least 20% lower than these results. In the United States, switchgrass yields appear to be highest in warm humid regions with long growing seasons such as the US Southeast and lowest in the dry short season areas of the Northern Great Plains. The energy inputs required to grow switchgrass are favorable when compared with annual seed bearing crops such as corn, soybean, or canola, which can require relatively high energy inputs for field operations, crop drying, and fertilization. Whole plant herbaceous perennial C4 grass feedstocks are desirable biomass energy feedstocks, as they require fewer fossil energy inputs to grow and effectively capture solar energy because of their C4 photosynthetic system and perennial nature. One study cites it takes from 0.97 to 1.34 GJ to produce 1 tonne of switchgrass, compared with 1.99 to 2.66 GJ to produce 1 tonne of corn. Another study found that switchgrass uses 0.8 GJ/ODT of fossil energy compared to grain corn's 2.9 GJ/ODT. Given that switchgrass contains approximately 18.8 GJ/ODT of biomass, the energy output-to-input ratio for the crop can be up to 20:1. This highly favorable ratio is attributable to its relatively high energy output per hectare and low energy inputs for production. Considerable effort is being expended in developing switchgrass as a cellulosic ethanol crop in the USA. In George W. Bush's 2006 State of the Union Address, he proposed using switchgrass for ethanol; since then, over US$100 million has been invested into researching switchgrass as a potential biofuel source. Switchgrass has the potential to produce up to 380 liters of ethanol per tonne harvested. However, current technology for herbaceous biomass conversion to ethanol is about 340 liters per tonne. In contrast, corn ethanol yields about 400 liters per tonne. The main advantage of using switchgrass over corn as an ethanol feedstock is its cost of production is generally about 1/2 that of grain corn, and more biomass energy per hectare can be captured in the field. Thus, switchgrass cellulosic ethanol should give a higher yield of ethanol per hectare at lower cost. However, this will depend on whether the cost of constructing and operating cellulosic ethanol plants can be reduced considerably. The switchgrass ethanol industry energy balance is also considered to be substantially better than that of corn ethanol. During the bioconversion process, the lignin fraction of switchgrass can be burned to provide sufficient steam and electricity to operate the biorefinery. Studies