“…And, finally, once we have the concentrated ore, we sell it and make money; and what do we do with the wasterock?” The ‘Mining and the Environment’ professor often finishes his lectures with this question, and the students all know what he wants to hear in response.
“Put it in the river.”
To the students of the class – whether they’re mining, geological, or environmental engineers – this is a sadly ironic joke. When you drink your morning coffee, you don’t have it with two creams and two pieces of garbage, so why do virtually that to the environment? A simple conclusion to draw is that the mining corporations just don’t care. The reality is a bit different.
Wasterock disposal means finding a place to put millions of tonnes of useless rock that needs to be moved before you can access valuable ore. The act of moving these rocks creates more exposed mineral surface that can weather, often resulting in harmful chemical runoff.
Take the example of leaving a pile of iron nails outside in the rain beside a block of iron. After a month of regular weather you’ll return to find a lot more rust on the nails than on the block, simply because of a difference in exposed surface. The block represents in-situ rock, the nails would be broken up wasterock.
Now, take the same situation, except put the nails in a bucket of water. When you come back a month later you’ll find little to no rust at all!
This is a simple example of the same science that leads mining companies to use rivers and lakes as waste disposal sites. It is the best of a very limited set of options. It isn't sustainable, but then again neither is mining. Outside of halting all metal making, what can be done?