Making metal is a dirty business, and we don't just mean in terms of getting your hands dirty. Creating useable metals from the ores that are dug from the ground is a heavily polluting endeavour. It might be about to get a whole lot cleaner.
Most metals are created in a two-step process. First, the excavated ores are ground down and filtered to get rid of the obvious junk and intruder metal ores, leaving just the metal oxides—metallic atoms bound up with other elements including oxygen, as opposed to in its pure form. Then, the metal has to be liberated—and that's where things get really bad for the planet. Typically, this stage will involve immersing oxides in a bath of molten salt and running electricity through the whole thing.
Not only does that process use vast quantities of power, it also releases greenhouse gases: one of the electrodes is made from carbon, and during the process it reacts with oxygen to release vast quantities of CO2. But a small startup, spun out of Boston University, thinks it might have a solution. Infinium has developed a new ceramic electrode, made of zirconium oxide, which can replace the carbon one and reduce emissions to zero.
It's not a new trick. Many researchers have mulled the idea before, but the molten salts cause most electrodes to rapidly corrode away to nothing. Infinium's solution was to develop new salts, too, which it's managed -- and then some. While it won't yet reveal all its secrets, it has announced that, as of this month, it will be using its new technique in a machine to produce a half tonne of rare metal per year; in September, that will be joined by another that will produce ten tonnes per year.
Why rare earth metals? Well, they're the most lucrative. The US is desperate to stockpile valuable metals—which are used heavily in modern electronics—and as a result, it's Infinium's first customer. The plant set to open in September will, apparently, just manage to make the startup profitable.
Great news for Infinium, then, but more interesting is what the development means for the rest of the industry. Fortunately, similar techniques could transfer to the metallic ores of aluminium, magnesium, titanium, and silicon—combined, some of the most prolific metals in engineering. While the new style of metal extraction isn't an environmental panacea (there's still impact from mining and separation processes, remember) it's a huge step in the right direction.
It's also reckoned, according to Technology Review, that extraction techniques like those being developed by Infinium could reduce processing costs by as much as 30 to 50 per cent. In other words, it's not just an ecologically sound development, but a financially savvy one, too. Forget ageing copper: all metal is about to go green. [Infinitum, Technology Review]
Image of Hobart zinc smelting plant by Brent Pearson under Creative Commons license.