Das Projekt "Wirtschaftliche Bewertung von Stickoxid-Minderungsverfahren in der europaeischen Zementindustrie" wird vom Umweltbundesamt gefördert und von Ökopol Institut für Ökologie und Politik GmbH durchgeführt. A variety of techniques have been developed that allow cement kilns to reduce their NOx emissions to levels below 800 mg NOx /Nm3. These include several primary measures, staged combustion, selective non-catalytic reduction (SNCR), and selective catalytic reduction (SCR). Although not every one of these techniques is applicable to each kiln type, for every kiln there is at least one technical option feasible that enables the operator to control the NOx emissions below the above-mentioned level. For most kilns, more than one technical option is applicable; some of these options are able to achieve still lower emission levels around 500 mg NOx per Nm3 or even less. Based on expert interviews with kiln operators and suppliers of DeNOx equipment, the costs for improved NOx abatement were analysed and compared with the external benefits of reduced NOx emissions. When the allowed NOx emission level for cement kilns is lowered to 800 mg / Nm3, the external benefit from the avoided damage caused by NOx emissions will be between three and 33 times higher than the necessary expenses for the reduction measures. The costs of the NOx reduction measures can be covered by co-incineration of wastes equivalent to between 5 and 12 per cent of the kilns total energy demand. In many cases, the expenses for NOx reduction measures will even be much lower than this. A legal limitation of NOx emissions to a level below 200 mg/Nm3 would force all kiln operators to install an SCR catalyst. The external cost-benefit ratio for such a reduction will lie between 1:7 and 1:42 and will thus be significantly greater than for the NOx reduction to 800 mg/Nm3. However, no long-term experiences with full-scale SCR installations have been made yet in the cement industry, thus leaving a certain degree of uncertainty about the life-time of the catalyst and the subsequent overall costs of this technique.