ore concentrations means that future mining will take more energy, water, and earth to produce the same amount of metal. We need a solution to clean energy’s dirty environmental footprint, fast.
“If it can’t be grown, it must be mined” is the old mining industry adage. But in the case of mining sustainably, growing things can help. We have an opportunity to leverage ancient talents of biology to produce metals more efficiently with fewer environmental downsides. This is the first of a series of posts in which I will outline not only the “why” of biomining and its enormous potential, but also the “how.”
“In these parts I have discovered very important secrets,” the priest Diego Delgado wrote in 1556 about the Spanish Rio Tinto river. Delgado was a man of little influence who had tried in vain to bring his king’s attention to the river’s peculiar chemistry for months.
In a last-ditch effort, Delgado risked an arduous journey to the capital to address the king in person. But only days after his arrival, Delgado mysteriously perished. Death may have at last been enough to win his words an audience, because the king himself noted “He is dead” in the margins of Delgado’s final letter. So began the fraught rediscovery of the 5000 year old Rio Tinto mine, now the namesake of the second largest mining corporation in the world.
Despite Delgado’s untimely demise, his secret survived. Delgado wrote down that Rio Tinto’s waters possessed a “very distinctive peculiarity or property, that if iron be placed in it, in a few days the iron disappears.” When enough iron was added, copper would spontaneously precipitate, a phenomenon that may have sent Spanish alchemists into a frenzy. It would take four more centuries for scientists to discover that this secret was not alchemical, but microbial in nature.
The metal-laden leachate that so mystified a 16th century priest was actually the byproduct of clever bacteria that siphon electrons from sulfurous rocks for energy and make sulfuric acid in the process. This acid dissolves copper and other metals locked within the rocks of Rio Tinto, which can later be separated out by humans with simple chemistry in a process called biomining. Delgado didn’t know it, but this process has been occurring naturally for millennia. 3000 years ago the Romans unintentionally bio-mined copper on Rio Tinto’s banks, foreshadowing how at least 15% of copper is produced by biomining today.
As our electrified world demands exponentially more metals like copper, we must start thinking about how to more ambitiously leverage this billion-year-old bacterial trick.
Our Dilemma: An unsustainable path to sustainability
The clean energy transition is supposed to save our planet, but the mining required casts a shadow on our progress towards net-zero emissions. The sheer amount of metals we need to dig out of the ground (40 megatons by 2050) for this transition poses significant environmental challenges.
The clean energy sector’s demand for critical minerals will triple by 2030. On our current trajectory, we’ll be short 50% the amount of lithium we’ll need by 2035 even with the mining projects that are already in development. That’s only 11 years till we run out of lithium, and a new mining project started today to combat that shortage could require 18 years or more to fully permit. We face similar challenges with copper, nickel, cobalt, and rare earths. Given the demand for metals, the energy transition could be responsible for a maximally resource-intensive era of mining and still not meet the needs of a net-zero world.
Centuries of mining the best ores first means that future sources will almost certainly be more dilute. As ore grades continue to decrease, we will use more energy and water per ton of metal that we extract. The amount of waste and the environmental footprint of mining will also grow in parallel. Mining efforts today already span an amount of land three times the size of Massachusetts, and future mining of energy transition metals will use a lot more.
Our land use will encroach on threatened species, as new mines are increasingly being built near protected areas important for biodiversity conservation. Future mining will also exacerbate the inequity of climate change impacts; the negative health outcomes of living near mines would not be evenly distributed, with two thirds of new energy-transition-metal mining projects located near Indigenous and poor rural populations.
The path we’re on now poses an unfortunate contradiction: Producing the metals we’d need for the energy transition with traditional mining comes with devastating environmental and social costs. It doesn’t have to be this way, and the dedicated implementation of biomining could present a better path forward.
Let’s blend the optimism of biotech with the realism of heavy industry
Today, biomining can reduce the amount of energy we need to produce certain metals like nickel, as well as eliminate toxic byproducts of smelting like arsenic and sulfur dioxide. However, biomining is often used because it is cost-effective, historically implemented to extract copper and other metals from otherwise uneconomical sources like low-grade ores and waste streams. Expanding implementation of biomining could address the metastasizing problem of decreasing ore grade with a solution that demands fewer resources to use poorer substrates. The pressing question becomes, which metals can emerging biomining technology extract, and how sustainable would this be compared to other available methods?
Biology has evolved to interact with metals on every scale: from small molecules (organics and acids) and complex biomolecules (nucleotides and peptides) to organisms (hyperaccumulators and biosorbents) and whole ecosystems (rock weathering, nutrient flux, and the mechanical forces of root systems). This gives us a robust and diverse toolkit from which we can derive solutions to the challenges we face today. Researchers continue to discover novel ways that organisms take advantage of the periodic table, and we must urgently build upon that body of work to realize the industrial potential of these processes.
Microbes are the original miners, and we can thank oxygen-producing microbes from 2.4 billion years ago for the variety of complicated chemistries they encounter in minerals today. However, it wasn’t until 1947 that researchers published evidence of microbial bioleaching, the most common way to biomine. They discovered that metal leachates seeping out of old mines across the United States — the “acid mine drainage problem” — was the fault of microbes. As it turns out, the same sulfur-oxidizing bacteria that leached precious metals into the Rio Tinto in Spain will bioleach indiscriminately into waterways everywhere. While bacterial miners have continued to be an environmental hindrance at mining sites, 80 years of research has allowed us to repurpose their talents for good.
Within a decade of their discovery, microbes like those found in acid mine drainages were implemented commercially to mine metals — first copper, and then many others, including cobalt, nickel, zinc, gold, silver, and even uranium. Yet, we’re still falling short.
There are so many theoretical ways that biology could help us access these critical resources. So despite the enormous potential of biomining to transform our industrial processes, the participating microbes remain grossly understudied relative to their colon-dwelling cousin E. coli. The overwhelming majority of public microbiology research has been done in the context of human pathogens, limiting our understanding of microbes and metals to chemistries found in the human body.
Scientists who set their sights on the diversity of biomolecule-metal interactions out there are primed to seize on 3.7 billion years of biology’s untapped potential and revolutionize the mining industry just as we need it most.
Delgado’s Ghost in the Dilemma
It took the death of an unlucky priest to bring attention to the then-poorly understood process of biomining in 1556. There is a grim poetry to the fact that we are facing the demise of ecosystem health and biodiversity as we reignite the conversation around biomining today.
To capitalize on the potential of biomining, we must aggressively ramp-up research and investment. We are already biomining copper at scale, and engaged researchers can improve the efficiency of this process with bioengineering. There are also efforts to understand how to biomine other metals critical to the clean energy transition. The minerals in which these metals are found present a diversity of chemistry problems that could very well be solved by an equally diverse set of biomining approaches. There are lots of exciting new technologies in the pipeline, and implementing impactful biomining developments quickly and at scale will require focus and community engagement.
I’ll be outlining how the scientific community can understand and deploy climate-minded biomining in a series of posts. First, I will address the challenges of mining specific metals, and which of these challenges biomining is best equipped to address. Next, I’ll outline the interactions of metals and biology. Finally, I will outline strategies for aspiring climate-driven biominers to get their projects and companies off (or perhaps, into) the ground.
We can’t do it alone. If you have ideas, would like to help us answer these questions, or want to talk about biomining, please reach out to us at hello@homeworld.bio
Acknowledgements:
Thank you to the Homeworld Team for collaboration, to Niko McCarty for early edits and perspective, and to Camille Fassett for guidance and final edits.