Though government policies can provide the impetus to promote the production and use of lignocellulosic biomass feedstocks, market interests will undoubtedly increase as demonstrated uses go beyond exclusive ethanol production. Prior to its use as a bioenergy crop, switchgrass was utilized as a forage crop noted for its high forage yields (Parrish and Fike 2005). Before widespread efforts at improving bioenergy-related traits, some of the initial improvement efforts in switchgrass were aimed at forage digestibility by cattle (Vogel 2004). Improvements here, as illustrated in a number of biological and economic metrics, led to the development of cv. Trailblazer (Vogel et al. 1991). Furthermore, switchgrass cv. Shawnee was the result of simultaneous improvements in yields and digestibility (Vogel et al. 1996). Such efforts are germane to those being pursued today relating to higher biomass and ethanol yields, as they are related to strategies for targeted traits of switchgrass and subsequent ethanol processing steps. While the future of switchgrass as a bioenergy crop may well be tied to its ability to remain a forage option, we argue that sustainable approaches along these lines will be complex, and ultimately should stray from switchgrass becoming embedded in a "food vs. fuel" dilemma. Multiple within-year harvests that include an early-season forage harvest may attract farmers concerned with ensuring profits. Early indications point towards subsequent late-season harvests of switchgrass produce admirable amounts of biomass (Mcintosh et al. 2012), though not as much as with a single harvest. How multiple harvests and management for multiple services (see Anderson et al. 2012) will impact N losses, carbon sequestration, and landscape-wide water quality and quantity is unknown.

Promoting other uses for switchgrass will increase its stock in the bioenergy and chemical product arena. Currently, switchgrass is noted primarily for its contribution to biofuels. Advances in technologies that can promote other energy and co-product uses are gaining attention. The co-firing of pelletized switchgrass with coal for electricity (Qin et al. 2006; Aravindhakshan et al. 2010; Khanna et al. 2011) is one area worth further exploration. In addition, high-value commodities that may be produced in or from the ethanol-making process in the future, such as bioplastics, extractives, and other metabolic coproducts, will increase the likelihood of a sustainable bioenergy market that promotes the use of switchgrass (Joyce and Stewart 2012). For bioenergy crops like switchgrass, quick success on these fronts could well dictate its immediate and future prominence.

Acknowledgments

We thank numerous colleagues for their input, and for their valuable contributions to the field of switchgrass biology. These people include, among many others, F. Allen, C. Auer, G. Bates, H. Bhandari, S. Bobzin, V. Dale, R. Efroymson, S. Jackson, Y. Jager, K. Kline, P. Keyser, D. Simberloff, A. Snow. This project was supported by the NIFA Biotechnology Risk Assessments Grant program and funds from the University of Tennessee.

933-948.