We'll need to fully replace them first, but even then, I don't think it's a significant number. In the US, there are about 50k workers left in the mining indust

We'll need to fully replace them first, but even then, I don't think it's a significant number. In the US, there are about 50k workers left in the mining industry, and other advanced nations mirror that. I'm not a fan of keeping coal mining around, but I don't believe it's a large issue, and I do believe that this is mostly a safety system. If all else fails due to some disaster, war or alien attack, you want to have the ability to scale coal mining back up. That'll only work if you retain the know how and technology.