A parametric study of the gasification of six biomass feedstocks (switchgrass, hardwood, softwood, fiber, cardboard and chicken manure), as representative of different types of biomass, has been performed on an experimental, pilot-scale 10 kWth down-draft gasification facility. A comparison was made of the performance of the gasifier as a function of feedstock, in terms of the producer gas production and composition. The variation of producer gas composition was analyzed in the range 600-1000 degrees C. The results indicated that switchgrass, as representative of energy crops, has greater potential to yield the main components of the producer gas (i.e., hydrogen and carbon monoxide) in comparison, with the other feedstocks. However, this did not guarantee the greatest suitability of the switchgrass for downstream applications due to low molar ratios of the ratio of hydrogen to carbon monoxide (H-2/CO), which measured at 1.01. To enhance the utility efficiency of producer gas, the downstream engines such as combustion engines require an adjusted,:molar ratio of H-2/CO to utilize certain types of fuels which typically ranges from 1.5 to 3. By means of the catalytic water gas shift reaction, an important portion of the CO content in the cracked gas can be used for additional hydrogen generation. The temperature variation of the down-draft reactor showed that the CO concentration increased with, an increase in gasification temperature followed by,a drop of temperature dependent on the different biomass feedstocks. Conversely, CO2 concentration follows an opposite trend that means an initial decreasing trend followed by an increase as' the temperature increases, H-2 concentration follows, a direct relationship with the gasifier temperature. The concentration of CH4 varies very slightly with the increase in gasifier temperature. The results of this study showed that there were significant differences between the energy crops and chicken manure mixed with wood chip, in terms of composition, In general, the variations in producer gas components,were smaller at higher temperatures whereas H-2/CO showed greater variation between individual feedstocks.