A method for producing clinker in a system having a rotary kiln and a pre-calciner, waste material is introduced into the inlet end of the pre-calciner to serve as secondary fuel for pre-calcining raw mix also fed into the pre-calciner. The waste material is substantially completely combustible and exothermic. In a preferred embodiment, the waste material includes tires, plastics and other combustible waste that has been shredded or chipped to a size that is sufficiently small to ensure substantially complete combustion of the particles as they fall through the pre-calciner.