[distances]

> On geological time-scales (tens of millions of years) fossil fuels will be replenished.

Will they? My understanding is that we have abundant coal thanks to the Carboniferous period, during which trees emerged but no organisms had yet adapted to break down lignin, causing massive fossilized tree deposits -- coal. As far as I see, that was an unique period in Earth's history that will not take place again.

[1] https://en.wikipedia.org/wiki/Carboniferous

[s1artibartfast]

My understanding is that the carboniferous was a particularly productive coal forming period, but in no way unique. The majority of the coal on earth has been formed since the carboniferous and the process is ongoing today.

Figure 1 in the link below provides a good demonstration of north american coal formation over time/

https://www.pnas.org/content/113/9/2442