The present study investigates the combustion of four kinds of biomass in a circulating fluidized bed. The combustion chamber is a steel cylinder with 145 mm inner diameter and 2 m height. Tests were conducted on wheat straw, sawdust-wood, cottonseed burs, and corncobs. Excess air was varied for each fuel. Temperature, heat flux and gas emissions were measured along the combustion chamber and at the chimney inlet. Results showed that sawdust-wood produces the highest values of CO emissions (about 3000 mg/Nm(3)). On the other hand, cottonseed burs produce the lowest values of CO emissions (about 250 mg/Nm(3)). The SO(2) emissions were very low in all tests (less than 20 mg/Nm(3)). The lowest emission value occurred at an excess air ratio (EA) of 1.24 except for cottonseed burs where it was 1.4. (C) 2009 Published by Elsevier Ltd.