I had an idea earlier to the effect of this, which makes the process a little more based on reality, (not that that's ever been very important in Minecraft) as well as allowing wood to be used in this process as well.
Instead of using straight plantballs, you would instead be able to burn plantballs for some amount of charcoal. (perhaps configurable in the config, by default, let's say you get 3 per plantball) You'd then have to macerate charcoal into charcoal dust (maybe integrate into charcoal dust mod?) and craft nine of these in a crafting table, to receive a Big Pile of Charcoal Dust. Compressing this yields a Charcoal Ball, and after that, the recipes are completely configurable in the config, with around 4-5 items added by this mod, to represent ever larger amounts of compressed charcoal (Not all of which are used by default).
By default, the recipes go: 8 charcoal dust + 1 Charcoal Ball (9 charcoal) = 1 Lump of Charcoal (17 charcoal), which is then compressed into 1 coal. This may sound OP at first, but consider that it would take 1088 (17 stacks of) pieces of wood to make one diamond in this way, slightly more then the total number of plant material currently needed, and 2901.3 (45.3 stacks) of other plant material, which should be reduced... buuuut, the plantballs to charcoal ratio above already provides over TWICE as much EU per plant versus biofuel cans... Maybe if it instead directly gave charcoal dust, it could be a higher plants to charcoal ratio?
Also, if you really wanted to be a
hippie sustainability advocate, you could also add recipes which allow you to use more charcoal/coal to replace flint and bricks/iron/obsidian in the later steps.