[02:54:49] [Server thread/WARN] [FML]: LLibrary loaded a new chunk [8, -11] in dimension 0 (overworld) while populating chunk [10, -10], causing cascading worldgen lag.
[02:54:49] [Server thread/WARN] [FML]: Please report this to the mod's issue tracker. This log can be disabled in the Forge config.

times 10x

Yup

LLibrary doesn't do any worldgen. Some other mod must be generating with an event handler not registered to their own modid. What other mods do you have installed?