Increasing worldwide demand for chicken and chicken products has led to increased production of chicken manure. Therefore, chicken manure has an important application potential in the energy industry. This study aims to dispose of chicken manure, which is harmful to soil and groundwater, for thermal energy purposes and to reduce the emissions of lignite coal. For this purpose, it concerns the design and manufacture of a Circulating Fluidized Bed Boiler (CFBB) with a novel combustion chamber for burning chicken manure (CM) and lignite (L) fuels and their mixtures. The combustion behaviors and contaminating emissions of the mentioned fuels in such a CFBB are investigated experimentally and numerically. Emissions of major gaseous pollutants, including CO, SO2 and NO, and the temperature distribution throughout the combustion chamber are measured during the tests. Experimental results show that increasing the amount of CM in the mixture increases CO and reduces SO2. For this condition, NO emission either increases or decreases. According to the numerical results, the temperature of the combustion chamber decreases with the increase of the CM fraction. In the CFBB, the CO emission decreases in the CM fraction up to 25 %, while it increases in the CM fraction above 25 %. For increasing CM fraction, NO emission decreases in the cyclone while it increases in the evaporator. In the experimental and numerical results, the CO2 emission for the L, CM and CM fractions are observed to be equivalent to each other. In conclusion, this study clearly shows that in situ burning of chicken manure or lignite and chicken manure mixtures reduces lignite emissions and meets the heat requirement and disposal of waste in chicken processing plants.