Biomass Productivity and Water Use of Perennial C4 Bioenergy Feedstocks in Southern USA.

Increased energy security, reductions in greenhouse gas emissions and economic growth are some of the expected benefits of a biofuel economy. However, the biofuels industry has experienced slow growth partly because of uncertainties surrounding the sustainability and profitability of feedstock production and potential competition for limited land and water resources, which could lead to higher agricultural commodity prices. This project focuses on regional water resources for feedstock production and will use a combination of farm-level investigations, computer simulations and economic analysis to address the growing issue of bioenergy impacts on water quantity and quality. Annual (biomass sorghum) and perennial (energy canes, miscanes) feedstocks have been established at four locations with different water availability scenarios that are representative of the southeast U.S. We are quantifying crop growth and yield potentials, as well as input requirements. First year data from seed cane scale-up fields indicate differences in growth, survival, yield and water use based on water availability and 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, TX) with supplemental irrigation. Yield estimates at northern locations (Markham, Vernon and Pecos, TX) were 29.2, 24.7, and 18.6 Mg·ha^-1 respectively. Even though northern locations received considerably more precipitation, thus reducing the need for irrigation, biomass yields could be limited by growing season duration. Severe winter conditions in northern-most locations could limit crop regrowth, necessitating replanting. Data derived from these observations will be used to parameterize simulation and economic models that can assist growers, biofuel producers, investors, and policy makers to determine which feedstocks are suitable for production in specific regions, and which feedstock combinations can result in profitable biofuel production while minimizing negative impacts on critical resources such as water.