Carnauba Straw as Feedstock for Solid Biofuel Production

Abstract

Carnauba straw (<em>Copernicia prunifera</em>), residual biomass derived from wax extraction, was evaluated as a potential feedstock for bioenergy production. The characterization was carried out using elemental analysis, proximate analysis, Higher Heating Value (HHV), FTIR spectroscopy, SEM, and FRX. The carbonization, using a Muffle Furnace, was applied as a thermal conversion technique to improve the fixed carbon content, and preliminary densification was done to assess the potential for future production of briquettes. The C, H, N, O, and S percentages were 44.43%, 5.34%, 2.25%, 46.17%, and 1.81%, respectively. The percentage of fixed carbon (14.17%) increased to 31.10% (250°C) and 35.68% (300°C) after carbonization. At 400°C, the HHV presented a decrease of 9.62%, and ash content increased by 177.66%. FTIR spectra showed bands characteristic of hemicellulose, cellulose, and lignin at 3414 - 3393 cm^-1 (O-H) and decrease of absorbance of 74.01% to 81.37% after carbonization; 1738 – 1603 cm^-1 (C=O), with reduction in the order of 73.94% to 78.31%, and 48.97% to 73.76%, when compared to the absorbances of the biomass in nature. The SEM of the carnauba straw in nature presented the main structural components (cellulose, lignin, and hemicellulose). After carbonization, evidence of degradation and coal formation was observed, which corroborates with the decrease in the HHV and increase of ash. The FRX was inserted in the SEM images, and the elements detected were Ca, K, and S. The quantities and order of abundance in biomass natural and carbonized were compatible with other biomasses used as biofuel. The carnauba straw in natural and carbonized was densified to understand the characteristics of the compacted material. The sample carbonized at 300°C presented a solid with the potential for future production of briquettes. All results follow other reported biomasses and could lead to further investigation of the carnauba straw as feedstock for solid fuel production without or in a mixture with other agricultural residues.