As an alternative fossil fuel garnering attention in the wake of unstable crude oil prices, oil shale faces several obstacles before its seemingly imminent commercialization. One of the largest environmental stumbling blocks to its widespread use is the primary byproduct of oil extraction processes: semicoke. With the majority of semicoke disposed of in open landfills, this waste stream poses a threat to the environment, and its disposal may well represent a waste of a potentially useable byproduct. Previous studies show that oil shale from Estonia, China, and the United States, pyrolyzed at 500 and 1000 degrees C at a rate of 20 degrees C min(-1), yield semicokes with relatively high organic char contents and high surface areas. To determine how shale origin and pyrolysis temperature impact the activation energy of oil shale semicoke combustion, we investigate the oxidation kinetics of oil shale semicokes pyrolyzed at these two temperatures. Activation energies in air are in the range of 108-130 kJ mol(-1) for the semicokes pyrolyzed at 500 degrees C and 147-195 kJ mol(-1) for samples pyrolyzed at 1000 degrees C. Depending on the oil shale pyrolysis temperature and extent of reaction, the semicoke oxidative reaction orders range from 0.55 to 0.72.