Variability in biomass yield, chemical composition, and ethanol potential of individual and mixed herbaceous biomass species grown in North Dakota

Chemical composition and biomass yields vary with plant species, environment, and management practices. To determine which herbaceous perennial species should be produced as feedstocks for future cellulosic biorefineries, it is important to understand the variability in carbohydrate content, biomass yield, and resulting potential ethanol yield. This study was done with 10 treatments of individual and mixed herbaceous perennial species grown in Williston and Minot, North Dakota. The structural carbohydrate contents (sum of glucan, xylan, arabinan, and galactan) were used to determine theoretical ethanol potential on a mass basis and combined with dry-matter yield to calculate the theoretical ethanol yield on an area basis. Total carbohydrate content for the biomass samples varied from 45 to 61% (dry basis), with significant variation between environments. None of the biomass species combinations tested had consistently higher or lower carbohydrate content across the different environments. Plots containing switchgrass (Panicum virgatum L.) as a monoculture or in mixed species treatments had higher biomass yields (9.6–14.4 Mg ha−1) and theoretical ethanol yields (3170–5081 L ha−1) in irrigated plots at Williston while mixtures containing intermediate wheatgrass (Thinopyrum intermedium) or tall wheatgrass (T. elongatum) produced higher biomass yields (5.9–8.3 Mg ha−1) on non-irrigated plots in Minot during establishment. Variability among treatments in theoretical ethanol yields on a mass basis (3.7–9.8%) was much less than the variability in dry-matter biomass yields (15.0–27.6%). Differences in biomass composition were generally insufficient to counteract differences in biomass yields in determining ethanol yield potential.

► Wheatgrass species had higher yields than switchgrass during establishment on dryland.
► Variability is lower for carbohydrate content than yield for herbaceous perennials.
► Yield is more important than composition in choosing species for ethanol potential.