Science | April 12th, 2019
Research identifies water reservoirs in sugarcane bagasse

Results contribute to improve processing technology and valorization of this resource

Sugarcane is cultivated in several countries around the world, mainly to produce sugar and alcohol obtained from the juice extracted during the milling process. The remaining fresh bagasse is a material rich in cellulose and lignin, but also in water. Even with the extreme efficiency of the operations in the sugarcane industry, after all the juice extraction stages in the mill, the fresh bagasse is still composed of almost 50% of water.

The remaining water in the bagasse has several important consequences. The extraction of sugar has efficiency between 94 and 98%. The remaining percentage remains trapped at the bagasse in some way associated with water. Thus, any percentage gain in this process can bring a million-dollar impact to the industry.

3D visualization os a selected bagasse fragment.

In the mills, bagasse is usually burned as fuel for electricity production. In this process, the evaporation of the water contained in the fresh bagasse consumes part of the heat generated and reduces the combustion temperature, hindering its efficiency. In addition, the presence of water, which is essential for biological degradation, is detrimental to the storage of fresh bagasse. Lastly, water wasted due to evaporation, whether in the warehouse or in the boiler, is an important environmental issue.

Despite the many consequences, the precise location of the remaining water inside the fresh bagasse remains unknown. Thus, Carlos Driemeier, from the Brazilian Bioethanol Science and Technology Laboratory (CTBE), et al. [1] used the IMX X-ray microtomography beamline from Brazilian Synchrotron Light Laboratory (LNLS) to obtain three-dimensional high-resolution images of the bagasse, in a non-invasive way, after the milling process for extraction of the juice.

The images allowed the group to visualize the volume of water inside the bagasse, confirm that the cells are partially filled with water, and identify which tissues are preferably wet or dry.

The fibrous cells surrounding the xylem vessels were frequently found filled with water. On the other hand, most of the xylem vessels and parenchyma cells were dry (i.e., filled with air). The epidermis region showed an intermediate behavior, showing both dry and wet cells in similar proportions.

Particles of mineral impurities of sizes from $rm 8$ to $rm 140 µ m$ were also observed. They were, in most cases, adhered to the outer surfaces of the bagasse fragments, with water presumably contributing to adhesion.

According to the researchers, these results provided new insight into water-related phenomena that occurs during sugarcane milling and drive advances to sugarcane processing technology and the bagasse valorization.

Sources: [1] Carlos E. Driemeier, Liu Y. Ling, Daison Yancy-Caballero, Paulo E. Mantelatto, Carlos S. B. Dias, Nathaly L. Archilha, Location of water in fresh sugarcane bagasse observed by synchrotron X-ray microtomography, PLoS ONE 13(12): e0208219. DOI: 10.1371/journal.pone.0208219

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