Gasification converts solid fuel into product gas which can be used in various applications. The product gas can be combusted to generate heat and electricity. It can also be used as a feedstock for the production of synthesis gas, liquid fuel and chemicals. This paper presents the experimental results of gasification of cotton stalk (C. S.) and hazelnut shell (H. S.) in a laboratory scale bubbling fluidized bed gasifier under air and steam atmospheres. The effects of equivalence ratio (ER) and steam to fuel ratio on the quality of the product gas are investigated for the air and steam atmospheres, respectively. Identical tests are conducted to investigate the repeatability of experimental results. The composition of the product gas is determined with an online gas analyzer which measures CO, CO2, CH4, H-2 and O-2 components. The lower heating value (LHV) of the product gas is calculated by using the gas composition measurements. The LHV is obtained in the range of 2.49-11.28 MJ/Nm(3). In the case of air gasification, the ER is varied in the range of 0.71-0.36 and 0.68-0.25 for the cotton stalk and hazelnut shell cases, respectively. The ER significantly affects the LHV for hazelnut shell. In the case of steam gasification, the steam to fuel ratio is changed in the range of 1.69-0.52 and 2.26-0.33 for the cotton stalk and hazelnut shell cases, respectively. The steam feeding rate can be maintained at minimum because it slightly changes the LHV. (C) 2013 Elsevier Ltd. All rights reserved.