Recommendations to Mitigate Potential Sources of Error in Preparation of Biomass Sorghum Samples for Compositional Analyses Used in Industrial and Forage Applications
2014
Whitfield, Matthew B. | Chinn, Mari S. | Veal, Matthew W.
Sweet and forage varieties of sorghum (Sorghum bicolor (L.) Moench) can produce large quantities of soluble sugars, starch, and fiber in a single crop and so are highly suited for bioenergy production. To develop this potential, it is critical to reliably quantify the components of the biomass: primarily carbohydrates (monosaccharides, sucrose, starch, and holocellulose) as well as lignin and extractives. Techniques compiled by the National Renewable Energy Laboratory (NREL) are commonly used for these analyses; however, some characteristics of sorghum require some adaptation of those methods. Here, we present an analysis of some of these characteristics and a modified analytical procedure to account for them. In particular, greater accuracy can be obtained by separating the pith and rind portions of the stalk prior to analysis. Several important properties of the stalk differ between the pith and rind, and in many cases, the magnitude of that difference varies among cultivars. As we demonstrate, analyzing the stalk without separating the pith and rind can lead to systematic bias in the measurement of these properties and lignocellulosic composition; if separation is not possible, the bias can be mitigated by exercising care in ensuring a representative subsampling of ground material. Some modifications to initial Soxhlet extraction procedures also improve the accuracy and practicality of the biomass analysis.
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