Except all those saplings have the potential to cause fps lag. Just try setting up a 25x25 mfr tree farm with vanilla jungle trees to see what I mean.Dude.. its an MFR farm.
Its not like you're going to be short on saplings anytime soon.-let 'em sit out anddiedespawn, it costs more to collect them than what you'll get out of them.
To be perfectly honest though, I don't know why people bother turning their saplings into biomass. The amount of infrastructure you need to produce energy is far less. On my last world I had a 25x25 MFR farm harvesting jungle trees. The amount of wood was enough to keep dozens of boilers going. Far more than I could've gotten from turning the saplings into biofuel, even if i'd used specially-bred ubertrees (not to mention solid fueled fireboxes are much cheaper than liquid fueled ones). They're both tree farms. Why do people make still make biofuel out of them?