Daza Laura1, Betancourt Ramiro1, Cardona Carlos A1**.
1 Universidad Nacional de Colombia sede Manizales, Instituto de Biotecnología y Agroindustria, (+57) (6) 879400 ext 55354.
** Corresponding author: email@example.com
Colombia is a tropical country assorted of soils and hydric resources which produces a wide variety of crops. The agricultural activities generates high amounts of waste biomass. Cassava stem and Plantain pseudostem are lignocellulosic residues generated during harvesting stage. The interest and use of these type of residues as raw materials for biorefineries to produce chemicals, biofuels and other products has been increasing as reported by authors as Moncada et al , . The available amounts and chemical composition are some advantages of this group of raw materials. Nevertheless, the morphologic arrangement of cellulose, hemicellulose and lignin becomes in the main drawback for enzymatic and microorganism attack. Pretreatments are used to reduce the cellulose crystallinity as well as the hemicellulose and lignin content.
The conventional pretreatments involves the use of hydrothermal, acid, alkaline and organosolv pretreatments . Non-conventional pretreatment includes supercritical H2O, ammonia and CO2among others . The pretreatments using supercritical carbon dioxide in presence of moderate to high moisture levels produce carbonic acid and generates biomass swelling. The produced carbonic acid cause a hydrolytic effect in the biomass .
Cassava stem and Plantain pseudostem were experimentally characterized by measuring moisture content (AOAC 928.09 method), Klason lignin content (TAPPI 222 om-83 method), acid-soluble lignin content (TAPPI 250UM-85 method) holocellulose content (ASTM Standard D1104 method), cellulose content (TAPPI 203 os-74 method), and ash content (TAPPI Standard T211 om-93 method). Then, the selected raw materials were submitted to a non-conventional and conventional pretreatment. Supercritical carbon dioxide was used as non-conventional pretreatment. The pressure, temperature and moisture content were experimentally evaluated. The conventional pretreatment was developed using 2% sulfuric acid. Later on, the pretreated samples were submitted to enzymatic hydrolysis to produce glucose by cellulases enzymes. The sugars, and inhibitory compounds yields were determined through spectrophotometric analysis.
The sugars production from lignocellulosic biomass using supercritical carbon dioxide and sulfuric diluted acid (case base) pretreatments were evaluated using the commercial software Aspen Plus V8.2 (ASPEN TECHNOLOGY INC). The economic evaluation was performed using the software commercial Aspen Process Economic Analyzer V8.2 (ASPEN TECHNOLOGY INC) taking into account the Colombian context with an annual interest rate of 16% and an income tax of 25%, with electricity and water costs according to the case study conditions. Furthermore, the evaluation was realized for a period of 10 years using as depreciation method the straight-line. Finally, the benefits provided by supercritical carbon dioxide pretreatment reduces the inhibitory compounds released compared to the conventional sulfuric diluted acid. However, the techno-economic analysis demonstrated that supercritical fluids pretreatment is still an expensive option in this case.
 J. Moncada, J. a. Tamayo, and C. a. Cardona, “Integrating first, second, and third generation biorefineries: Incorporating microalgae into the sugarcane biorefinery,” Chem. Eng. Sci., vol. 118, pp. 126–140, 2014.
 L. E. Rincon, J. Moncada Botero, and C. A. Cardona Alzate, Catalytic Systems for Integral Transformations of Oil Plants through Biorefinery concept., First Edit. Manizales, Colombia: Universidad Nacional de Colombia sede Manizales, 2013.
 C. E. Wyman, S. R. Decker, M. E. Himmel, J. W. Brady, and C. E. Skopec, “Hydrolysis of Cellulose and Hemicellulose,” in Polysaccharides Structural Diversity and Functional Versatility, Second., S. Dimitriu, Ed. New York, 2005.
 M. Gao, F. Xu, S. Li, X. Ji, S. Chen, and D. Zhang, “Effect of SC-CO2 pretreatment in increasing rice straw biomass conversion,” Biosyst. Eng., vol. 106, no. 4, pp. 470–475, 2010.
 N. Narayanaswamy, A. Faik, D. J. Goetz, and T. Gu, “Supercritical carbon dioxide pretreatment of corn stover and switchgrass for lignocellulosic ethanol production,” Bioresour. Technol., vol. 102, no. 13, pp. 6995–7000, 2011.