Production of napiergrass as a forage and bioenergy feedstock with swine-lagoon effluent

Abstract

Studies are lacking on the performance of napiergrass (Pennisetum purpureum Schum.) fertilized with swine (Sus scrofa domestica)-lagoon effluent. This study (2011–2013) determined biomass yield, nutrient removal, nutritive value, and ethanol yield in cultivar ‘Merkeron’ at a single, late-season harvest. Effluent irrigations provided 727 kg ha^–1 nitrogen (N) annually (3-yr average). Napiergrass removed 92% of N and 73% of phosphorus (P) applied in 2013, the peak year of production (58.9 Mg ha^–1). As compared to stems, leaves had greater (p < .01) crude protein (32 vs. 100 g kg^–1) and less acid detergent fiber (482 vs. 340 g kg^–1). Ethanol yield was approximately 36% lower in stems than leaves (98 vs. 153 g kg^–1), and xylose yield was 7% lower (170 vs 183 g kg^–1); however, stems account for a larger amount of lignocellulosic biomass for estimating bioethanol production than leaves. Ethanol yield potential was approximately 109 g kg^–1 grass biomass.