Lignin extraction--reassessment of the severity factor with respect to hydroxide concentration.

Steam processes have often been associated with a severity factor, correlating the cooking temperature, time and catalyst used in the process. Although equations for treatments with and without acid catalyst have been suggested, there is so far no simple equation allowing a precise estimation of the amount of lignin extracted from lignocellulosic biomass. In this work, a new version of the severity factor equation is proposed. This has been shown to correlate effectively to the amount of lignin extracted from various types of lignocellulosic materials and different extraction methods. The resulting severity factor is robust with potential to be utilized both for acid and base-catalyzed extraction of lignin. Finally, the proposed correlation between the severity factor and extracted lignin under base conditions has been correlated with empirical data to validate the entire model and especially under mild condition where lesser information was available from open literature.