I'm still trying to find an "optimal" automated design.
Even with the recent changes to the solid fueled fireboxes a single turbary and logger (turning all the wood into charcoal) can ALMOST keep a 36HP boiler running after the temperature has been maxed (which takes about 4 hours and a lot of extra fuel). I have this coupled with a farm, mushroom farm, moistener, squeezer, fermenter, still, 2 carpenters (1 for humus, 1 for bog), powered furnace, aqueous accumulator and a few tanks. Everything except seeds (gets about a stack an hour surplus which doesnt seem worth the trouble to turn into seedoil) gets turned into fuel (using water in fermenter, apple juice production is too unreliable). This runs a turbine and 10 industrial steam engines.
I added a second arbor/logger for rubber trees, but with all the extra sand get too much bog.It also produces way more rubber than I could ever need. A second bog/turbary would probably balance everything out well (and use up the surplus mulch) and keep the boiler going. The other option would be to cut down to a 12 HP or two, and possibly not burn all the wood.
I have only just added in a liquidfueled boiler. I also have a huge tank of biomass but only recently started up the still. It doesnt seem to me that it would be able to keep up with more than a 12HP boiler though (still heating it).