Frai 43+ Acid Pretreatment Of Lignocellulosic Biomass. Acid pretreatment involves the use of concentrated and diluted acids to break the rigid structure of the lignocellulosic material. The most commonly used acid is dilute sulphuric acid (h2so4), which has been commercially used to pretreat a wide variety of biomass types—switchgrass 54, 55, corn. Acid impregnation point out that after 10 minutes the acid uptake reaches a plateau of 20g per kg of dry biomass.