Performance of Annual and Perennial Biofuel Crops: Yield during the First Two Years

Increasing demand for renewable fuel sources has stimulated the need for alternative biomass crops. A study was conducted to determine grain, stover, total biomass, and estimated ethanol yields of annual and perennial crops at two locations in Kansas in 2007 and 2008. This study included corn (Zea mays L.) grown continuously and rotated with soybean [Glycine max (L.) Merr]; five sorghum cultivars, brown midrib (bmr), photoperiod sensitive, sweet, and two dual-purpose forage varieties; and three perennial warm-season grasses, switchgrass (Panicum virgatum L.), big bluestem (Andropogon gerardu Vitman), and Miscanthus (Miscanthus X giganteus). Corn and sorghum plants were harvested for grain and biomass and sweet sorghum stalks were pressed to extract juices. Perennial grasses were harvested for biomass. Highest grain yields were achieved with corn across both years and locations with yields averaging 10.1 Mg ha(-1). Total biomass yields were greatest for sweet sorghum (32.6 and 28.2 Mg ha-1 in 2007 and 2008, respectively) and photoperiod-sensitive sorghum (26.8 Mg ha(-1) in 2007). Sweet sorghum extracted fermentable carbohydrate yields averaged 4.8 Mg ha(-1). Perennial grass biomass yields ranged from 7.7 to 12.8 Mg ha(-1) in 2008, the second year after establishment. Highest average estimated ethanol yields were achieved with sweet sorghum (9920 L ha(-1)). These results indicate that the highest total biomass and estimated ethanol yields for renewable fuel production can be achieved from sweet sorghum and that perennial grasses were as productive as annual crops at producing biomass in the first 2 yr after planting.