Abstract: This invention relates to a method for the conversion of lignocellulosic biomass into ethyl esters of carboxylic acids. Said method consists of treating the biomass material with an oxidizing agent that is incorporated in an solution comprising one or more acids, one or more alcohols and water, and subsequently performing a catalytic reaction at a higher temperature using the same acidic solution into which a larger volume of alcohol is added, in such a way that the catalytic conversion occurs in a medium with a much higher concentration of alcohol, i.e. with a much higher alcohol-to-water wt ratio. Such a method results in relatively high yields of ethyl esters, such as ethyl esters of formic, acetic, and levulinic acids, while producing a low yield of dialkyl ethers, which are unwanted by-products. The concentration of the oxidizing agent in the pre-treatment step is preferably higher than 6.0 wt %.