A report out telling us that mining for Bitcoin – and other cryptocurrencies – costs rather more than going out and mining for real metals that might be of value. Something that might well be true but isn’t actually of any great value or interest in itself. For we don’t use the mining of metals to create our money for us. The comparison between cryptomining and other forms of currency should be the energy or other costs of using currency. What’s the energy cost of shipping trucks full of pennies, nickels and euro coins then?
But even after that there’s something that sets the teeth on edge. The people reporting on the subject don’t seem to understand metals at all:
Other cryptocurrencies also fair poorly in comparison, the researchers write in the journal Nature Sustainability, ascribing a cost-per-dollar of 7MJ for ethereum and 14MJ for the privacy focused cryptocurrency monero. But all the cryptocurrencies examined come off well compared with aluminium, which takes an astonishing 122MJ to mine one dollar’s worth of ore.
Obviously, that’s The Guardian, wrong about everything, all the time. But still that’s bad. The energy cost of mining aluminium ore is trivial. Stick a big JCB like shovel into the right piece of the Earth and you’ve got your tonnes of aluminium ore. Fractions of a litre of diesel per many tonnes of ore that is.
What they mean is that the production of aluminium metal is energy hungry, which it is. That’s why we recycle aluminium, not for the recycling of the basic resource, the ore – that’s 8% or summat of the surface of the Earth, not something we’re going to run out of – but to recycle the energy embedded in that process of turning the ore into the metal.
Just to be clear. Aluminium ore is bauxite, something available in abundance and cheaply. It sells, at the minehead, for something in the $50 to $80 a tonne type money. That’s not something that has 122MJ of energy involved in its extraction. Not unless every bauxite mine in the world is losing a vast fortune. That’s then processed into aluminium oxide, alumina – by being boiled in caustic soda – and that uses some energy but not that much. We might have upgraded to a $200 to $300 level per tonne at this point, we can’t be using that much energy. Aluminium metal is made by passing electricity through the Al2O3 and that’s where the energy use is. Rule of thumb is $400 worth of electricity per tonne aluminium metal. That’s what we recycle when we send those Coke cans off, that $400 of electricity.
So, The Guardian, wrong on everything, always, aluminium ore, that bauxite, doesn’t take 122 MJ to produce.
This isn’t a mistake the main paper makes. It manages another one, a different one:
Aluminium mining is much more energy-intensive on a per US$ generated basis than all other assets.
Err, no, you don’t go mining for aluminium. You go mining for bauxite. Something which is, as above, not energy intensive. But more:
Weng et al.37 developed a cradle to gate lifecycle impact assessment of rare earth oxides (REOs; that is, rare earth metals).
No, REO is not rare earth metal, it’s rare earth oxide. And energy requirements are going to be quite different too. Recall that an oxide is what we get after something has burned – that’s what burning is, the high speed production of an oxide. If the process of making an oxide is exothermic then we’ve got to add energy in to turn an oxide into a metal. And yes, rare earth metals production processes do start with the oxide and add energy.
Yes, yes, of course, this is mere pendantry. And yet in science – which is what is purported here – details matter.