**1. Introduction**

According to the United States (U.S.) Department of Energy–Office of Energy Efficiency and Renewable Energy (DOE–EERE), agricultural crop and forest residues, grasses, and woody energy crops that are grown specifically for their energy, together with algae, industrial wastes, sorted municipal solid waste, urban wood waste, and food waste, are considered to be biomass, which can be used for the production of fuels and chemicals [1]. Liquid fuels produced from biomass can also act as a supplement to petroleum-based liquid transportation fuels, such as gasoline and diesel [1]. In addition, biomass can be used to produce valuable chemicals and electricity. According to the DOE Billion-Ton report [2], there are more than a billion tons of biomass produced annually in the U.S., which could sustainably be accessed for continuous biofuels production. A 2005 study conducted by both the U.S. Department of Agriculture (USDA)/DOE indicated that both woody and herbaceous perennial bioenergy crops should be considered for bioenergy and bioproducts production [3].

The southeastern United States is projected to supply almost 50% of the 16 billion gallons of advanced cellulosic biofuels mandated by the Renewable Fuels Standard [4]. Assuming typical yields of 80 gallons of fuel per dry ton and 4–8 dry tons/acre, this demand translates to roughly 200 million tons of biomass produced on 25 million acres [5]. This target is considered to be readily achievable, playing to the region's strength of lignocellulosic biomass production [5]. An analysis conducted by the DOE Logistics for Enhanced Attributes Feedstock (LEAF) project estimates that by using the Billion-Ton report as a base-case scenario, primary sources of available biomass are residues generated from forest-products industry and agricultural residues. However, in future, a diverse portfolio of forest, agriculture biomass and second generation bioenergy crops such as miscanthus, switchgrass, and energy cane are going to play a major role in biofuels production. One of the major cost contributors in bioenergy production is feedstock. To make bioenergy a reality, reducing feedstock cost and improving feedstock quality are important for commercial-scale implementation of biomass conversion technologies for fuels and chemical production.
