A significant cost factor comes from product purification of a biofuel prod­uct. Even if a highly selective chemical transformation process is adopted, the nonuniform and heterogeneous nature of biomass feedstock invariably produces products of a broad spectrum of chemical species, targeted ver­sus nontargeted, or desired versus not desired. The unwanted species in the product composition include source-specific and treatment-specific ingredi­ents that need to be separated out from the principal products. Examples include ethanol purification from crude ethanol beer, separation of methanol and salt from crude glycerin that was produced by the transesterification process, removal of trace minerals from biosyngas and bio-oil for upgrad­ing, char removal from bio-oil, denitrification of bio-oil, removal of carbon dioxide from biosyngas, and so on.