fert + 2 scrap = 2 fert
And otherwise a cow/pig/chicken/sheep farm with an MFR Sewer should also produce all the fertilizer you could ever want. And in 1.5 you can always make a Skeleton grinder and use the bonemeal in good'ol Dispensers to grow trees as well, so whatever you go for I think it will never be hard to grow trees faster than a Harvester (SC, MFR, Forestry, it doesn't matter) can harvest them.
I have a tree farm with Copper upgrades and a bit of Xycraft Soil (so it's not a solid block of trees) and it produces plenty of saplings and wood (from regular Oak trees) to keep itself running, produce biofuel and charge up a Redstone Energy Cell (which is hooked up to my ore processing as well). I'm sure if I made the entire area Xycraft Soil (1 block deep) and actually use the wood to generate power it would produce way more power then I need, even after the nerfs to Biomass/Biofuel.