The effect of organic nitrogenous compound content and different pretreatments on agricultural lignocellulosic biomass characterization methods

Considering the diverse compounds contained in lignocellulosic biomasses, especially in agricultural biomass, and the complexity of the different chemical and physical structural connections between these compounds, appropriate analytical methods must be used to characterize these biomasses. In this study, two extraction processes and two analytical methods were used to characterize the main compounds in corn stover residue before and after different pretreatments. The results of this study suggest that pretreatment and organic nitrogenous compound content greatly affect the most common extraction processes and analytical methods used for biomass characterization. For raw corn stover biomass residue, the extraction process using neutral detergent fiber solvent removed more extractives and more organic nitrogenous compounds (18.5 and 2.4%, respectively) than the combination of extractions using water and ethanol (13.4% of extractives and 1.8% of organic nitrogenous compounds). This study also showed that the different pretreatments improve the efficiency of both extraction processes and that these processes seem to be more effective with the neutral detergent solvent extraction than the combination of extractions with water and ethanol. Organic nitrogenous compounds represent a significant proportion of agricultural biomasses; therefore, insufficient organic nitrogenous compound extraction can cause interference with different characterization methods. It was observed that, for the same analytical method and with the raw biomass, the value of insoluble lignin after the extractions with water and ethanol was higher than that obtained after the extraction with the neutral detergent solvent 16.1 and 13.2%, respectively. This can be explained by the fact that there are more organic nitrogenous compounds in the samples after the extraction with water and ethanol than in the samples after the extraction with the neutral detergent solvent. This result was also observed for the pretreated samples. These results, therefore, show that the extraction step is very important because it can remove more organic nitrogenous compounds before the main compounds are characterized (lignin, carbohydrates).