Hight Quality Bioethanol Characteristics of Rice Straw Raw Materials

The Department of Mechanical Engineering, Universitas Negeri Surabaya, Campus Ketintang, Surabaya, 60213, Indonesia

^* Corresponding author: muhaji61@unesa.ac.id

Abstract

Bioethanol is a renewable fuel derived from agricultural resources. This study aimed to examine the characteristics of bioethanol produced from rice straw, including ethanol concentration, methanol concentration, water content, copper (Cu) and chloride (Cl) levels, gum content, pH, heating value, density, viscosity, flash point, and octane number. An experimental method was employed, with the production process consisting of four stages: preparation, saccharification, three-day fermentation using 25 grams of Saccharomyces cerevisiae, and fractional distillation at four levels at 78 °C with 10 grams of zeolite rock adsorbent (70 mesh). Bioethanol quality tests followed ASTM standards (D5501 for ethanol, D550 for methanol, D1744 for water content, D1688 for Cu, D1613 for Cl, D381 for gum, D4806 for pH, D240 for heating value, D1298 for density at 20 °C, D445 for viscosity at 20 °C, D93 for flash point, and D2699 for octane number). The chemical analysis revealed 99.75% ethanol, 0.0024% methanol, 0.0019% vol water, 0.002 mg/kg Cu, 15.73 mg/l Cl, and 1.3 mg/100 ml gum. The physical analysis revealed a pH of 6.1 mg/L, a heating value of 6975 kcal/kg, a density of 0.781 g/cm³, a viscosity of 1.26 cSt, a flash point of 15 °C, and an octane number of 105. Overall, the results confirm that rice straw bioethanol possesses superior performance and environmental advantages, making it a feasible substitute or additive for gasoline.