The lignin (LN) contents of 13 biomass samples were correlated with their fixed carbon (FC) contents. There was a highly significant correlation between the percentage of LN (PLN) of the biomass sample and the percentage of FC (PFC). The PLN of the biomass sample as a function of the PFC was correlated using the following equations: For the biomass samples with lower PLN: PLN = 0.0608(PFC)(2) - 1.7057(PFC) + 27.2309 For the biomass samples with higher PLN: PLN = -0.4281 (PFC)(2) + 29.4897(PFC) - 445.2179 For all of the biomass samples: PLN = -0.0146(PFC)(3) + 1.1804(PFC)(2) - 27.8766(PFC) + 215.5597 for which the squares of the correlation coefficients (r(2)) were 0.9937, 0.9871 and 0.8400, respectively.