(111d) A Comparative Study on the Pyrolysis and Gasification Behavior of Sugarcane Tops/Leaves and Sugarcane Bagasse

After extracting sugar at sugarcane mill, bagasse is left as a residual byproduct. Some of this bagasse is used to meet the energy requirements of the mill. The remaining bagasse could be pyrolyzed and gasified to provide additional feedstock for producing renewable fuels and chemicals. Also, a portion of the sugarcane tops and leaves (“SCT”) left in the fields can also be delivered to the bagasse processing unit to provide additional feedstock for making fuels and chemicals. Often SCT is burned in the fields because there is too much SCT remaining to properly maintain the fields. Burning of SCT in the fields creates environmental problems.

The chemical composition of SCT is not the same as bagasse. This study was done to characterize differences in pyrolysis and gasification of these two feedstocks. TGA weight loss data during pyrolysis indicates that cellulose peak reactivity in SCT is shifted to a lower temperature compared to bagasse. Based on simultaneous screening by TGA and DSC, the SCT showed a lower activation energy and higher gasification reactivity in CO₂ than bagasse. This trend is consistent with the higher inorganic content in SCT since some of the inorganics present may catalyze these reactions. The heat effects associated with pyrolysis and gasification are different for these two feedstocks. Slow pyrolysis in nitrogen (at 15 K/min) indicated mildly endothermic reaction with sugarcane bagasse while the reaction is nearly heat neutral with SCT. Higher reactivity of SCT during oxidative pyrolysis (with 5% O₂ in N₂) resulted in a much higher exotherm than bagasse. The differences observed are not likely to require that the bagasse and SCT need to be pyrolyzed and gasified separately.