AbstractStudies 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.