Rice straw is one of the more abundant lignocellulosic waste materials in the world (Fig. 4.12), reaching 731 million tons per year. This amount of rice straw can potentially produce 205 billion litres bioethanol per year, which would be the largest amount from a single biomass feedstock (Bohlmann, 2006). By selecting high — biomass yielding species, combined with high nutrient and water use efficiency, economically efficient production of biofuel feedstock may be realised on less optimal land without pressuring prime grain crop territories (Jakob et al., 2009).

Panicum virgatum

Panicum virgatum, also known as switchgrass (Fig. 4.13), is a native perennial warm-season (C4 plant) grass with deep roots, growing on relatively poor quality lands, where water and nutrient availability would prevent the successful production of conventional crops. A widely adapted endemic species, it is an important ecological component of North American native grassland ecosystems (Lewandowski et al., 2003).

One of the advantages of switchgrass is that it can be harvested and handled with conventional hay-making equipment (Cundiff and Marsh, 1996; Sokhansanj et al., 2009). Switchgrass combines more of the attributes desirable for bioenergy feedstock production than other grasses. These attributes include distribution and high productivity across a wide geographical range and on diverse agricultural sites, high water use and nutrient use efficiency, and positive environmental attributes — including effects on soil quality and stability, cover value for wildlife and relatively low inputs of energy, water and agrochemicals required per unit of energy produced (McLaughlin and Walsh, 1998). Comparing corn and switchgrass on marginal soils for biofuel production, Varvel et al. (2008) found that the potential ethanol yield from switchgrass was equal to or greater than the potential total ethanol yield from corn grain.