A quantitative method applicable for various biomass species to determine their chemical constituents was explored. The widely used wood analytical method was found to be not entirely applicable to different biomass species. It was then demonstrated that by incorporating protein and starch determinations, by ash-correcting the Klason lignin and holocellulose and also by protein-correcting Klason lignin and holocellulose of high protein content species, reliable summative results that enable comparison between different types of biomass materials were achieved. Thus, an analytical method with starch and protein determinations as well as ash and protein corrections was proposed for quantitative assay of chemical composition of various biomass species. (C) 2011 Elsevier Ltd. All rights reserved.