An apparatus was developed for treatment of biomass in which reactants are added to biomass and the biomass mixture is moved through the apparatus without compacting under force of a non-compacting piston. Treatment systems used in this reactor result in effectively treated biomass that is particularly suitable for subsequent saccharification to produce fermentable sugars.
STATEMENT OF GOVERNMENT RIGHTS
 This invention was made with United States Government support under Contract Nos. 04-03-CA-70224 and DE-FC36-03GO13146 awarded by the Department of Energy. The government has certain rights in this invention.