A lot of the worst polluters are state owned coal plants. There are some private energy producers, but from what I understand, most energy companies just act as interstate brokers between local agencies.
Then, buy the biggest coal mining companies and shut them down (or convert to renewables).
In 2016, Australia was the world's biggest net coal exporter[1] with 32% of global exports and the fourth highest producer. As far as I know, all coal mining in Australia is undertaken by private companies who hold a mining lease.
The $10billion could be used to buy controlling interests in some of the 10 biggest listed coal mining companies in Australia[2] and stop mining.
What I don't know is if the Australian Government can withdraw a coal mining lease if it's not being used (then just reduce production to miniscule levels) or what the impact would be when the lease expires. Still, I'd suggest such a move would have a crippling near term impact on the coal mining industry, which might be enough to kick renewables along further to fill the gap.
It's an interesting idea. Buy up any lease you can and sit on it. Probably a risky way to burn through a few billion, and at the risk that new companies pop up anyway and undo all your work.
I would rather they focus on drowning out coal on the supply side, or furthering carbon capture technology.
Don't forget to allow a few hundred million to donate to political parties (particularly the incumbents), as the current minerals/mining lobby is quite entrenched.
