Evaluation of Fifteen Cultivars of Cool‐Season Perennial Grasses as Biofuel Feedstocks Using Near‐Infrared

Abstract

Cool-season (C3) perennial grasses have a long history of cultivation and use as animal forage. This study evaluated 15 cultivars of C3 grasses, when harvested in late June for increased biomass yield, as biofuel feedstocks using near-infrared spectroscopy (NIR) based partial least square (PLS) analysis. These grasses were grown near Iliff, CO, for three growing seasons (2009)(2010)(2011). The carbohydrate composition and released carbohydrates (total glucose and xylose released from dilute acid pretreatment and enzymatic hydrolysis [EH]) were predicted for samples from the study using NIR/PLS. The results were analyzed from a biofuels perspective, where composition combined with harvest yield provided information on the carbohydrate yield available for biomass conversion processes, and released carbohydrate yield provided information on the accessibility of those carbohydrates to conversion methods. The range in harvest yields varied more among cultivars (2900 kg ha -1 ) than did the range in carbohydrate composition (56.0 g kg -1 ) or released carbohydrates (60.0 g kg -1 ). When comparing carbohydrate yield to released carbohydrate yield between cultivars, an efficiency as high as 87% release of available carbohydrates was obtained for pubescent wheatgrass [Thinopyrum intermedium (Host) Barkworth & D.R. Dewey 'Mansaka'], with a low of 71% for hybrid wheatgrass [Elytrigia repens (L.) nevski ´ pseudoroegneria spicata (PURSH) A. Love 'Newhy']. Though hybrid wheatgrass had the lowest release efficiency, its high harvest yield resulted in release of more total carbohydrates than half the other cultivars analyzed. This suggested that harvest yield, carbohydrate release, and carbohydrate composition, togetherplay significant roles in biofuel feedstock evaluation.

Comparative Evaluation of Industrial Hemp Cultivars: Agronomical Practices, Feedstock Characterization, and Potential for Biofuels and Bioproducts

“…Principal component analysis (PCA) of the NIR spectra revealed two main clusters (Figure S2C) categorizing the raw and pretreated samples. The differentiation between the raw and pretreated samples can be attributed to the composition modification during dilute acid pretreatment, such as removal of hemicelluloses and redeposition of lignin. − However, within each cluster, the NIR spectra cannot be clearly separated into groups, suggesting that the composition differences between the hemp cultivars were not distinct enough for NIR to distinguish, especially for the pretreated samples. , In general, FTIR and NIR results revealed that dilute acid pretreatment selectively removed hemicellulose, and no significant compositional and structural differences could be spotted among the 11 pretreated hemp cultivars.…”

“…43−45 However, within each cluster, the NIR spectra cannot be clearly separated into groups, suggesting that the composition differences between the hemp cultivars were not distinct enough for NIR to distinguish, especially for the pretreated samples. 46,47 In general, FTIR and NIR results revealed that dilute acid pretreatment selectively removed hemicellulose, and no significant compositional and structural differences could be spotted among the 11 pretreated hemp cultivars. Theoretical and Predicted Bioethanol Yields.…”

Key environmental and production factors for understanding variation in switchgrass chemical attributes

“…The PLS2 model has been described previously (Payne & Wolfrum, 2015). Calibration samples were analyzed using NREL Laboratory Analytical Procedures (Sluiter et al, 2010) and consisted of perennial cool season grasses as described in Payne et al, (2017), corn stover ( Zea mays L.), Miscanthus × giganteus, sorghum ( Sorghum bicolor (L.) Moench), switchgrass ( Panicum virgatum L.), and rice straw ( Oryza sativa L.). A summary of calibration and validation statistics is in Table S1.…”