I have been looking at a variety of sources and it appears that cellulase is not extremely expensive. It should be noted that enzymes act as catalysts, and are not consumed by the reactions that they catalyze…a little goes a long way.
Cellulase is an enzyme that breaks cellulose down into glucose. So after a passive treatment (stuff sits in a vat), your biomass is dissolved and you end up with sugar water that has all of the water insoluble stuff either floating on it, suspended in it, or precipitated out.
Plant elements (non-polar compounds) that are not dissolved in the water phase, of the enzyme bath, can be separated through filtration. It may be possible to isolate desirable compounds, using just this filtration.
The water phase would not be wasted either. Separate out the sugar water and use it to make ethanol, if you want to, just throw in some brewer’s yeast.
I have suggested enzymes as a pre-treatment, but it could just as easily be used to post-treat whatever biomass remains after standard extraction. No more spent biomass waste disposal, plus you reclaim that final bit that would have been thrown away.
If you don’t want to make alcohol, you could also process pure glucose powder. And in the case that you just don’t want to be bothered at all, it is sugar water, nothing hazardous at all. Disposal should be simple, unlike biomass that can contain residual solvents.