Water Requirements for Sustainable Bioenergy Feedstock Production in Sub-Tropical Regions of the United States.

Among production inputs, water is one of the most critical limiting factors that will directly impact bioenergy feedstock production, conversion processes and the industry’s sustainability/profitability. The objective of this study was to characterize water requirements of newly-developed lignocellulosic feedstocks in production regions with varying water resources, and to identify feedstock traits associated with increased abiotic stress tolerance. Field plots of selected feedstocks (energy canes, high biomass sorghum, and Miscanes) were established at four locations with varying agro-climatic conditions (especially water resource) that are representative of the spectrum of production conditions in the Southeastern United States. These were: Weslaco (south TX), Pecos (West TX), Vernon (North TX), and Markham (East TX). Preliminary first year data from seed cane scale-up fields indicated differences in growth, survival, yield and water use based on growing season duration. The highest dry-biomass yield (36 Mg·ha^-1) and water use (966 mm) estimates for energy canes were recorded in the southern-most location (Weslaco). Yield estimates at Markham, Vernon and Pecos were 29.2, 24.7, and 18.6 Mg·ha^-1 respectively. Sorghum yield estimates range from 2 to 18 Mg·ha^-1. Even though northern locations (Vernon and Markham) received considerably more precipitation, thus reducing the need for irrigation, yields were limited by growing season duration.  Severe winter conditions in the northern-most location (Vernon) severely limited crop regrowth, necessitating replanting.