Biomining: the next mineral revolution

With the help of biotechnology the race is on to discover the magic bug that will revolutionise the mining industry. Julian Cribb reports.

Jason Plumb was prospecting around the flanks of Rabaul's grumbling volcanic ash cone when a thunderous blast caused him to look up. It's just as well he did.

Moments later a hail of boulders, rocks and debris smashed down, leaving the CSIRO researcher scant seconds to seek shelter beneath a slight overhang. His two local companions simply bolted.

Plumb dusted himself off and continued his perilous quest. He wasn't in search of minerals, but of something far more valuable. He was looking for the bugs that have the potential to revolutionise the mineral industry and unlock boundless new wealth for Australia. Tiny microbes that inhabit the scalding hydrothermal springs around active volcanic sites - and which dine on ores of copper, gold, lead, zinc, nickel or silver.

Biotechnology is poised to transform mineral extraction in the same way it is already transforming healthcare and agriculture, predicts Dr Rod Hill, Chief of CSIRO Minerals.

Bioprocessing is already used in some mineral operations, to concentrate gold or copper, or to purify waste-streams. But nothing compared with what is on the horizon, when bugs may actually be sent underground to extract minerals or energy, when bugs will win metals more cheaply, cleanly and greenly than any existing process, when bugs will open up vast mineral reserves yet untapped.

With the world's mineral wealth concentrating in fewer and fewer hands, the race is on to find the technologies that confer decisive market edge - and which satisfy the triple bottom line requirements of economic, social and environmental sustainability.

Entered in that race are some of the oldest living creatures on the planet, archaea, or ancient bacteria that have been around for two or three billion years. Long before humans were even a gleam in evolution's eye, these microbes developed an extraordinary tolerance to extreme conditions - boiling heat, intense pressures, salinity, extreme acidity or alkalinity, toxic solutions. And they evolved to subsist on the sulfides and other compounds that surrounded them.

Jason Plumb was sampling springs at the foot of the cone when he had his Pompeii-like experience. The hot, mineral-rich waters were aswim with novel life-forms. Carefully, he stored his samples in thermos flasks, keeping them warm with infusions from his hotel electric jug for the flight back to the Perth laboratory, where they are now happily leaching copper into sky-blue sulfate solution.

The search for 'extremophiles', or bugs which tolerate extreme conditions, is driven by the observation that they out-perform microbes that operate at lower temperatures, says microbiologist Dr Peter Franzmann of CSIRO Land and Water. High temperatures literally thrust the bugs' metabolism into overdrive. This seems to offer the brightest prospects for efficient new mineral extraction processes in situations where conventional techniques are uneconomic and/or would have a negative impact on the environment.

Some microbes extract the target mineral, and must themselves be processed to purify it. Some devour the elements compounded in the ore, leaving the mineral behind. Some excrete substances that leach the mineral from its matrix. Compared with current extraction technologies bioprocessing is slow - but it is also cheap, natural, clean and sure.

The research focus now is on identifying the right mix of bugs for various tasks and designing the most effective ways to manage them for peak production, says Dr Franzmann.

"We are starting to see bioprocessing and bioextraction as serious alternatives to chemical or engineering methods of mineral extraction, particularly for metals," says Dr Hill. "Hence the race to be first to discover the 'magic bug'."

"Fourteen per cent of Australia's total electric power is currently consumed in crushing and grinding ore. Imagine the savings in both energy and greenhouse emissions if we can eliminate the grinding step and bioprocess part of the ore instead.

"Nowadays, with an average gold ore, we need to crush 2.5 cubic metres of rock to get enough gold to make a wedding ring. But microbes can perform the same task using much less energy."

Major international mining operations are already starting to use bioprocessing to extract mineral residue from waste-heaps which, if processed by conventional methods, would be uneconomic.

To Hill this opens up one of the most exciting prospects of all: a mineral industry no longer reliant on the discovery of giant high-grade ore deposits. The advent of bioprocessing makes low-grade resources an economic prospect.

"In theory you can bioextract minerals from just about anywhere including your own backyard, if you have the right bugs, the right process and are prepared to be patient," he says. "Using the combined expertise in four of its Divisions, CSIRO has put together a multi-disciplinary team of researchers, co-ordinated by Dr Helen Watling of CSIRO Minerals. Only with a team of this scope will we be able to address this exciting opportunity with the necessary cross-boundary flexibility. Likely strategies include optimising the conditions for existing bugs from mining environments to work better, selecting and applying families of bugs from other environments (for example, the extremophiles), and perhaps generating new strains by careful manipulation of their optimum attributes."

Hill believes the advent of bioprocessing will be to the metals sector what the carbon-in-pulp processing technology was to Australia's gold industry twenty years ago, turning it from a minor player into the world's third largest producer.

"Bioprocessing can give us an edge in so many ways.

"It can be used for the extraction of metals from sulfide ores of copper, gold, nickel and zinc.

"It could be used to exploit gold deposits so low in grade that they are uneconomic by other methods.

"We could use bugs with block-caving of ore deposits underground, bioleaching the ores inside the earth and bringing only the concentrated target minerals to the surface."

Dr Hill says that its clean environmental qualities are one of the most attractive features of bioprocessing - reducing both the direct and indirect impacts of mineral extraction and minimising disturbance to the landscape.

Among the scientific challenges is learning how to manipulate the bugs for peak productivity - controlling the heat, nutrients, air supply and other micro-environmental factors to enhance their output.

In some cases this may be achieved by processing minerals in a bioreactor, where the entire process is sealed. In others, by learning how to control the bugs' performance in surface heaps, or in underground locations.

In the race to find the 'magic' bug, scientists are going to extremes - not only risking their necks around volcanoes, but also exploring hydrothermal vents in the lightless ocean depths where populations of cryptic microbes subsist on the mineral-rich discharges that spew from the earth's mantle along deep mid-ocean trenches.

In recent times, CSIRO researchers like Dr Ray Binns from its Exploration and Mining Division have plumbed the deeps of the Bismarck Sea, north of PNG, for promising new life-forms with a taste for metals. Other scientists, from CSIRO's Molecular Science Division, are studying the genetic structure of the bugs to get a better understanding of their 'lifestyles' and what can be done to make them live longer, eat better and work faster.

"It's tremendously exciting," says Dr Hill. "Both we and the mining industry are now starting to see real potential in biological extraction, not only in terms of its efficiency but also because of its low environmental impact. These bugs are an absolutely natural part of our environment, and all we are doing is starting to harness their amazing potential."

In one respect biomining could change every Australian's life for the better. Many of our best and biggest mineral resources are now starting to run out, and there has been no world-class discovery in more than a decade.

If biomining of low-grade reserves becomes a reality, the lifetime of Australia's total mineral resources, and the wealth that they generate for ordinary Australians, will be extended by hundreds of years.