BACKGROUND: Acid hydrolysis using organic acids is a promising approach for liquefying biomass without introducing any additional inorganic salt species into the reaction media. Formicacid may be a very useful acid catalyst for biomass pre-treatment because (i) it is an effective, strong acid catalyst, (ii) it is no more corrosive than sulfuric acid, (iii) it is an organic acid, so it adds noinorganic salt species that might negatively impact downstream catalysis, and (iv) it can be produced from biomass, making ita green reagent. RESULTS: At pH(25 degrees C) = 1.65, formic acid yielded high dissolution of switchgrass (52 wt%) at a high temperature (200 degrees C), comparable with the dissolution yield achieved using sulfuric acid. When treated 9/1 wt/wt with an 8 wt% aqueous solution of formic acid at 150 degrees C for 1 h, 44 wt% of switchgrass was dissolved, yielding 63 wt% of the carbohydrates from switchgrass. CONCLUSIONS: The efficiency of formic acid for the hydrolysis and dissolution of the carbohydrate fraction of switchgrass was proved and compared with other organic and mineral acids. The liquid product of pretreatment of switchgrass using formic acid at both 150 degrees C and 200 degrees C showed that 24 wt% and 28 wt%, respectively, of soluble monosaccharides after enzymatic hydrolysis consisted of glucose. (C) 2011 Society of Chemical Industry