A method to convert at least a majority of native cellulose Iβ to cellulose IIII in pretreated or untreated densified biomass is disclosed. The densified biomass (cellulosic or lignocellulosic) is pretreated with anhydrous liquid ammonia or liquid ammonia comprising a solution of at least 80% ammonia. The pretreating can be performed at a temperature from about 4° C. to about 140° C. and a pressure from about 14.7 to about 200 psi. In one embodiment, the densified cellulosic converting pretreatment process is followed by lignin extraction (LE). The total moisture content of the densified biomass and the solution is 30% or less and a weight ratio of liquid ammonia to the densified biomass is from about 0.3:1 to about 2:1. Various products and systems are also disclosed.