Landfill restoration combustible wastes and plastic wastes could be utilized as auxiliary fuels since such wastes having enough calorific value give economic benefit to save energy in the facility. However environmental issue during the use of wastes as a fuel in the kiln is always arising and the operator must show the environmental soundness in air pollutants emission into atmosphere and containment of heavy metals in cement product. Comparative experiments were carried out by introducing RPF (refuse plastic fuel), fluff type wastes, which are prior to processing into RDF, and pre-treated landfill restoration wastes as auxiliary fuels at a commercial cement kiln plant. Heavy metals content in all wastes (RPF, fluff, landfill waste) and concentration in emission gases were measured and checked with Korean regulatory limit values. Most of particulate matter was properly collected in air pollution control devices and mercury compounds were mainly contributed from coal. The results of heavy metal concentrations in clinker product showed that the amount of chromium containing clinker was under the regulatory limit value and it seemed to be also contributed from the waste fed. In overall the use of a certain limited amount (about 20% inclusion of wastes in this study) of landfill restoration combustible wastes pre-treated could be acceptable as co-burning fuels. Further systematic tests could be needed for reliable environmental assessment in future utilization.