Sugarcane bagasse that is a byproduct of sugarcane extraction process is majorly used in the paper making process. Approximately 40% of this residue is considered small fiber, sugarcane bagasse pith that is eliminated from the pulp for papermaking. Compared to a good number of agricultural residues, sugarcane bagasse pith is also a lignocellulostic material composed of lignin, hemicelluloses and cellulose. A large proportion of this byproduct is normally used for electricity production, but this comes with more carbon dioxide emissions.
Therefore, most researchers have focused on how it can be used for biological fuel production as well as chemicals that can offer economic, strategic, and environmental advantage. Reducing sugars, a biomass precursor that can be changed to fuel alcohol by fermentation, appears to be the best high-added product that can be extracted from sugarcane bagasse pith.
In order to extract reducing sugars from the sugarcane bagasse pith, the hemicelluloses as well as cellulose should be hydrolyzed. Some of the methods for achieving this include, acidic, enzymatic and alkali hydrolysis. Nevertheless, implementing concentrated acids, for instance, hydrochloric and sulfuric acids demands corrosion resistant reactors. Long process time as well as high cost of enzyme production are the major bottlenecks for enzymatic hydrolysis.
Researchers led by professor Xiaopeng Chen from the Department of Chemistry and Chemical Engineering at Guangxi University in China investigated the subcritical carbon dioxide water hydrolysis of sugarcane bagasse pith in the production of reducing sugars. In their study, an orthogonal test method was used to optimize a combination of process parameters, which include stirring speed, reaction temperature, carbon dioxide initial pressure, total reducing sugars, and reaction time. Their work is published in peer-reviewed journal, Bioresource Technology.
The authors carried out the hydrolysis of sugarcane bagasse pith in a stainless steel reactor, which was equipped with a magnetic driven paddle agitator. The reactor was heated and the temperature inside measured and controlled at operating temperature. A magnetic stirrer was then used to continuously mix the content of the reaction.
For carbon dioxide reaction, a stainless steel tube was connected to a valve and fitted to the reactor to allow for controlled introduction of carbon dioxide from a gas cylinder. The initial pressure of the carbon dioxide was then controlled using a high-pressure reactor regulator.
The hydrolysis of the sugarcane bagasse pith to generate reducing sugars under subcritical carbon dioxide-water led to the highest total reducing sugars production of approximately 45.8% at the optimal conditions established by orthogonal design of 200 °C, 1MPa initial carbon dioxide pressure, 40 minutes reaction time, 500rmin-1 stirring speed, and 50:1 liquid-to-solid ratio.
FT-IR analysis indicated that xylose, arabinose, and glucose were the major components in the hydrolysis liquor. Elementary kinetic processes of biomass solubilisation represented by severity factors could not adequately define the hydrolysis of the sugarcane bagasse pith. Decomposition of the reducing sugars, rate constants, and activation energy of reducing sugar formation were obtained on the first-order kinetic model of consecutive reactions.
Jiezhen Liang, Xiaopeng Chen, Linlin Wang, Xiaojie Wei, Huasheng Wang, Songzhou Lu, Yunhua Li. Subcritical carbon dioxide-water hydrolysis of sugarcane bagasse pith for reducing sugars production. Bioresource Technology, volume 228 (2017), pages 147–155.Go To Bioresource Technology