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Cellulosic biomass, the most abundant organic matter on earth, is comprised of cellulose, hemicellulose, and lignin. Its structural complexity, along with the existence of lignin, makes it recalcitrant to enzymatic and microbial attacks and thus serves a serious obstacle to the commercialization of biomass-based fuels [1, 2]. To make cellulose content more susceptible to subsequent enzymatic hydrolysis, therefore, raw biomass feedstocks must go through a pretreatment process. Thus far, a substantial number of such pretreatment techniques have been extensively examined to process various biomass feedstocks on scale of both laboratory and pilot plants [3, 4, 5]. Nevertheless, none of those options has demonstrated to be fully satisfactory, because each method has its intrinsic benefits and drawbacks [6]. Our research was aimed at the development of economical pretreatment of cellulosic biomass for bioethanol production. Three innovative approaches were investigated to pretreat rice straw such as FeCl3, alkali, and sono-assisted dilute sulfuric acid (SADA) pretreatment process. Ferric iron (Fe3+), a strong catalyst on hydrolysis of hemicellulose, was found to be reduced to ferrous iron (Fe2+) by oxidizing xylose and lignin. Furthermore, this ferrous iron was completely oxidized at anode in a fuel cell generating a power of 1110 mW/m2 at optimal conditions; pH of 7.0 and ferrous iron concentration above 0.008 M. Thus, FeCl3 pretreatment combining with fuel cell system proved a green process that could be successfully employed for integrated energy production system using waste species (agriculture residue, Fe2+). Pretreatment via alkali and sono- assisted dilute acid process was studied using response surface methodology (RSM). Pretreatment time, concentration and temperature were selected as process factors. For alkali pretreatment, NaOH concentration (1.0−4.0%), temperature (60−100°C) and pretreatment time (30−90 min) were employed. The maximum glucose yield of 254.5 ± 1.2 g/kg was obtained at the optimal pretreatment factor levels of 2.96%, 81.79°C and 56.66 min respectively. In case of SADA pretreatment, sulfuric acid concentration (5−10%), temperature (70−90°C) and sonication time (30−50 min) were employed. The process was optimized at factor levels (10%, 80°C and 50 min) respectively against a sugar yield of 31.78 g/100g. The results suggested that SADA process was probably feasible for simultaneous pretreatment and saccharification of biomass. Further research was needed to investigate the recovery of spent acid and application of hydrodynamic cavitation than sonication in order to improve the process economics. Thus, the study of three pretreatment processes presented innovative and economical pretreatment technologies for cellulosic biomass.