BACKGROUND: Acid hydrolysis using organic acids is a promising approach for liquefying biomass without introducing any additional inorganic salt species into the reaction media. Formic acid 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.