This study simulated ammonia production from biomass gasification using cow waste, pig waste, prune pits, and alfalfa stems. The process included gasification, carbon capture, and ammonia synthesis in Aspen Plus. Feed analysis with the C-H-O ternary and Van Krevelen diagrams showed a consistent composition trend among the four feedstocks. Cow waste was more carbon-rich and less oxygenated, while pig waste was the most oxygen-rich feedstock. Higher O/C ratios increased CO₂ formation and reduced CO production during gasification. Lower O/C ratios favored CO formation and reduced the tendency toward CO₂ generation. Hydrogen production depended on both H/C and O/C₂, not on a single ratio alone. Alfalfa stems produced the highest fraction because they had the most favorable balance between hydrogen availability and oxygen content. A higher H₂/N₂ ratio in the cleaned gas led to a higher ammonia mass fraction in the synthesis section. On a mass-input basis, the simulated ammonia yields were 0.1089, 0.0915, 0.0919, and 0.0864 kg NH₃ per kg of cow waste, pig waste, prune pits, and alfalfa stems, respectively. Overall, alfalfa stems produced the purest ammonia stream, whereas cow waste delivered the highest overall ammonia yield per unit feedstock mass, indicating that feedstock ranking depends on whether synthesis-gas purity or total mass-based productivity is prioritized.