On the other hand, when ammonia was released at the end of the pretreatment process via AFEX, neither lignin nor hemicellulose was physically removed from cellulose and other components. When water was pushed through biomass in a flow through mode, virtually all of the hemicellulose and up to about 75% of the lignin were removed with or without addition of very dilute sulfuric acid (Wyman et al., 2005b)