The process design and economic analysis of process plants to produce activated carbons from waste tires and coal have been performed. The potential range of products from each process has been considered, namely for waste tire--pyro-gas, active carbon, carbon black and pyro-oil; for coal--pyro-gas and active carbons. Sensitivity analyses have been carried out on the main process factors; these are product price, production capacity, total production cost, capital investment and the tipping fee. Net present values for the two plants at various discount factors have been determined and the internal rates of return have been determined as 27.4% and 18.9% for the waste tire plant and the coal plant, respectively.