There is no natural sequestration on any kind of timescale that can possibly help us. During the carboniferous era, bacteria had not yet evolved that could break down dead plants. Now, those bacteria exist.
That's a pretty strong absolute, which probably means it is not true. It is possible to oversimplify things from multiple angles.
Recent work[1] has argued that microbal and fungal diversity did not play a significant role in the development of coal deposits, but rather it was a combination of environmental effects that generated swamps where anaerobic conditions prevented plant decay. These conditions still exist today, we are just actively removing them.
Recent work[1] has argued that microbal and fungal diversity did not play a significant role in the development of coal deposits, but rather it was a combination of environmental effects that generated swamps where anaerobic conditions prevented plant decay. These conditions still exist today, we are just actively removing them.
[1] https://www.pnas.org/content/113/9/2442