(622ah) Ultrasound Assisted Pretreatment of Rice Husk and Plantain

Lignocellulosic biomass such as rice husk and plantain pseudostem represents a potential source of sugars that can be used as raw material in biorefineries to produce chemical, biofuels, bioenergy, biomolecules and other kind of compounds [1], [2]. This type of biomass is arranged in a matrix composed by cellulose, hemicellulose and lignin. Reduction of polymerization degree and crystallinity are the principal objectives for lignocellulosic material pretreatment. The enhancement of the cellulose availability, surface area and lignin matrix destruction are allowed through hydrothermal, acid, alkaline and organosolv pretreatments. These conventional operations release inhibitory compounds affecting the fermentation yields and the microorganism performance. Some non-conventional operations such as ultrasound assisted pretreatment have been studied to enhance the pretreatment stage of the lignocellulosic materials [3], [4]

Ultrasonic technology is based on acoustic radiation phenomena in which mechanic energy form is transformed to chemical energy generating chemicals, physicals and biochemical energies [5]. Ultrasonic waves are the expression of this kind of energy they create pressure drops at frequencies beyond audible range between 20-1000 kHz. This phenomenon could generate bubbles that produce shock waves which create a flow patterns generating a hydrodynamic shear stress capable of inducing changes in the lignocellulosic material structure [6][7].

In this work different sonication times (10 to 60 minutes) and temperatures (25°C to 80°C) were evaluated for rice husk and plantain pseudostem pretreatment in 2% sulfuric acid medium. The ultrasonic irradiation at a frequency of 30 kHz was transferred through a cylindrical horn from a UP100H device. Rice husk 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 results were compared with the base case without ultrasound assistance. 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. All the experimental procedures were performed in the Biotechnology and Agribusiness Institute at Universidad Nacional de Colombia at Manizales.

With the purpose of understanding the effect of different composition profiles (after pretreatment) a biorefinery [8] [9] scheme to produce ethanol, citric acid, xylitol and energy considering the non-conventional and conventional pretreatment (Ultrasound assisted and diuted acid) 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. Finally, was evidenced the ecomonical improvement provided by the use of ultrasound assisted pretreatments in the biorefinery performance.

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