Biofuels from biomass have the potential to reduce the dependency on fossil fuels. An efficient pretreatment method is required to accomplish the target of the Energy Act 2005. Extrusion could be a viable continuous pretreatment method to be explored. The objectives of the current study were to investigate the influence of screw speed and barrel temperature on sugar recovery from the selected warm season grasses and to select a suitable enzyme combination and dose for enzymatic hydrolysis. The ground, moisture-balanced biomasses were pretreated using a single screw extruder at various screw speeds (100, 150, and 200？rpm) and barrel temperatures (50, 75, 100, 150, and 200°C). Cellulase or multienzyme with β-glucosidase was varied from 1？:？1 to 1？:？4 during enzymatic hydrolysis to accomplish the second objective. Screw speed, barrel temperature, and their interaction had a significant influence on sugar recovery from the selected biomasses. A maximum of 28.2, 66.2, and 49.2% of combined sugar recoverywasachieved for switchgrass, big bluestem, prairie cord grass when pretreated at a screw speed of 200, 200, and 150？rpm and at a barrel temperature of 75, 150, and 100°C, respectively, using cellulase and β-glucosidase at a ratio of 1？:？？4. Extrusion pretreatment of these biomasses used only 28–37% of the rated extruder power. 1. Introduction Renewable energy from biomass has the potential to reduce dependency on fossil fuels, in addition to combat the environmental issues. The Energy Policy Act of 2005 mandates blending of 7.5 billion gallons of alternative (biofuel) fuels by 2012 [1]. The biofuels such as ethanol and biodiesel available in the market are predominantly produced from corn, sugar cane, and soybean oil [2]. It has been reported that biomass and bioenergy provides only about 4% of the total primary energy used in the US [3]. Lignocellulosic materials are the most abundant renewable resources on earth [4]. According to Kadam and McMillan [5], about 80–100 dry tons of corn stover/year can be utilized for ethanol production. Corn stover was the most researched biomass and it alone might not be able to fulfill the fuel requirement of the US. Warm season grasses such as switchgrass, big bluestem, and prairie cord grass are grown in most part of the nation. In general, the warm season grasses have higher sugar content than cool season grasses [6]. Several studies have indicated that these warm season grasses have greater potential as feedstock to produce biofuels [6–8]. The sugars in lignocellulosic materials mostly exist as polysaccharides such as
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