Catalytic decomposition of NOx precursors during gasification of wet and dried pig manures and their composts was investigated over a commercial Ni/Al2O3 and nickel loaded on Loy Yang brown coal char (Ni/LYBCC) in a two-stage fixed-bed reactor. A substantial amount of NH3 (0.52 wt %, wet basis) was emitted during the dehydration of wet pig manure (WPM). During WPM pyrolysis, the nitrogen in volatiles was mainly converted to NH3, nitrogen in tar, and N-2. The Ni-based catalysts are active for removing all the NOx precursors from pyrolysis of wet and dried livestock wastes at 650 degrees C. However, the moisture emitted during WPM pyrolysis can promote Ni/LYBCC gasification, causing the catalyst deactivation for NH3 decomposition. The possible nitrogen transformation routes for WPM gasification are also discussed in this work. Such an approach may lead to the development of a clean livestock waste gasification technology.